The purpose of center drilling is to start the hole exactly where intended
without the drill point wandering all over the place, yes? This is then
normally followed by a twist drill of the desired size etc. From this
concept I would assume that the axes of the drills are concentric, or in
other words the hole drilled by the twist drill is exactly concentric with
the hole started by the center drill.

This does not seem happening in my case and I am wondering why.

Example: Using my mini-mill, I start the hole with a No.1 center drill and
then change to a twist drill (say 7/64"). X and Y are locked. As I bring the
drill down it is clearly off centre - today I measured it and it is quite
consistent: The drill point moves 0.010" "east" and 0.005" "south" to enter
the starter hole. If the full hole is then drilled it is slanted ever so
slightly - perhaps 0.001" over 0.25" length. This happened with two
different 7/64" twist drills.

I tried a different No. 1, I tried both ends, same result. Looking at the
slowly rotating point with a magnifying glass it describes a small circle
which is not obvious when I bring it down on the metal. However, there is
perceptible vibration of the mill which is absent if I drill with the twist
drill. I interpret this that the mill head is doing the circles while the
point is embedded. If I had a more rigid set-up the circle would perhaps be
apparent.

I tried the same experiment with a No.2 and No.3 - same result.

I thought I'd better find out which is the true center: The "center drill"
or the "twist drill" one. This was even more complicated than I expected. I
used two centere finders on small punch marks. They both showed center
differently! The centre found by the barrel-type coincided with the center
drill point, the wiggler type was quite significantly off (I use 10x
magnifying glass to get the best accuracy with both).

So the questions at this stage we
1) Is this a normal behavior? I thought unlikely...
2) Is this because of cheap Chinese center drills?
3) Is this a function of the mill chuck?
4) Is there some other reason?

I was wondering about the way the drills are clamped in the chuck and I
tried different degrees of tightening. The last effort involving only light
tightening of the chuck both for the centre drill and the twist drill I
managed to hit the centre-found punch mark with both the centre and twist
drill.

Is it possible that over-tightening the chuck throws things out of kilter? I
hope to repeat this with the bigger center drills tomorrow but I would
appreciate any insight.


--
Michael Koblic,
Campbell River, BC

Michael Koblic writes:

So the questions at this stage we

Have you checked the tramming of the head?

Have you chucked a dowel pin, gage pin, or other precision cylinder, and
indicated the runout?

On 2010-11-10, Michael Koblic wrote:
The purpose of center drilling is to start the hole exactly where intended
without the drill point wandering all over the place, yes?

Actually -- that is the purpose of spot drilling -- with a spot
drill, not a center drill.

The purpose of a center drill is to make a conical depression
with a precise 60 degree angle and a bit of clearance to allow room for
the point of a live or dead center to stablize the end of a workpiece in
a lathe.

Yes, people do use center drills for the purpose of spotting
drills -- but that is not what they were made for.

This is then
normally followed by a twist drill of the desired size etc. From this
concept I would assume that the axes of the drills are concentric, or in
other words the hole drilled by the twist drill is exactly concentric with
the hole started by the center drill.

This does not seem happening in my case and I am wondering why.

Example: Using my mini-mill, I start the hole with a No.1 center drill and
then change to a twist drill (say 7/64"). X and Y are locked. As I bring the
drill down it is clearly off centre - today I measured it and it is quite
consistent: The drill point moves 0.010" "east" and 0.005" "south" to enter
the starter hole. If the full hole is then drilled it is slanted ever so
slightly - perhaps 0.001" over 0.25" length. This happened with two
different 7/64" twist drills.

Hmm ... sounds like a tramming error -- the axis of the spindle
is not perpendicular to the bed. And likely the column axis as well.
Your drill is longer than the center drill, so you have to move the head
up the column. If it is not perfectly vertical, this will drift the
center line of the axis to the side -- and front to back as well. The
column on a lot of the small mills tilts, so it provides adjustment for
the side-to-side part. However, the fore and aft takes a bit more
tricky work to get straight -- using shim stock is the usual approach.

Get a machinist's square (a blade with a heavy right-angle
piece) and resting that on the bed, check for a slight angle between the
blade and a piece of precision ground rod in the chuck. (or better, in
the collet, as chucks can introduce errors too.) (Actually -- get *two*
machinist's squares, and check them against each other as well. They can
come out of square to start with.)

Is yours one of those whose column has a pivot at the bottom, so
you can drill holes at an angle? If so, have you checked that the
column is truly vertical?

Or is yours one with a head which pivots on the carriage which
moves up the column? In that case, that might not be set quite right.

I tried a different No. 1, I tried both ends, same result. Looking at the
slowly rotating point with a magnifying glass it describes a small circle
which is not obvious when I bring it down on the metal.

That is either runout in the chuck, or a bent arbor for the
chuck. I forget -- does your machine use R8 collets? If so, how are
you holding your drill chuck? An R8 arbor, or a straight shank arbor
held in a collet? In either case, the arbor might be slightly bent.

However, there is
perceptible vibration of the mill which is absent if I drill with the twist
drill. I interpret this that the mill head is doing the circles while the
point is embedded. If I had a more rigid set-up the circle would perhaps be
apparent.

If you had a more rigid setup, the center drill would simply
make the hole a bit oversized as it swept around. And depending on the
orientation of the flutes to the eccentricity, it would either rub hard,
or cut oversized like a fly cutter.

I tried the same experiment with a No.2 and No.3 - same result.

Did you try a runout indicator on the shank of the drill? How
about with a longer rod (best would be a drill blank -- or an unusually
long dowel pin, but you might get away with some drill rod if it has not
been bent.

I thought I'd better find out which is the true center: The "center drill"
or the "twist drill" one. This was even more complicated than I expected. I
used two centere finders on small punch marks. They both showed center
differently! The centre found by the barrel-type coincided with the center
drill point, the wiggler type was quite significantly off (I use 10x
magnifying glass to get the best accuracy with both).

I presume that you started with the wiggler a bit off center,
and pressed a finger against the side until it stopped wiggling? *That*
is what sets it on center.

So the questions at this stage we
1) Is this a normal behavior? I thought unlikely...
2) Is this because of cheap Chinese center drills?
3) Is this a function of the mill chuck?
4) Is there some other reason?

Possibly the chuck or its arbor -- possibly the tram of the
column and head. More likely, a combination of the two.

The chuck or its arbor will produce the circles.

The tram of the head will produce the shift of the center point
as the head goes up and down.

I was wondering about the way the drills are clamped in the chuck and I
tried different degrees of tightening.

The proper way is to tighten equally using all three holes, one
after the other.

The last effort involving only light
tightening of the chuck both for the centre drill and the twist drill I
managed to hit the centre-found punch mark with both the centre and twist
drill.

Hmm -- the chuck is not a firm fit on the arbor? The arbor is
not a firm fit in the spindle?

Is it possible that over-tightening the chuck throws things out of kilter? I
hope to repeat this with the bigger center drills tomorrow but I would
appreciate any insight.

First get the runout indicator and check for runout on a ground
hardened rod (e.g. a drill blank or a dowel pin) both just where it
exits the chuck and down closer to the end. If it is better where it
exits the chuck, then the arbor may be bent. If it is equally off down
the length of the rod, it is likely a bur on one of the jaws in the
chuck.

Lots of things to check.

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Tue, 9 Nov 2010 18:27:53 -0800, "Michael Koblic"
wrote:

The purpose of center drilling is to start the hole exactly where intended
without the drill point wandering all over the place, yes? This is then
normally followed by a twist drill of the desired size etc. From this
concept I would assume that the axes of the drills are concentric, or in
other words the hole drilled by the twist drill is exactly concentric with
the hole started by the center drill.

snip
First -- center drill and spotting drills are like
everything else, you can get cheap ones.

While center drills are commonly used for this purpose, they
are intended to drill holes for lathe centers for turning
between centers. While 60 degree is the most common because
most lathe centers are 60 degrees, 82 degrees and 90 degrees
are also available. the 60 degree center drill is the least
expensive because it is the most common.
for examples see
http://www.google.com/images?q=%22tu...w=1336&bih=701
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32

The more correct tool is what is called a spotting drill.
These come in several included point angles and should be
matched to your drill bit geometry, i.e. 135 degree or 118
degree point. These come in several sizes and if you use
one slightly larger than the drill or limit the depth to
limit the size of the taper, you will get a chamfered edge.
These come in 90 degree, 120 degree and 150 degree included
angle.
for examples see
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32
http://www.use-enco.com/CGI/INSRIT?P...PMPXNO=3007493
These drill tend to be stiffer and last longer as these do
not have the small "tit" like a center drill that isprone to
drift or break off.

for a discussion see
http://bbs.homeshopmachinist.net/showthread.php?t=38729

Depending what you are doing, the standard jobber length
drill may be introducing run out and is more flexible than a
short drill like a screw machine length. I suggest you get
one or a few good screw machine length drills with 135
degree split points and give these a try with the spotting
drill. Most likely you wont need a complete set, just the
sizes you use for you usual tap drills.
for examples see
http://www.use-enco.com/CGI/INSRIT?P...MPXNO=19503626

The sites are examples only and most any mill supply should
stock.

Let the group know what you discover for your shop.



-- Unka George (George McDuffee)
...............................
The past is a foreign country;
they do things differently there.
L. P. Hartley (1895-1972), British author.
The Go-Between, Prologue (1953).

On Nov 9, 9:27*pm, "Michael Koblic" wrote:
...
Example: Using my mini-mill, I start the hole with a No.1 center drill and
then change to a twist drill (say 7/64"). X and Y are locked. As I bring the
drill down it is clearly off centre - today I measured it and it is quite
consistent: The drill point moves 0.010" "east" and 0.005" "south" to enter
the starter hole. If the full hole is then drilled it is slanted ever so
slightly - perhaps 0.001" over 0.25" length. This happened with two
different 7/64" twist drills.

I tried a different No. 1, I tried both ends, same result. Looking at the
slowly rotating point with a magnifying glass it describes a small circle
which is not obvious when I bring it down on the metal. However, there is
perceptible vibration of the mill which is absent if I drill with the twist
drill. I interpret this that the mill head is doing the circles while the
point is embedded. If I had a more rigid set-up the circle would perhaps be
apparent....

Michael Koblic,
Campbell River, BC

I've seen those problems and think I've traced them to wear and play
in the quill and dirt or an accumulation of tolerances in the chuck
tapers and jaws. My cheap drill press shifts visibly when I pull on
the handle enough to make a drill bite into steel, and the loading on
the quill rack changes from supporting it to forcing it down.

I've see a center drill make the mill head vibrate, don't remember
which chuck but the fix was clamping the drill in a collet. Possibly
there was a chip in the taper?

You can check runout and shift under load by indicating a chucked rod,
and quill perpendicularity by chucking the indicator and running it
down an angle plate. This isn't the same as tramming it since the
spindle axis may not be parallel to the quill.

jsw

A very useful piece of tooling for checking various machine problems is a
drill or reamer blank, as suggested by DoN.

The blanks I have are Cleveland brand, and are fairly precisely round,
straight and have a conical point on one end. Several sizes of blanks will
facilitate checking many different conditions of chucks, and different sizes
of collets.

Clamping a blank in a chuck or collet can reveal several aspects of
center-of-axis and runout, and likely to be very helpful in indicating a
condition of direction of travel of the inaccurately placed drill in this
situation, shown clearly by using a square or angle plate as recommended.

Some folks may recommend a rod from a printer, which may be ground fairly
accurately, but may also have worn spots (probably near the center of the
length) from many cycles of the printer's head assembly.

The chattering can be expected for the stated drilling situation, as one
cutting edge of the drill is very likely catching metal before the other
cuting edge, beginning the rapid rotational skipping/flexing of the drill.
After the centering alignment issue is corrected, chatter may still occur
since the 60 degree sides of the center drill's hole don't match the angle
of the drill's point.
One method that eliminates chatter is lightly contacting the drill point
with the workpiece before the power is turned on. When the power switch is
flipped on, adding moderate down-feed pressure will generally cause the
drill to cut without chatter.

I prefer to use a straight-drilled pilot hole, that is approximately the
same size of the web section of the larger drill. This eliminates the need
for the chisel point of the web in the large drill to displace the metal
directly under the web.
Split-point drills generally don't need a smaller pilot hole (with or
without a center punch or prick punch mark), since they begin to cut as soon
as the points contact the workpiece, and continue to cut without having to
force the web of a conventionally ground twist drill into the workpiece.

--
WB
..........


"Michael Koblic" wrote in message
...
The purpose of center drilling is to start the hole exactly where intended
without the drill point wandering all over the place, yes? This is then
normally followed by a twist drill of the desired size etc. From this
concept I would assume that the axes of the drills are concentric, or in
other words the hole drilled by the twist drill is exactly concentric with
the hole started by the center drill.

This does not seem happening in my case and I am wondering why.

Example: Using my mini-mill, I start the hole with a No.1 center drill and
then change to a twist drill (say 7/64"). X and Y are locked. As I bring
the drill down it is clearly off centre - today I measured it and it is
quite consistent: The drill point moves 0.010" "east" and 0.005" "south"
to enter the starter hole. If the full hole is then drilled it is slanted
ever so slightly - perhaps 0.001" over 0.25" length. This happened with
two different 7/64" twist drills.

I tried a different No. 1, I tried both ends, same result. Looking at the
slowly rotating point with a magnifying glass it describes a small circle
which is not obvious when I bring it down on the metal. However, there is
perceptible vibration of the mill which is absent if I drill with the
twist drill. I interpret this that the mill head is doing the circles
while the point is embedded. If I had a more rigid set-up the circle would
perhaps be apparent.

I tried the same experiment with a No.2 and No.3 - same result.

I thought I'd better find out which is the true center: The "center drill"
or the "twist drill" one. This was even more complicated than I expected.
I used two centere finders on small punch marks. They both showed center
differently! The centre found by the barrel-type coincided with the center
drill point, the wiggler type was quite significantly off (I use 10x
magnifying glass to get the best accuracy with both).

So the questions at this stage we
1) Is this a normal behavior? I thought unlikely...
2) Is this because of cheap Chinese center drills?
3) Is this a function of the mill chuck?
4) Is there some other reason?

I was wondering about the way the drills are clamped in the chuck and I
tried different degrees of tightening. The last effort involving only
light tightening of the chuck both for the centre drill and the twist
drill I managed to hit the centre-found punch mark with both the centre
and twist drill.

Is it possible that over-tightening the chuck throws things out of kilter?
I hope to repeat this with the bigger center drills tomorrow but I would
appreciate any insight.


--
Michael Koblic,
Campbell River, BC

On Nov 9, 6:27*pm, "Michael Koblic" wrote:
The purpose of center drilling is to start the hole exactly where intended
without the drill point wandering all over the place, yes? This is then
normally followed by a twist drill of the desired size etc. From this
concept I would assume that the axes of the drills are concentric, or in
other words the hole drilled by the twist drill is exactly concentric with
the hole started by the center drill.

This does not seem happening in my case and I am wondering why.

Example: Using my mini-mill, I start the hole with a No.1 center drill and
then change to a twist drill (say 7/64"). X and Y are locked. As I bring the
drill down it is clearly off centre - today I measured it and it is quite
consistent: The drill point moves 0.010" "east" and 0.005" "south" to enter
the starter hole. If the full hole is then drilled it is slanted ever so
slightly - perhaps 0.001" over 0.25" length. This happened with two
different 7/64" twist drills.

I tried a different No. 1, I tried both ends, same result. Looking at the
slowly rotating point with a magnifying glass it describes a small circle
which is not obvious when I bring it down on the metal. However, there is
perceptible vibration of the mill which is absent if I drill with the twist
drill. I interpret this that the mill head is doing the circles while the
point is embedded. If I had a more rigid set-up the circle would perhaps be
apparent.

I tried the same experiment with a No.2 and No.3 - same result.

I thought I'd better find out which is the true center: The "center drill"
or the "twist drill" one. This was even more complicated than I expected. I
used two centere finders on small punch marks. They both showed center
differently! The centre found by the barrel-type coincided with the center
drill point, the wiggler type was quite significantly off (I use 10x
magnifying glass to get the best accuracy with both).

So the questions at this stage we
1) Is this a normal behavior? I thought unlikely...
2) Is this because of cheap Chinese center drills?
3) Is this a function of the mill chuck?
4) Is there some other reason?

I was wondering about the way the drills are clamped in the chuck and I
tried different degrees of tightening. The last effort involving only light
tightening of the chuck both for the centre drill and the twist drill I
managed to hit the centre-found punch mark with both the centre and twist
drill.

Is it possible that over-tightening the chuck throws things out of kilter? I
hope to repeat this with the bigger center drills tomorrow but I would
appreciate any insight.

--
Michael Koblic,
Campbell River, BC

As mentioned elsewhere, your mill needs to be trammed. If your drill
bit does not project (stick out) the exact same length as your center
drill, they will not hit the same center of the work piece. The
offset will be proportional to the tangent of your tram angle error.

Ivan Vegvary

"DoN. Nichols" wrote in message
...
On 2010-11-10, Michael Koblic wrote:
The purpose of center drilling is to start the hole exactly where
intended
without the drill point wandering all over the place, yes?

Actually -- that is the purpose of spot drilling -- with a spot
drill, not a center drill.

The purpose of a center drill is to make a conical depression
with a precise 60 degree angle and a bit of clearance to allow room for
the point of a live or dead center to stablize the end of a workpiece in
a lathe.

Yes, people do use center drills for the purpose of spotting
drills -- but that is not what they were made for.


Very informative as usual Don.

*****
Wiki
Center drills, numbers 1 to 6Center drill bits are used in metalworking to
provide a starting hole for a larger-sized drill bit or to make a conical
indentation in the end of a workpiece in which to mount a lathe center. In
either use, the name seems appropriate, as the drill is either establishing
the center of a hole or making a conical hole for a lathe center. However,
the true purpose of a center drill is the latter task, while the former task
is best done with a spotting drill (as explained in detail below).
Nevertheless, because of the frequent lumping together of both the
terminology and the tool use, suppliers may call center drills
combined-drill-and-countersinks in order to make it unambiguously clear what
product is being ordered. They are numbered from 00 to 10 (smallest to
largest).[9]
*****

Hmmm... Would it not lend itself then to the thought that even on a lathe
you should first spot drill and then center drill?

On Nov 10, 10:23*am, "Bob La Londe" wrote:
...
Hmmm... *Would it not lend itself then to the thought that even on a lathe
you should first spot drill and then center drill?

In my experience a #2 center drill is stiff enough to start a hole at
the spindle axis even if the punch mark is off, while a 1/8" spotting
drill will shift slightly into the punch dimple. Which one is better
varies with the job and the layout accuracy.

My personal preference is a #3 center drill 4" long, to avoid cranking
the table up to spot and and down to drill.

jsw

On 10 Nov 2010 04:39:20 GMT, "DoN. Nichols"
wrote:

[...]

Windows Live Mail has done it again. Not only did it swallow my
original post but also your reply. Fortunately I now have two other
news readers.

Hmm ... sounds like a tramming error -- the axis of the spindle
is not perpendicular to the bed. And likely the column axis as well.
Your drill is longer than the center drill, so you have to move the head
up the column. If it is not perfectly vertical, this will drift the
center line of the axis to the side -- and front to back as well. The
column on a lot of the small mills tilts, so it provides adjustment for
the side-to-side part. However, the fore and aft takes a bit more
tricky work to get straight -- using shim stock is the usual approach.

Get a machinist's square (a blade with a heavy right-angle
piece) and resting that on the bed, check for a slight angle between the
blade and a piece of precision ground rod in the chuck. (or better, in
the collet, as chucks can introduce errors too.) (Actually -- get *two*
machinist's squares, and check them against each other as well. They can
come out of square to start with.)

Is yours one of those whose column has a pivot at the bottom, so
you can drill holes at an angle? If so, have you checked that the
column is truly vertical?

That's the one. Last time I did this it was within 0.001" from
end-to-end and front-to-back. I will do this again - but first have to
clear things off the table. Oh, joy! The opportunity to re-align the
vise. Again :-)

[...]

I tried a different No. 1, I tried both ends, same result. Looking at the
slowly rotating point with a magnifying glass it describes a small circle
which is not obvious when I bring it down on the metal.

That is either runout in the chuck, or a bent arbor for the
chuck. I forget -- does your machine use R8 collets? If so, how are
you holding your drill chuck? An R8 arbor, or a straight shank arbor
held in a collet? In either case, the arbor might be slightly bent.

Before I read your post I checked the run-out just under the chuck. No
dowel pins or drill blanks here so I used the drill shanks. I did two
just incase. Both (3/8" and 9/64") showed TIR 0.0005" about 3/8" under
the chuck. BTW my spindle is MT3. I have never had to take the chuck
off so I am not sure how it is attached at the other end. I just
change the whole thing for a collet chuck when I need to.

I was out of town today and took the opportunity to look for dowel
pins etc. No luck.

However, there is
perceptible vibration of the mill which is absent if I drill with the twist
drill. I interpret this that the mill head is doing the circles while the
point is embedded. If I had a more rigid set-up the circle would perhaps be
apparent.

If you had a more rigid setup, the center drill would simply
make the hole a bit oversized as it swept around. And depending on the
orientation of the flutes to the eccentricity, it would either rub hard,
or cut oversized like a fly cutter.

I tried the same experiment with a No.2 and No.3 - same result.

Did you try a runout indicator on the shank of the drill? How
about with a longer rod (best would be a drill blank -- or an unusually
long dowel pin, but you might get away with some drill rod if it has not
been bent.

I shall go through the drawers and see if I have any unusually long
drills or anything else which might do the job.

I thought I'd better find out which is the true center: The "center drill"
or the "twist drill" one. This was even more complicated than I expected. I
used two centere finders on small punch marks. They both showed center
differently! The centre found by the barrel-type coincided with the center
drill point, the wiggler type was quite significantly off (I use 10x
magnifying glass to get the best accuracy with both).

I presume that you started with the wiggler a bit off center,
and pressed a finger against the side until it stopped wiggling? *That*
is what sets it on center.

Yes, but then you have to bring the point over the mark. I find that
challenging without the magnification. Even using the other center
finder (this one, so there is no confusion:
http://www.busybeetools.com/products...RE-FINDER.html )
the alignment of the two parts of the barrel are tricky and much
easier with a magnifying glass.

BTW I thought that the wiggler should be more accurate. However, it
was the other one that was consistently agreeing with the center drill
entry point.

[...]

I was wondering about the way the drills are clamped in the chuck and I
tried different degrees of tightening.

The proper way is to tighten equally using all three holes, one
after the other.

I would go round al of them 2-3 times. With the No. 1 the feeling is
of never really tightening enough. With, say, 1/4" drill you go around
and you know when the thing is tight. There is a definite "stop". With
the No. 1 there is a sort of springy feeling even after you have been
around 3 times. That is what made me wonder about the possible
distortion caused by the chuck. I thought this was supported by the
fact (yet to be confirmed) that if I tightened only lightly the center
drill run straighter (see the last effort where the center finder,
center drill and the twist drill all managed to coincide).

[...]

First get the runout indicator and check for runout on a ground
hardened rod (e.g. a drill blank or a dowel pin) both just where it
exits the chuck and down closer to the end. If it is better where it
exits the chuck, then the arbor may be bent. If it is equally off down
the length of the rod, it is likely a bur on one of the jaws in the
chuck.

Lots of things to check.

Tomorrow is a good time. After 11 AM...

Michael Koblic,
Campbell River, BC

On Wed, 10 Nov 2010 00:24:41 -0600, F. George McDuffee
wrote:


snip

First -- center drill and spotting drills are like
everything else, you can get cheap ones.

While center drills are commonly used for this purpose, they
are intended to drill holes for lathe centers for turning
between centers. While 60 degree is the most common because
most lathe centers are 60 degrees, 82 degrees and 90 degrees
are also available. the 60 degree center drill is the least
expensive because it is the most common.
for examples see
http://www.google.com/images?q=%22tu...w=1336&bih=701
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32

The more correct tool is what is called a spotting drill.
These come in several included point angles and should be
matched to your drill bit geometry, i.e. 135 degree or 118
degree point. These come in several sizes and if you use
one slightly larger than the drill or limit the depth to
limit the size of the taper, you will get a chamfered edge.
These come in 90 degree, 120 degree and 150 degree included
angle.
for examples see
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32
http://www.use-enco.com/CGI/INSRIT?P...PMPXNO=3007493
These drill tend to be stiffer and last longer as these do
not have the small "tit" like a center drill that isprone to
drift or break off.

for a discussion see
http://bbs.homeshopmachinist.net/showthread.php?t=38729

Depending what you are doing, the standard jobber length
drill may be introducing run out and is more flexible than a
short drill like a screw machine length. I suggest you get
one or a few good screw machine length drills with 135
degree split points and give these a try with the spotting
drill. Most likely you wont need a complete set, just the
sizes you use for you usual tap drills.
for examples see
http://www.use-enco.com/CGI/INSRIT?P...MPXNO=19503626

The sites are examples only and most any mill supply should
stock.

Let the group know what you discover for your shop.

Thank you very much for the references.

I recall some time ago someone here mentioning spotting drills as
being distinct from center drills. For some reason I did not
investigate this further.

The forum discussion is most valuable and I bookmarked it. I read
about half of it and will finish it in peace. Then I will read it
three more times to make sure I understand it fully :-)

The drift seems to be that a) spotting drills are the correct tools
for what I have been doing, b) they can be ground from old twist
drills, c) the center drills are self-centering if used on a lathe as
intended, and d) one could therefore conclude that their behavior in a
drill press/mill such as I describe is entirely possible.

I do have a set of machine screw drills which I use exclusively on my
mill and in the Taig, one of the reasons being the space limitations.
I should add that they behaved similarly to what I described with
jobber drills.

Still, all of this is a good excuse to go through the tramming,
run-out-etc. tests again.

However, I have some broken 1/4" drills lying about so I shall have a
go at converting them into spotting drills.

Michael Koblic,
Campbell River, BC

On Wed, 10 Nov 2010 04:16:40 -0800 (PST), Jim Wilkins
wrote:

[...]

I've seen those problems and think I've traced them to wear and play
in the quill and dirt or an accumulation of tolerances in the chuck
tapers and jaws. My cheap drill press shifts visibly when I pull on
the handle enough to make a drill bite into steel, and the loading on
the quill rack changes from supporting it to forcing it down.

I've see a center drill make the mill head vibrate, don't remember
which chuck but the fix was clamping the drill in a collet. Possibly
there was a chip in the taper?

You can check runout and shift under load by indicating a chucked rod,
and quill perpendicularity by chucking the indicator and running it
down an angle plate. This isn't the same as tramming it since the
spindle axis may not be parallel to the quill.


I started to repeat the tests on my drill press to see if it behaves
differently from the mill. I did not do enough to come to any
conclusions. I have to check if my drill spindle is MT3 also which
would make it simple to exchange the chucks.

Michael Koblic,
Campbell River, BC

wrote in message
...
On 10 Nov 2010 04:39:20 GMT, "DoN. Nichols"
wrote:

(snip)

Yes, but then you have to bring the point over the mark. I find that
challenging without the magnification. Even using the other center
finder (this one, so there is no confusion:
http://www.busybeetools.com/products...RE-FINDER.html )
the alignment of the two parts of the barrel are tricky and much
easier with a magnifying glass.


When I use the pointy end, I feel the joint with my finger nail. It is easy
to tell if it is overhanging or under-hanging a small fraction of .001"

On Wed, 10 Nov 2010 18:04:31 -0800, wrote:
snip
I was out of town today and took the opportunity to look for dowel
pins etc. No luck.
snip
see
drill blanks
http://www.use-enco.com/CGI/INPDFF?P...PARTPG=INLMK32
gage pins
http://www.meyergage.com/products/in...ass_z_pins.htm
http://www.deltronic.com/products/plug-gages.html
dowel pins
http://www.wttool.com/product-exec/p...Pins_Brighton_
http://www.wttool.com/category-exec/...849/page_num/8

Try your local Fastenall store. Only problem is they like
to sell boxes of 100.
http://www.fastenal.com/web/home.ex

-- Unka George (George McDuffee)
...............................
The past is a foreign country;
they do things differently there.
L. P. Hartley (1895-1972), British author.
The Go-Between, Prologue (1953).

"F. George McDuffee" wrote:

On Wed, 10 Nov 2010 18:04:31 -0800, wrote:
snip
I was out of town today and took the opportunity to look for dowel
pins etc. No luck.
snip
see
drill blanks
http://www.use-enco.com/CGI/INPDFF?P...PARTPG=INLMK32
gage pins
http://www.meyergage.com/products/in...ass_z_pins.htm
http://www.deltronic.com/products/plug-gages.html
dowel pins
http://www.wttool.com/product-exec/p...Pins_Brighton_
http://www.wttool.com/category-exec/...849/page_num/8

Try your local Fastenall store. Only problem is they like
to sell boxes of 100.
http://www.fastenal.com/web/home.ex


I have had no trouble buying single items from the local Fastenal
stores.


--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

On 2010-11-11, wrote:
On 10 Nov 2010 04:39:20 GMT, "DoN. Nichols"
wrote:

[...]

Windows Live Mail has done it again. Not only did it swallow my
original post but also your reply. Fortunately I now have two other
news readers.

Hmm ... not from Microsoft I hope? :-)

Hmm ... sounds like a tramming error -- the axis of the spindle
is not perpendicular to the bed. And likely the column axis as well.

[ ... ]

Get a machinist's square (a blade with a heavy right-angle
piece) and resting that on the bed, check for a slight angle between the

[ ... ]

Is yours one of those whose column has a pivot at the bottom, so
you can drill holes at an angle? If so, have you checked that the
column is truly vertical?

That's the one. Last time I did this it was within 0.001" from
end-to-end and front-to-back.

And with the head moved up and down?

I will do this again - but first have to
clear things off the table. Oh, joy! The opportunity to re-align the
vise. Again :-)

:-)

[...]

I tried a different No. 1, I tried both ends, same result. Looking at the
slowly rotating point with a magnifying glass it describes a small circle
which is not obvious when I bring it down on the metal.

That is either runout in the chuck, or a bent arbor for the
chuck. I forget -- does your machine use R8 collets? If so, how are
you holding your drill chuck? An R8 arbor, or a straight shank arbor
held in a collet? In either case, the arbor might be slightly bent.

Before I read your post I checked the run-out just under the chuck. No
dowel pins or drill blanks here so I used the drill shanks. I did two
just incase. Both (3/8" and 9/64") showed TIR 0.0005" about 3/8" under
the chuck.

Pretty close. What happens to the runout when you shift from
light to tight tightening of the chuck?

BTW Drill shanks are soft, and the chuck's jaws can bite into them
so they won't slip. End mill shanks are hardened and ground
smooth so they work well in collets or end mill holders, and are
*not* best used in a drill chuck. (The same applies to the
center drills, FWIW.)

The soft shanks on drill bits also means that it is possible for
the shank to bend, so the tip will describe a circle even if the chuck
is prefect.

And -- you are unlikely to find a long drill bit which has a
shank long enough to allow runout measurements. (Aircraft drills are
the exception -- but they may be too long for your machine.)

BTW my spindle is MT3. I have never had to take the chuck
off so I am not sure how it is attached at the other end. I just
change the whole thing for a collet chuck when I need to.

O.K. So R8 is not in the game. It is possible that the arbor
(MT-3 to whatever Jacobs taper the chuck uses) is bent -- but less
likely with that 0.0005" TIR. This then suggests that the jaws in the
chuck either have burrs in them, or there is wear in the body of the
chuck. Different brands of chucks have different quality levels. The
Albrecht keyless chucks are very accurate and can handle a long service
before they start showing problems. (But they are larger, so they leave
less space between the spindle and the table, so check for that too.)

What happens if you use collets for the center drill and the
plain drills? (Assuming that the plain drill is of a size which matches
a collet which you have.)

I was out of town today and took the opportunity to look for dowel
pins etc. No luck.

They are hardened and ground -- but fairly short usually. The
best thing is drill blanks, which are hardened and ground to precise
diameters -- but much longer. (And quite expensive, which is why I
don't have an index full of the standard sizes. :-) But that length
makes it easier to check for the drill chuck holding the drill at an
angle, thus causing the circle. Measure runout just below the chuck,
and close to the end (but before the diameter starts to fall).

[ ... ]

Did you try a runout indicator on the shank of the drill? How
about with a longer rod (best would be a drill blank -- or an unusually
long dowel pin, but you might get away with some drill rod if it has not
been bent.

I shall go through the drawers and see if I have any unusually long
drills or anything else which might do the job.

Aha! This is what I was answering somewhere above. You are
unlikely to find a drill whose smooth shank is long enough. Usually the
extra length is in the flutes.

[ ... ]

I presume that you started with the wiggler a bit off center,
and pressed a finger against the side until it stopped wiggling? *That*
is what sets it on center.

Yes, but then you have to bring the point over the mark. I find that
challenging without the magnification.

So -- use magnification -- and a small LED flashlight for
illumination.

Even using the other center
finder (this one, so there is no confusion:
http://www.busybeetools.com/products...RE-FINDER.html )
the alignment of the two parts of the barrel are tricky and much
easier with a magnifying glass.

And if the axis of the chuck is not parallel to that of the
spindle, you will still have the point wandering in a circle. One of
the reasons for the sliding offset is so you can push it while spinning
slowly until the point stops moving in a circle. That is the center of
the spindle axis -- but perhaps not the center of the chuck's own axis.

BTW I thought that the wiggler should be more accurate. However, it
was the other one that was consistently agreeing with the center drill
entry point.

But both of those are longer than the center drill, so you will
have had to move the head up to get them in the space. And, BTW, it is
possible that your column is truly vertical, but the head is slightly
off so its axis is at a tiny angle to the column. Another reason for
measuring with a machinist's square and a drill blank.

Yes -- as someone else suggested, hardened steel rods from dead
printers (or some older dead disk drives) can be used in place of the
drill blanks -- if not badly worn.

[...]

I was wondering about the way the drills are clamped in the chuck and I
tried different degrees of tightening.

The proper way is to tighten equally using all three holes, one
after the other.

I would go round al of them 2-3 times. With the No. 1 the feeling is
of never really tightening enough.

Give in the chuck somewhere -- a jaw with a chip under it, or
something similar. Try another chuck. Or check with collets.

With, say, 1/4" drill you go around
and you know when the thing is tight. There is a definite "stop". With
the No. 1 there is a sort of springy feeling even after you have been
around 3 times.

Your No. 1 is not fully deep in the chuck, so you are only
holding it with the tip of the jaws -- and they may be flexing in their
ways. Try another chuck. Yes, more money for a chuck *does* mean a
more accurate one.

That is what made me wonder about the possible
distortion caused by the chuck. I thought this was supported by the
fact (yet to be confirmed) that if I tightened only lightly the center
drill run straighter (see the last effort where the center finder,
center drill and the twist drill all managed to coincide).

Yes -- flex of the jaws in the body when you don't have a shank
contacting the jaws the full length into the chuck is a possibility.

Again -- try collets.

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Thu, 11 Nov 2010 00:01:45 -0500, "Michael A. Terrell"
wrote:

Try your local Fastenall store. Only problem is they like
to sell boxes of 100.
http://www.fastenal.com/web/home.ex


I have had no trouble buying single items from the local Fastenal
stores.
==========
Must just be my local Fastenall.

You can also use round tool steel blanks. These are ground
very accurately to consistant size.
see
http://www.wttool.com/category-exec/category_id/15887
http://www.wttool.com/category-exec/...887/page_num/2
http://www.wttool.com/product-exec/p...ound_Tool_Bits
http://www.wttool.com/product-exec/p...ound_Tool_Bits

Carbide also available but spendy.
http://www.wttool.com/category-exec/category_id/15850
-- Unka George (George McDuffee)
...............................
The past is a foreign country;
they do things differently there.
L. P. Hartley (1895-1972), British author.
The Go-Between, Prologue (1953).

"F. George McDuffee" wrote:

On Thu, 11 Nov 2010 00:01:45 -0500, "Michael A. Terrell"
wrote:

Try your local Fastenall store. Only problem is they like
to sell boxes of 100.
http://www.fastenal.com/web/home.ex

I have had no trouble buying single items from the local Fastenal
stores.
==========
Must just be my local Fastenall.


It could be. But then, I've only ought from them for a couple years
and some things might be by the pacakage only.


You can also use round tool steel blanks. These are ground
very accurately to consistant size.


That is a comon purchase for me at Fastenal.


see
http://www.wttool.com/category-exec/category_id/15887
http://www.wttool.com/category-exec/...887/page_num/2
http://www.wttool.com/product-exec/p...ound_Tool_Bits
http://www.wttool.com/product-exec/p...ound_Tool_Bits

Carbide also available but spendy.
http://www.wttool.com/category-exec/category_id/15850


--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

On Nov 11, 12:59*am, F. George McDuffee gmcduf...@mcduffee-
associates.us wrote:
...
You can also use round tool steel blanks. *These are ground
very accurately to consistant size. *
...

Two birds with one stone:
http://www.wttool.com/product-exec/p...ter_Drills_WT_

jsw

On Wed, 10 Nov 2010 23:59:36 -0600, F. George McDuffee
wrote:

You can also use round tool steel blanks. These are ground
very accurately to consistant size.
see
http://www.wttool.com/product-exec/p...ound_Tool_Bits

What's the percentage of fat in these, Unka?

--
Education is when you read the fine print.
Experience is what you get if you don't.
-- Pete Seeger

On 11/10/2010 10:36 PM, F. George McDuffee wrote:
On Wed, 10 Nov 2010 18:04:31 -0800, wrote:
snip
I was out of town today and took the opportunity to look for dowel
pins etc. No luck.
snip

Find a junk printer - dot matrix, laser, or inkjet.
They all have precision ground rods within.
That's what I use.

Also, for the best precision in drilling holes with my minimill, I use a
collet to hold the drill. The chuck that came with it isn't very good.

--
I can see 2012 from my front porch

"F. George McDuffee" wrote in message
...
On Wed, 10 Nov 2010 18:04:31 -0800, wrote:
snip
I was out of town today and took the opportunity to look for dowel
pins etc. No luck.
snip
see
drill blanks
http://www.use-enco.com/CGI/INPDFF?P...PARTPG=INLMK32
gage pins
http://www.meyergage.com/products/in...ass_z_pins.htm
http://www.deltronic.com/products/plug-gages.html
dowel pins
http://www.wttool.com/product-exec/p...Pins_Brighton_
http://www.wttool.com/category-exec/...849/page_num/8

Try your local Fastenall store. Only problem is they like
to sell boxes of 100.
http://www.fastenal.com/web/home.ex

Yeah! Even when they already have broken packages on the shelf.

On 11/11/2010 8:34 AM, RBnDFW wrote:
On 11/10/2010 10:36 PM, F. George McDuffee wrote:
On Wed, 10 Nov 2010 18:04:31 -0800, wrote:
snip
I was out of town today and took the opportunity to look for dowel
pins etc. No luck.
snip

Find a junk printer - dot matrix, laser, or inkjet.
They all have precision ground rods within.
That's what I use.

Also remembered another good tool: Piston wristpins from large diesel
engines. I have 3 that are about 3" dia x 6" tall. They are accurately
ground and make great squares. You can set one on the table alongside
the spindle and look at the gap angle between the two.

Also, for the best precision in drilling holes with my minimill, I use a
collet to hold the drill. The chuck that came with it isn't very good.



--
I can see 2012 from my front porch

RBnDFW wrote:
On 11/10/2010 10:36 PM, F. George McDuffee wrote:
On Wed, 10 Nov 2010 18:04:31 -0800, wrote:
snip
I was out of town today and took the opportunity to look for dowel
pins etc. No luck.
snip

Find a junk printer - dot matrix, laser, or inkjet.
They all have precision ground rods within.
That's what I use.

Also, for the best precision in drilling holes with my minimill, I use
a collet to hold the drill. The chuck that came with it isn't very good.

Maybe a bit large for a mini mill but the rod used on car damper struts
could be of use and readily available. Last dampers that came out of my
VW I kept and were 22mm OD chromed ground bar and while I could see the
wear area by the finish the difference in size from the unworn sections
was almost indistinguishable with a 0.01mm graduated non digital
micrometer, maybe in the order of 0.001 mm to 0.002mm.

On Nov 11, 4:56*pm, David Billington
wrote:
...

Maybe a bit large for a mini mill but the rod used on car damper struts
could be of use and readily available. Last dampers that came out of my
VW I kept and were 22mm OD chromed ground bar and while I could see the
wear area by the finish the difference in size from the unworn sections
was almost indistinguishable with a 0.01mm graduated non digital
micrometer, maybe in the order of 0.001 mm to 0.002mm.

IIRC Rollie's Dad used a shock absorber rod.

jsw

John wrote in
rec.crafts.metalworking on Wed, 10 Nov 2010 21:25:39 -0500:

A 120 degree spotting drill makes it easy to calculate the spotting
drill depth if you want to pre chanfer the hole. The chamfer diameter
will be twice the drilling depth of the spotting drill. If you are
drilling and tapping a 5/16 rhreaded hole you would drill half the 5/16
depth plus the added depth for the chamfer.

John

Are you sure that's not 90 degree spotting drills that work that way?
--

Dan H.
northshore MA.

On 2010-11-11, Jim Wilkins wrote:
On Nov 11, 4:56*pm, David Billington
wrote:
...

Maybe a bit large for a mini mill but the rod used on car damper struts

[ ... ]

IIRC Rollie's Dad used a shock absorber rod.

Same thing -- different terminology.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 11 Nov 2010 05:50:14 GMT, "DoN. Nichols"
wrote:

BIG snip

So, here is the result of 3 hours' work:

1) I found a dowel pin. At least I am pretty sure it is a dowel pin.
It is pretty and shiny, 0.5" x 6", it has those black caps either end
and on it it says USA made, 1/2". I do not know how I got it.

2) In the chuck, using a different indicator from last time, the TIR
3/8" under the jaws, 2" and 4" respectively was 0.001", 0.003" and
0.006". Re-tightening made no difference.

3) In a collet the figures were 0.001", 0.0015" and 0.002"

4) Repeat test with the same 3/8" drill I used before the TIR under
jaws was 0.001"

5) I tried my 3/8" reamer. Under the jaws the TIR was the same but
2-1/4" down the shank 0.0115" !

6) The No. 3 center drill runs out at 0.008"

7) The No. 4 at 0.007"

8) I repeated the center finding tests. the two instruments varied
sometimes by as much as 0.02"

9) As the punch mark have definite dimensions I tried just locating
crossed lines. This is quite difficult: Just because you can see the
lines on the bench does not mean you will see them clearly under the
spindle, paint etc. notwithstanding. The results, confirmed with
center drilling , were considerably worse than center-finding a punch
mark, however small.

10) In view of the discussion spotting drills vs. center drills I
thought it made more sense to abandon using No.1 and No.2 and I used
No. 3 instead to make a small dimple with the pilot only. This should
approximate a starter hole produced by a spotting drill. This was a
definite improvement and the difference between the center drill hole
and subsequent 1/8" twist drill position was only 0.005" on the Y axis
only.

It should be noted that I used my machine screw length drills so the
actual distance from the chuck jaws to the point was pretty much the
same for both the center drill and the twist drill.

11) I cleared the table and returned to the dowel pin in the collet. I
used the machinist square and could not see any deviation at all. The
two squares I have pretty much agreed with each other. Note I did this
along the X axis with the spindle in 4 different positions. The table
is too small to do this effectively along the Y axis.

12) Tramming:

a) The machine was out of tram to the tune of 0.008" over the X axis.
This was quickly corrected to 0.0005" with the head low. With the
head high this increased to 0.0035".
b) Moving the table along the Y axis produced no significant change. I
interpret this as the table being flat.
c) A spindle sweep in an arc from back to front, however, showed a
change of 0.005" over the 2" available in the Y axis. I interpret this
as the axis of the spindle being off in the Y axis plane.

Conclusions:

1) Do not use digital indicators for this sort of work.
2) Change the center drilling procedure as outlined above.
3) Grind a spotting drill?
4) To locate cross lines on a work piece it seems preferable to use
optical punch first and then locate the center on the machine. This
probably makes center finder and spotting drill unnecessary and can be
done with a twist drill directly.
5) Consider acquiring better center drills.
6) Use collets whenever possible.
7) Ideally one should try to correct the spindle axis. From what I
read of others' experience this is very difficult with this machine.

It is what it is. Like they say on South Park "I have learned
something today". I should be able to minimize the errors by being
aware of the pitfalls.

Thanks again for the help.

Michael Koblic,
Campbell River, BC

On Thu, 11 Nov 2010 18:52:24 -0800, wrote:

As the punch mark have definite dimensions I tried just locating
crossed lines. This is quite difficult: Just because you can see the
lines on the bench does not mean you will see them clearly under the
spindle, paint etc. notwithstanding. The results, confirmed with
center drilling , were considerably worse than center-finding a punch
mark, however small.
==================
different problem -- from what you describe in the complete
post you are doing better than expected. For ultra precise
work you need to go to a jig borer or grinder $$$$$$$.
Google on SIP and Moore for examples
http://www.weldershop.info/205/moore-jig-borer/
for some discussion see
http://bbs.homeshopmachinist.net/showthread.php?t=1468


for one less expensive solution see
http://www.wttool.com/product-exec/p...m_source=froog

and the one I have and like
http://www.skidmoreengineering.com/i...s/Page1171.htm

Key is to use a very light hammer and just a tap to mark the
metal, and then enlarge with a more robust punch and hammer.
A mighty blast on the punch with the optical center finder
will destroy the tip.

For high precision layout invest in a surface plate, a right
angle plate, and a space block set and use this with a flat
scribe (make from HSS lathe tool)
for example
http://www.use-enco.com/CGI/INSRIT?P...&PARTPG=INLMK3
http://www.use-enco.com/CGI/INSRIT?P...&PMPXNO=950511
http://www.use-enco.com/CGI/INPDFF?PMPAGE=461&PMCTLG=00
http://www.use-enco.com/CGI/INSRIT?P...PMAKA=418-4525

Bright light at the machine tool will help.

Also consider
http://www.use-enco.com/CGI/INSRIT?P...MPXNO=25219105
after you are set up to do precision layout. Problem with
smaller machines is quill to table/workpiece distance.
cheaper
http://compare.ebay.com/like/3503879...=263602_304662
http://www.amazon.com/Made-852-6-ran.../dp/B0006J3E4Y


-- Unka George (George McDuffee)
...............................
The past is a foreign country;
they do things differently there.
L. P. Hartley (1895-1972), British author.
The Go-Between, Prologue (1953).

On Thu, 11 Nov 2010 01:16:42 -0500, "Michael A. Terrell"
wrote:


"F. George McDuffee" wrote:

On Thu, 11 Nov 2010 00:01:45 -0500, "Michael A. Terrell"
wrote:

Try your local Fastenall store. Only problem is they like
to sell boxes of 100.
http://www.fastenal.com/web/home.ex

I have had no trouble buying single items from the local Fastenal
stores.
==========
Must just be my local Fastenall.


It could be. But then, I've only ought from them for a couple years
and some things might be by the pacakage only.


[...]

I find Fastenal problematic at best.

There are two branches within reach of here. One I will not use at
all. The other is more helpful but it tends to be a continuing
struggle to get what one wants without having to have 100 units of
it.

Furthermore, what it shows in their on-line catalog bears no relation
to what is available from or through the local branches at least
quantity-wise.

Not so long ago one was able to walk into a branch and pick up common
stock like mild steel square rods of several dimensions etc. Now the
shelves stand empty, still labeled with the items they previously
contained. Yet the manager blames lack of stock on "shortage of
storage space". BTW this particular branch is housed in a space the
size of a small hangar with a few shelves huddled round the middle.
The rest is completely wasted.

Having said that, I had good luck there yesterday, they had all the
stuff I wanted including metric lock washers (at $3 I did not mind
getting a 100) and a retaining compound they told me last week they
would not have.

One has to count one's blessing when one finds them especially now
that McMaster-Carr will not ship to new customers in Canada.

Michael Koblic,
Campbell River, BC

wrote:

On Thu, 11 Nov 2010 01:16:42 -0500, "Michael A. Terrell"
wrote:


"F. George McDuffee" wrote:

On Thu, 11 Nov 2010 00:01:45 -0500, "Michael A. Terrell"
wrote:

Try your local Fastenall store. Only problem is they like
to sell boxes of 100.
http://www.fastenal.com/web/home.ex

I have had no trouble buying single items from the local Fastenal
stores.
==========
Must just be my local Fastenall.


It could be. But then, I've only ought from them for a couple years
and some things might be by the pacakage only.


[...]

I find Fastenal problematic at best.

There are two branches within reach of here. One I will not use at
all. The other is more helpful but it tends to be a continuing
struggle to get what one wants without having to have 100 units of
it.

Furthermore, what it shows in their on-line catalog bears no relation
to what is available from or through the local branches at least
quantity-wise.

Not so long ago one was able to walk into a branch and pick up common
stock like mild steel square rods of several dimensions etc. Now the
shelves stand empty, still labeled with the items they previously
contained. Yet the manager blames lack of stock on "shortage of
storage space". BTW this particular branch is housed in a space the
size of a small hangar with a few shelves huddled round the middle.
The rest is completely wasted.


That branch may have low sales, resulting in lower acceptable stock
levels. I have never found an empty slot for steel rod or angle at the
store I use.


Having said that, I had good luck there yesterday, they had all the
stuff I wanted including metric lock washers (at $3 I did not mind
getting a 100) and a retaining compound they told me last week they
would not have.


I buy most small hardware by the 100 package. Only oddball threads
or very rarely used sizes are bought in small quantities. It isn't
worth the trouble to pick up the exact quantity of something you need,
when you'll need more in a couple weeks.


One has to count one's blessing when one finds them especially now
that McMaster-Carr will not ship to new customers in Canada.


Canada! Well, what do you expect? Those polar bears never where
reliable at delivering packages, anyway. ;-)


--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

On 2010-11-12, wrote:
On 11 Nov 2010 05:50:14 GMT, "DoN. Nichols"
wrote:

BIG snip

So, here is the result of 3 hours' work:

1) I found a dowel pin. At least I am pretty sure it is a dowel pin.
It is pretty and shiny, 0.5" x 6", it has those black caps either end
and on it it says USA made, 1/2". I do not know how I got it.

2) In the chuck, using a different indicator from last time, the TIR
3/8" under the jaws, 2" and 4" respectively was 0.001", 0.003" and
0.006". Re-tightening made no difference.

O.K. The drill chuck, or its arbor is not true. Bent arbor, or
burred chuck jaw.

3) In a collet the figures were 0.001", 0.0015" and 0.002"

Better, but not perfect. How are your collets mounted? Since
you don't use R8, presumably you have a Morse taper shank socket and a
Morse taper holder for something like ER collets. (Or perhaps you are
using Morse taper collets?) I can't remember the details of your
machine at a distance like this. :-)

Anyway -- since there is runout with the collet, and still a
lack of parallelism to the spindle, check for burrs in the Morse taper
socket in the spindle. (Try spotting blue (Prussian blue) in a very
thin film on the Morse taper shank of the tool, then put it into the
socket lightly, twist a few degrees, and pull it back out. Check the
bluing for where it is rubbed off. If widely spread on one side, and in
a narrow location on the other side, then there is likely a burr in the
socket (which will need application of a Morse taper finishing reamer to
clean off). Or -- there *could* be a burr on the Morse taper arbor
instead -- patterns of blue built up around a clean spot could indicate
that, and require a little stoning to remove the burr. There could be
burrs on both the collet's arbor (assuming ER style collets) or the
individual collet (assuming a Morse taper collet).

4) Repeat test with the same 3/8" drill I used before the TIR under
jaws was 0.001"

5) I tried my 3/8" reamer. Under the jaws the TIR was the same but
2-1/4" down the shank 0.0115" !

Reamers (assuming a chucking reamer instead of one with a square
tap wrench drive on the end) have a soft shank which can bend, so you
can't trust that for indicating runout away from the chuck.

6) The No. 3 center drill runs out at 0.008"

Weird.

7) The No. 4 at 0.007"

Again weird. This is in the chuck, or in the collet?

8) I repeated the center finding tests. the two instruments varied
sometimes by as much as 0.02"

Still using the chuck -- or the collet?

9) As the punch mark have definite dimensions I tried just locating
crossed lines. This is quite difficult: Just because you can see the
lines on the bench does not mean you will see them clearly under the
spindle, paint etc. notwithstanding. The results, confirmed with
center drilling , were considerably worse than center-finding a punch
mark, however small.

One of the little pocket sized gooseneck LED illuminators is
nice for dealing with this. It has a magnetic base so you can stick it
nearby and bend the neck so it illuminates the cross scribe.

10) In view of the discussion spotting drills vs. center drills I
thought it made more sense to abandon using No.1 and No.2 and I used
No. 3 instead to make a small dimple with the pilot only. This should
approximate a starter hole produced by a spotting drill. This was a
definite improvement and the difference between the center drill hole
and subsequent 1/8" twist drill position was only 0.005" on the Y axis
only.

O.K. but note that you will have a chisel point on the tip of
the center drill (like on the normal jobber's length drill bits), while
the spotting drill comes to a sharp point.

It should be noted that I used my machine screw length drills so the
actual distance from the chuck jaws to the point was pretty much the
same for both the center drill and the twist drill.

O.K. The machine screw length drills may have split points, so
they can start more accurately even without a dimple or a spotting
drill.

11) I cleared the table and returned to the dowel pin in the collet. I
used the machinist square and could not see any deviation at all. The
two squares I have pretty much agreed with each other. Note I did this
along the X axis with the spindle in 4 different positions. The table
is too small to do this effectively along the Y axis.

O.K. The axis is pretty perpendicular to the table, then. Did
you have a light behind the square and pin?

12) Tramming:

a) The machine was out of tram to the tune of 0.008" over the X axis.
This was quickly corrected to 0.0005" with the head low. With the
head high this increased to 0.0035".
b) Moving the table along the Y axis produced no significant change. I
interpret this as the table being flat.
c) A spindle sweep in an arc from back to front, however, showed a
change of 0.005" over the 2" available in the Y axis. I interpret this
as the axis of the spindle being off in the Y axis plane.

Yes. And this can cause a drift in Y-axis position with
different length drills or mills.

Conclusions:

1) Do not use digital indicators for this sort of work.

You had been using a digital one? I don't remember you saying
this. *Some* digital ones are more accurate than some mechanical ones.
The Starrett "Last Word" mechanical if the bias spring is not applying
bias throughout the range. (A bump on the side of the point can cause
it to skip in the spiral, so there is a major deadband in the range.)

2) Change the center drilling procedure as outlined above.
3) Grind a spotting drill?

How about *buy* at least one, so you know what it needs to look
like? I recently got (from a sale flyer from MSC) a couple of 1/4" x 60
degree spotting/centering drills (MSC #FJ71332167). If the sale from
that flyer is over, the "FJ" won't do any good, and the price will be
back up to whatever it was.)

4) To locate cross lines on a work piece it seems preferable to use
optical punch first and then locate the center on the machine. This
probably makes center finder and spotting drill unnecessary and can be
done with a twist drill directly.

Probably -- especially with a drill with split points. For
larger standard bits, the chisel point may be wider than the dimple left
with the optical punch, in which case the drill is likely to walk away
from the punched center point.

5) Consider acquiring better center drills.

Consider acquiring at least one or two proper spotting drills,
so you can compare them with what else you have and what you make later.

6) Use collets whenever possible.

Yes!

7) Ideally one should try to correct the spindle axis. From what I
read of others' experience this is very difficult with this machine.

It is certainly a source of error.

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Thu, 11 Nov 2010 22:16:59 -0800, "Michael Koblic"
wrote:
snip
2) I have *two* bright lights at the machine but still could not see the
damn lines! I think the surface of the scrap piece of metal had something to
snip

Are you using layout dye [dykem]? This makes a big
difference when trying to see the fine layout lines. Also
for precision work you will need a smooth flat machined
surface.
for some examples see
http://www.use-enco.com/CGI/INSRIT?P...&PARTPG=INLMK3
http://www.use-enco.com/CGI/INSRIT?P...&PARTPG=INLMK3
http://www.use-enco.com/CGI/INSRIT?P...&PARTPG=INLMK3
http://www.use-enco.com/CGI/INPDFF?P...&PARTPG=INSRIT


Most shops use blue but red traditionally was supposed to
work better on brass. I have used red and blue on aluminum,
brass and steel and can't see any difference.

Most any mill supply should stock. The thinner the coat of
layout dye and the thinner the layout lines [i.e. the
sharper the scriber] the better.


-- Unka George (George McDuffee)
...............................
The past is a foreign country;
they do things differently there.
L. P. Hartley (1895-1972), British author.
The Go-Between, Prologue (1953).

On Nov 12, 1:16*am, "Michael Koblic" wrote:
....
1) I have the optical punch. I think I mentioned it passing in my
conclusion. I certainly prefer it, more so now after I
tried the hard way :-)
....
Michael Koblic,
Campbell River, BC

I use a fine-tipped prick punch (home-made from a broken tap) to make
a very small dimple at the line crossing, followed by a center punch
ground somewhat sharper than the angle of a drill bit. Usually the
drilled hole position is within 0.005".

jsw

By taking the MT arbor out of the spindle and rotating it 180 degrees
(required for arbors with tangs, obviously), one could take comparison
measurements. Differences may reveal where the inaccuracies are.

I would be switching arbors and substituting a different chuck, too. After
switching tooling, and another set of measurements, it should become clear
where all of the runout is coming from.

One of those MT arbor blanks with just a 1" (or other size) head/stub on
them, could be very helpful in checking out the MT socket relative to the
spindle's center axis.
I'd make a durable mark on the spindle and start checking runout on the
stub, which would be located cloe to the end of the spindle at this time.
The arbor stub OD might not be perfectly concentric with the centerline of
the MT taper, but it should be very close if the arbor was finish ground
between centers.

If the stub doesn't have a center hole, then it probably wasn't finish
ground between centers, so a little touchup may be required. I'd then make a
durable mark on the arbor in line with the previous mark on the spindle, and
touch the stub with a die grinder stone (held by a rigid fixture mounted to
the machine table) to make a small zone/pathway that's concentric to the
spindle's centerline.

Measurment of the newly ground path should show nearly perfect
concentricity.
If the error is excessive, I'd probably suspect a very poor grade of
bearings.

I suppose this procedure could also be used on a drill chuck arbor, since
the grinding zone only needs to be small, and could be outside of the taper
where the chuck body seats.

The previous steps would verify if the bore of the MT spindle socket is
good, but won't help with the head/spindle-to-base perpendicularity issue.

--
WB
..........


"DoN. Nichols" wrote in message
...

some random snippages

Better, but not perfect. How are your collets mounted? Since
you don't use R8, presumably you have a Morse taper shank socket and a
Morse taper holder for something like ER collets. (Or perhaps you are
using Morse taper collets?) I can't remember the details of your
machine at a distance like this. :-)

Anyway -- since there is runout with the collet, and still a
lack of parallelism to the spindle, check for burrs in the Morse taper
socket in the spindle. (Try spotting blue (Prussian blue) in a very
thin film on the Morse taper shank of the tool, then put it into the
socket lightly, twist a few degrees, and pull it back out. Check the
bluing for where it is rubbed off. If widely spread on one side, and in
a narrow location on the other side, then there is likely a burr in the
socket (which will need application of a Morse taper finishing reamer to
clean off). Or -- there *could* be a burr on the Morse taper arbor
instead -- patterns of blue built up around a clean spot could indicate
that, and require a little stoning to remove the burr. There could be
burrs on both the collet's arbor (assuming ER style collets) or the
individual collet (assuming a Morse taper collet).

Reamers (assuming a chucking reamer instead of one with a square
tap wrench drive on the end) have a soft shank which can bend, so you
can't trust that for indicating runout away from the chuck.

6) The No. 3 center drill runs out at 0.008"

Weird.

7) The No. 4 at 0.007"

Again weird. This is in the chuck, or in the collet?

8) I repeated the center finding tests. the two instruments varied
sometimes by as much as 0.02"

Still using the chuck -- or the collet?

One of the little pocket sized gooseneck LED illuminators is
nice for dealing with this. It has a magnetic base so you can stick it
nearby and bend the neck so it illuminates the cross scribe.

O.K. but note that you will have a chisel point on the tip of
the center drill (like on the normal jobber's length drill bits), while
the spotting drill comes to a sharp point.

It should be noted that I used my machine screw length drills so the
actual distance from the chuck jaws to the point was pretty much the
same for both the center drill and the twist drill.

O.K. The machine screw length drills may have split points, so
they can start more accurately even without a dimple or a spotting
drill.

11) I cleared the table and returned to the dowel pin in the collet. I
used the machinist square and could not see any deviation at all. The
two squares I have pretty much agreed with each other. Note I did this
along the X axis with the spindle in 4 different positions. The table
is too small to do this effectively along the Y axis.

O.K. The axis is pretty perpendicular to the table, then. Did
you have a light behind the square and pin?

12) Tramming:

a) The machine was out of tram to the tune of 0.008" over the X axis.
This was quickly corrected to 0.0005" with the head low. With the
head high this increased to 0.0035".
b) Moving the table along the Y axis produced no significant change. I
interpret this as the table being flat.
c) A spindle sweep in an arc from back to front, however, showed a
change of 0.005" over the 2" available in the Y axis. I interpret this
as the axis of the spindle being off in the Y axis plane.

Yes. And this can cause a drift in Y-axis position with
different length drills or mills.

Conclusions:

1) Do not use digital indicators for this sort of work.

You had been using a digital one? I don't remember you saying
this. *Some* digital ones are more accurate than some mechanical ones.
The Starrett "Last Word" mechanical if the bias spring is not applying
bias throughout the range. (A bump on the side of the point can cause
it to skip in the spiral, so there is a major deadband in the range.)

2) Change the center drilling procedure as outlined above.
3) Grind a spotting drill?

How about *buy* at least one, so you know what it needs to look
like? I recently got (from a sale flyer from MSC) a couple of 1/4" x 60
degree spotting/centering drills (MSC #FJ71332167). If the sale from
that flyer is over, the "FJ" won't do any good, and the price will be
back up to whatever it was.)

4) To locate cross lines on a work piece it seems preferable to use
optical punch first and then locate the center on the machine. This
probably makes center finder and spotting drill unnecessary and can be
done with a twist drill directly.

Probably -- especially with a drill with split points. For
larger standard bits, the chisel point may be wider than the dimple left
with the optical punch, in which case the drill is likely to walk away
from the punched center point.

5) Consider acquiring better center drills.

Consider acquiring at least one or two proper spotting drills,
so you can compare them with what else you have and what you make later.

6) Use collets whenever possible.

Yes!

7) Ideally one should try to correct the spindle axis. From what I
read of others' experience this is very difficult with this machine.

It is certainly a source of error.

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. |
http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Fri, 12 Nov 2010 02:35:37 -0600, F. George McDuffee
wrote:

On Thu, 11 Nov 2010 22:16:59 -0800, "Michael Koblic"
wrote:
snip
2) I have *two* bright lights at the machine but still could not see the
damn lines! I think the surface of the scrap piece of metal had something to
snip

Are you using layout dye [dykem]? This makes a big
difference when trying to see the fine layout lines. Also
for precision work you will need a smooth flat machined
surface.
[...]

Yes to the dye, no to the surface - it was awful.

[...]

Michael Koblic,
Campbell River, BC

On Fri, 12 Nov 2010 07:44:48 -0800 (PST), Jim Wilkins
wrote:

On Nov 12, 1:16*am, "Michael Koblic" wrote:
....
1) I have the optical punch. I think I mentioned it passing in my
conclusion. I certainly prefer it, more so now after I
tried the hard way :-)
...
Michael Koblic,
Campbell River, BC

I use a fine-tipped prick punch (home-made from a broken tap) to make
a very small dimple at the line crossing, followed by a center punch
ground somewhat sharper than the angle of a drill bit. Usually the
drilled hole position is within 0.005".

I have grown partial to an automatic punch if I can see the marks well
enough. That also needs a follow-up punch with something bigger. But
for the tricky bits I have found nothing that beats the optical punch.

The punches are a kind of side issue to the original problem, i.e..
the center drill not agreeing with the twist drill. The obvious
question was "which one hits the true center". That is when I
discovered that defining the true center is not as simple as I thought
it would be.

If I define the drilling point by edge-finding and measurement from
edges on the mill will the center drill hit that point accurately?
Will the twist drill? I know you cannot use the latter to start the
hole, but if the center drill is off, the twist drill will be off
also.

Michael Koblic,
Campbell River, BC

On Fri, 12 Nov 2010 18:39:13 -0500, Joseph Gwinn
wrote:

[...]

What I do is to use an optical centering scope that mounts in the 3-jaw
or collet chuck of the spindle, followed by a large spotting drill.

http://www.use-enco.com/CGI/INSRIT?PMAKA=240-0404

I have found that with this scope, it's more accurate to not
center-punch the workpiece. I just center on the scribed lines and use
the spotting drill to make the initial dimple. A center-punch dimple
tends to pull the spotting drill sideways, reducing accuracy.

The other thing the scope is good for is locating zero-reference
features on a workpiece, subsequently using the DRO to move to places
where holes are desired. This is fast and accurate. I often scribe all
the hole centers, to catch errors, but again I don't center punch the
hole locations.

The only problem with the scope is that it was a bit expensive.


You are not kidding about the price, but wow, what a cool toy! I can
see that it would solve all sorts of problems.

Then of course you are relying on the center drill being on the mark
which is something the OP questions :-)

Another tool that comes to mind and which nobody mentioned is this:
http://littlemachineshop.com/product...y=131031042 9

I have heard conflicting opinions on it.

Michael Koblic,
Campbell River, BC

On 12 Nov 2010 06:01:52 GMT, "DoN. Nichols"
wrote:

My WML hates you. It swallowed your post again. OTOH it is not
prejudiced, it swallowed my last reply, too.

[...]

2) In the chuck, using a different indicator from last time, the TIR
3/8" under the jaws, 2" and 4" respectively was 0.001", 0.003" and
0.006". Re-tightening made no difference.

O.K. The drill chuck, or its arbor is not true. Bent arbor, or
burred chuck jaw.

3) In a collet the figures were 0.001", 0.0015" and 0.002"

Better, but not perfect. How are your collets mounted? Since
you don't use R8, presumably you have a Morse taper shank socket and a
Morse taper holder for something like ER collets. (Or perhaps you are
using Morse taper collets?) I can't remember the details of your
machine at a distance like this. :-)

I did some repeats after the tramming today. The collets are Chinese
ER look-alikes on a MT3 shank.

Today the dowel pin run perfectly parallel at 0.0015" in a collet.

I put the No. 3 and 4 center drills in their respective collets and
they run at 0.001" both.

I put the chuck back in. The dowel pin run 0.002 at "zero" and 4"! But
then I repositioned it slightly and re tightened and the wobble
appeared - 0.004" at 4".

I tried the center drills: No.3 was better initially at 0.003", but re
tightening I could make it 0.005".

No. 4 was 0.007"

For the sake of comparison I put the dowel pin in my drill press:
0.0035" and 0.007" at "zero" and 4".


Anyway -- since there is runout with the collet, and still a
lack of parallelism to the spindle, check for burrs in the Morse taper
socket in the spindle. (Try spotting blue (Prussian blue) in a very
thin film on the Morse taper shank of the tool, then put it into the
socket lightly, twist a few degrees, and pull it back out. Check the
bluing for where it is rubbed off. If widely spread on one side, and in
a narrow location on the other side, then there is likely a burr in the
socket (which will need application of a Morse taper finishing reamer to
clean off). Or -- there *could* be a burr on the Morse taper arbor
instead -- patterns of blue built up around a clean spot could indicate
that, and require a little stoning to remove the burr. There could be
burrs on both the collet's arbor (assuming ER style collets) or the
individual collet (assuming a Morse taper collet).

I tried this with the chuck arbor MT3 taper. I got somewhat
inconsistent result but no large areas. Nothing I would want to attack
with abrasives remembering that I could screw things up rather than
help.

I thought it would be helpful to check the run-out of the JT33 arbor
and tried to remove the chuck. I made a wooden jig to support it but
it seems that the helpful Chinese glued the thing in so I desisted
before things got out of hand.

4) Repeat test with the same 3/8" drill I used before the TIR under
jaws was 0.001"

5) I tried my 3/8" reamer. Under the jaws the TIR was the same but
2-1/4" down the shank 0.0115" !

Reamers (assuming a chucking reamer instead of one with a square
tap wrench drive on the end) have a soft shank which can bend, so you
can't trust that for indicating runout away from the chuck.

A lesson learned...


6) The No. 3 center drill runs out at 0.008"

Weird.

7) The No. 4 at 0.007"

Again weird. This is in the chuck, or in the collet?

See above. I am beginning to think that the main problem is how this
chuck grips things in the jaws. I think it likes longer shanks. The
area between the flutes on the center drill is quite short. In a
collet it does not matter.

8) I repeated the center finding tests. the two instruments varied
sometimes by as much as 0.02"

Still using the chuck -- or the collet?

Chuck. I forgot to do the collet test today.

[...]

11) I cleared the table and returned to the dowel pin in the collet. I
used the machinist square and could not see any deviation at all. The
two squares I have pretty much agreed with each other. Note I did this
along the X axis with the spindle in 4 different positions. The table
is too small to do this effectively along the Y axis.

O.K. The axis is pretty perpendicular to the table, then. Did
you have a light behind the square and pin?

I put a piece of white paper behind.

[...]

1) Do not use digital indicators for this sort of work.

You had been using a digital one? I don't remember you saying
this. *Some* digital ones are more accurate than some mechanical ones.
The Starrett "Last Word" mechanical if the bias spring is not applying
bias throughout the range. (A bump on the side of the point can cause
it to skip in the spiral, so there is a major deadband in the range.)

I did the first time. It was a part of an existing set-up. They are
nice for some things, axis movement, measurements over 0.1", but for
this analog is better IMHO.

2) Change the center drilling procedure as outlined above.
3) Grind a spotting drill?

How about *buy* at least one, so you know what it needs to look
like? I recently got (from a sale flyer from MSC) a couple of 1/4" x 60
degree spotting/centering drills (MSC #FJ71332167). If the sale from
that flyer is over, the "FJ" won't do any good, and the price will be
back up to whatever it was.)

Probably right. Getting the point exactly co-axial is probably
something I could not do with a Dremel.

4) To locate cross lines on a work piece it seems preferable to use
optical punch first and then locate the center on the machine. This
probably makes center finder and spotting drill unnecessary and can be
done with a twist drill directly.

Probably -- especially with a drill with split points. For
larger standard bits, the chisel point may be wider than the dimple left
with the optical punch, in which case the drill is likely to walk away
from the punched center point.

In that case I would probably be drilling a smaller pilot hole anyway.

[...]

7) Ideally one should try to correct the spindle axis. From what I
read of others' experience this is very difficult with this machine.

It is certainly a source of error.

One has to consider at what point the error generated this way exceeds
that introduced by the operator.

Michael Koblic,
Campbell River, BC