Make your own knobs fast and easy FREE PLANS

[Toolmaker51]

Hard to outrun a good drill jig like this.
1 suggestion; since you are drilling solid material with bushings, create a brad point drill. Grind a small lead chamfer to guide the edges in without loosing the cutting edges, especially the corners. They score and cut a hole from the outside, with huge reduction of splinters and tear out. Makes the 'deburring' almost nil.