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Vibratory Ball Burnishing


Hello folks,

We are currently working on trying to put a finer finish on the end of a small shaft (6 inches by .375 dia.). The end of the shaft has to be ground using a 180 grit PSA AO pad. Once it is ground the surface finish ranges from a 45 Ra to a 35 Ra. The part is hardened to approximately 55 Rc in a previous operation. We currently process about 10,000 parts per day on the AO disk so other microfinishing operations may not be feasible.

We have been exploring ball burnishing using stainless steel ballcones or cylinders in a vibratory bowl. I was curious if anyone would know what the time requirement would be to see this finish drop to below a 24 Ra? I have been told, as a general rule, that 30 minutes of finishing will show a 50% drop in Ra. Any credibility to this? Thanks much folks!

Casey Calloway
centerless grinding shop - Marquette, Michigan, USA

Hmmmmm. Credibility? That depends on what Ra/Rms you are starting with. Yes it is possible to reduce the surface profile of up to 50% however, that is not as important as getting below 40Ra. Steel media will get you a nice looking part and will work harden it, but smooth is another question. Normally I'd make some media suggestions; however, if you are only concerned with the ends of a shaft nd everything is uniform, I'd look into automating a bush line instead of messing with media.

tony kenton
AF Kenton
retired business owner - Hatboro, Pennsylvania

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