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Removing pits when buffing aluminum castings

2003

We are buffing aluminum castings and creating pits in the material. We first sand with an abrasive belt to @240 grit, followed with a cutting compound on blue treat airway buffs.

The last step is with a coloring compound and stiff white airway buffs. We seem to be creating pits that were not there after the belting operation.

The final finish does not have to be of very high luster, but should not have these pits. What could we be doing wrong?

Ken Cramer
metal finishing - Sacramento, California, USA

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Sounds as if you are doing OK as is. I think you should check your surface finish porosity after your first step by cleaning the part to see if the problem is the casting. Try ultrasonic cleaning and then look under magnification. Belt systems have a tendency to push debris/materials into porosity rather than remove them.

AF Kenton
retired business owner - Hatboro, Pennsylvania
2003