It's taken way too much time to get to this point, but in this case the reward may well have been worth the pain - 40 x M5 holes tapped in my new fixture plate in short order and no broken taps!
I brought the tapping head on ebay many months back a US made SPV SA-0E, in good order but missing an arbor, which should have been an easy an afternoon in the workshop....
Firstly, apart from a sales catalogue and general info there was almost no info on this model available on line. The tapping head mounts on a JT33 taper, but with a captive threaded nut. I brought and scrapped my first R8 stub arbor machining the wrong taper pitch, setting up for 3.64 rather than 1.82...
Second attempt worked better - nice fit on the taper, I messed up the thread for the captive nut. I had measured this out as M27 x 1.25 pitch and cut. Close, but no cigar - after some messing around I worked out it was actually 1 1/16 by 20 tpi UNF. I probably could have got away with M27 x 1.25, it's only 1/1000 out per thread, but decided I would have to cut the pitch exactly and purchased a 28 tooth change wheel for my lathe to get the exact pitch. I also purchased a third stub arbor, but then realised this would not fit the supplied box and I could machine a 20mm straight shank arbor from some 40mm bar off cuts. fitting this in an R8 collet I gain an extra inch clearance on my RF45 mill
Got there in the end, but probably wasted two good days in the workshop and £60-70 on arbors, the change wheel and a couple of carbide inserts. Measure twice, cut once as both my Dad and Grandad would have pointed out. Good job this is a hobby!
All works very nicely and the adjustable clutch is very nice. The supplied collets all appear to be for BA size taps, but I will keep an eye out for a few others to join the set. Max capacity for this head is probably 8mm or 5/16"
