Blair Rotabroach is a nice set up. Replacement cutters go for $8-$9 each, 5/16" and 3/8", 3 teeth. Buy extra locating pins too. Cut like a lathe but are brittle. I would get upwards of 1000 spots cut before it got dull (if I didnt break it first )
Been using the spotweld cutters from Harbor Freight lately. $3.99-$4.99 (depending on sale)Two sided cutter bit, also an "annular" (ring) cutter like the Blair. 8 teeth, not as brittle, will continue to work with a broken tooth or two. Maybe 200 cuts per side of cutter so upwards of 400 per unit.
Dont overheat either one or it wont last long. I use bacon fat for cutting lube