Awl--

I'm sure I can "solve" this by being more vigilant, but that it happens at
all seems sort of strange.

Briefly, I'm drilling a 3/16 hole 3/4" deep in 1/4" round brass: face,
c-drill, then a 3/16 drill (tailstock/drill chuck, 5C collets).
Then, I'm turning down a piece of 1/4" round brass to 3/16" OD, for about a
3/8" insertion into the other piece w/ the 3/16 hole, for a "nice" fit.
Using a live center.
Have DRO, Aloris tooling, good for half a thou, I'm pretty sure--at least
the DRO says so!

Problem is, the 3/16 OD pc gets in only about half way before it hits some
kind of "step"!!!
To achieve the full 3/8" insertion, the fit winds up being far too sloppy!
Still works, but annoys the hell out of me.

Seems like a simple no-brainer, and I'm sure I could solve it w/ sequential
drill sizes, reaming, etc., but it doesn't seem to me like this should be
necessary, as there is nothing complicated or exotic here.

I would have anticipated any other type of problem--holes too big, holes too
small, ragged/jagged sides, holes off-center, etc.
But an invisible step??

Any idears?
Mebbe on my next have-at-it here, I'll test the female portion w/ a 3/16"
dowel, to at least try to identify the offending piece/operation.
It's pretty clear what the problem is (diameters!), but puzzling as to *why*
this problem is occuring.

TIA.
----------------------------
Mr. P.V.'d
formerly Droll Troll

Proctologically Violated©® wrote:

Awl--

I'm sure I can "solve" this by being more vigilant, but that it happens at
all seems sort of strange.

Briefly, I'm drilling a 3/16 hole 3/4" deep in 1/4" round brass: face,
c-drill, then a 3/16 drill (tailstock/drill chuck, 5C collets).
Then, I'm turning down a piece of 1/4" round brass to 3/16" OD, for about a
3/8" insertion into the other piece w/ the 3/16 hole, for a "nice" fit.
Using a live center.
Have DRO, Aloris tooling, good for half a thou, I'm pretty sure--at least
the DRO says so!

Problem is, the 3/16 OD pc gets in only about half way before it hits some
kind of "step"!!!
To achieve the full 3/8" insertion, the fit winds up being far too sloppy!
Still works, but annoys the hell out of me.

Seems like a simple no-brainer, and I'm sure I could solve it w/ sequential
drill sizes, reaming, etc., but it doesn't seem to me like this should be
necessary, as there is nothing complicated or exotic here.

I would have anticipated any other type of problem--holes too big, holes too
small, ragged/jagged sides, holes off-center, etc.
But an invisible step??

Any idears?
Mebbe on my next have-at-it here, I'll test the female portion w/ a 3/16"
dowel, to at least try to identify the offending piece/operation.
It's pretty clear what the problem is (diameters!), but puzzling as to *why*
this problem is occuring.

That's 4 diameters deep, quite a bit. Probably the chips are scoring up the ID
somewhat. Maybe you should take Harold's oft-offered suggestion and rough the
part out and don't try to do a finish bore 4 diameters deep in one push?

Also, another idea is maybe there's a spot on your tailstock ram which isn't as
tight as the rest, and maybe your drills are grabbing a little in brass, trying
to pull themselves in, like they do, and maybe when it gets to that spot on your
tailstock ram, it "jumps" a little so you have a little bulge.

I normally machine brass dry, so I agree it likely isn't a lubricant issue.

You can also try a brand new 3/16" drill bit and see if you still get the problem.

GWE

Proctologically Violated©® wrote:
Awl--

I'm sure I can "solve" this by being more vigilant, but that it happens at
all seems sort of strange.

Briefly, I'm drilling a 3/16 hole 3/4" deep in 1/4" round brass: face,
c-drill, then a 3/16 drill (tailstock/drill chuck, 5C collets).
Then, I'm turning down a piece of 1/4" round brass to 3/16" OD, for about a
3/8" insertion into the other piece w/ the 3/16 hole, for a "nice" fit.
Using a live center.
Have DRO, Aloris tooling, good for half a thou, I'm pretty sure--at least
the DRO says so!

Problem is, the 3/16 OD pc gets in only about half way before it hits some
kind of "step"!!!
To achieve the full 3/8" insertion, the fit winds up being far too sloppy!
Still works, but annoys the hell out of me.

Seems like a simple no-brainer, and I'm sure I could solve it w/ sequential
drill sizes, reaming, etc., but it doesn't seem to me like this should be
necessary, as there is nothing complicated or exotic here.

I would have anticipated any other type of problem--holes too big, holes too
small, ragged/jagged sides, holes off-center, etc.
But an invisible step??

Any idears?
Mebbe on my next have-at-it here, I'll test the female portion w/ a 3/16"
dowel, to at least try to identify the offending piece/operation.
It's pretty clear what the problem is (diameters!), but puzzling as to *why*
this problem is occuring.

I think I'd do a test with a different sized
drill and pin to try to isolate whether it's
the drill or the lathe.

I will be interested in what the senior wizards have to say about this
as I am experiencing the same problem. In my situation it appears as
if it's the hole and not the shaft since I can measure the shaft along
its length.

I get the feeling that the drill is having a little trouble early in
the hole and kind of wanders around making the early part of the hole
bigger than the later part -- where there the drill gets a little more
discipline from the sides of the hole. I suspect that drilling of
sequential pilot holes might help -- as would keeping drill length down
to a minimum. Or maybe it is a poorly sharpened drill since, in my
case, many of my drills are three generations old having belonged to my
grandfather.....

I recently retired from engineering with electrons, but took ME201
years ago in college and got a taste for making chips. So now I have a
little lathe and mill and have been reading this group (and the
archives) from start to finish. There is so much to be learned and so
many 'unusual characters'.

Thanks Guys

Rye

Proctologically Violated©® wrote:
Awl--

I'm sure I can "solve" this by being more vigilant, but that it happens at
all seems sort of strange.

Briefly, I'm drilling a 3/16 hole 3/4" deep in 1/4" round brass: face,
c-drill, then a 3/16 drill (tailstock/drill chuck, 5C collets).
Then, I'm turning down a piece of 1/4" round brass to 3/16" OD, for abouta
3/8" insertion into the other piece w/ the 3/16 hole, for a "nice" fit.
Using a live center.
Have DRO, Aloris tooling, good for half a thou, I'm pretty sure--at least
the DRO says so!

Problem is, the 3/16 OD pc gets in only about half way before it hits some
kind of "step"!!!
To achieve the full 3/8" insertion, the fit winds up being far too sloppy!
Still works, but annoys the hell out of me.

Seems like a simple no-brainer, and I'm sure I could solve it w/ sequential
drill sizes, reaming, etc., but it doesn't seem to me like this should be
necessary, as there is nothing complicated or exotic here.

I would have anticipated any other type of problem--holes too big, holes too
small, ragged/jagged sides, holes off-center, etc.
But an invisible step??

Any idears?
Mebbe on my next have-at-it here, I'll test the female portion w/ a 3/16"
dowel, to at least try to identify the offending piece/operation.
It's pretty clear what the problem is (diameters!), but puzzling as to *why*
this problem is occuring.

TIA.
----------------------------
Mr. P.V.'d
formerly Droll Troll

I will be interested in what the senior wizards have to say about this
as I am experiencing the same problem. In my situation it appears as
if it's the hole and not the shaft since I can measure the shaft along
its length.

I get the feeling that the drill is having a little trouble early in
the hole and kind of wanders around making the early part of the hole
bigger than the later part -- where there the drill gets a little more
discipline from the sides of the hole. I suspect that drilling of
sequential pilot holes might help -- as would keeping drill length down
to a minimum. Or maybe it is a poorly sharpened drill since, in my
case, many of my drills are three generations old having belonged to my
grandfather.....

I recently retired from engineering with electrons, but took ME201
years ago in college and got a taste for making chips. So now I have a
little lathe and mill and have been reading this group (and the
archives) from start to finish. There is so much to be learned and so
many 'unusual characters'.

Thanks Guys

Rye

Proctologically Violated©® wrote:
Awl--

I'm sure I can "solve" this by being more vigilant, but that it happens at
all seems sort of strange.

Briefly, I'm drilling a 3/16 hole 3/4" deep in 1/4" round brass: face,
c-drill, then a 3/16 drill (tailstock/drill chuck, 5C collets).
Then, I'm turning down a piece of 1/4" round brass to 3/16" OD, for abouta
3/8" insertion into the other piece w/ the 3/16 hole, for a "nice" fit.
Using a live center.
Have DRO, Aloris tooling, good for half a thou, I'm pretty sure--at least
the DRO says so!

Problem is, the 3/16 OD pc gets in only about half way before it hits some
kind of "step"!!!
To achieve the full 3/8" insertion, the fit winds up being far too sloppy!
Still works, but annoys the hell out of me.

Seems like a simple no-brainer, and I'm sure I could solve it w/ sequential
drill sizes, reaming, etc., but it doesn't seem to me like this should be
necessary, as there is nothing complicated or exotic here.

I would have anticipated any other type of problem--holes too big, holes too
small, ragged/jagged sides, holes off-center, etc.
But an invisible step??

Any idears?
Mebbe on my next have-at-it here, I'll test the female portion w/ a 3/16"
dowel, to at least try to identify the offending piece/operation.
It's pretty clear what the problem is (diameters!), but puzzling as to *why*
this problem is occuring.

TIA.
----------------------------
Mr. P.V.'d
formerly Droll Troll

I will be interested in what the senior wizards have to say about this
as I am experiencing the same problem. In my situation it appears as
if it's the hole and not the shaft since I can measure the shaft along
its length.

I get the feeling that the drill is having a little trouble early in
the hole and kind of wanders around making the early part of the hole
bigger than the later part -- where there the drill gets a little more
discipline from the sides of the hole. I suspect that drilling of
sequential pilot holes might help -- as would keeping drill length down
to a minimum. Or maybe it is a poorly sharpened drill since, in my
case, many of my drills are three generations old having belonged to my
grandfather.....

I recently retired from engineering with electrons, but took ME201
years ago in college and got a taste for making chips. So now I have a
little lathe and mill and have been reading this group (and the
archives) from start to finish. There is so much to be learned and so
many 'unusual characters'.

Thanks Guys

Rye

Proctologically Violated©® wrote:
Awl--

I'm sure I can "solve" this by being more vigilant, but that it happens at
all seems sort of strange.

Briefly, I'm drilling a 3/16 hole 3/4" deep in 1/4" round brass: face,
c-drill, then a 3/16 drill (tailstock/drill chuck, 5C collets).
Then, I'm turning down a piece of 1/4" round brass to 3/16" OD, for abouta
3/8" insertion into the other piece w/ the 3/16 hole, for a "nice" fit.
Using a live center.
Have DRO, Aloris tooling, good for half a thou, I'm pretty sure--at least
the DRO says so!

Problem is, the 3/16 OD pc gets in only about half way before it hits some
kind of "step"!!!
To achieve the full 3/8" insertion, the fit winds up being far too sloppy!
Still works, but annoys the hell out of me.

Seems like a simple no-brainer, and I'm sure I could solve it w/ sequential
drill sizes, reaming, etc., but it doesn't seem to me like this should be
necessary, as there is nothing complicated or exotic here.

I would have anticipated any other type of problem--holes too big, holes too
small, ragged/jagged sides, holes off-center, etc.
But an invisible step??

Any idears?
Mebbe on my next have-at-it here, I'll test the female portion w/ a 3/16"
dowel, to at least try to identify the offending piece/operation.
It's pretty clear what the problem is (diameters!), but puzzling as to *why*
this problem is occuring.

TIA.
----------------------------
Mr. P.V.'d
formerly Droll Troll

Proctologically Violated©® wrote:
Awl--

I'm sure I can "solve" this by being more vigilant, but that it happens at
all seems sort of strange.

Briefly, I'm drilling a 3/16 hole 3/4" deep in 1/4" round brass: face,
c-drill, then a 3/16 drill (tailstock/drill chuck, 5C collets).
If you want a round hole of constant diameter, you should bore it.
Twist drill bits are notorious for drilling oversize, not round holes
that wander through the workpiece. If you want a hole for a bolt to
pass through, they usually do OK. If you want a hinge-type fit, a
drill bit is really too imprecise. For just a few, use a boring
bar. An impromptu boring bar can be just an end mill of suitable
diameter, set so that one cutting edge is level and facing toward
the operator, with just a slight angle such that the side of the
cutter doesn't rub the side of the bore. Sometimes an end mill with
a broken flute can be used for this.

You will get a smooth hole that is quite round, concentric, straight
and of constant diameter if you bore it.
Any idears?
Mebbe on my next have-at-it here, I'll test the female portion w/ a 3/16"
dowel, to at least try to identify the offending piece/operation.
It's pretty clear what the problem is (diameters!), but puzzling as to *why*
this problem is occuring.
A dial caliper's inside points should be able to detect the changing
ID, if you are careful. As you say you are using a twist drill, I'd
think it is most likely that the ID is where the problem lies. You
can often SEE the 3- or 5- lobed pattern that develops as a twist drill
bores into a piece. As it gets deeper, the side of the drill supports
the shaft better, and it starts to drill straighter and with less
vibration. So, the first diameter's worth of hole is really out of
whack, and then it gets closer to the stated drill diameter. I think
a re-sharpened twist drill that has uneven grinding on the flutes
is more likely to cause this problem. And brass may be more prone
to develop these problems, as it has a "digging in" nature when
positive rake tools are used.

Jon

Briefly, I'm drilling a 3/16 hole 3/4" deep in 1/4" round brass: face,
c-drill, then a 3/16 drill (tailstock/drill chuck, 5C collets).


A drill bit will wonder and they don't always drill round holes
either. Try a reamer.

On Tue, 1 Nov 2005 12:38:26 -0500, "Proctologically Violated©®"
wrote:

Awl--

I'm sure I can "solve" this by being more vigilant, but that it happens at
all seems sort of strange.

Briefly, I'm drilling a 3/16 hole 3/4" deep in 1/4" round brass: face,
c-drill, then a 3/16 drill (tailstock/drill chuck, 5C collets).
Then, I'm turning down a piece of 1/4" round brass to 3/16" OD, for about a
3/8" insertion into the other piece w/ the 3/16 hole, for a "nice" fit.
Using a live center.
Have DRO, Aloris tooling, good for half a thou, I'm pretty sure--at least
the DRO says so!

Problem is, the 3/16 OD pc gets in only about half way before it hits some
kind of "step"!!!
To achieve the full 3/8" insertion, the fit winds up being far too sloppy!
Still works, but annoys the hell out of me.

Seems like a simple no-brainer, and I'm sure I could solve it w/ sequential
drill sizes, reaming, etc., but it doesn't seem to me like this should be
necessary, as there is nothing complicated or exotic here.

I would have anticipated any other type of problem--holes too big, holes too
small, ragged/jagged sides, holes off-center, etc.
But an invisible step??

Any idears?
Mebbe on my next have-at-it here, I'll test the female portion w/ a 3/16"
dowel, to at least try to identify the offending piece/operation.
It's pretty clear what the problem is (diameters!), but puzzling as to *why*
this problem is occuring.

TIA.
----------------------------
Mr. P.V.'d
formerly Droll Troll


Hey PV,

First, as to what it is, have a look at :

http://mathworld.wolfram.com/ReuleauxTriangle.html

then at :

http://www.integerspin.co.uk/polygon.htm

You can see why it occurs.

So, use the least chuck overhang you can, and if possible use steps of
drill lengths, as in center, spotting, screw machine, then jobbers,
taper, etc.,

One thing that will help with your particular problem is instead of
the general use drills for steels at 118 degrees, use drill bits
sharpened at 100 degrees with 12 degrees or less rake for use in
brass. And make the centre drilling step as deep as practical for
your purpose.

Take care.

Brian Lawson,
Bothwell, Ontario.
XXXXXXXXXXXXX

And here's one, right from the old horses mouth!! teenut said:


From: Robert Bastow
Newsgroups: rec.crafts.metalworking
Subject: Newbie: Drilling Brass/drill grind
Date: Tue, 14 Sep 1999 15:04:05 GMT

Hi George,

Unlike a lot of the problems/queries encountered on this NG yours is
simple
enough to explain and even simpler to rectify. 8^)

In days of yore, and even now if you care to track them down, there
were/are
available special STRAIGHT FLUTE BRASS DRILLS..No spiral therefore, no
positive
rake on the cutting edge of the drill lip.

It is this positive cutting rake that is causing your problems..Brass
being such
a (Relatively) easy and amenable material to machine, it always seems
in a hurry
to get it over with and tries to hurry things along by grabbing at,
and trying
to ride up that positive rake!!

The solution is simple..remove the temptation!! Take your drill to
the grinder,
align the axis parallel to the flat side of the wheel and gently
remove the
sharp positive rake edge of the drill lips, equally on both sides. For
your
3/4" drill, a flat, somewhat less than a 1/16th of an inch will be
perfect.

Voila! you now have a negative rake "Brass Drill"!

Now, you can go search out a special set of straight flut drills,
especially as
you do a lot of brass work. OR, do as I and alot of other machinists
do..Get a
new set of regular drills, modify the lot and keep them just for brass
and
bronze. In doing this, of course, as you get to the smaller sizes the
flat you
need gets smaller and smaller..to the pont that, under about 3/16"
diameter you
can achieve it with just a few wipes with a slip stone.

Quite frankly I recommend the latter course of action..If only because
it is
probably cheaper. But another good reason is because the remaining
spiral on
the drills does help clear chips out of the hole easier I think, than
a
straight flute drill.

Happy drilling

teenut

George Glines wrote:

I want to modify a new 3/4" MT2 (118 degrees) drill bit I have to drill 360
(free-machining) brass. The hole is 1 1/4 inches deep completely through
the material. I'm drilling a pilot hole but having some trouble with the
brass grabbing the drill bit.

My metalworking books, including Machinery's Handbook have been no help as
to the way to sharpen/grind the bit. I searched through DejaNews, and
posters mention either grinding a flat on the drill, or grinding a zero rake
on the helix???

Does this mean that I would hold the drill at a 90 degree angle to the
grinding wheel to remove all rake on the flutes? It appears that the drill
is grabbing on the flutes not on the point.

To make things more complicated, I've looked in all the big tool catalogs
for special purpose drills. Several show "fast-spiral" drills as good for
drilling deep holes in brass, then on the next page, recommend "slow-spiral"
as good for cutting brass. Since I work with brass quite a bit, I wouldn't
mind dedicating a group of drill bits just for that material, but since
these bits are all expensive, I don't want to buy the wrong ones.

Thanks,

George


Search for Google's copy of this article
--------------------------------------------------------------------------------

From: Robert Bastow
Newsgroups: rec.crafts.metalworking
Subject: Newbie: Drilling Brass/drill grind
Date: Tue, 14 Sep 1999 16:47:14 GMT

There is far more tendency to grab when opening up a hole in ANY
material..Brass
is no exception! The center of any drill..being a less than efficient
cutting
zone, helps hold the work down against the forces tending to make it
grab.

If you must use a regular drill and don't like the idea of zero rake
flats, then
just BLUNT THE POINT a bit, run slower than usual and feed steadily.

The blunt point, while not best practice, may at least reduce the
tendency to
grab. and save the job, your nerves..even your fingers!!

teenut

John Hofstad-Parkhill wrote:

What I have found is that the combination of a small pilot and a big drill
works very well.
If I need a 1/2" hole or larger, I'll spot, pilot with 1/8" then use the
1/2" jobber twist drill. My theory is that with more material to remove the
less tendancy to grab,


Search for Google's copy of this article
--------------------------------------------------------------------------------

From: Robert Bastow
Newsgroups: rec.crafts.metalworking
Subject: Newbie: Drilling Brass/drill grind
Date: Wed, 15 Sep 1999 03:34:51 GMT

Hmmm!! I KNEW you were going to ask that question...This is like
trying to
describe Gina Lollobrigida without using your hands!!

OK, you are familiar with a regular twist drill...Ok..It might help to
hold the
drill horizontally eyeball the cutting edge and imagine it is a
regular HSS
lathe tool. You can see that the cutting edge of the drill has a
distinct wedge
shape..just like your lathe tool

The angle of the "point" face is pretty well fixed..this is the
CLEARANCE
angle...It is like the FRONT FACE on a lathe tool!

However, the angle of the top face..the RAKE ANGLE..., is variable..It
is
determined by the HELIX if the drill...It corresponds to the top face
of a lathe
tool.

With a fast spiral drill, this angle is very acute, with a slow spiral
it is a
blunter wedge, and with a straight spiral it is at 90 deg to the drill
axis..In
other words George, you have a ZERO top cutting rake on your
wedge/cutting
edge...Just like a zero top rake on a lathe tool (Oft described as
NEGATIVE
rake..but it ain't really!!)

Now imagine what you would have to do to a positive top rake lathe
bit..to turn
it into a zero top rake bit? Grind a bit off the top! "Bust" that
sharp
angle... Blunt the wedge...Right!

This is what we want to duplicate! So what we do is "Blunt" the wedge
on a
regular drill by grinding or honing...INSIDE THE FLUTE and PARALLEL TO
THE
CUTTING EDGE. Just "busting" it enough to produce a visible flat on a
small
drill, is all that is necessary..so long as the flat is wider than the
depth of
the chip (depth of cut) then you are fooling that dumb 'ole brass into
thinking
it is being cut by a zero rake drill!!!

I hope to have my web page up soon so I will be able to post pictures
and
sketches to illustrate points..(no pun intended!!!)

That will save me a bunch of peck, peck, sh*t! peck, with my tired old
finger.

I hope this helps..please don't hesitate to ask again if all I have
done is
confuse you further!! It has been known to happen before!!

teenut

George Glines wrote:

Robert,

Many thanks!!!! I want to be sure I understand correctly. Am I grinding
the "side/flutes" of the drill or the "point/tip" of the drill? I'll
practice on some old bits first, but having a brass only set would be great.

Search for Google's copy of this article
--------------------------------------------------------------------------------
Index Home About

"Proctologically Violated©®" wrote in
:

Awl--

I'm sure I can "solve" this by being more vigilant, but that it
happens at all seems sort of strange.



Think "angularity".....

--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

On Tue, 1 Nov 2005 9:38:26 -0800, Proctologically Violated©® wrote
(in message ):

Awl--

Major snip

Have you tried leaving a "vent" for the air to escape through?

Roger in Vegas
Worlds Greatest Impulse Buyer

Proctologically Violated©® wrote:
Awl--

I'm sure I can "solve" this by being more vigilant, but that it happens at
all seems sort of strange.

Briefly, I'm drilling a 3/16 hole 3/4" deep in 1/4" round brass: face,
c-drill, then a 3/16 drill (tailstock/drill chuck, 5C collets).
Then, I'm turning down a piece of 1/4" round brass to 3/16" OD, for about a
3/8" insertion into the other piece w/ the 3/16 hole, for a "nice" fit.
Using a live center.
Have DRO, Aloris tooling, good for half a thou, I'm pretty sure--at least
the DRO says so!

Problem is, the 3/16 OD pc gets in only about half way before it hits some
kind of "step"!!!
To achieve the full 3/8" insertion, the fit winds up being far too sloppy!
Still works, but annoys the hell out of me.

Seems like a simple no-brainer, and I'm sure I could solve it w/ sequential
drill sizes, reaming, etc., but it doesn't seem to me like this should be
necessary, as there is nothing complicated or exotic here.

I would have anticipated any other type of problem--holes too big, holes too
small, ragged/jagged sides, holes off-center, etc.
But an invisible step??

Any idears?
Mebbe on my next have-at-it here, I'll test the female portion w/ a 3/16"
dowel, to at least try to identify the offending piece/operation.
It's pretty clear what the problem is (diameters!), but puzzling as to *why*
this problem is occuring.

TIA.
----------------------------
Mr. P.V.'d
formerly Droll Troll


Is the step at the same depth as the c'drill depth?

Taunt wrote:
Proctologically Violated©® wrote:
Awl--

I'm sure I can "solve" this by being more vigilant, but that it
happens at all seems sort of strange.

Briefly, I'm drilling a 3/16 hole 3/4" deep in 1/4" round brass:
face, c-drill, then a 3/16 drill (tailstock/drill chuck, 5C collets).
Then, I'm turning down a piece of 1/4" round brass to 3/16" OD, for
about a 3/8" insertion into the other piece w/ the 3/16 hole, for a
"nice" fit. Using a live center.
Have DRO, Aloris tooling, good for half a thou, I'm pretty sure--at
least the DRO says so!

Problem is, the 3/16 OD pc gets in only about half way before it
hits some kind of "step"!!!
To achieve the full 3/8" insertion, the fit winds up being far too
sloppy! Still works, but annoys the hell out of me.

Seems like a simple no-brainer, and I'm sure I could solve it w/
sequential drill sizes, reaming, etc., but it doesn't seem to me
like this should be necessary, as there is nothing complicated or
exotic here. I would have anticipated any other type of problem--holes
too big,
holes too small, ragged/jagged sides, holes off-center, etc.
But an invisible step??

Any idears?
Mebbe on my next have-at-it here, I'll test the female portion w/ a
3/16" dowel, to at least try to identify the offending
piece/operation. It's pretty clear what the problem is (diameters!), but
puzzling as
to *why* this problem is occuring.

TIA.
----------------------------
Others have mentioned using a reamer to achieve an accurate hole.
I would suggest a 'D' bit for final dimensioning. They are rather easy to
make and produce precision results.
Use a twist drill out to a few thou (or next drill under - it is not that
critical, specially in brass) under required size and finish with the D bit.
A really simple type of D bit is a piece of drill rod of the required size
with one end cut off at a 45 degree angle. File, grind and polish the angle
flat to the best finish you can achieve - then harden and temper.
That's it. No relief or other fancy stuff.
Try it and you will love it!

Regards.
Ken.

"Ken Davey" wrote in message
...

Others have mentioned using a reamer to achieve an accurate hole.
I would suggest a 'D' bit for final dimensioning. They are rather easy to
make and produce precision results.
Use a twist drill out to a few thou (or next drill under - it is not that
critical, specially in brass) under required size and finish with the D
bit.
A really simple type of D bit is a piece of drill rod of the required size
with one end cut off at a 45 degree angle. File, grind and polish the
angle flat to the best finish you can achieve - then harden and temper.
That's it. No relief or other fancy stuff.

I'm curious about the "harden & temper" part. First, what type of drill rod
steel do you recommend? Second, since this is to be a precision tool
(substitute for a reamer), then how do you harden without risk of
distortion? (Assuming that a heat treat furnace is not available.)

- Michael

On Tue, 01 Nov 2005 15:01:41 -0500, Brian Lawson
wrote:

Summary of Teenut's brass drilling posts.

Thanks for the repeat, I missed them as I was travelling east at
the time, now saved.
Alan
in beautiful Golden Bay, Western Oz, South 32.25.42, East 115.45.44 GMT+8
VK6 YAB ICQ 6581610 to reply, change oz to au in address

Is the step at the same depth as the c'drill depth?


That was my guess too.

DeepDiver wrote:
"Ken Davey" wrote in message
...

Others have mentioned using a reamer to achieve an accurate hole.
I would suggest a 'D' bit for final dimensioning. They are rather
easy to make and produce precision results.
Use a twist drill out to a few thou (or next drill under - it is not
that critical, specially in brass) under required size and finish
with the D bit.
A really simple type of D bit is a piece of drill rod of the
required size with one end cut off at a 45 degree angle. File, grind
and polish the angle flat to the best finish you can achieve - then
harden and temper. That's it. No relief or other fancy stuff.

I'm curious about the "harden & temper" part. First, what type of
drill rod steel do you recommend? Second, since this is to be a
precision tool (substitute for a reamer), then how do you harden
without risk of distortion? (Assuming that a heat treat furnace is
not available.)
- Michael

Firstly it probably isn't really necessary to harden if you are only
drilling a few pieces in brass.
If you are making a bazillion parts it would probably be better to purchase
a bit specifically for the purpose.
I have the impression that oil hrdening drill rod is less prone to warping.
I'm no expert on this so best ask around for better informed opinions.
Technique is important when hardening to avoid distortion.
Done correctly I would suggest you can keep the tolerance within a few
tenths.
Drawing the temper should pose no problems.
Instructions for doing all this are available in many places.

Regards.
Ken.