Hello Group,
I spec'd. out a 7/8-20UNEF male thread on an aluminum part and called out for a Ø.800 ±.005 thread relief groove. The shop doing the work said the groove wasn't small enough for the tool not to clear. Machinery's Handbook says minor dia. is .8155. I am .015 smaller than nominal, where did I go wrong and how does everyone else calculated thread relief grooves?
Thanks in advance,
Pat