Amazingly inexpensive and the description says "Accurate to 0.0001" per inch".
Also, the picture does seem to show some of the holes are threaded:
Just take a carbide endmill and open the non-threaded holes for clearance. Solves the problem. Did that to mine. Worked like a charm.Wonder if it's the good kind of threaded or the stupid ones that are practically useless.
Actually it was a used 1/2” EM from a tool buy. Was not even very sharp. Lots of cutting oil and slow speed (rpm) and relatively high hand feed to be sure it would make a chip & through it went. I think it was a Niagara Cutter (or some other US made one - I’d have to check for you).@RobinHood that's good to know. Was there anything special about the endmill type? I've heard the core is a bit softer than outer skin but not for the first 0.2" or so. I'll check with my new fangled (somewhat subjective) hardness files.
I was actually thinking about buying a dedicated (offshore) donor carbide tool for this purpose in case it went 'snap' but couldn't decide between a drill & EM. The EM was actually cheaper but I was concerned about the the delicate EM cutting edges vs. conical edges on drill. One would think a drill would be better at.... drilling? But I have also seen people drill with ball ended EM's.