Cutting External Threads

Cutting External Threads

Joined: September 28th, 2006, 7:53 pm

December 17th, 2009, 4:58 am #1


Ive seen mention of a tailstock die holder for making threads on the lathe.Could someone please explain exactly what it looks like and how it works. A pic would be great. Another question does it matter which way the cross slide is turned 29 1/2 degrees whether it be to the right or left? Thanks.
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Joined: September 21st, 2007, 12:13 pm

December 17th, 2009, 1:05 pm #2

purposes. With the tailstock die holder, a std. die is inserted in a fixture that is held true in the tailstock.

The 29 1/2 deg. compound angle is used when threads are cut with the toolpost & gearbox.
As for a pic of a tailstock die holder, most of the machine tool suppliers sell them. If you have a Shars Tool cat. they are on pg. 10
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Joined: September 25th, 2006, 2:19 pm

December 19th, 2009, 5:27 pm #3

is only a machinist trick to produce a smooth cut thread. This angle supposedly leaves a tad of finishing stock on the trailing side of the 30 degree thread form where the threading tool only drags against the previous cut and is wont to create a rough final finish on that side of the thread.
Then, on the final sizing of the thread, the machinist should feed in with the cross slide and the tool will "shave" off that roughness and chatter marks created by tool drag.

The norm is to set compound at 30 degrees.

In my opinion, there is no place for those dieholders in a custom or hobiest shop. For several reasons:

1. Dies are expensive. So you want to preserve their life

2. The opperator is wont to cut that thread in one gulp and losses the opportunity to "break" the chip.

3. A die cut thread is more expedient than a chased thread. But if you utilize a quick setup to chase the thread to only "rough it out", then the die will track the precut thread without the need of a special die holder. In general, to much work is already put into the piece part to risk a poorly cut thread.

But as stated, it's just my opinion.




Last edited by oo7fuzz on December 20th, 2009, 3:56 am, edited 1 time in total.
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