I needed to make a 0.75 inch diamter disk with two small holes in it
for 3-48 mounting screws.

I drilled the holes in the mill and then parted the disk off about
..070 thick on the lathe. The parting tool when quite a bit off
when it encounter the holes leaving the back of the disk very
irregular. I managed to grind the disk flat, but I want to learn
how to do this better next time. Obviously parting an irregular
cut is not desirable and I got away with it because the holes are
tiny. Bigger holes probably would have broken the parting tool.

If I use the banksaw to slice the disk off, I suspect it will be
just as irregular as using the parting tool.

If I part the disk off before drilling the holes, I think it would be
difficult to mount the disk and indicate it to accurately locate the
holes. The only idea I can come up with it to superglue it to an
aluminum stub shaft and drill.

Looking for good ideas for next time.

chuck

You don't say what size your lathe is.

It sounds like you have problems with the parting, or cutoff operation.
This is common to all small lathes. The best solution I've found so far
is to mount a toolpost on the rear of my cross-slide table and in that
rear-mounted toolpost, to mount a parting tool upside down. I used the
cross-slide table and rear toolpost kit from MLA.

To do this without any parting whatever:

1. turn the bar to 0.75" round, face smooth
2. cut off with hacksaw or bandsaw, leaving excess
3. mount disc faced side down in 5C step collet held in collet fixture
in milling vise
4. face off to thickness and mill holes as desired

Grant Erwin

Charles A. Sherwood wrote:

I needed to make a 0.75 inch diamter disk with two small holes in it
for 3-48 mounting screws.

I drilled the holes in the mill and then parted the disk off about
.070 thick on the lathe. The parting tool when quite a bit off
when it encounter the holes leaving the back of the disk very
irregular. I managed to grind the disk flat, but I want to learn
how to do this better next time. Obviously parting an irregular
cut is not desirable and I got away with it because the holes are
tiny. Bigger holes probably would have broken the parting tool.

If I use the banksaw to slice the disk off, I suspect it will be
just as irregular as using the parting tool.

If I part the disk off before drilling the holes, I think it would be
difficult to mount the disk and indicate it to accurately locate the
holes. The only idea I can come up with it to superglue it to an
aluminum stub shaft and drill.

Looking for good ideas for next time.

chuck

Charles A. Sherwood wrote:

I needed to make a 0.75 inch diamter disk with two small holes in it
for 3-48 mounting screws.

I drilled the holes in the mill and then parted the disk off about
.070 thick on the lathe. The parting tool when quite a bit off
when it encounter the holes leaving the back of the disk very
irregular. I managed to grind the disk flat, but I want to learn
how to do this better next time. Obviously parting an irregular
cut is not desirable and I got away with it because the holes are
tiny. Bigger holes probably would have broken the parting tool.

If I use the banksaw to slice the disk off, I suspect it will be
just as irregular as using the parting tool.

If I part the disk off before drilling the holes, I think it would be
difficult to mount the disk and indicate it to accurately locate the
holes. The only idea I can come up with it to superglue it to an
aluminum stub shaft and drill.

Looking for good ideas for next time.

chuck





If the disk you're making is .070" thick you could shallow drill or end
mill the holes so they stop just shy of the cutoff plane, then finish
drilling them after parting the piece off.

You should be able to figure out a way to hold the disk well enough to
let you hand position it and drill through the already located holes in
a drill press. You could use a shallow 3/4" diameter recess in a piece
of hardwood or aluminum with a little homemade hold down clamp if you
want to make sure the piece doesn't fly away.

HTH,

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"

On 6 Dec 2004 17:18:20 GMT, (Charles A.
Sherwood) wrote:

If I part the disk off before drilling the holes, I think it would be
difficult to mount the disk and indicate it to accurately locate the
holes. The only idea I can come up with it to superglue it to an
aluminum stub shaft and drill.

Looking for good ideas for next time.

Might be a good idea to look into the techniques used by the watch and
clockmaking crowd to work on thin, flat stock. I seem to remember
things like hardwood facings on lathe faceplates, and double-backed
tape.

"Charles A. Sherwood" wrote in message
...

I needed to make a 0.75 inch diamter disk with two small holes in it
for 3-48 mounting screws.

I drilled the holes in the mill and then parted the disk off about
.070 thick on the lathe. The parting tool when quite a bit off
when it encounter the holes leaving the back of the disk very
irregular. I managed to grind the disk flat, but I want to learn
how to do this better next time. Obviously parting an irregular
cut is not desirable and I got away with it because the holes are
tiny. Bigger holes probably would have broken the parting tool.

If I use the banksaw to slice the disk off, I suspect it will be
just as irregular as using the parting tool.

If I part the disk off before drilling the holes, I think it would be
difficult to mount the disk and indicate it to accurately locate the
holes. The only idea I can come up with it to superglue it to an
aluminum stub shaft and drill.

Looking for good ideas for next time.

chuck

Holes are best done last, regardless of the size of your machine.

Do you have soft jaw capabilities? That's the slickest way to do a thin
item. Once you've turned and cut off the piece, the bored soft jaws will
hold it dead perpendicular and concentric within a half thou easily. Face
to length, deburr, then drill your holes as required.

You can also turn it from sheet metal of the proper thickness after cutting
it out oversized, then pressing between a piece of stock held in a chuck and
a plug that is center drilled to accept a live center in the tailstock.
Light cuts are required, but it works fine. I use both methods, depending
on the job at hand.

Harold

On 6 Dec 2004 17:18:20 GMT, Charles A. Sherwood wrote:

I needed to make a 0.75 inch diamter disk with two small holes in it
for 3-48 mounting screws.

I drilled the holes in the mill and then parted the disk off about
.070 thick on the lathe. The parting tool when quite a bit off
when it encounter the holes leaving the back of the disk very
irregular. I managed to grind the disk flat, but I want to learn
how to do this better next time. Obviously parting an irregular
cut is not desirable and I got away with it because the holes are
tiny. Bigger holes probably would have broken the parting tool.


If I part the disk off before drilling the holes, I think it would be
difficult to mount the disk and indicate it to accurately locate the
holes. The only idea I can come up with it to superglue it to an
aluminum stub shaft and drill.

Looking for good ideas for next time.

chuck


Part off your discs.
Bore a shallow hole (.070" deep) in your mill vise soft jaws. You now know
the center of that hole and can easily locate the disc to drill the tap
drill in the proper location.
--
Skuke
Reverse the domain name to send email

If you can use copper, I have a large number of 3/4" by @0.050" copper disks
available for just $.05 ea. in packs of 50.


"Charles A. Sherwood" wrote in message
...

I needed to make a 0.75 inch diamter disk with two small holes in it
for 3-48 mounting screws.

I drilled the holes in the mill and then parted the disk off about
.070 thick on the lathe. The parting tool when quite a bit off
when it encounter the holes leaving the back of the disk very
irregular. I managed to grind the disk flat, but I want to learn
how to do this better next time. Obviously parting an irregular
cut is not desirable and I got away with it because the holes are
tiny. Bigger holes probably would have broken the parting tool.

If I use the banksaw to slice the disk off, I suspect it will be
just as irregular as using the parting tool.

If I part the disk off before drilling the holes, I think it would be
difficult to mount the disk and indicate it to accurately locate the
holes. The only idea I can come up with it to superglue it to an
aluminum stub shaft and drill.

Looking for good ideas for next time.

chuck

It sounds like you have problems with the parting, or cutoff operation.
This is common to all small lathes. The best solution I've found so far

The lathe is a fairly good sized Rockwell 11x24. I was using a 1/16
parting tool which was deflected by the holes. Maybe a 3/32 parting
tool would go straight.


3. mount disc faced side down in 5C step collet held in collet fixture
in milling vise

Will the collet hold a disk that is only 1/16 inch thick?
How do I find the center so I can located the mounting holes?

Do you have soft jaw capabilities? That's the slickest way to do a thin
item. Once you've turned and cut off the piece, the bored soft jaws will
hold it dead perpendicular and concentric within a half thou easily. Face
to length, deburr, then drill your holes as required.

NO, But I think it time. It sounds like you are suggesting boring some
soft jaws about 1/16 deep to hold the parted disk. I guess a 5C soft
collet would work too.



You can also turn it from sheet metal of the proper thickness after cutting
it out oversized, then pressing between a piece of stock held in a chuck and
a plug that is center drilled to accept a live center in the tailstock.
Light cuts are required, but it works fine. I use both methods, depending
on the job at hand.

I could also make a fixture to hold the sheet metal with pins that
would accurately center the blank. Nice idea.

Part off your discs.
Bore a shallow hole (.070" deep) in your mill vise soft jaws. You now know
the center of that hole and can easily locate the disc to drill the tap
drill in the proper location.

Another clever idea.
thanks
chuck

In article , Charles A. Sherwood says...


I needed to make a 0.75 inch diamter disk with two small holes in it
for 3-48 mounting screws.

Drill the holes after the disk has been parted off.

Use a pot chuck (collet, with a counterbored front that is
just about the depth of the disk thickness) to hold it.

That's the way you make those two-headed nickels and all.

Or parking lot tokens if you are so inclined.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

In article , Charles A. Sherwood says...

I guess a 5C soft
collet would work too.

Yep, a brass one works fine. You can also turn a hard one with
carbide boring bars if you have an old collet you don't care about.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

"Charles A. Sherwood" wrote in message
...
snip--

NO, But I think it time. It sounds like you are suggesting boring some
soft jaws about 1/16 deep to hold the parted disk. I guess a 5C soft
collet would work too.

The sole negative of soft collets or step chucks is their inability to hold
lengths reliably. Soft jaws are an absolute stop, whereas collets of any
style are subject to length variations due to variations in diameter and
tightening of the drawbar. It can be an issue when you're trying to hold
a length closely. Otherwise they work great. Holding thin items by either
of the methods is far superior to any other method. The support added by
backing the piece prevents it from moving about under cut. Soft jaws hold
parts without distorting or marking, due to the identical radius one
machines in the jaws. Same applies to machined collets.


You can also turn it from sheet metal of the proper thickness after
cutting
it out oversized, then pressing between a piece of stock held in a chuck
and
a plug that is center drilled to accept a live center in the tailstock.
Light cuts are required, but it works fine. I use both methods,
depending
on the job at hand.

I could also make a fixture to hold the sheet metal with pins that
would accurately center the blank. Nice idea.

It's far easier to machine blanks, then drill your holes. You can stack
multiple pieces, then turn them all at once. If you rely on pins to locate,
unless you use a diamond pin for one side, the holes must be perfectly
located. I guess it all depends on the job at hand, and circumstances
particular to the specific application, for both methods work.

Harold

The sole negative of soft collets or step chucks is their inability to hold
lengths reliably. Soft jaws are an absolute stop, whereas collets of any


Ok. I have a buck 6 jaw with 2 piece jaws. Seems like I can make some
aluminum blocks for the top jaws and bore them for the job at hand.
Buck soft jaws seem outragously expensive. Not sure how much soft or
brass 5C collets cost but it strikes me as wasteful to use one for a
a "one off" project.

chuck

Tom Gardner wrote:

If you can use copper, I have a large number of 3/4" by @0.050" copper disks
available for just $.05 ea. in packs of 50.

Y'sure they're all copper and some aren't copper clad zinc? G

You just jogged my memory...I still remember the time my chops were
saved right on a Philadelphia street when I discovered that a dime was
exactly the right diameter to replace the little dished plug which
somehow fell out of the back end of my '57 Chevy's 6 cylinder engine's
die cast choke vacuum pulloff cylinder. I pushed it in with ball point
pen and it jammed there well enough to let the engine run fine. Talk
about falling into ****e and coming out smelling like a rose. It was one
of those fortuitous events I'll never completely forget.

Thanks for the mammaries,

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"

On 6 Dec 2004 21:12:57 GMT, Charles A. Sherwood wrote:

The sole negative of soft collets or step chucks is their inability to hold
lengths reliably. Soft jaws are an absolute stop, whereas collets of any


Ok. I have a buck 6 jaw with 2 piece jaws. Seems like I can make some
aluminum blocks for the top jaws and bore them for the job at hand.
Buck soft jaws seem outragously expensive. Not sure how much soft or
brass 5C collets cost but it strikes me as wasteful to use one for a
a "one off" project.

chuck



Good suggestion all for using softjaws in a 3 jaw chuck or machinable
collets, but you'll still have the problem of too thin a parting tool and
deflection.

Also, you'll *still* need to drill on a mill unless you want both your 3-48
holes in the center :-) It's awkward at best to drill a non-centered hole
on a regular 'ol lathe.

--
Skuke
Reverse the domain name to send email

Good suggestion all for using softjaws in a 3 jaw chuck or machinable
collets, but you'll still have the problem of too thin a parting tool and
deflection.

Also, you'll *still* need to drill on a mill unless you want both your 3-48
holes in the center :-) It's awkward at best to drill a non-centered hole
on a regular 'ol lathe.

Good point. I figured the 5C collet could be used on the mill
(in a collet holder that you clamp in the vise) to hold the disk
for drilling. Positioning would have to be done with a longer rod though.

I guess that means soft jaws on the mill solve two problems.
First it hold the part secure enough to mill or flycut the top flat.
Second it positions the part so it can be drilled.

Maybe I'm overlooking the obvious. It might be adequate to use
layout lines to locate the screw holes and center punch them.
chuck

"Charles A. Sherwood" wrote in message
...

I needed to make a 0.75 inch diamter disk with two small holes in it
for 3-48 mounting screws.

You don't specify what kind of finish you want, or how dished the back
surface of your part can be (and don't say *perfect*).

While I appreciate others' suggestions on extra fixturing, this road will at
least double the length of your work (especially frivolous on a single
piece).

You should try a larger parting tool. I've had good success with a brazed
carbide parting tool at work. Just neutral rake with clearance on the sides
to prevent rubbing. I believe it was at least 1/8" wide. If you want to go
nuts, the indexable carbide parting/grooving tools are nice and you'll have
invested in a usefull tool.

I would try to drill the holes before parting as you tried originally. Being
so thin, you're asking for deformation due to clamping and drilling.

Just my $0.02 worth.

Regards,

Robin

In article ,
Charles A. Sherwood wrote:

I needed to make a 0.75 inch diamter disk with two small holes in it
for 3-48 mounting screws.

I drilled the holes in the mill and then parted the disk off about
.070 thick on the lathe. The parting tool when quite a bit off
when it encounter the holes leaving the back of the disk very
irregular. I managed to grind the disk flat, but I want to learn
how to do this better next time. Obviously parting an irregular
cut is not desirable and I got away with it because the holes are
tiny. Bigger holes probably would have broken the parting tool.

Probably not -- but interrupted cuts do spoil the finish. The
more rigid your lathe, the less it will impact the finish, but there
will always be *some* effect.

If I use the banksaw

Bandsaw, perhaps?

to slice the disk off, I suspect it will be
just as irregular as using the parting tool.

Maybe not as bad -- especially if you cut through both holes at
once. But you will probably want to turn or grind the side which has
been bandsawn anyway.

If I part the disk off before drilling the holes, I think it would be
difficult to mount the disk and indicate it to accurately locate the
holes. The only idea I can come up with it to superglue it to an
aluminum stub shaft and drill.

How about taking a 5C soft collet, and making a shallow bore in
it to receive the disk, then putting that collet in one of those square
or hex collet holders in the mill to allow you to hold the disc steady
and index it properly.

Out of curiosity -- what was the material being cut?

Looking for good ideas for next time.

Now to see what others have suggested.

Good Luck,
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 ---

On 6 Dec 2004 22:28:42 GMT, Charles A. Sherwood wrote:



Good point. I figured the 5C collet could be used on the mill
(in a collet holder that you clamp in the vise) to hold the disk
for drilling. Positioning would have to be done with a longer rod though.

You can locate the collet block with mill stops then sweep in the bore
before installing the 3/4 collet.

If you want to go this route, might I suggest that rather than buying and
machining a soft collet, do the following:

Buy a collet stop. Get the one that is made of steel and threads into the
back of a 5C collet (internal thread on collet). It has a 1/2 through hole
and two set screws into that hole. It comes with a variety of pre-made
stops and you can make many more.

Get a piece of Aluminum rod turned to .73-.745" for about 1 inch. It needs
to be long enough to reach the bottom of the collet to the stop you bought.
The stop end of the Aluminum has a 1/2-13 threaded hole about 1/2" deep or
so. Bottom a stud into the hole and locate into the 1/2 thru hole in the
stop. Tighten set screws. Your collet should now have a piece of AL barely
sticking out of the collet (or flush) and tightend into the stop. It should
be a reasonably rigid setup.

Now, install the 5C collet in your lathe. Face the piece of aluminum so
that it finishes about .070" below (into) the flush surface of the collet.
This is where your decision to turn the OD anywhere from .73-.745" may make
life more difficult or not. You should now have a positive stop .070" in
the collet that will hold a part flat. You will also be able to drill thru
your disc and into the Al stop.

As with the machinable collet, you can easily drill multiple parts that will
have holes perpendicular to the disc face. But this method is cheaper,
takes about the same amount of time to setup and you'll still have a stop at
the end of the day. With the machinable collet, you'll eventually "use up"
the collet.

I've done the above method and it works well for thin disc.



I guess that means soft jaws on the mill solve two problems.
First it hold the part secure enough to mill or flycut the top flat.
Second it positions the part so it can be drilled.

And, you'll have a pair of soft jaws for your mill vise!


Maybe I'm overlooking the obvious. It might be adequate to use
layout lines to locate the screw holes and center punch them.
chuck

Well, only you know your part tolerances and abilities so if you think
that'll work, then it certainly is quick and dirty.


--
Skuke
Reverse the domain name to send email

On 6 Dec 2004 22:28:42 GMT, Charles A. Sherwood wrote:



Good point. I figured the 5C collet could be used on the mill
(in a collet holder that you clamp in the vise) to hold the disk
for drilling. Positioning would have to be done with a longer rod though.

You can locate the collet block with mill stops then sweep in the bore
before installing the 3/4 collet.

If you want to go this route, might I suggest that rather than buying and
machining a soft collet, do the following:

Buy a collet stop. Get the one that is made of steel and threads into the
back of a 5C collet (internal thread on collet). It has a 1/2 through hole
and two set screws into that hole. It comes with a variety of pre-made
stops and you can make many more.

Get a piece of Aluminum rod turned to .73-.745" for about 1 inch. It needs
to be long enough to reach the bottom of the collet to the stop you bought.
The stop end of the Aluminum has a 1/2-13 threaded hole about 1/2" deep or
so. Bottom a stud into the hole and locate into the 1/2 thru hole in the
stop. Tighten set screws. Your collet should now have a piece of AL barely
sticking out of the collet (or flush) and tightend into the stop. It should
be a reasonably rigid setup.

Now, install the 5C collet in your lathe. Face the piece of aluminum so
that it finishes about .070" below (into) the flush surface of the collet.
This is where your decision to turn the OD anywhere from .73-.745" may make
life more difficult or not. You should now have a positive stop .070" in
the collet that will hold a part flat. You will also be able to drill thru
your disc and into the Al stop.

As with the machinable collet, you can easily drill multiple parts that will
have holes perpendicular to the disc face. But this method is cheaper,
takes about the same amount of time to setup and you'll still have a stop at
the end of the day. With the machinable collet, you'll eventually "use up"
the collet.

I've done the above method and it works well for thin disc.



I guess that means soft jaws on the mill solve two problems.
First it hold the part secure enough to mill or flycut the top flat.
Second it positions the part so it can be drilled.

And, you'll have a pair of soft jaws for your mill vise!


Maybe I'm overlooking the obvious. It might be adequate to use
layout lines to locate the screw holes and center punch them.
chuck

Well, only you know your part tolerances and abilities so if you think
that'll work, then it certainly is quick and dirty.


--
Skuke
Reverse the domain name to send email

"Robin S." wrote in message
. ..

snip---
I would try to drill the holes before parting as you tried originally.
Being
so thin, you're asking for deformation due to clamping and drilling.

Just my $0.02 worth.

Regards,

Robin


Chuckle! Having spent the vast majority of my years in the shop doing small
work, I would be at a loss to understand how it would get distorted. I
could clamp and drill a .010" thick dead soft copper disc without harming
it in the least. When you do small work, you work and think differently.

Harold

Out of curiosity -- what was the material being cut?

Steel; I used drill rod just just because I had it.
cs

You can locate the collet block with mill stops then sweep in the bore
before installing the 3/4 collet.

If you want to go this route, might I suggest that rather than buying and
machining a soft collet, do the following:

Thanks. I like this approach.
chuck

"Harold & Susan Vordos" wrote in message
...

Chuckle! Having spent the vast majority of my years in the shop doing
small
work, I would be at a loss to understand how it would get distorted. I
could clamp and drill a .010" thick dead soft copper disc without harming
it in the least. When you do small work, you work and think differently.

That's true. You'll have to forgive me. I work on dies that weigh 40 tons so
things are slightly different...

Regards,

Robin

"Robin S." wrote in message
. ..

"Harold & Susan Vordos" wrote in message
...

Chuckle! Having spent the vast majority of my years in the shop doing
small
work, I would be at a loss to understand how it would get distorted. I
could clamp and drill a .010" thick dead soft copper disc without
harming
it in the least. When you do small work, you work and think
differently.

That's true. You'll have to forgive me. I work on dies that weigh 40 tons
so
things are slightly different...

Regards,

Robin


Heh! To each, his own. I would be just as lost working on a 40 ton item,
in spite of being in the shop since 1957. Don't like large work. Never
have!

Harold

In article ,
Charles A. Sherwood wrote:

Out of curiosity -- what was the material being cut?

Steel; I used drill rod just just because I had it.

A bit tougher to machine cleanly than some others, I would
suggest getting some 12L14 -- probably the nicest machining steel around,
if you don't need it to be hardenable.

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 ---

On Tue, 7 Dec 2004 20:40:21 -0800, Harold & Susan Vordos wrote:


That's true. You'll have to forgive me. I work on dies that weigh 40 tons
so
things are slightly different...



Heh! To each, his own. I would be just as lost working on a 40 ton item,
in spite of being in the shop since 1957. Don't like large work. Never
have!



I agree! My basic rule is I don't like to work on it if I can't pick it up
by myself. ...controlling a crane by myself doesn't count either! :-)
--
Skuke
Reverse the domain name to send email