i showed it to the previous TUFFHEAD owner about 5 years ago. perhaps he 'remembered' the design. i'd graciously split the profit 60/40
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making something that will fit most shafts is always going to be a compromise but you can't bring into production something to fit every combo out there you just wouldn't sell them all. that's just the nature of manufacturing.
that's why i played around with making a small run of exactly what i wanted for myself.
if you make one like mine to suit axis shafts internal diameter on the small shank and the outside diameter of axis 400 or 340 on the big shank with a 23/64" taper i'd buy a few.
good luck, good to see a variety of good components to compliment the tuffheads.