The AAMCO 7" shaper has a 'feature' I don't understand. Maybe one (or
more) of you guys has an answer.

All the machine tool feed collars I have used (not really all that
many) have been graduated in some even numbered manner. Fifty marks,
sixty marks, two hundred, etc.

The graduated collar on the tool slide of this unit is different.

There is the usual '0' then the fifth mark is '5', then '10', etc.
This goes to the '60' mark.
Then there is one tick mark (two spaces) and then the orig. '0'

This actually _does_ result in a measured 62thou. advance per rev.

Nothing major, but I sure do have to keep it in mind when feeding more
than one turn.

Anyone ever seen something like this elsewhere?

Any one have a reason as to why this feed and calibration?
rgentryatozdotnet

Bob Gentry wrote:
The AAMCO 7" shaper has a 'feature' I don't understand. Maybe one (or
more) of you guys has an answer.

All the machine tool feed collars I have used (not really all that
many) have been graduated in some even numbered manner. Fifty marks,
sixty marks, two hundred, etc.

The graduated collar on the tool slide of this unit is different.

There is the usual '0' then the fifth mark is '5', then '10', etc.
This goes to the '60' mark.
Then there is one tick mark (two spaces) and then the orig. '0'

This actually _does_ result in a measured 62thou. advance per rev.

Nothing major, but I sure do have to keep it in mind when feeding more
than one turn.

Anyone ever seen something like this elsewhere?

Any one have a reason as to why this feed and calibration?
rgentryatozdotnet

Sounds to me like the feed screw is 16 TPI . The X and Y axes on my RF45
clone are 8TPI , and advance .125/rev .

--
Snag

On Wed, 27 May 2015 18:11:05 -0500, "Terry Coombs"
wrote:

snip

Sounds to me like the feed screw is 16 TPI . The X and Y axes on my RF45
clone are 8TPI , and advance .125/rev .

Yes, I see how the pitch determines the the advance. Just don't see
_why_ 62. grin
Bob
rgentryatozdotnet

Bob Gentry wrote in news:88ocmap4pjc1sbp1g9h4l1kh8ea9cj0oqv@
4ax.com:

On Wed, 27 May 2015 18:11:05 -0500, "Terry Coombs"
wrote:

snip

Sounds to me like the feed screw is 16 TPI . The X and Y axes on my RF45
clone are 8TPI , and advance .125/rev .

Yes, I see how the pitch determines the the advance. Just don't see
_why_ 62. grin

It's a natural consequence of a 16TPI lead.
16 threads per inch = 1/16 inch per thread
1/16" = 0.0625" so my guess is that you actually have an advance of 62 and a half thou per
revolution instead of exactly 62.

"Bob Gentry" wrote in message
...
The AAMCO 7" shaper has a 'feature' I don't understand. Maybe one
(or
more) of you guys has an answer.

All the machine tool feed collars I have used (not really all that
many) have been graduated in some even numbered manner. Fifty
marks,
sixty marks, two hundred, etc.

The graduated collar on the tool slide of this unit is different.

There is the usual '0' then the fifth mark is '5', then '10', etc.
This goes to the '60' mark.
Then there is one tick mark (two spaces) and then the orig. '0'

This actually _does_ result in a measured 62thou. advance per rev.

Nothing major, but I sure do have to keep it in mind when feeding
more
than one turn.

Anyone ever seen something like this elsewhere?

Any one have a reason as to why this feed and calibration?
rgentryatozdotnet

I have an AA/Sears lathe with 5/16-24 TPI screws on the carriage,
0.041667" per turn.

-jsw

"Bob Gentry" wrote in message
...
On Wed, 27 May 2015 18:11:05 -0500, "Terry Coombs"

wrote:

snip

Sounds to me like the feed screw is 16 TPI . The X and Y axes on
my RF45
clone are 8TPI , and advance .125/rev .

Yes, I see how the pitch determines the the advance. Just don't see
_why_ 62. grin
Bob
rgentryatozdotnet

Is the feed screw Acme?

-jsw

On Wed, 27 May 2015 22:05:48 -0400, "Jim Wilkins"
wrote:

"Bob Gentry" wrote in message
.. .
On Wed, 27 May 2015 18:11:05 -0500, "Terry Coombs"

wrote:

snip

Sounds to me like the feed screw is 16 TPI . The X and Y axes on
my RF45
clone are 8TPI , and advance .125/rev .

Yes, I see how the pitch determines the the advance. Just don't see
_why_ 62. grin
Bob
rgentryatozdotnet

Is the feed screw Acme?

Does not appear to be. The thread _is_ 16TPI and fits a standard 'v'
gage nice and tight except for the points which seem to be just
slightly flatter than standard.

As a side note. . The threads appeared to be buttress style. . . .
untill I hit them with a toothbrush and cleaned off the oil. grin

Bob
rgentryatozdotnet

On Thu, 28 May 2015 00:33:25 +0000 (UTC), Doug Miller
wrote:

Bob Gentry wrote in news:88ocmap4pjc1sbp1g9h4l1kh8ea9cj0oqv@
4ax.com:

On Wed, 27 May 2015 18:11:05 -0500, "Terry Coombs"
wrote:

snip

Sounds to me like the feed screw is 16 TPI . The X and Y axes on my RF45
clone are 8TPI , and advance .125/rev .

Yes, I see how the pitch determines the the advance. Just don't see
_why_ 62. grin

It's a natural consequence of a 16TPI lead.
16 threads per inch = 1/16 inch per thread
1/16" = 0.0625" so my guess is that you actually have an advance of 62 and a half thou per
revolution instead of exactly 62.

You are correct. Put a 1" dial indicator on it and measured two turns
at just a wee bit under 125thou. Guessing on a gage that reads .001
about .1248.
Bob
rgentryatozdotnet

"Bob Gentry" wrote in message
...
On Wed, 27 May 2015 22:05:48 -0400, "Jim Wilkins"
wrote:

"Bob Gentry" wrote in message
. ..
On Wed, 27 May 2015 18:11:05 -0500, "Terry Coombs"

wrote:

snip

Sounds to me like the feed screw is 16 TPI . The X and Y axes on
my RF45
clone are 8TPI , and advance .125/rev .

Yes, I see how the pitch determines the the advance. Just don't
see
_why_ 62. grin
Bob
rgentryatozdotnet

Is the feed screw Acme?

Does not appear to be. The thread _is_ 16TPI and fits a standard
'v'
gage nice and tight except for the points which seem to be just
slightly flatter than standard.

As a side note. . The threads appeared to be buttress style. . . .
untill I hit them with a toothbrush and cleaned off the oil. grin

Bob
rgentryatozdotnet

Then the screw and dial may be a repair, used to avoid buying an Acme
tap. I did that on my worn surface grinder with 3/4-10 threaded rod.
It isn't difficult to engrave a custom dial with a rotary index, using
a spreadsheet to calculate the turns. Were the numbers hand-stamped?

-jsw

"Bob Gentry" wrote in message
...
The AAMCO 7" shaper has a 'feature' I don't understand. Maybe one (or
more) of you guys has an answer.

All the machine tool feed collars I have used (not really all that
many) have been graduated in some even numbered manner. Fifty marks,
sixty marks, two hundred, etc.

The graduated collar on the tool slide of this unit is different.

There is the usual '0' then the fifth mark is '5', then '10', etc.
This goes to the '60' mark.
Then there is one tick mark (two spaces) and then the orig. '0'

This actually _does_ result in a measured 62thou. advance per rev.

Nothing major, but I sure do have to keep it in mind when feeding more
than one turn.

Anyone ever seen something like this elsewhere?

Any one have a reason as to why this feed and calibration?
rgentryatozdotnet

As you've heard it is a 16tpi screw. It is original.

Why didn't use a nice round number?
Because they didn't need to.
The round numbers are nice on a dial where you expect to pass zero multiple
times. This is not how you use the toolslide on a shaper.
Ordinarily you rough cut to a scribed line, mike the piece and crank the
toolslide the 6 or 8 clicks you need for the finish cut.

The number of times you will go past zero is fairly low (keyways, channels
etc) and you usually pass zero only once or twice.

They could have used a 1/4-20 thread like the Atlas, but 3/8-16 was more
robust and still readily replaceable in the field.

They could have made their own thread, but that would have been anal
retentive.

Paul K. Dickman

On Thu, 28 May 2015 06:43:51 -0400, "Jim Wilkins"
wrote:


rgentryatozdotnet

Is the feed screw Acme?

Does not appear to be. The thread _is_ 16TPI and fits a standard
'v'
gage nice and tight except for the points which seem to be just
slightly flatter than standard.

As a side note. . The threads appeared to be buttress style. . . .
untill I hit them with a toothbrush and cleaned off the oil. grin

Bob
rgentryatozdotnet

Then the screw and dial may be a repair, used to avoid buying an Acme
tap. I did that on my worn surface grinder with 3/4-10 threaded rod.
It isn't difficult to engrave a custom dial with a rotary index, using
a spreadsheet to calculate the turns. Were the numbers hand-stamped?

If the numbers are hand stamped (and I don't think they are) sombody
did a _VERY_ nice job of stamping.

I think both the down feed and the table cross feed are both 'V'
thread. Both fit the 'V' thread gage very well and the form just
isn't Acme.

I have the feeling that to keep the orig. cost down 'V' threads were
acceptable. Also makes it easier to fix if they ever go bad grin.

Bob
rgentryatozdotnet

On Thu, 28 May 2015 08:03:05 -0500, "Paul K. Dickman"
wrote:

snip

As you've heard it is a 16tpi screw. It is original.

Why didn't use a nice round number?
Because they didn't need to.
The round numbers are nice on a dial where you expect to pass zero multiple
times. This is not how you use the toolslide on a shaper.
Ordinarily you rough cut to a scribed line, mike the piece and crank the
toolslide the 6 or 8 clicks you need for the finish cut.

The number of times you will go past zero is fairly low (keyways, channels
etc) and you usually pass zero only once or twice.

They could have used a 1/4-20 thread like the Atlas, but 3/8-16 was more
robust and still readily replaceable in the field.

They could have made their own thread, but that would have been anal
retentive.

Paul K. Dickman

Thanks Paul!

Your thoughts make a lot of sense.

I'll look at it as you have and get on with making chips grin.

Thanks again for the insight!

Bob
rgentryatozdotnet

On 2015-05-27, Bob Gentry wrote:
The AAMCO 7" shaper has a 'feature' I don't understand. Maybe one (or
more) of you guys has an answer.

All the machine tool feed collars I have used (not really all that
many) have been graduated in some even numbered manner. Fifty marks,
sixty marks, two hundred, etc.

Sure -- convenient leadscrew pitches make for nice increments
on the collars.

The graduated collar on the tool slide of this unit is different.

There is the usual '0' then the fifth mark is '5', then '10', etc.
This goes to the '60' mark.
Then there is one tick mark (two spaces) and then the orig. '0'

This actually _does_ result in a measured 62thou. advance per rev.

The same as my Rockwell/Delta 7" shaper (a descendant of the
AAMCO).

What this means is that they cheaped out and used some 16 TPI
shaft (not even an Acme thread, but a more common V-thread) as the feed
screw here. I've been tempted to try making something more reasonable.
But a 10 TPI would be way too coarse for that small a diameter. (Wrong,
after looking and measuring it, it is 3/8" diameter, not the smaller
diameter that I though that I remembered). 20 TPI could get you 0.050"
per revolution, but if you make it Acme, it results in problems finding
a tap to cut that. You would have to make some more Acme threaded stock
using drill rod, cut flutes, and harden it properly to have a chance at
tapping the nut. So -- I haven't yet been motivated to do this. :-)

Nothing major, but I sure do have to keep it in mind when feeding more
than one turn.

Anyone ever seen something like this elsewhere?

Yep. Emco F2 desktop milling machine, with metric leadscrews,
but inch graduations on the dials. 0.126" per revolution works out to
3.2004 mm/revolution, so it must have really been 3.2 mm/rev.

Even worse was a Jet 13x40" lathe at work which had a cross-feed
dial of something similar. I forget the details, and can't look it up
now, as I am retired, and the machine has no doubt been surplused long
since. We had to fight to keep the shop while I was there. (Actually an
Army R&D lab, and a lot of the work had to be done in the separate
machine shop elsewhere in the compound. :-)

Any one have a reason as to why this feed and calibration?

Sure -- cheap to make. Standard pitch screw -- just use
3/8-16 allthread, make a threaded collar to go on one side of the
bearing plate, and the crank with the dial on the other side.

O.K. MSC offers 3/8-10 threaded rod and matching nuts. 36"
long, and $52.36 with the nut. You would want to make a new dial,
larger in diameter to make 100 divisions readable. Their #01205863, and
other versions.

Looking at it, the base of the compound would have to be re-made
and tapped Acme 3/8-10, as there is not enough meat to drill it out and
press fit the nut into it, even after turning off the flange. This
means one of the double taps -- front end cuts V threads as a guide, and
the back end finishes to the proper Acme thread form.

O.K. MSC does *not* carry the 3/8-10 tap, so you would have to
make it after all.

Hmm ... they *do* have 1/2-10 Acme taps, so maybe you could go
that way. Since you would have to make the base of the compound anyway,
make it thicker, so you could tap it 1/2-10, and make a new bearing
plate for the mount of the screw to the crank and dial to offset the
center line to match. But the taps are up near $100.00, too. :-)
#04794103

At least the design is for a right-hand thread, the left-hand
taps are even more expensive. :-)

And -- the 1/2-10 rod is less expensive, at least. :-)

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) 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 2015-05-28, Jim Wilkins wrote:
"Bob Gentry" wrote in message
...
On Wed, 27 May 2015 22:05:48 -0400, "Jim Wilkins"
wrote:

"Bob Gentry" wrote in message
...
On Wed, 27 May 2015 18:11:05 -0500, "Terry Coombs"

wrote:

[ ... ]

Is the feed screw Acme?

Does not appear to be. The thread _is_ 16TPI and fits a standard
'v'

[ ... ]

Then the screw and dial may be a repair, used to avoid buying an Acme
tap. I did that on my worn surface grinder with 3/4-10 threaded rod.
It isn't difficult to engrave a custom dial with a rotary index, using
a spreadsheet to calculate the turns. Were the numbers hand-stamped?

Nope -- the V-thread was the standard on the 7" shapers --
AMMCO, and my Rockwell/Delta which was a descendant of it. 3/8-16
screw, and the index marks and numbers appear to be rolled into the
dial, not hand stamped.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) 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 29 May 2015 03:02:12 GMT, "DoN. Nichols"
wrote:

On 2015-05-27, Bob Gentry wrote:
The AAMCO 7" shaper has a 'feature' I don't understand. Maybe one (or
more) of you guys has an answer.

All the machine tool feed collars I have used (not really all that
many) have been graduated in some even numbered manner. Fifty marks,
sixty marks, two hundred, etc.

Sure -- convenient leadscrew pitches make for nice increments
on the collars.

The graduated collar on the tool slide of this unit is different.

There is the usual '0' then the fifth mark is '5', then '10', etc.
This goes to the '60' mark.
Then there is one tick mark (two spaces) and then the orig. '0'

This actually _does_ result in a measured 62thou. advance per rev.

The same as my Rockwell/Delta 7" shaper (a descendant of the
AAMCO).

What this means is that they cheaped out and used some 16 TPI
shaft (not even an Acme thread, but a more common V-thread) as the feed
screw here. I've been tempted to try making something more reasonable.
But a 10 TPI would be way too coarse for that small a diameter. (Wrong,
after looking and measuring it, it is 3/8" diameter, not the smaller
diameter that I though that I remembered). 20 TPI could get you 0.050"
per revolution, but if you make it Acme, it results in problems finding
a tap to cut that. You would have to make some more Acme threaded stock
using drill rod, cut flutes, and harden it properly to have a chance at
tapping the nut. So -- I haven't yet been motivated to do this. :-)

Nothing major, but I sure do have to keep it in mind when feeding more
than one turn.

Anyone ever seen something like this elsewhere?

Yep. Emco F2 desktop milling machine, with metric leadscrews,
but inch graduations on the dials. 0.126" per revolution works out to
3.2004 mm/revolution, so it must have really been 3.2 mm/rev.

Even worse was a Jet 13x40" lathe at work which had a cross-feed
dial of something similar. I forget the details, and can't look it up
now, as I am retired, and the machine has no doubt been surplused long
since. We had to fight to keep the shop while I was there. (Actually an
Army R&D lab, and a lot of the work had to be done in the separate
machine shop elsewhere in the compound. :-)

Any one have a reason as to why this feed and calibration?

Sure -- cheap to make. Standard pitch screw -- just use
3/8-16 allthread, make a threaded collar to go on one side of the
bearing plate, and the crank with the dial on the other side.

O.K. MSC offers 3/8-10 threaded rod and matching nuts. 36"
long, and $52.36 with the nut. You would want to make a new dial,
larger in diameter to make 100 divisions readable. Their #01205863, and
other versions.

Looking at it, the base of the compound would have to be re-made
and tapped Acme 3/8-10, as there is not enough meat to drill it out and
press fit the nut into it, even after turning off the flange. This
means one of the double taps -- front end cuts V threads as a guide, and
the back end finishes to the proper Acme thread form.

O.K. MSC does *not* carry the 3/8-10 tap, so you would have to
make it after all.

Hmm ... they *do* have 1/2-10 Acme taps, so maybe you could go
that way. Since you would have to make the base of the compound anyway,
make it thicker, so you could tap it 1/2-10, and make a new bearing
plate for the mount of the screw to the crank and dial to offset the
center line to match. But the taps are up near $100.00, too. :-)
#04794103

At least the design is for a right-hand thread, the left-hand
taps are even more expensive. :-)

And -- the 1/2-10 rod is less expensive, at least. :-)

Enjoy,
DoN.
Greetings DoN,
If a person wanted to replace the 3/8-16 vee thread with an Acme
thread form a tap is not required. The stub Acme thread form would
work fine in this application and the minor diameter of a 3/8-10 stub
Acme thread is .315. If a person had the skill to grind a 60 degree
thread single point tool and use this tool to make a 3/8-16 nut then
this same person would have the skill to grind a stub Acme single
point tool and could single point a 3/8-10 stub Acme thread. The
tougher part would be single point threading a long lead screw because
it would need support while threading. A follow rest works well for
this, I know because I have done this type of threading many times.
The tough part is adjusting the follow rest as it wears. Lubing steady
and follow rests can be problematical. I solved this problem by
putting an oiler on my steady and follow rests. I use the old type
with a glass reservoir and a sight so the oil flow can be observed. I
direct the oil flow with a piece of piano wire that I stuff up inside
a small diameter tube that the oil flows from. I pull the wire out so
that it just barely clears the work. The drops of oil follow the wire
and land directly where I want it to land.
Eric

In article , DoN.
Nichols wrote:

On 2015-05-27, Bob Gentry wrote:
The AAMCO 7" shaper has a 'feature' I don't understand. Maybe one (or
more) of you guys has an answer.

All the machine tool feed collars I have used (not really all that
many) have been graduated in some even numbered manner. Fifty marks,
sixty marks, two hundred, etc.

Sure -- convenient leadscrew pitches make for nice increments
on the collars.

The graduated collar on the tool slide of this unit is different.

There is the usual '0' then the fifth mark is '5', then '10', etc.
This goes to the '60' mark.
Then there is one tick mark (two spaces) and then the orig. '0'

This actually _does_ result in a measured 62thou. advance per rev.

The same as my Rockwell/Delta 7" shaper (a descendant of the
AAMCO).

What this means is that they cheaped out and used some 16 TPI
shaft (not even an Acme thread, but a more common V-thread) as the feed
screw here. I've been tempted to try making something more reasonable.
But a 10 TPI would be way too coarse for that small a diameter. (Wrong,
after looking and measuring it, it is 3/8" diameter, not the smaller
diameter that I though that I remembered). 20 TPI could get you 0.050"
per revolution, but if you make it Acme, it results in problems finding
a tap to cut that. You would have to make some more Acme threaded stock
using drill rod, cut flutes, and harden it properly to have a chance at
tapping the nut. So -- I haven't yet been motivated to do this. :-)

One reason to avoid threads too coarse for a given diameter is that the
nut may spin on the leadscrew under pressure, making it difficult to
machine parts with any accuracy.

The issue is the coefficient of friction of nut on screw while well
oiled, and the angle the screw thread makes with the screw axis. If
this angle is too large for the coefficient of friction, the nut will
spin relative to the screw, rather than remaining where put.

Joe Gwinn

On 2015-05-29, wrote:
On 29 May 2015 03:02:12 GMT, "DoN. Nichols"
wrote:

On 2015-05-27, Bob Gentry wrote:

[ ... ]

The same as my Rockwell/Delta 7" shaper (a descendant of the
AAMCO).

What this means is that they cheaped out and used some 16 TPI
shaft (not even an Acme thread, but a more common V-thread) as the feed
screw here. I've been tempted to try making something more reasonable.
But a 10 TPI would be way too coarse for that small a diameter. (Wrong,
after looking and measuring it, it is 3/8" diameter, not the smaller
diameter that I though that I remembered).

[ ... ]

Hmm ... they *do* have 1/2-10 Acme taps, so maybe you could go
that way. Since you would have to make the base of the compound anyway,
make it thicker, so you could tap it 1/2-10, and make a new bearing
plate for the mount of the screw to the crank and dial to offset the
center line to match. But the taps are up near $100.00, too. :-)
#04794103

At least the design is for a right-hand thread, the left-hand
taps are even more expensive. :-)

And -- the 1/2-10 rod is less expensive, at least. :-)

Enjoy,
DoN.
Greetings DoN,
If a person wanted to replace the 3/8-16 vee thread with an Acme
thread form a tap is not required. The stub Acme thread form would
work fine in this application and the minor diameter of a 3/8-10 stub
Acme thread is .315.

The problem being that the existing thread in the dovetailed
base of the compound is already 16 TPI, and changing to 10 TPI would
mean irregular areas where the two threads remove metal from different
places, thus weakening the thread overall, and making it wear out
faster.

If a person had the skill to grind a 60 degree
thread single point tool and use this tool to make a 3/8-16 nut then
this same person would have the skill to grind a stub Acme single
point tool and could single point a 3/8-10 stub Acme thread. The
tougher part would be single point threading a long lead screw because
it would need support while threading.

Without pulling the compound apart, I can't state the length of
the leadscrew with any certainty, but I doubt that the working part is
any longer than 3".

The bearing nut and the crank with dial both thread onto the
shaft, so you would also need to replace those parts so you could thread
them properly.

At 3" length, and 3/16" diameter you might be able support it
with a half point dead center, if you took gentle cuts.

A follow rest works well for
this, I know because I have done this type of threading many times.

I've done it too. Including the time I made a test cross-feed
leadscrew for my Clausing, and when I went to test it with an old nut, I
discovered that I forgot to make it left-hand thread as needed. :-) At
least this uses right-hand thread on the compound.

The tough part is adjusting the follow rest as it wears. Lubing steady
and follow rests can be problematical. I solved this problem by
putting an oiler on my steady and follow rests. I use the old type
with a glass reservoir and a sight so the oil flow can be observed. I
direct the oil flow with a piece of piano wire that I stuff up inside
a small diameter tube that the oil flows from. I pull the wire out so
that it just barely clears the work. The drops of oil follow the wire
and land directly where I want it to land.

That sounds like a nice system. Thats for the description.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) 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 30 May 2015 02:59:22 GMT, "DoN. Nichols"
wrote:

On 2015-05-29, wrote:
On 29 May 2015 03:02:12 GMT, "DoN. Nichols"
wrote:

On 2015-05-27, Bob Gentry wrote:

[ ... ]

The same as my Rockwell/Delta 7" shaper (a descendant of the
AAMCO).

What this means is that they cheaped out and used some 16 TPI
shaft (not even an Acme thread, but a more common V-thread) as the feed
screw here. I've been tempted to try making something more reasonable.
But a 10 TPI would be way too coarse for that small a diameter. (Wrong,
after looking and measuring it, it is 3/8" diameter, not the smaller
diameter that I though that I remembered).

[ ... ]

Hmm ... they *do* have 1/2-10 Acme taps, so maybe you could go
that way. Since you would have to make the base of the compound anyway,
make it thicker, so you could tap it 1/2-10, and make a new bearing
plate for the mount of the screw to the crank and dial to offset the
center line to match. But the taps are up near $100.00, too. :-)
#04794103

At least the design is for a right-hand thread, the left-hand
taps are even more expensive. :-)

And -- the 1/2-10 rod is less expensive, at least. :-)

Enjoy,
DoN.
Greetings DoN,
If a person wanted to replace the 3/8-16 vee thread with an Acme
thread form a tap is not required. The stub Acme thread form would
work fine in this application and the minor diameter of a 3/8-10 stub
Acme thread is .315.

The problem being that the existing thread in the dovetailed
base of the compound is already 16 TPI, and changing to 10 TPI would
mean irregular areas where the two threads remove metal from different
places, thus weakening the thread overall, and making it wear out
faster.

If a person had the skill to grind a 60 degree
thread single point tool and use this tool to make a 3/8-16 nut then
this same person would have the skill to grind a stub Acme single
point tool and could single point a 3/8-10 stub Acme thread. The
tougher part would be single point threading a long lead screw because
it would need support while threading.

Without pulling the compound apart, I can't state the length of
the leadscrew with any certainty, but I doubt that the working part is
any longer than 3".

The bearing nut and the crank with dial both thread onto the
shaft, so you would also need to replace those parts so you could thread
them properly.

At 3" length, and 3/16" diameter you might be able support it
with a half point dead center, if you took gentle cuts.

A follow rest works well for
this, I know because I have done this type of threading many times.

I've done it too. Including the time I made a test cross-feed
leadscrew for my Clausing, and when I went to test it with an old nut, I
discovered that I forgot to make it left-hand thread as needed. :-) At
least this uses right-hand thread on the compound.

The tough part is adjusting the follow rest as it wears. Lubing steady
and follow rests can be problematical. I solved this problem by
putting an oiler on my steady and follow rests. I use the old type
with a glass reservoir and a sight so the oil flow can be observed. I
direct the oil flow with a piece of piano wire that I stuff up inside
a small diameter tube that the oil flows from. I pull the wire out so
that it just barely clears the work. The drops of oil follow the wire
and land directly where I want it to land.

That sounds like a nice system. Thats for the description.

Enjoy,
DoN.
Greetings Don,
You're welcome. When I put the oilers on the steadys I just drill and
tap the steady for the pipe thread size of the oiler. For the steady
on my 14 inch lathe I drilled a 1/4 pipe hole into the part of the
steady that holds the vertical rest. So the oiler screws into a 90
degree elbow that screws into the steady. I then drilled a 1/8 hole
that intersects the 1/4 pipe hole and pressed a 1/8 O.D. stainless
tube into the hole and the wire then goes into the tube. This lets me
guide the oil drops to exactly where I want them.
Eric

On 30 May 2015 02:59:22 GMT, "DoN. Nichols"
wrote:
snip
The problem being that the existing thread in the dovetailed
base of the compound is already 16 TPI, and changing to 10 TPI would
mean irregular areas where the two threads remove metal from different
places, thus weakening the thread overall, and making it wear out
faster.
/snip
7/16X20 UNF allthread?
http://tinyurl.com/od8jppc
include a piece of nylon weedwhacker line to both take out
any slop and provide friction drag.


--
Unka' George

"Gold is the money of kings,
silver is the money of gentlemen,
barter is the money of peasants,
but debt is the money of slaves"

-Norm Franz, "Money and Wealth in the New Millenium"