On Oct 30, 9:51 pm, Bill Schwab wrote:
Hello all,

In such a situation, how close to the edge of an Al part would you
consider it "safe" to tap for 4-40 and 8-32, respectively? Again, the
concern is not so much ultimate strength as robustness and common sense.

There are already good posts regarding the wall thickness and good
design practice. I would be cautious, though, about using roll-forming
taps if you are by chance tapping cast aluminum (e.g., Mic-6). I
haven't had a
great deal of experience with these taps, but they are designed to
form (displace) the material, and in a more brittle, crystalline
matrix
there will be a tendency toward fracture rather than flow. In a thin-
wall
situation, this is not desirable.