I have a plasma cutter and it is an awesome tool but incredibly tough to use properly. It’s not that the tool has some issue or is unreliable, the problem is it cuts through metal so well and so quickly that the slightest twitch of the hand can screw up a cut pretty badly. One thing that will help will be simply more practice with it but still, like most things, I am the weak link in that system and unless I use a straight edge or brace with the cutter, my cuts look like rubbish and I’m filled with shame.
Any time I can take the human error factor out of building something by using a straight edge or a fixture of some sort I try to because it makes my work so much better. Even if something is square and perfect when I start a cut or start drilling a hole or start tack welding, sometimes stuff creeps midway through and my final product isn’t as perfect as I wanted it. Jigs, fixtures, and similar tools really help prevent set up errors as well as that creeping inaccuracy that sometimes happens mid way through that makes me want to rip my hair out.
Here’s a video showing one of the more high end fixture systems that, to get one, I’d do shameful shameful things.
But even if you don’t have a whiz bang setup like the build pro, clamping your work piece to a sturdy base in the shape you want it to stay will really help your projects stay straight, level, and square.
Also, check out this blog post by Joy in which she shows some of the cool stuff you can do with an example of an off the shelf jig system. Also check out the other stuff on her blog, it’s good.