I saw a chopper made out of nuts and bolts for sale and I thought "I could do that". I have plenty of parts to choose from so I gave it a shot. The only trouble I had was welding the different metals together. It was tough to get the heat right so I wouldn't melt the soft metal and be sure to stick to the harder metal. It took about an hour to build partly due to picking the parts I thought would work.
My welding skills are terrible and I was able to attach all the pieces, so it isn't very difficult. Give it a shot!