Basically, a cool idea I think. A homebuilt slider “mini radial arm”) to use your angle grinder with. Parts are simple hardware & shop scrap.
Offhand, I only question the end result in one way. He demonstrates cutting MDF or
wood with a saw-tooth grinder head. I wish he had demo’ed the set-up using a zip-disk on metal plate of say 3/16-inch or so. (Obviously, the cutting time would be more, but it is the sort of material he used in
making the little apparatus. If it
could work for cutting plate, you might have to intermittently push the grinder ahead, backing off for a few moments to let the disk cool.)
I do have a metal chop saw, but it has no slider, so there’s a limit to how wide a piece of plate I can cut with it. Cutting-torch cuts leave too sloppy an edge… too much grinding involved to clean them up.