A couple of weeks ago I made a fire piston on the lathe, but forgot to post about it. For those who haven't heard of a fire piston, they are a way to start a fire without matches using adiabatic compression. When you compress the piston quickly, the air inside heats up enough to ignite a piece of tinder held is a slight recess at the end of the piston. This one was tough because the tolerances had to be just right to prevent air from escaping when the piston was compressed - I actually ended up having to make the piston twice - on the first one, the o-ring didn't quite seal the chamber. For materials, the main part of the handle is aluminum, the handle end cap is brass, and the piston is brass. It can't be seen from the pictures, but the top cap of the piston can be unscrewed to reveal a small storage compartment in the piston - this can be used to store extra tinder (char cloth, specifically).