Cut a recess for a speed knob, a la PRS?

[bdplaid]

To cut recesses where there are already holes, use a big cove bit with a guide bearing. The most common guide bearing sizes are 3/8" and 1/2". They swap easily. 3/8" guide bearing fits inside CTS style pot holes, 1/2" fits in the bigger toggle switch holes.
The bit in the pic has the 1/2" guide bearing on it.

View attachment 5092479

Works well. Centers the dish very nicely, too.

Rick

Thanks. I was thinking that. But wasn't sure how well it would work.

 

[Changed5Times]

$7 spade bit.

10 minutes with a fiber sanding disc on the angle grinder. It's not very refined yet, but the battery ran out (I generally avoid cordless tools, but this one was purchased with a work gift card that had very limited options). I tried to maintain wedges on the sides (lips) of the bit.

Looks good to me: