On 23/02/13 06:35, RogerN wrote:
I have some Aluminum parts, 7075 T6, for machining and will anodize at home
using the sulfuric acid / battery charger method, or a variation. For the
tight tolerance parts, do I need to machine, ream, oversize to allow for the
anodizing? If so, how much? I've seen recommendations of .001"-.002" per
surface, is that about right? For example, one of the hole sizes in the
drawing is .251" +/- .001, the instructions by others that have built these
parts say to use a .251 reamer, so that's what I bought. But now reading
the anodizing info I'm wondering if I need to ream to .253 or so?

RogerN


I've had decorative anodising down professionally once and they
mentioned that they did a reverse current etch first which removed a
small amount of the surface, 0.002" ish from memory but it was a few
years ago, then the normal anodising to end up with nominally the same
size. The items in question were shelf support brackets so size wasn't
an issue but it might be worthwhile looking at the process.