thread pitch

[rickdavis]

Finishing up my integral 22/45. Tube is steel 1"od with .065 walls. Going with a 15/16 thread, would you use a 20 or 24 tpi? Original thought was 20 but would only leave around.020 of meat left. Wasn't sure if that was enough.

[partsguy22]

Make them 15/16x28

http://theoreticalmachinist.com/Threads ... erial.aspx

[fishman]

I wouldn't do 15/16" x whatever. I would do whatever decimal amount gives you full thread engagement with maximized tube thickness.

[rickdavis]

Hadn't thought about doing a custom thread size but that does make sense

[yondering]

I wouldn't do 15/16" x whatever. I would do whatever decimal amount gives you full thread engagement with maximized tube thickness.

This. There's no reason to stick with a specific fractional size.

I would do 28tpi for even more remaining tube thickness; the only advantage to a coarser pitch is fewer turns to mate the parts together, it doesn't improve strength.

[T-Rex]

I add 5thou (per side), to the ID, and use this as my Dmin. Keeps your B crests out of the way when sliding in baffles. I agree with 28tpi, 24 being the coarsest I'd go. You don't need a lot thread area for 22, either.

[fishman]

I wouldn't do 15/16" x whatever. I would do whatever decimal amount gives you full thread engagement with maximized tube thickness.

This. There's no reason to stick with a specific fractional size.

I would do 28tpi for even more remaining tube thickness; the only advantage to a coarser pitch is fewer turns to mate the parts together, it doesn't improve strength.

+1

I add 5thou (per side), to the ID, and use this as my Dmin. Keeps your B crests out of the way when sliding in baffles. I agree with 28tpi, 24 being the coarsest I'd go. You don't need a lot thread area for 22, either.

+1

[jreinke]

I'd go with 28 tpi. So, assuming you have a lathe, and can cut internal and external threads, this is the route I would take. Using the formula TD (tap drill or tube ID) = MD (major diameter or thread size) - P (pitch of thread or 1/28), I'd fill in the information that you have. TD (.870) = MD (?) - P (.0357) or MD = TD (.870) + P (.0357), MD = .9057. So make your end caps with a .906-28 thread, then just cut the internal threads in the tube to fit the cap threads. Easy peasy!

[rickdavis]

Thanks for the advice. And for making it easy to understand.

[curtistactical]

We thread all of our baffles together to make the core of our suppressors, every thread on ours utilizes 32tpi, this allows to run our wall thickness lower to keep the weight down.

[mcmaster]

Any reason not to use a square thread or acme?
Noob here just wondering.

How do HSS tool bits cut titanium anyway?

edit, I guess I just realized I have heard V threads tend to tighten up and stick under load compared to acme or square, that might be desirable?

[yondering]

Any reason not to use a square thread or acme?
Noob here just wondering.

Yes, plenty of reason. 60* V threads are standard for most fasteners and other threaded connections. They're easier to cut and can use the same single point tool for a wide range of thread pitches. They're also self centering, unlike a square thread.

[fishman]

How do HSS tool bits cut titanium anyway?

Perfectly fine. Take a look at the link in my signature.