I'm no jeweler or metallurgist, but I am a mechanical engineer that specialized in strength analysis.

If you want it to be tough, then get a stainless steel or tungsten carbide ring. They offer two different kinds of "toughness" and it depends on the kind of "abuse" you give it.

Tungsten carbide is very *hard*, meaning it can only be scratched by diamond or corundum. If your rings get abraded, scuffed or otherwise scratched up, and you don't like that, then TC is a good choice. It also has a kind of cool appearance.

If your rings get crushed or bent, then you probably want stainless steel, which is about twice as resistant to bending as tungsten carbide.

Everyone thinks that titanium is a super-strong miracle metal. The truth is that it is merely strong for its weight. Steel is considerably stronger. Titanium is also reactive in acids, but stainless steel, gold and platinum are not. Non-reactivity is quite important in jewelry metal.

My recommendation is far and away stainless steel. Rather than having it made by a jeweler (who make rings by lost-wax casting), have it made in a machine shop. There is no reason to cast stainless steel as it is very easily machined, and casting it will anneal any heat treatment hardening that has been applied to the stock.

If you can get your hands on a lathe, you could make it yourself, which you might really enjoy. The stock should cost you less than a buck or two, and an experienced machinist could make you one very quickly.

All that said, realize that you should never wear rings around machinery that can damage them, as that means that the ring could also cost you your finger.