thread pitchs?

[madbear]

what would be the best pitch for the end caps on a 1 .5" x .065 wall 316 stainless tube and what would be the mim. length for that thread?
thanks for any help;
madbear

[twodollarbill]

I would do 24tpi that would be .028 deep for .065 tubing,
if your wall was thicker I'd opt for 20tpi that's .033 deep.
You should be able to make your end caps with 1/2" of threads.
The mount could be made slightly longer, just back bore it for some of the expansion chamber.

[epicdoom]

agree with twodollarbill any courser and you will probably have issues with such a thin wall. for sure 1/2" thread lenth maybe even 5/8 but 1/2 should be enough.

Joe

[PaulNoiseLess]

Hi,

Here you have a comparison of 20 vs. 24 TPI: Going 24 gives you a thicker outside wall while going 20 gives you stronger threads.

For any of them, I’ll make the ID little bit bigger so after threading you don’t have issues sliding Baffles or Spacers. Also, you can think on having some sort of shoulder (thread depth x ¼ or so) so threading job do not start at the beginning of the Tube (edge) and rear cap threading ends up before reaching the OD: Easier to machine, better fit and extra protection for the threads in the Tube.

Best,

Paul

[jreinke]

Use the standard tap drill formula in reverse to find out the major thread diameter for any tube. MD-P=TD where MD is major diameter, P is pitch of the thread (1/tpi) and TD equals tap drill. So to find the end cap thread size the formula is TD+P=MD. The ID of you tube is the TD. For an 0.065" wall I like to use 28 TPI, so the P for 28 is 0.0357. So TD (1.37) plus P (0.0357) = 1.4057" or 1-13/32". What I've done at this point is cut the threads on the end caps and measure the pitch diameter with thread wires, then just cut the threads in the ends of the tube until the end caps screw in with a little friction.