Metal finishing Q&As since 1989

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Aluminum surface finish

February 18, 2009

Hi,
We have a machine shop for job work. We machine aluminum blocks for various valves on milling machine using a 45 degree shoulder mill cutter.
The finishing is some times not very good which results in poor quality black anodizing leaving white marks where the machining is a little rough.
How do I measure the machining surface finish , so that we may maintain a consistent finish without any anodizing problems.

LOKESH WAGHELA
MACHINING - VADODARA, GUJARAT, INDIA

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I am not sure that I will go along with a rough surface being the ONLY cause of the anodize problem. I think that it could be the cutting fluid being retained in the groves and not properly rinsed off. A remote possibility is some of the prep step chemicals are being retained in the groves.

The answer to your question is to buy a moderate priced profilometer and then establish a go-no go roughness from practical experience.

James Watts
- Navarre, Florida
February 20, 2009

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I does sound like a corrosion or residue issue rather than surface roughness. Raw bare aluminum must not remain dirty or moist before finishing.

Leo Herringon
- Grand Rapids, Michigan
March 4, 2009

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Lokesh

If your cutter isn't sharp, the feed and speed not dialed in, and an adequate flow of quality coolant provided, you easily could be smearing the aluminum. The smearing will re-deposit pieces of aluminum back onto the surface that may or may not anodize properly. It also can entrap coolant in cavities caused by the smearing, that can effect the quality of the coating.

Willie Alexander
- Colorado Springs, Colorado
March 5, 2009