How to make root relief when making a thread gauge?

[SmokeWalker]

Hey all,

I need to make some 40 TPI thread gauges (Go/NoGo external, Go/NoGo ring gauges, and a Go/NoGo master gauge to set the ring gauges) and I don't know how to put root relief onto them. Any suggestions?

SW.

 

[RJSakowski]

Check out this. https://en.wikipedia.org/wiki/Unified_Thread_Standard
If you make your gauges with clearance at the areas you are not trying to measure you will be good. Any diameter equal or greater than the pitch diameter less H/2 will give you the root relief. The specified tap diameter for 75% threads will give you that for a ring gage.

 

[Kernbigo]

i used to work for besley taps and made thread gages for 8 years. We used to dress a thread grinding wheel down to .004-.006 thickness and go back in and relief the root on certain gages that required root clearance. The included angle was around 6-8 degrees

 

[4ssss]

I have a couple 40 TPI plug gages what diameter do you need?