Posted by willie (68.78.128.79) on September 09, 2008 at 16:48:54:
In Reply to: Thickness Calculation for Type III Hard Anodize posted by Ricardo Lapizco on September 08, 2008 at 20:34:29:
: I have problems how to calculate dimensions before anodized, I have dimensions like .6650 +.0007/-.0000 and .650 +.002/-.000. I was reading the anodize will penetrate 1/2 of thickness an AL-6061-T6, How to calculate this dimension for machining?
BAsically stays the same. On an outside diameter, half the coating will be on both sides adding up to your .002 thickness so the OD is .002 smaller.
Inside holes should be the thickness of the coating bigger, so the hole will close to the dimension.
Threads should be masked if possible because the root diameter is what changes most causing lots of problems. Anodize builds perpindicular, so the root of the threads change where the major diameter changes somewhat, and minor diameters build up even from both sides.
The hardest part of the coating is in the penetration and many people do secondary grinding operations after the part is coated to end up with a perfect dimension of the hardest coating afterward.