well, i tried, and failed on the first try. . . . then i found this:
"maj. dia minus ((.01299 times the percentage of engagement) divided by the threads per inch)
being i failed algebra / geomerty i will attempt to decipher that formula into my needed number.
.938 minus ((65 x .01299) divided by 16 = x
.938 minus .05277 = 0.88527
x = 0.88527
sounds and looks logical
is that correct ? ? ?
so my hole was bored to .892 /.895, then threaded about .052 on the half dial, i think. really hard to see the itty bitty numbers. . . and i did three spring passes to where there was no more material coming off the cutter. the part would screw on about half way and stop. . .
the poor little lathe was vibrating about half way thru every cut. . . . . and of course i can see the vibrations in the threads so, into the scrap bucket with the first one, and time to try again. . . if the numbers are correct.
thanks for the help.