Cold Forming and Surface Finishes

[Scra99tch]

What effect does the surface finish have on the finished part or the longevity of the forming tool. OUr shop forms our threads in 303 SS using tool steel dies. WOuld the micro structure of the surfacec finish be causes for stress points and contribute to shorter die life. Does the surface finish play a part in the sliding action of the thread being formed, a smoother surface less work required on die and machine?

Would moly help in these sliding actions of die on thread?

Thanks for your replies

 

[benmychree]

I'd think that better finishes on the die would result in longer die life between sharpenings; you do not say what type of die is being used, but usually it would be an automatic die, such as a Geometric or other removable chaser type of die; they come in hobbed, tapped and ground chaser types, the ground type of thread profile will produce the best finish and most accurate threads, and likely the longest chaser life.
Lubrication is quite important in both chaser life and finish, there should be a constant generous flow of cutting oil to the die, and addition of some cutting fluid such as TapMagic is helpful as well. Stainless 303 is quite easy to work with and is not difficult to cut and maintain nice finishes. I do not think Moly would be of much value with 303; with proper tooling and lubrication, there should be no problems. In my business we used it for nearly all our products, and there were no problems in working with it, it is made to be free machining, unlike 304, which can present challenges, such as work hardening.

 

[Scra99tch]

We are forming threads between two dies.

Thread Rolling is the technical term, with no actual cutting. I just wonder even though dies are hardened throughout how much of them get burnished being hydraulically pressed together on the 303. and if moly would facilitate any friction reduction because of the sliding surfaces of the metal being formed.

 

[benmychree]

At any rate I'd doubt that moly would hurt, but I'd wonder, is there a problem needing solving?

 

[Scra99tch]

Die life is the biggest hurdle we have. Once they get coated their life goes 3x more typically.

Low temperature Ferritic Nitrocarburizing is the coating process our tooling suppliers use.