Review on Optimized Kempston Keyhole Cutter - 501011, Enhanced Cutting Diameter by Jeff Labore

It's not a lot but it was just the size I needed. I was concerned that the bit might be brittle in hard wood so I bought 2 just in case. I cut out most of the material with a straight drill BEFORE setting up the keyhole/T-slot cutout. So this tiny cutter only survived being cut through the actual slit. The bit worked great and stayed sharp through over 50 feet of slot in the maple groove. The groove is a little hard to see in the photo above left. Really very satisfied.