Best tap for 17-4 SS 17-4 heat treat question

moonlight machine · Oct 22, 2019

I need to tap a 10 hole bolt circle in the end of a 16" long piece of 17-4? 12mm on one end and 14mm on the other. What is the best tap to use? This project needs heat treated to 48r, will it hold size? It will finish out to 3.97 dia. 16.07 long.

SND · Oct 22, 2019

17-4 moves quite a bit if starting from annealed, we were losing like .030" on 9" long parts.
I tap lots of it with OSG hand taps, this material cuts quite nice.
Good luck getting it to 48HRC though... pretty sure H900 usually comes out closer to low/mid 40's.

Larry Dickman · Oct 22, 2019

I would use an OSG VC10, or threadmill them

cmccull166 · Oct 22, 2019

Im doing some 17-4 rc bought from McMaster Carr already hardened came in at 46RC.
Drilled .063 hole for a 2mm x.4 tap...Taps great just using some left over Morse plug taps I had laying around ,

Drilling with hss was a bit challenging,had to stand over them using Union Butterfeild Drilling tapping fluid...Forget flood coolant..

So far carbide endmills HSM cuts like a dream using flood ...

I dont know how stable it will be, I still have to mill the excess off the back surface ..After a keyway and some .050 slots :vomit:

but havent gotten this far with them yet.

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Best tap for 17-4 SS 17-4 heat treat question

moonlight machine

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