hi guys this is slightly off topic because i dont intend on useing it on a knife but it is still quite relevant.
I was wondering if anyone knew how i could make a mold to cast that will finish with a real nice surface. You know those wings that pilots wear on their shirts, i need to cast some of those. i would imagine that a steel mold would work but the setup cost would be too large.
so any one got any ideas?

brett

All of the casting that I have done there is always some cleanup that is needed. Even if the mold is polished smooth you will still have some oxides and some micro bubbles to deal with. I started casting to get the rough ancient look with the oxides and mold lines.

There are a few members that have done alot of lost wax casting that could give you better ideas.

what metal? lost wax spin casting would work well for pewter/gold etc might even work well for sliver/ brass/bronse
MP

I've cast pewter that didn't require much in the way of cleanup. You still have to cut the sprew, and clean that. After that, I just toss the castings in a rock polisher with some stainless steel shot, and a drop of dish detergent. They come out with a nice finish after an hour or so.

All the higher temp stuff I've done needs more cleanup. Though, I am far from an expert.

Jeff

Commercial badges & pins are almost always made using rubber wax-injection molds and vacuum / centrifugal lost-wax casting techniques. If you can make the model polished, you can cast into nearly that state with bronze, silver, gold & many other non-ferrous metals.

Try Tim McCreight's book Practical Casting.

Here is a technique for getting the smoothest surface with sand casting from "Practicle Casting". It's called skin casting and it toughens the surface and gives a smooth surface if done right. After making the impression for the mold, separate the cope and drag and remove the model. Spray the surface of the mold with a solution of 1 part molasses and 10 parts water. Air dry and then heat the mold with a gentle flame to set the malasses mixture.

Doug Lester