I guess I’ve got holes on the brain lately as I am finishing up the Hole Wizard for the G-Wizard Conversational CNC product.  Be that as it may, here is a neat idea from Flyboy Accessories for cutting larger holes in sheet metal:

It’s meant for creating lightening holes of the type seen when building aircraft (or maybe just toolboxes and furniture that are built like WWII fighter planes).  I’ve messed with trepanning tools, abrasive wheels, hole saws, and all manner of other stuff for cutting large holes in sheet metal.  So far all of these tools are a painful nuisance.  Typically, the hole is large and the sheet metal won’t fit on my CNC milling machine, so I’m left flailing.  With this tool, you stick an endmill in a die grinder, put the grinder in the little fixture so it can pivot, drill yourself a pilot hole for the pivot, and away you go.  Presumably you can switch it out for a little drum sanding attachment to debur the hole when done.

I like it!