Threading Question

[David DeCristoforo]

Well, we are getting into some serious stuff here... But my question has been answered and I have ordered a set of 16TPI chasers. If I need any others, I will probably take a shot at making them. Thanx for all the helpful input.

[John Keeton]

Ummm......

John,

Does wood turning involve math!!!? Oh no... NOT THAT!

Only for those of us that are anal enough to let it!! And, even at that, I apparently misstated the last sentence, which should read "For example, if you can comfortably thread 16tpi at 320rpm, then your CRT is 20. That would produce a speed at 10tpi of 200rpm."

[Josh Bowman]

Actually, your speed should be adjusted so that the "advance" speed of the chaser is the same in all situations. The 10 tpi will advance faster, but if the lathe speed is slowed to your "comfort" level (CRT = Correct Rate of Travel), then the feel should be the same. As I recall, once one finds their comfort speed with any given tpi, take the rpm – and divide it by the tpi. That will give you a CRT that is unique to you. Then, for another thread size, simply multiply the tpi by your CRT and that should give you the same comfortable advance speed.

For example, if you can comfortably thread 16tpi at 320rpm, then your CRT is 20. That would produce a CRT at 10tpi of 200rpm.

John and right you are, however my first experience was with a lathe with not so low variable speed control and 10 tpi was just too fast.