Another thread grinding question

[sliprock]

I just bought a Foredom to grind some threads with, and I have a couple of questions before I get started.

First: For grinding a 5/16X18 thread, Do I leave the tenon at .312? Or do I need to undercut it like I do with the dyes?

Second: For 18 t.p.i., how deep of a cut do I need to make? I think my thread gauge at home has this info, but I'm not sure.

Thanks for your help..

 

[paul fanelli]

threading

Sliprock...The exact answer to your question depends on how your ferrules are tapped. You can probably use .312 as O.D., but make some test cuts and test fit your ferrules. Use the depth of cut that gives the best fit, and note that this may vary for ferrules from different sources.

paul

 

[Sheldon]

Get some old pieces of maple out and experiment..... Like paul said, the initial size and the depth of cut will vary.
If I use a cutting tool for ferrule threads, I usually go .290 and cut about .035 deep with the grinder.