Metal finishing Q&As since 1989

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Whites spots on 6061 Al

In regards to finishing 6061 T-6 (extruded) Aluminum; I find that after the turning process, I end up with very visible white freckles or splotches on the finished surface. My cutting cond. are as follows .007 R.tool, 35 degree vnmg style , .012" DOC. .0035" per rev. surface V., 3500 rpm, .860" (fin.) dia.,and "cimcool 1070" (12-15%) cutting fluid... is this normal? the intensity of the spots seem to vary from batch to batch. Thank you very much.

David m Haney
high end audio manuf. - Milford, New Hampshire
2005

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How big are the spots? Are they about the size of 1-2 mm in diameter?

I think it's aluminium oxide inclusions from your supplier.

And since it varies, I think it's more from the manufacturer problem.

I have a question, does your company do the lapping process for the aluminium? Does white spots appear on the lapped surface over 50x magnification?

Yong Tze Shoong
- - Johor, Malaysia
2005

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By "finished surface", do you mean before anodizing or after anodizing?

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2005