[Peter Matteson]

Originally Posted by DonRotolo

Small features like rivet holes are best drilled - although you can 'mark' their location with the plasma torch. Better are larger features, but the edge condition may not be as smooth as you prefer. It isn't like milled, laser or waterjet surface finish.

With aluminum, beware the effects of heat on the material - aluminum expands as you torch it, and so when it cools everything gets a little smaller (and closer together...).

Don hit the nail on the head what we do to put holes in parts. We undersize and finish the holes on a drill press.

For bearing holes we precision ground a step drill to finsh the holes for a perfect press fit.

The thermal expansion is manageable by controlling feeds and knowing how much you can cut before pausing the cutter and letting things cool along with the order of the cuts. We do primary holes first (location critical items like bearings or interfaces) and then leave lightening holes and frame cutting for later with cooling down time allowed between the patterns.

Also the best way to clean the edges and remove the slag is a scotchbrite pad on a die-grinder. Deburring tools are a bad idea to try on the slag they skip off easily and don't clean it well.