THREAD GAGES

Thread plug gages and thread ring gages are used to measure threaded parts. The only outcome of gaging with thread gages is pass or fail, the part is either accepted or rejected. They are not recommended for SPC, they can not measure the actual pitch diameter.

Go Gages

If the part is made to the correct tolerance the Go gage will Go. The Go gage should easily and completely screw into all the threads in your part. If you have to force the Go gage it means your part is smaller than the minimum size allowed. Forcing the gage may increase the size of your part, slightly, but will cause wear on the gage and drastically reduce the usable life of your thread plug gage.

Don’t force it.


NoGo Gages

When gaging inch threads a NoGo gage should not go, or turn, beyond the third thread.

When gaging metric threads with a NoGo gage you should begin to feel a little drag by the second thread.

If the gage goes beyond these limits your part is smaller than the minimum size allowed.

Don’t force it.

You may have to modify these parameters when your part is thin, with only a few complete threads, or when the product is a softer material that may stretch.