I am slowly going through the milling machine. I have cleaned it, greased
it, trammed it all successfully. I have adjusted the gibs on all axes.There
is some backlash on the X and Y but nothing to worry too much about. The
run-out is 0.001" on the spindle and 0.002" on the chuck (but the rod I used
is of unknown concentricity so I am happy).

The one thing that drives me nuts is the Z-axis feed: For a start the
backlash is almost the whole revolution (.050" on a 0.060" wheel).
Furthermore, it is not very crisp or consistent (it is hard to tell when the
drive is actually engaged). I can see no way to improve on this and the
manuals are no help at all (the manual that came with the machine is brief
and Chinese - or might as well be!). I have downloaded two others related to
similar equipment including the notes from the Little Machine Shop (which is
the best) but none of them deal with this.

One of the jobs I do regularly is drilling and tapping shallow blind holes
in thin plates (5 mm or so). It is important to get the hole as deep as
possible to get at least 2 threads of 32 pitch without breaking through on
the other side. I had great hopes for the mill to improve my accuracy with
this. At this point the procedure is:
1) Get the drill bit touching the plate.
2) Back off two full turns on the Z
3) Move off the plate completely on X or Y or combination of both.
4) Reverse two full turns on Z
5) Add the calculated depth (usually plate thickness minus 0.025")
6) Fix the Z stop plate at this level (NB if you lock the spindle it changes
the Z-position by about 0.010-0.015"! They have a sort of back-stop bar
which I suspect is an afterthought - it is not mentioned in any of the
manuals)
7) Disengage the fine Zdrive. Lift spindle
8) Relocate the hole on X and Y
9) Drill
10) Repeat 1-9 with a cut-off drill bit of the same size (gives me better
depth at sides without the point going through - I reckon worth about half
to one thread)
11) Tap

I am not at all sure that this is the right procedure but cannot think of
any other on this machine. I do not seem to be getting consistent depths.

With the drill press and a credit card I can do this much more quickly and
dare say consistently.

Should there not be a better way to pre-set the depth/Z-distance travel
without going through this palaver? Is this amount of backlash on the Z-axis
reasonable? Can it be corrected?

Thanks,

--
Michael Koblic,
Campbell River, BC

On Thu, 13 Nov 2008 18:33:07 -0800, Michael Koblic wrote:
[...]
The one thing that drives me nuts is the Z-axis feed: For a start the
backlash is almost the whole revolution (.050" on a 0.060" wheel).
Furthermore, it is not very crisp or consistent (it is hard to tell when
the drive is actually engaged). I can see no way to improve on this and
the manuals are no help at all (the manual that came with the machine is
brief and Chinese - or might as well be!). I have downloaded two others
related to similar equipment including the notes from the Little Machine
Shop (which is the best) but none of them deal with this.

One of the jobs I do regularly is drilling and tapping shallow blind
holes in thin plates (5 mm or so). It is important to get the hole as
deep as possible to get at least 2 threads of 32 pitch without breaking
through on the other side. I had great hopes for the mill to improve my
accuracy with this. At this point the procedure is: 1) Get the drill bit
touching the plate. 2) Back off two full turns on the Z
3) Move off the plate completely on X or Y or combination of both. 4)
Reverse two full turns on Z
[snip other 7 steps]

With the drill press and a credit card I can do this much more quickly
and dare say consistently.

Should there not be a better way to pre-set the depth/Z-distance travel
without going through this palaver? Is this amount of backlash on the
Z-axis reasonable? Can it be corrected?
....

(IIRC, your machine is somewhat like:
http://www.harborfreight.com/cpi/cta...emnumber=44991
)

I don't know for certain what the proper approach is for the
problem you describe, but here are a few observations that might
help until someone gives definitive answers.

-- Backlash will be less of an issue if you consistently pull down or
push up on the spindle head when you are using the fine Z dial to
lower the head. Otherwise, the spring counterbalance system lets
the head move or stick unpredictably in a fairly wide range.

-- Consider using a center-cutting end-mill from the start, rather
than a regular drill followed by a square-cut drill.

-- Use a collet or (preferably) an end-mill holder to hold the
end-mill; don't try to hold an end-mill in the chuck.

-- Attach a DTI or a digital caliper to indicate depth. Say you
want a 4mm or .157" deep hole in 5mm or .197" material. If you
zero the indicator when the tool tip touches the work, or set it
to -.001" when it touches a cigarette paper on the work, then
you will be at desired depth of cut when the indicator reads .157".

-- Make a 4mm thick shim. When the tool tip touches the work, set
the limit block (the Z stop plate) by putting the shim between the
limit block and the head. I think this will cut out a few steps
of your procedure, and should let you mill the holes without
engaging the find Z feed.

--
jiw

Michael Koblic wrote:

I am slowly going through the milling machine. I have cleaned it, greased
it, trammed it all successfully. I have adjusted the gibs on all axes.There
is some backlash on the X and Y but nothing to worry too much about. The
run-out is 0.001" on the spindle and 0.002" on the chuck (but the rod I used
is of unknown concentricity so I am happy).

The one thing that drives me nuts is the Z-axis feed: For a start the
backlash is almost the whole revolution (.050" on a 0.060" wheel).
Furthermore, it is not very crisp or consistent (it is hard to tell when the
drive is actually engaged). I can see no way to improve on this and the
manuals are no help at all (the manual that came with the machine is brief
and Chinese - or might as well be!). I have downloaded two others related to
similar equipment including the notes from the Little Machine Shop (which is
the best) but none of them deal with this.

One of the jobs I do regularly is drilling and tapping shallow blind holes
in thin plates (5 mm or so). It is important to get the hole as deep as
possible to get at least 2 threads of 32 pitch without breaking through on
the other side. I had great hopes for the mill to improve my accuracy with
this. At this point the procedure is:
1) Get the drill bit touching the plate.
2) Back off two full turns on the Z
3) Move off the plate completely on X or Y or combination of both.
4) Reverse two full turns on Z
5) Add the calculated depth (usually plate thickness minus 0.025")
6) Fix the Z stop plate at this level (NB if you lock the spindle it changes
the Z-position by about 0.010-0.015"! They have a sort of back-stop bar
which I suspect is an afterthought - it is not mentioned in any of the
manuals)
7) Disengage the fine Zdrive. Lift spindle
8) Relocate the hole on X and Y
9) Drill
10) Repeat 1-9 with a cut-off drill bit of the same size (gives me better
depth at sides without the point going through - I reckon worth about half
to one thread)
11) Tap

I am not at all sure that this is the right procedure but cannot think of
any other on this machine. I do not seem to be getting consistent depths.

With the drill press and a credit card I can do this much more quickly and
dare say consistently.

Should there not be a better way to pre-set the depth/Z-distance travel
without going through this palaver? Is this amount of backlash on the Z-axis
reasonable? Can it be corrected?

Thanks,


I think you may be doomed to frustration with trying to rely on the Z
axis drive.

You may be able to improve things with a stripdown and some fettling,
but probably not. It's the price of small and cheap tools, esp. machine
tools.

Consider setting yourself up with a solid, clamp-on stop, that you can
use to set the depth that the drill can reach to, if there is not one
built in. Once the depth of cut is set by some trial and error, you can
then get on with cutting all the holes required. Or use a dial
indicator, or one of the cheap digital calipers, to build yourself a
crude "DRO" to use when moving the head up and down, and thus separate
the movement of the crank, from the movement of the head, if that makes
any sense.

Cheers
Trevor Jones

"James Waldby" wrote in message
. ..
(IIRC, your machine is somewhat like:
http://www.harborfreight.com/cpi/cta...emnumber=44991

Pretty much identical bar minor differences.
)

I don't know for certain what the proper approach is for the
problem you describe, but here are a few observations that might
help until someone gives definitive answers.

-- Backlash will be less of an issue if you consistently pull down or
push up on the spindle head when you are using the fine Z dial to
lower the head. Otherwise, the spring counterbalance system lets
the head move or stick unpredictably in a fairly wide range.

The procedure I outlined is supposed to allow for that. Yet the results are
poor.

-- Consider using a center-cutting end-mill from the start, rather
than a regular drill followed by a square-cut drill.

-- Use a collet or (preferably) an end-mill holder to hold the
end-mill; don't try to hold an end-mill in the chuck.

No mills in the house else i would have done. I use No. 22 drill bit but the
5/32 is as close as makes no difference. This is the procedure I followed
before i had the mill.

-- Attach a DTI or a digital caliper to indicate depth. Say you
want a 4mm or .157" deep hole in 5mm or .197" material. If you
zero the indicator when the tool tip touches the work, or set it
to -.001" when it touches a cigarette paper on the work, then
you will be at desired depth of cut when the indicator reads .157".

-- Make a 4mm thick shim. When the tool tip touches the work, set
the limit block (the Z stop plate) by putting the shim between the
limit block and the head. I think this will cut out a few steps
of your procedure, and should let you mill the holes without
engaging the find Z feed.

I like the shim idea. The problem is that these plates are of rather
inconsistent thickness and the depth of cut has to be adjusted individually.
I shall look at all these ideas tomorrow.
Thanks,

--
Michael Koblic,
Campbell River, BC

"Trevor Jones" wrote in message
newsr8Tk.571$o15.112@edtnps83...

I think you may be doomed to frustration with trying to rely on the Z
axis drive.

You may be able to improve things with a stripdown and some fettling, but
probably not. It's the price of small and cheap tools, esp. machine tools.

Consider setting yourself up with a solid, clamp-on stop, that you can
use to set the depth that the drill can reach to, if there is not one
built in. Once the depth of cut is set by some trial and error, you can
then get on with cutting all the holes required. Or use a dial indicator,
or one of the cheap digital calipers, to build yourself a crude "DRO" to
use when moving the head up and down, and thus separate the movement of
the crank, from the movement of the head, if that makes any sense.


Or just go back to doing it faster and better on a drill press :-)
1) Clamp the plate to a flat wooden board.
2) Put a thin (0.018") credit card next to the plate on the board.
3) Touch the credit card with the tip of the drill bit. Set the drill press
stop.
4) Line-up the punch mark and drill
5) Repeat with the cut off drill
6) Tap

I am concerned that if I cannot do this simple operation on the milling
machine what will happen when I have to face mill etc. to precise depths. I
suppose the whole dial indicator thing will come to play. That will mean
getting a better one as the one I bought from Samona is a bugger to use - I
went through a whole period this morning when I thought the mill was
misbehaving when all along it was my indicator.

I have no previous experience with milling machines. Your initial comment
suggests that a bigger better machine is less likely to suffer from these
issues. Is that correct? I am kind of disappointed as I have seen home-made
mills which had better organized Z-depth stop and adjustment than this.

I may have to rethink the whole issue and priorities.

Thanks,

--
Michael Koblic,
Campbell River, BC

Michael Koblic wrote:


I have no previous experience with milling machines. Your initial comment
suggests that a bigger better machine is less likely to suffer from these
issues. Is that correct? I am kind of disappointed as I have seen home-made
mills which had better organized Z-depth stop and adjustment than this.

I may have to rethink the whole issue and priorities.

Thanks,


It's simply that to build a milling machine, of any usefulness at all,
costs, and in order that the makers meet the price point determined by
the purchaser (the guy that ordered a sea can full) they make them to
meet that price.

Simply put, there have had to be compromises made, otherwise, we the
consumers of these goods, could not afford to enter the game.

Look at your mill as a pre-assembled kit of parts.

You may have to go in and redo some of the work that was not done to a
standard that you find acceptable. Such is the way of things.

You may find that you can smooth up the action of the Z axis enough to
suit your needs. Track down the play in the works, and see if you can
find out where it's moving. It may be something silly easy to fix, like
a part not tightened in it's place, or it may be something not so simple
to fix.
Did it come with a parts diagram? Look it over and see if there are
any obvious places that there could be that much play.

IIRC LittleMachineShop.com has some spares as well as some upgrade
stuff for these mills. Have you looked at that ? You may be able to pick
up some ideas there.

Cheers
Trevor Jones

"Michael Koblic" wrote in message
...
I like the shim idea. The problem is that these plates are of rather
inconsistent thickness and the depth of cut has to be adjusted
individually. I shall look at all these ideas tomorrow.
Thanks,

A further thought occurred to me: A pack of cards!
However, another issue: To mill properly, I have to lock the spindle, right?
I would have thought that the change in Z-depth by the simple act of locking
the spindle is quite undesirable, especially as it is unpredictable and of
the order of 0.010". Am I wrong?

"Trevor Jones" wrote in message
news:hMaTk.269$jr4.87@edtnps82...
It's simply that to build a milling machine, of any usefulness at all,
costs, and in order that the makers meet the price point determined by the
purchaser (the guy that ordered a sea can full) they make them to meet
that price.

Simply put, there have had to be compromises made, otherwise, we the
consumers of these goods, could not afford to enter the game.

Look at your mill as a pre-assembled kit of parts.

You may have to go in and redo some of the work that was not done to a
standard that you find acceptable. Such is the way of things.

You may find that you can smooth up the action of the Z axis enough to
suit your needs. Track down the play in the works, and see if you can find
out where it's moving. It may be something silly easy to fix, like a part
not tightened in it's place, or it may be something not so simple to fix.
Did it come with a parts diagram? Look it over and see if there are any
obvious places that there could be that much play.

IIRC LittleMachineShop.com has some spares as well as some upgrade stuff
for these mills. Have you looked at that ? You may be able to pick up some
ideas there.

Right. I did not know what to expect really, nor do I know what reasonable
expectations are, hence the whole thread. As I mentioned elsewhere, now I am
almost more concerned about the change in Z-dimension when I lock the
spindle. It is not an issue with drilling, obviously, but I suspect it will
be a big issue when milling.

"Michael Koblic" wrote in message
...
snip---

Lose the circular handle and use the lever handle, assuming you have one.
Set a permanent stop, so the spindle stops at the same place every time,
then use the knee to achieve the depth you desire. I'm assuming you have a
knee on the machine. If not, none of this is relevant.

If you have multiple holes to drill in the same piece, mark your dials and
do each operation to all of the holes in each piece before doing the next
operation. For example, center drill all locations, then drill all
locations, then tap them. If you learn to trust the dials and understand
how to mark them, keeping backlash in the proper direction at all times,
you can revisit hole locations within a thou with no trouble at all.

Do not use end mills as drills. That is **** poor advice. They, at best,
suck for drilling due to their geometry. They evacuate chips poorly, and
will cut drastically ovesized holes should one flute load. They are often
the cause of mis-located holes due to the end mill moving the table or
saddle about when that happens. It's easy enough to grind a flat bottomed
drill, which will remove the tapered portion of an existing hole without
issues, with no risk of oversizing.

None of this is rocket science, just procedures you'd use on a daily basis
if you were operating manual machines. I've done them since the late 50's.
No big deal.

Did I mention you should not use end mills to drill holes? :-)

Harold

On Fri, 14 Nov 2008 00:57:59 -0800, Michael Koblic wrote:
"Michael Koblic" mkoblic@... wrote ...
I like the shim idea. The problem is that these plates are of rather
inconsistent thickness and the depth of cut has to be adjusted
individually. I shall look at all these ideas tomorrow. Thanks,

A further thought occurred to me: A pack of cards! However, another
issue: To mill properly, I have to lock the spindle, right? I would have
thought that the change in Z-depth by the simple act of locking the
spindle is quite undesirable, especially as it is unpredictable and of
the order of 0.010". Am I wrong?

If you cut a groove or slot, or mill a horizontal surface,
then yes, the Z-axis should be locked -- ie, the fine-feed
meshed, the vertical gib tightened by handle on side of
head, and the limit block tight against the bottom of the
head. If you set the limit block first, that should keep
the depth from increasing beyond what you want.

In previous post, I wrote:

-- Attach a DTI or a digital caliper to indicate depth. Say you
want a 4mm or .157" deep hole in 5mm or .197" material. If you
zero the indicator when the tool tip touches the work, or set it
to -.001" when it touches a cigarette paper on the work, then
you will be at desired depth of cut when the indicator reads .157".

I forgot to mention the alternative of setting the zero so that
the indicator reads zero when you are at the desired depth. If
you do so, then varying thickness of metal you are drilling
into won't matter, as long as the surface not being drilled
through is clamped against the same reference surface each
time.

--
jiw

On Thu, 13 Nov 2008 18:33:07 -0800, Michael Koblic wrote:


I am not at all sure that this is the right procedure but cannot think of
any other on this machine. I do not seem to be getting consistent depths.

With the drill press and a credit card I can do this much more quickly and
dare say consistently.

Should there not be a better way to pre-set the depth/Z-distance travel
without going through this palaver? Is this amount of backlash on the Z-axis
reasonable? Can it be corrected?

Put a collar on the drill bit.

On Nov 13, 9:33*pm, "Michael Koblic" wrote:
...
(NB if you lock the spindle it changes
the Z-position by about 0.010-0.015"! They have a sort of back-stop bar
which I suspect is an afterthought - it is not mentioned in any of the
manuals)
....
Michael Koblic,
Campbell River, BC

The new RF-31 I bought for Unitrode shifted by up to 0.005" when
locked. I had to mill some shims to better than 0.001" and spent close
to an hour futzing with the damn mill without success, then took the
parts home and milled them on my Clausing.

The Clausing isn't always accurate in the Z direction either, probably
due to wear and the old Wilton vise. I have to tap the work down while
tightening the handle, then check the parallels under the work for
looseness.

You can change the height of work in your mill with two small
adjustable parallels. Set them to some even-numbered size, mill close
to finish dimension and measure, raise the parallels to take up the
difference. You will need a stop on the fixed jaw of the vise to
relocate the work after loosening the vise but that's a good thing to
have anyway. I tapped the cast iron on the left end of the fixed jaw
and screwed on a small plate that can be swung out of the way. I set
the dials to 0,0 with a 1-2-3 block pushed against this stop.

The less you spend on a machine, the more you have to understand and
cope with its problems. You learn what it can do easily, or with
difficulty, and design accordingly. On a mill-drill the axes may be
measurably out of square with each other.

Since the RF-31 wasn't mine I didn't disassemble it or add a Z
indicator but I've found poorly machined small parts on other import
machinery that were easily cleaned up or replaced. Especially on the
older ones it looked like the major parts were made fairly well but
the minor ones had been filed out in someone's kitchen. PBS once
filmed a family making Toyota taillight lenses at home, apparently a
common practice that substitutes for providing daycare.

Jim Wilkins

James Waldby wrote:

On Thu, 13 Nov 2008 18:33:07 -0800, Michael Koblic wrote:
[...]
The one thing that drives me nuts is the Z-axis feed: For a start the
backlash is almost the whole revolution (.050" on a 0.060" wheel).
Furthermore, it is not very crisp or consistent (it is hard to tell when
the drive is actually engaged). I can see no way to improve on this and
the manuals are no help at all (the manual that came with the machine is
brief and Chinese - or might as well be!). I have downloaded two others
related to similar equipment including the notes from the Little Machine
Shop (which is the best) but none of them deal with this.

One of the jobs I do regularly is drilling and tapping shallow blind
holes in thin plates (5 mm or so). It is important to get the hole as
deep as possible to get at least 2 threads of 32 pitch without breaking
through on the other side. I had great hopes for the mill to improve my
accuracy with this. At this point the procedure is: 1) Get the drill bit
touching the plate. 2) Back off two full turns on the Z
3) Move off the plate completely on X or Y or combination of both. 4)
Reverse two full turns on Z
[snip other 7 steps]

With the drill press and a credit card I can do this much more quickly
and dare say consistently.

Should there not be a better way to pre-set the depth/Z-distance travel
without going through this palaver? Is this amount of backlash on the
Z-axis reasonable? Can it be corrected?
...

(IIRC, your machine is somewhat like:
http://www.harborfreight.com/cpi/cta...emnumber=44991
)

I don't know for certain what the proper approach is for the
problem you describe, but here are a few observations that might
help until someone gives definitive answers.

-- Backlash will be less of an issue if you consistently pull down or
push up on the spindle head when you are using the fine Z dial to
lower the head. Otherwise, the spring counterbalance system lets
the head move or stick unpredictably in a fairly wide range.

-- Consider using a center-cutting end-mill from the start, rather
than a regular drill followed by a square-cut drill.

-- Use a collet or (preferably) an end-mill holder to hold the
end-mill; don't try to hold an end-mill in the chuck.

-- Attach a DTI or a digital caliper to indicate depth. Say you
want a 4mm or .157" deep hole in 5mm or .197" material. If you
zero the indicator when the tool tip touches the work, or set it
to -.001" when it touches a cigarette paper on the work, then
you will be at desired depth of cut when the indicator reads .157".

-- Make a 4mm thick shim. When the tool tip touches the work, set
the limit block (the Z stop plate) by putting the shim between the
limit block and the head. I think this will cut out a few steps
of your procedure, and should let you mill the holes without
engaging the find Z feed.

--
jiw

If you look on sites like CNC zone you will find quite a bit of tweaking
info. For CNC operation folks generally ditch the rack and pinion Z axis
setup for a leadscrew type drive, and the stock counterbalance is always
tossed in favor of something more consistent.

For counterbalance I used a couple gas springs mounted vertically inside
the column sticking out the top, with a cross bar and pulleys across the
top and 1/16" steel cables connecting to the column and the head. I
still have the stock Z setup at present since I was in a big hurry with
the project, but it's slated to be changed to a leadscrew eventually.

On Thu, 13 Nov 2008 23:18:38 -0800, "Michael Koblic"
wrote:



I have no previous experience with milling machines. Your initial comment
suggests that a bigger better machine is less likely to suffer from these
issues. Is that correct? I am kind of disappointed as I have seen home-made
mills which had better organized Z-depth stop and adjustment than this.

These pics may give you some ideas. I made this attachment for when I
want very fine control over Z depths and tweaks. It can be set up to
use the head, table, work or vise as a reference. On a knee mill it
allows one to make adjustments to both the quill and knee without
losing relative position.

A rod could replace the indicator if just a simple stop is needed. For
example, if you want to drill to a constant depth and the workpieces
vary in thickness, mount a rod parallel to your drill that bumps the
top of the work.
http://www.suscom-maine.net/~nsimmon...ndicator01.JPG
http://www.suscom-maine.net/~nsimmon...ndicator02.JPG

While I was looking for those photos I came across these that show a
magnetic mount I made that allows one to use any convenient rule (mm,
fractional, decimal inch) as a quill scale. The rule position can be
adjusted to move the zero point as desired.
http://www.suscom-maine.net/~nsimmon...lScale01sm.jpg
http://www.suscom-maine.net/~nsimmon...lScale02sm.jpg


--
Ned Simmons

This is the quill stop I made for the Clausing;
http://picasaweb.google.com/KB1DAL/Tools#
The usual round design won't work because the screw is half buried in
the head.

Michael Koblic wrote:
I am slowly going through the milling machine. I have cleaned it, greased
it, trammed it all successfully. I have adjusted the gibs on all axes.There
is some backlash on the X and Y but nothing to worry too much about. The
run-out is 0.001" on the spindle and 0.002" on the chuck (but the rod I used
is of unknown concentricity so I am happy).

The one thing that drives me nuts is the Z-axis feed: For a start the
backlash is almost the whole revolution (.050" on a 0.060" wheel).
Furthermore, it is not very crisp or consistent (it is hard to tell when the
drive is actually engaged). I can see no way to improve on this and the
manuals are no help at all (the manual that came with the machine is brief
and Chinese - or might as well be!). I have downloaded two others related to
similar equipment including the notes from the Little Machine Shop (which is
the best) but none of them deal with this.

No surprise, the rack and pinion drive has to have
a lot of backlash. If you want fine control, you
need a screw drive of some sort. The rack and
pinion is only good for a drill press. You might
be able to rig a caliper to the Z axis to measure
the position. That will make your positioning
much more controllable, as at least you can READ
the position.

Should there not be a better way to pre-set the depth/Z-distance travel
without going through this palaver? Is this amount of backlash on the Z-axis
reasonable? Can it be corrected?
Does the machine have a depth stop? Most have
some sort of clamp-type gadget that can be
attached to stop at some particular depth.

Jon

"Harold and Susan Vordos" wrote in message
. net...

"Michael Koblic" wrote in message
...
snip---

Lose the circular handle and use the lever handle, assuming you have one.
Set a permanent stop, so the spindle stops at the same place every time,
then use the knee to achieve the depth you desire. I'm assuming you have
a knee on the machine. If not, none of this is relevant.

I have worked that one out. The issue is the correect positioning of the
depth stop. The shim method which someone suggested seems the best with this
machine.

If you have multiple holes to drill in the same piece, mark your dials and
do each operation to all of the holes in each piece before doing the next
operation. For example, center drill all locations, then drill all
locations, then tap them. If you learn to trust the dials and
understand how to mark them, keeping backlash in the proper direction at
all times, you can revisit hole locations within a thou with no trouble at
all.

Do not use end mills as drills. That is **** poor advice. They, at best,
suck for drilling due to their geometry. They evacuate chips poorly, and
will cut drastically ovesized holes should one flute load. They are often
the cause of mis-located holes due to the end mill moving the table or
saddle about when that happens. It's easy enough to grind a flat bottomed
drill, which will remove the tapered portion of an existing hole without
issues, with no risk of oversizing.

Which is what I have been doing very succesfully on the drill press...

None of this is rocket science, just procedures you'd use on a daily basis
if you were operating manual machines. I've done them since the late
50's. No big deal.

Did I mention you should not use end mills to drill holes? :-)


OK, I won't. In any case, there was not a 5/32 mill in the whole of Campbell
River today, so I could not even try this heinous crime :-)
Thanks,

--
Michael Koblic,
Campbell River, BC

"Jim Wilkins" wrote in message
...
On Nov 13, 9:33 pm, "Michael Koblic" wrote:
...
(NB if you lock the spindle it changes
the Z-position by about 0.010-0.015"! They have a sort of back-stop bar
which I suspect is an afterthought - it is not mentioned in any of the
manuals)
....
Michael Koblic,
Campbell River, BC

The new RF-31 I bought for Unitrode shifted by up to 0.005" when
locked. I had to mill some shims to better than 0.001" and spent close
to an hour futzing with the damn mill without success, then took the
parts home and milled them on my Clausing.

The Clausing isn't always accurate in the Z direction either, probably
due to wear and the old Wilton vise. I have to tap the work down while
tightening the handle, then check the parallels under the work for
looseness.

***Actually, the flex is more like 3 or 4 thou now. My measuring technique
left something to be desired.

You can change the height of work in your mill with two small
adjustable parallels. Set them to some even-numbered size, mill close
to finish dimension and measure, raise the parallels to take up the
difference. You will need a stop on the fixed jaw of the vise to
relocate the work after loosening the vise but that's a good thing to
have anyway. I tapped the cast iron on the left end of the fixed jaw
and screwed on a small plate that can be swung out of the way. I set
the dials to 0,0 with a 1-2-3 block pushed against this stop.

The less you spend on a machine, the more you have to understand and
cope with its problems. You learn what it can do easily, or with
difficulty, and design accordingly. On a mill-drill the axes may be
measurably out of square with each other.

*** Like I said, I have no base-line to go on and all the comments here have
been immensely helpful. To complete your statement I would say also that the
cheaper the machine, the better the supporting and measuring tools should
be. My kids will be giving me a new indicator for Christmans!

Since the RF-31 wasn't mine I didn't disassemble it or add a Z
indicator but I've found poorly machined small parts on other import
machinery that were easily cleaned up or replaced. Especially on the
older ones it looked like the major parts were made fairly well but
the minor ones had been filed out in someone's kitchen. PBS once
filmed a family making Toyota taillight lenses at home, apparently a
common practice that substitutes for providing daycare.

*** I think the first decision that had to be made was to keep or not to
keep. Once the decision to keep has been made, all sorts of follow-up
actions are possible.

"James Waldby" wrote in message
news

If you cut a groove or slot, or mill a horizontal surface,
then yes, the Z-axis should be locked -- ie, the fine-feed
meshed, the vertical gib tightened by handle on side of
head, and the limit block tight against the bottom of the
head. If you set the limit block first, that should keep
the depth from increasing beyond what you want.

I repeated the measurements and the change is more like 3-4 thou. Between
myself and the sucky caliper I got it wrong first time.

In previous post, I wrote:

-- Attach a DTI or a digital caliper to indicate depth. Say you
want a 4mm or .157" deep hole in 5mm or .197" material. If you
zero the indicator when the tool tip touches the work, or set it
to -.001" when it touches a cigarette paper on the work, then
you will be at desired depth of cut when the indicator reads .157".

I forgot to mention the alternative of setting the zero so that
the indicator reads zero when you are at the desired depth. If
you do so, then varying thickness of metal you are drilling
into won't matter, as long as the surface not being drilled
through is clamped against the same reference surface each
time.

I should look at that. However, I tried the shimming and I suspect it is the
way to go. I just used an improvised 0.13" shim which gave me one and a half
turns of the screw. I can make something up to be 0.145" thick and use it
every time. It will give me 2 turns of the screw and for the application it
does not need any more. Then the thickness of the plate will not matter: If
it too thin for the drill to go through with this shim it would be too thin
to use anyway.

--
Michael Koblic,
Campbell River, BC

"Ned Simmons" wrote in message
...
On Thu, 13 Nov 2008 23:18:38 -0800, "Michael Koblic"
wrote:



I have no previous experience with milling machines. Your initial comment
suggests that a bigger better machine is less likely to suffer from these
issues. Is that correct? I am kind of disappointed as I have seen
home-made
mills which had better organized Z-depth stop and adjustment than this.

These pics may give you some ideas. I made this attachment for when I
want very fine control over Z depths and tweaks. It can be set up to
use the head, table, work or vise as a reference. On a knee mill it
allows one to make adjustments to both the quill and knee without
losing relative position.

A rod could replace the indicator if just a simple stop is needed. For
example, if you want to drill to a constant depth and the workpieces
vary in thickness, mount a rod parallel to your drill that bumps the
top of the work.
http://www.suscom-maine.net/~nsimmon...ndicator01.JPG
http://www.suscom-maine.net/~nsimmon...ndicator02.JPG

While I was looking for those photos I came across these that show a
magnetic mount I made that allows one to use any convenient rule (mm,
fractional, decimal inch) as a quill scale. The rule position can be
adjusted to move the zero point as desired.
http://www.suscom-maine.net/~nsimmon...lScale01sm.jpg
http://www.suscom-maine.net/~nsimmon...lScale02sm.jpg


That's great. I shall archive these for future reference. Thanks.

On Fri, 14 Nov 2008 17:54:00 -0800, "Michael Koblic"
wrote:


"Harold and Susan Vordos" wrote in message
.net...

Did I mention you should not use end mills to drill holes? :-)


OK, I won't. In any case, there was not a 5/32 mill in the whole of Campbell
River today, so I could not even try this heinous crime :-)
Thanks,
My first end mill was a highly modified, very short 3/8" drill bit
used in my unimat 3 milling setup to balance a die cast disk sander
disk.
Gerry :-)}
London, Canada

"Gerald Miller" wrote in message
...
My first end mill was a highly modified, very short 3/8" drill bit
used in my unimat 3 milling setup to balance a die cast disk sander
disk.

Mine was (today!) a stubby little 4-flute 1/4" I picked in the same auction
as all the other bits and pieces. One of the flutes is chipped at the tip so
forget face milling, but it worked a treat as a side mill - after I cut a
little slot which would normally take me 4 times as long to do otherwise and
looking at the quality of the finish I was sold...

I did learn more lessons though, such as that good clamping in a vise is
necessary - I was trying to side mill one of the faces of the piece (itself
tiny - 5/16" square and 1" long) and the mill just lifted the piece out of
the vise.

Also do not ignore your wife if she tells you that you are climb-milling
instead of conventional - she has been watching the same DVDs and paying
attention!

"Michael Koblic" wrote in message
...

"Gerald Miller" wrote in message
...
My first end mill was a highly modified, very short 3/8" drill bit
used in my unimat 3 milling setup to balance a die cast disk sander
disk.

Mine was (today!) a stubby little 4-flute 1/4" I picked in the same
auction as all the other bits and pieces. One of the flutes is chipped at
the tip so forget face milling, but it worked a treat as a side mill -
after I cut a little slot which would normally take me 4 times as long to
do otherwise and looking at the quality of the finish I was sold...

I did learn more lessons though, such as that good clamping in a vise is
necessary - I was trying to side mill one of the faces of the piece
(itself tiny - 5/16" square and 1" long) and the mill just lifted the
piece out of the vise.

When you're working on short pieces, having to machine an end, it's always a
good idea to have a second piece on the opposite end. If you're working off
parallels, the piece can even sit on the bottom of the vise, just as long as
it's there to absorb the clamping effort. That way the jaws will clamp
parallel and have much greater holding power. The pieces should be
identical in thickness , so the jaws old parallel. Keep them separated as
much as is possible for effective holding power. If you have them both on
the same side of center, it won't work worth a damn.


Also do not ignore your wife if she tells you that you are climb-milling
instead of conventional - she has been watching the same DVDs and paying
attention!

You have a keeper! Many women do not support their husbands in these
endeavors. Like you, I'm fortunate to have one that does.

Harold

"Gerald Miller" wrote in message
...
snip----

My first end mill was a highly modified, very short 3/8" drill bit

I trust part of the modification was to grind the perimeter of the drill?

Drills are circular ground, and not backed off, unlike an end mill. As close
as they get is to have the lands narrowed, to minimize contact with the
hole. While you can get them to cut, they do it with considerable protest.
You'd have less than acceptable results with tough materials.

Harold

On Nov 14, 9:00 pm, "Michael Koblic" wrote:
.....
*** I think the first decision that had to be made was to keep or not to
keep. Once the decision to keep has been made, all sorts of follow-up
actions are possible.

I suggest you keep it and learn its capabilities and limitations by
using it. If you eventually find that it's inadequate you will know
much more about what you really need, and what to look for.

Most of my commercial machine shop work has been for electronics and
optics, typically sheet metal or thin aluminum plates, rarely as much
as 2" high, and not usually requiring better than 0.005" accuracy. I
did some of it on a mill drill, some on my Clausing, some on a similar
Enco 100-5100 knee mill (http://grizzly.com/products/Vertical-Mill/
G3102), and some on a CNC Bridgeport. Generally if I set the head
height so a drill bit would almost reach the bed of the vise and used
end mill holders the mill drill would do fine, and I didn't need to
move the knee which would lose the Z axis zero on the EZ Trak CNC.

My home projects are more 3-dimensional and really need the extra
vertical travel of the knee. If I had the space I'd buy a Bridgeport.

Don't give up on the chipped end mill. It probably still works for
facing if you feed slower, since only one flute is cutting. The
chipped edge got shorter, not longer, and shouldn't scratch the work.
You can salvage a broken one by grinding the end flat, then copying
the 5 degree and 30 degree (roughly) angles of another end mill
freehand on a bench grinder or belt sander. The cutting edges should
slope slightly inwards towards the center so only the tips cut as you
feed sideways. One flute will of course be longer than the other and
do all the work at the bottom of the cut, so feed slowly.

If you need to mill a blind pocket with it, drill a starting hole
almost full depth and then run the end mill down it. You can deepen
the pocket slightly to reach finish depth by lowering the end mill
very slowly as you feed it sideways.

Once I have a replacement I use these degraded end mills for roughing
out deep slots and steps, and taking the first cut on mystery metal. I
can resharpen them correctly on my surface grinder and have been using
one pair of salvaged high-quality end mills for 15 years, saving the
new ones for finish cuts. I only hand-grind broken ones when it's a
rush job, someone broke the size I need, and a purchase order to
replace it takes 3 weeks. Small company shops can be even more
restricted than a home shop because both time and money are limited.

If you can't follow Harold's valuable advice on clamping, pad the
moving jaw with a piece of wood to spread the grip area and keep the
cuts light. I do the end facing first and use the cut-off remainder of
the stock to balance the vise.

Jim Wilkins

"Jim Wilkins" wrote in message
...
On Nov 14, 9:00 pm, "Michael Koblic" wrote:
.....
*** I think the first decision that had to be made was to keep or not to
keep. Once the decision to keep has been made, all sorts of follow-up
actions are possible.

I suggest you keep it and learn its capabilities and limitations by
using it. If you eventually find that it's inadequate you will know
much more about what you really need, and what to look for.

The important distinction to make is what is inadequate: the machine or the
operator :-)

Don't give up on the chipped end mill. It probably still works for
facing if you feed slower, since only one flute is cutting. The
chipped edge got shorter, not longer, and shouldn't scratch the work.
You can salvage a broken one by grinding the end flat, then copying
the 5 degree and 30 degree (roughly) angles of another end mill
freehand on a bench grinder or belt sander. The cutting edges should
slope slightly inwards towards the center so only the tips cut as you
feed sideways. One flute will of course be longer than the other and
do all the work at the bottom of the cut, so feed slowly.

In its current state even the chipped mill exceeds my abilities to do the
job otherwise. It is going to be heavily employed for finishing a few stands
for the dials until the new set arrives

I can resharpen them correctly on my surface grinder and have been using
one pair of salvaged high-quality end mills for 15 years, saving the
new ones for finish cuts. I only hand-grind broken ones when it's a
rush job, someone broke the size I need, and a purchase order to
replace it takes 3 weeks. Small company shops can be even more
restricted than a home shop because both time and money are limited.

This is something I shall have to consider learning. I have never needed to
sharpen drill bits as they are cheap and plentiful.

If you can't follow Harold's valuable advice on clamping, pad the
moving jaw with a piece of wood to spread the grip area and keep the
cuts light. I do the end facing first and use the cut-off remainder of
the stock to balance the vise.

The case in question was even worse than that. I am ashamed to admit that I
clamped the workpiece the way I would have done for drilling in the press -
in the top groove of the vise. Not surprisingly, the grip area was very
small. When I spotted the error I reclamped using some of the lathe tools as
parallels and managed OK. However, Harold's advice is indeed valuable and
will be followed in future.

--
Michael Koblic,
Campbell River, BC

On Nov 15, 6:11*pm, "Michael Koblic" wrote:
"Jim Wilkins" wrote in message
....
I suggest you keep it and learn its capabilities and limitations by
using it. If you eventually find that it's inadequate you will know
much more about what you really need, and what to look for.

The important distinction to make is what is inadequate: the machine or the
operator :-)
Michael Koblic,

I trashed the first end mill I used, then learned not to push them so
hard.

The operator seems very open to advice. I learned the essentials of
machining by working in factories and much more by taking night
classes at the Voc-Tech. The first shaft I needed to thread cost me
$40 in tuition to get time on a good lathe.

On Sat, 15 Nov 2008 08:56:10 GMT, "Harold and Susan Vordos"
wrote:


"Gerald Miller" wrote in message
.. .
snip----

My first end mill was a highly modified, very short 3/8" drill bit

I trust part of the modification was to grind the perimeter of the drill?

Drills are circular ground, and not backed off, unlike an end mill. As close
as they get is to have the lands narrowed, to minimize contact with the
hole. While you can get them to cut, they do it with considerable protest.
You'd have less than acceptable results with tough materials.

Harold

I was working with very little depth of cut so got away with it.
Gerry :-)}
London, Canada

"Jim Wilkins" wrote in message
...

I trashed the first end mill I used, then learned not to push them so
hard.

The operator seems very open to advice. I learned the essentials of
machining by working in factories and much more by taking night
classes at the Voc-Tech. The first shaft I needed to thread cost me
$40 in tuition to get time on a good lathe.

***I am on a waiting list of the local community college if, maybe,
sometimes, before I die, they decide to put on a machining course...

On 2008-11-15, Michael Koblic wrote:

"Jim Wilkins" wrote in message
...

[ ... ]

If you can't follow Harold's valuable advice on clamping, pad the
moving jaw with a piece of wood to spread the grip area and keep the
cuts light. I do the end facing first and use the cut-off remainder of
the stock to balance the vise.

The case in question was even worse than that. I am ashamed to admit that I
clamped the workpiece the way I would have done for drilling in the press -
in the top groove of the vise. Not surprisingly, the grip area was very
small. When I spotted the error I reclamped using some of the lathe tools as
parallels and managed OK. However, Harold's advice is indeed valuable and
will be followed in future.

Another trick for when you don't have another piece of the same
dimensions is to use an adjustable parallel set to the same size to
place in the other side of the vise. They are fairly expensive, though,
so be careful not to mill them while milling the workpiece. :-)

They can also be used to support one side of a workpiece which
has two different heights.

Enjoy,
DoN.

--
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 ---