Hard anodizing question

I need to tap some holes in some 6061 and it need to get hard anodized. How big should I go with the oversized tap so I don't have any problems?

Thanks

Why don't your just plug the holes?
B

customer wants everything black hardcoat

Aluminum gets etched (cleaned) before anodizing, which removes some material. The anodizing adds about the same amount that was etched away. One H size on the larger should be plenty. There is a very informative post at this site on this matter including stress distortion problems from anodizing.

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Originally Posted by JimBoyce

Aluminum gets etched (cleaned) before anodizing, which removes some material. The anodizing adds about the same amount that was etched away. One H size on the larger should be plenty. There is a very informative post at this site on this matter including stress distortion problems from anodizing.

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do you know where it is located?
thanks

Look up mil-a-8625 for the spec. Not sure if it has the thickness there but the anodize usually is .002" thick, where .001" of that eats into the material. So it is usually .001" off the original surface.