Lot slower than mine will go. Bottom end at 20hz is about 67rpm (not tested yet, just calculated), my cover will have to be removed and a new safety shield manufactured, atleast for the front, the rest makes it easier to change pulleys when needed. ACORN recomends a rotory encoder for tapping. Alternatively a tapping mill and a run a helical program instead, and tapping head for smaller stuff (the latter which I already have).Although you can't see it in the photo, the casting of the head frame didn't allow me to put anything above the pulley. Mine is running 60 pulses per rev IIRC plus the index of course. I've been able to do power tapping with that. The other day I ran it 6 RPM to ream some 3D printed PLA and not melt it while reaming.
Shows that there is more than one solution to a problem.