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Reading this thread (no pun
intended) has me looking back through some of my old school texts. So far the
best one has been 'Technology of Machine Tools, 4th Ed.'. It has a section on
cutting multiple-lead threads. The advice there states this;
' Double-start threads with an odd-numbered
lead may be cut using the thread-chasing dial.'
1. Take one cut on the thread by engaging the split nut at a
numbered line on the dial.
2. Without changing the depth of cut, take another cut at an unnumbered
line on the chasing dial.
3. Continue cutting the thread to depth, taking two
passes (one on a numbered line, the other on an unnumbered line) for every
This is a
very good book and there is way more information in there on this subject than I
can relate here without scanning.
----- Original Message -----
Sent: Saturday, April 30, 2005 7:43
Subject: [southbendlathe] Re: Double
Depending on the TPI of the leadscrew, the tooth count of
the gear on
the threading dial, and the TPI of the threads to be cut, it
possible to manage multiple leads by different markings on the
I do 4 lead 36 TPI threads on my Atlas machine. I
set up the gearing
for 9 TPI. The leadscrew is 16 TPI and the threading
dial has 16 teeth -
- therefore each rotation of the thread dial is one
inch of carriage
traversal. Each helix is therefore marked by each of the
on the thread dial.
Your mileage may
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