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?
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.
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>
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
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>.
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.
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
Paul K. Dickman
Sure -- convenient leadscrew pitches make for nice increments
on the collars.
The same as my Rockwell/Delta 7" shaper (a descendant of the
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. :-)
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. :-)
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
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. :-)
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. :-)
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.
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
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
At 3" length, and 3/16" diameter you might be able support it
with a half point dead center, if you took gentle cuts.
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.
That sounds like a nice system. Thats for the description.
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.
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.
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