Hmm, build a tool box or buy one and reinforce it with aluminum sheets and stainless or if your on a budget, mild steel. I say stainless and aluminum because it will be harder for the thief to try and cut it with a grinder and impossible with a OA torch. Bolt that sucker down to the concrete/wall and when you are ready to pack up for the night, put the welder, grinders and other expensive tools in there. Forget Masterlocks and ANY padlock you get at Lowes, HD etc! Get an Abloy padlock or pucklock, they are far superior than anything else period!

A box like structure with lots of flat metal that is fully enclosed is alot harder to try and grind or even plasma through. Run square tubing within the box structure to make it even more of a chore to cut through. Grinders can cut less than half of the diameter of their blade until they are maxed out.

You gotta think what types of shapes of metals are hard to cut through when you are fabbing up stuff and apply that to your security enclosure.

Another good, cheap, and easy way to make it difficult for someone to try and make off with your welders is to back up an old truck or car to the machines carefully and then take out a fuse or something.