Reasonable Profile Capability for Center-Cutting Ball End Mill 1

[patdh1028]

Howdy! I'm designing a part with some curvature-matching and I'd like to produce a spherical indentation in a piece of Nitronic 60 SS. I am wondering if I can expect the surface profile to be reasonable in a cutting operation with a center-cutting ball end mill. If I'd like the indentation surface profile .125 spherical dia. with -0/+.003" tolerance and a depth ~.075", is it reasonable to expect that can be cut or will I have to have embossed or something?

 

[JNieman]

With a tolerance like that on the diameter, I think I'd just use an undersized ball mill and use an interpolated toolpath to mill that feature, unless I was making hundreds and hundreds where the seconds would add up to significant dollars of time.

However, plunge cutting with center-cutting ball mills is doable. If you can allow a possible 'nipple' to the divot, for relief, one could even drill the center with a small drill before the ball mill comes in, to extend tool life. Otherwise, drilling to ~90% depth and then using the ball mill will still help and not leave any possible extra dimple in the center of the bottom.

 

[ornerynorsk]

Be forewarned that ball endmills do not react well when used as drills. As JNieman said, it is doable, but your feedrates will need to be far slower than the optimum numbers normally associated with milling or drilling. It is a very good suggestion to relief drill most of the material prior to finishing up the profile with the ball endmill. Embossing or forming may also work if you can tolerate the upset material at the "crater", but 0.075" deep is quite deep for the diameter, well past the tangency of the spherical portion.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.