Finally, I'm just curious about the original intended purpose of the spin
index. I realize that it's pressed into many applications where you need
to
machine a part in increments of degrees. But then again, there are several
other tools available for that purpose such as the dividing head and
rotary
table (and those tools are typically more versatile). Was the spin index
purposely built specifically for end mill or reamer flute grinding, or was
it always intended to be a general purpose rotary index?



We use them to make small core pins on a surface grinder. Their size is much
handier than a rotary table would be.
My guess is they were always intended for general purpose grinding. Their
accuracy typically isn't good enough for cutter sharpening. Depending of
course on the accuracy you need for your cutter.