Subject: Thread-cutting

From: [email-masked] (Jonathan Henry)
Date: 7 Jan 1994 20:35:14 GMT

Does anyone know of a way to use a metric thread dial to cut english
threads (on a metric lathe) or how to use a english thread dial to cut
english threads (on an english lathe)?  Perhaps someone has devised a
formula?

Metal Meister

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From: [email-masked] (Ed Richley)
Date: 10 Jan 1994 18:31:33 GMT

>english threads (on an english lathe)?  Perhaps someone has devised a

If you use change gears (127/50) I'm pretty sure the answer is that you
just can't disengage the half-nut. 

Also, while we're on the subject, there is a very interesting technique
for cutting metric threads on an English lathe, and vice-versa. It involves
using the taper attachment AND the tailstock set-over, both set to the
same angle. I think you choose the next finest pitch to the one you want, 
and then do the trig to determine what the set-over should be for the
desired thread. For this, you might be able to use the thread dial and
disengage the half-nuts as usual.

Ed 

[email-masked]

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From: [email-masked] (Joseph Stoltzfus)
Date: Tue, 11 Jan 1994 01:27:42 GMT

>english threads (on an english lathe)?  Perhaps someone has devised a

One reason that the conversion factor between metric and US Customary 
was changed a few years ago was for the benefit of machinists and
machine-tool makers.

It used to be that 1 yard = 3600/3937 meter.
Now, 1 inch = 25.4 millimeters.

If your lucky, you may have a pair of change gears with 127
and 50 teeth; that will change centimeters and inches. 
With some ingenuity in setting up the rest of the gears, you
can solve your problem.

Since 127 is prime, without 127 teeth or an integer multiple,
you're outaluck.

OK, folks, show me another way.

Joe Sz.

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From: [email-masked] (Joe Landau)
Date: Wed, 12 Jan 1994 04:40:16 GMT

>Since 127 is prime, without 127 teeth or an integer multiple,
I've seen articles in Model Engineer (but don't think I could find them
again) based on the idea of approximating the ratio you need to cut the
thread you want.  In many cases you can get quite close by compounding
with more available gearing.  L.C. Mason in "Using the Small Lathe" asserts
that using a 63 tooth gear instead of a 127 tooth for the converting gear is
"near enough for most purposes, especially on a short length of thread".   In
this case the error is 1 part in 127. For most uses, I guess it's not
really the length of thread that counts, but the length of engagement.  For
1/2 inch of engagement, the error would be less than .005".

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From: [email-masked] (Clive Washington)
Date: Thu, 20 Jan 1994 15:30:10 +0000

> >>english threads (on an english lathe)?  Perhaps someone has devised a
Rather than use  63 tooth gear, a 21 (=63/3) tooth is often easier to
work in.  There is a table on my ML7 for most metric threads using an 8tpi
screw with this gear.  I'll mail it if anyone wants it.  If I get too
many requests, I'll post it!