How much draft does a mold need?

[Drew P]

I’m going to make some molds for diving weights and current design is a rather deep mold. So, I included a 2° draft to the walls but I’m concerned with the details if that will be enough. It looks like a lot, but hard to say. Does anyone have input on a general draft angle required?
These will be cnc from billet aluminum.

[fcvan]

The last dice weight mold I saw was kind of like an ingot mold, open on top. My buddy investment cast (sand) the weight shape with the bell loops cast as one piece. When cooled, he bent the loops the weight was snug against the nylon web belt and used liquid rubber coating to seal them. I don't recall the angle but it wasn't much. I guess everyone has their own mental picture of what they are trying to create. His vision turned into some very usable wights. Another buddy sewed his out of neoprene and nylon for straps, and just filled the neoprene pouches with bird shot.

[Calamity Jake]

2 degrees. Is plenty, go for it.

[dverna]

Alloy will have an impact due to differing shrink rates. Pure lead should be the most forgiving. Linotype the least.

[Drew P]

Good to know. Thanks! I’ll use pure I guess, no reason I can think of not too. I’m almost ready to cut the mold. I’ll post up pics when I get there.

[CastingFool]

When I started messing around with lead, I wanted an ingot mold. Not knowing where I could get one, I simply made a pattern, took it to school and the guys in the metal casting class poured one mold in aluminum for me. I wish I had asked for 3 or 4. I used a 1lb ingot as a "pattern" for the cavities. Don't recall measuring angles or anything like that. Just cut it so it would look good.

[Drew P]

Looks like more than 2° from here

[Drew P]

Finally got my weight mold ready to test. It’s works! 2° was barely adequate for draft however, and I’m going to try 2.5 next. Not great quality like my custom bullet molds from the top mfg, but for my first mold I’m happy.

[lightman]

Thats pretty cool! Please remember to post up some pictures of the actual weight whenever you get to cast some.

[Drew P]

Thats pretty cool! Please remember to post up some pictures of the actual weight whenever you get to cast some.

The second pic are two of the weights.
I’m a little disappointed in the release action of the mold unfortunately. At increased draft of 2.5° they still don’t want to drop free. Partly because of machining marks maybe holding on the walls, but I can’t really sand them out too easily. I was wondering if bread blasting might smooth them enough to help drop free?

[Drew P]

Btw these weights weigh 9000 grains lol