Threading Stainless Steel

I have checked the search but cant find some information on threading stainless steel. I'm making a steam valve and used 4mm stainless part turned down to 2.95mm to thread 3mm, put a start on but the thread was rounded of, the stainless is to tough for the die. I used 4mm mild steel rod instead and had a nice thread with the same die, problem is I would have preferred stainless. Are there stainless rods that can be threaded that's not tough, I have around 4 meters of this stainless. I have some old cooker oven grills which are just over 4mm chrome plated that could be used.

Bob

With stainless it is all about the grade. 303 is nice to machine and thread. 316 a bit tough but good for anti corrosion. 304 is a bitch to be avoided at all costs unless you need to weld it. What grade is your 4mm rod ?

Have you cut a thread with this specific die and then decided the tread was too tight and readjusted the die. Then tried to rethread the stainless thread. then tried to cut another thread.

Even tough stainless can be thread cut using dies, but stainless will work harden very easily and become tougher than the die if you are not careful

Thanks for the reply Chris and old Al I checked back on my orders for the stainless and its 304, I will pay more attention next time when ordering stainless.

Bob

Edited By BOB BLACKSHAW on 14/11/2020 10:52:10

I agree with Chris, it all depends upon the type of stainless steel. I love 303, beautiful to machine and easy to get a good finish. I've just finished this regulator rod in 303 stainless steel:

The thread is 1/4" BSF. It was cut at 500rpm with a Coventry diehead, but a decent quality die ought to work well. Stainless steel seems to like be worked hard, so power feeding when threading is an advantage.

Andrew

try turning the diameter down slightly more than you have