[Gregski]

... and now Metal Fab Advice from A Guy Who Should Not Be Giving Metal Fab Advice

if you want straight / even cuts when cutting with an angle grinder, anything thicker than sheet metal, so something like square tubing or pipe, only cut through the surface on each edge, then flip or rotate the piece and cut the other side only through the surface, reason being is that as you cut downwards the blade will go slightly at an angle either one way or the other way depending if you are right or left handed, this is a common problem as you try to stare down at the cut, it's a natural bad habit, but if you only penetrate that wall then rotate the piece then you will not cut far deep enough to skew your line, kapish?