Buttress thread

[pyromech]

Couple of questions on buttress thread.

1. Determine if wall thickness of steel tube (60 ksi) can withstand internal pressure of 4,500 ksi on a buttress thread, 0.5-20 BUTT-2? The max tube dia is 0.544 that can't be changed. I am stuck with thread major dia 0.5" because is the lowest specified in the ASME B1.9. Now i am worried that the wall thickness might be compromised
2. Is the flank or front face in the diagram oriented correctly?
3. LH and RH is equivalent to 2B and 2A respectively?

thx

 

[desertfox]

Hi

I think you are right to be concerned I looked at this site for the actual dimensions of the buttress thread

https://amesweb.info/Screws/buttress-thread-chart-calculator.aspx

The wall thickness is very small and not to even mention the stress raiser in the thread.
As a starting point why don’t you use the OD of the tube minus the height of the thread and calculate the stress in the wall thickness as though it were a pressure vessel, if it comes out over the allowable stress which I think it will, then you need to review the design. Is it possible that the tube can be sealed below the end of the buttress thread?

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[rothers]

Weld a 3/4" dia boss on the end of your tube and machine the thread in that.