I've been asked to mill out a casting which is to be a mold for lead fishing weights. I'm wondering if I have to leave some angle on the sides for the easier removal of the cast weight.
The weight wanted is a 3/4 inch diameter slug of lead about 6 inches long. If I had a round nose 3/4 inch endmill I wouldn't be asking this. But I don't have this animal. The weight doesn't have to be round- it could be roughly square with rounded corners, and I can get this with my 1/4 inch round nose endmill. But that means the sides of the cavity will be straight up and down for about 1/4 inch. I'm thinking that this will make the cast part hard to remove.
I don't want to muck about with trying to angle the mold, since it will be hard enough already to align both parts separately to get the cavities aligned. Do I make myself a 3/4 inch round nose cutter to get this job done? The two halves of the mold are cast aluminum, or some aluminum alloy. It shouldn't be hard to machine, but I haven't tried it yet.