[patrickrd]

I tried your method and failed! But perhaps I got something wrong...

I first broke a standard 4-40 tap in a 0.092" aluminum hole (actually one of my teammates did).

Then I was excited to finally have the opportunity to use alum and dissolve the tap. Since the part was quite small, I filled up a pepsi can (with the top cut off) with boiling water, and added in about a teaspoon or tablespoon of alum. I then mixed it up, threw in the part, and waited. When I came in today (after a full night of the alum doing its thing), I couldn't get the tap out, and it still seems to be the same as it was.

So, I'm thinking of two possible errors:
1) I didn't put in enough alum (what are the correct proportions of alum to water?)
2) The water quickly cooled to room temperature... Maybe I should keep it boiling like the instructions say.

Any input would be appreciated!! Thanks!