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Brett Hurt
12-05-2010, 01:16 AM
Iam tapping stainless on the lathe 12-24 out side dia. And the thread comes out very badly. Iam doing all the right stuff tailstock die holder, and doing all by hand also using tap lube for stainless. so the question is is my dia bad the treads are all pitted. This is the help I need Brett

djc
12-05-2010, 02:53 AM
I am tapping stainless on the lathe 12-24 out side dia. And the thread comes out very badly. I am doing all the right stuff tailstock die holder, and doing all by hand also using tap lube for stainless.

Are you tapping female threads or using a die to form male threads?

What grade of stainless? What is the actual outside dia. of the stock you are using, or the size of the tapping drill you are using? Are you using a name brand, fairly new tap or die? If it is a die, are you expanding it a little for your first cut? Are you using the die the correct way round? Are you chamfering the end of the stock? If tapping, are you using a taper or second cut tap before the bottoming one?

beanbag
12-05-2010, 04:52 AM
Use a good quality HSS die, not some cheapo high carbon steel.
Tap oversize the first time, and to size the second time.
Also, in real life, screw outside diameters tend to be smaller than what they are supposed to, so maybe you can start with your stock slightly undersize and you won't need to take as deep of a cut.