Mechanical Finishing Clinic: Steel, Stainless Burnishings for Edge Dulling

Q. We have a precision 5 x 6-inch stainless machined part with various small holes. We need to dull the many edges and brighten the part. We’ve tried vibratory mass finishing, but the medias wear down and lodge into the holes. What finishing system would you recommend?

A. Steel ball burnish with stainless media in a bowl vibratory machine does both: dulls edges and brightens the part. Stainless media is a product that is cold-formed from wire, then hardened and polished and is available in many shapes and sizes. They have precise measurements and wear very slowly with service life up to 10,000 hours.

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The steel and stainless steel burnishing media weighs approximately 300 pounds per cubic foot. Machines have to be heavy-duty to handle the weight. The applications include burnishing, cleaning, peening for strength, and light deburring, without media lodging in the part. 

Your part must be tested in the stainless media to make sure it will do the job without lodging. Once a media is selected, it’s important to know the tolerances of the media, which is ± 0.010. Add the media tolerance to the tolerances of your hole sizes to determine potential lodging problems. Often, if not calculated properly, the accumulation of these tolerances will disqualify a media that originally looks like it works in testing and fails after you buy the media.

Only choose quality manufacturers of steel media. This assures tight tolerance media and systems that work.

Originally published in the November 2016 issue.