[quote=“newman,post:6,topic:39841"”]
is it NPT?
1 1/4 NPT has a pitch of 11.5 TPI, so you will only have 5.75 Threads less the chamfer… For pressure rated applications it’s usually a good idea to have 6 threads of engagement, and about 9 total threads.
However, if you’re planning getting it welded, don’t let some hack do it. Pressure vessels are fairly important to have welded properly.
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1/2" is on the low side too. The hole is beveled a bit on the inside.