When using a 1/16" thick cut-off wheel on an angle grinder, you can "score" the line you draw with a marker by lightly touching it to the metal and letting it trench in a bit. After you have done this a few times you can allow it to cut a little deeper and the grinder blade itself will keep your line straight along the mark you have made. Not sure if this reads like I want it to or not but if'n you were standing next to me and I could show you what I'm talking about you would understand. I teach 15 year old youngins little tricks like that every day. I've got some freshmen girls in my first year shop class that can freehand cut a straight line with a angle grinder that looks like it was cut using CNC.
BBQ ADDICT and Ag Teacher