Re: Double Helix Threading


 

    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 depth-of-cut setting.'
 
        This is a very good book and there is way more information in there on this subject than I can relate here without scanning.
 
                                                                        Keith
 
 

----- Original Message -----
From: azbruno
Sent: Saturday, April 30, 2005 7:43 PM
Subject: [southbendlathe] Re: Double Helix Threading

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 may be
possible to manage multiple leads by different markings on the
threading dial.

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 four markings
on the thread dial.

Your mileage may vary.

-Bruno





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