I’m threading some brass rod but results aren’t what I expected. The major diameter of the thread is supposed to be about 0.070 - 0.073" but I’m consistently getting about 0.059" - 0.060".
Is there anything in technique (AKA operator error) that could account for such a big discrepancy?
Thread: 1-72 UNF
Set-up: Lathe with ww collet, 1/72 UNF die, tailstock die holder
Not threading under power
Since this is suspiciously like the major diameter of a 0-80 UNF, I guess one possibility is that my cheap Chinese die is mis-labeled. I’ve never used it before.
It’s possible I suppose, but I wouldn’t think it’s deflection. The rod is only protruding 1/4" from the collet. The first couple attempts it was only protruding about 1/8"
If you have a tap that is the same size as the die, it should fit inside, the threads of the tap should be slightly smaller than the die. If it doesn’t go in, then the die is being squeezed. Short of a calibration G/NG gage that would be my method, or use a manufactured thread to see if it fits.