Are there any differences between NT40 and CAT40 spindle tapers? I've also
seen reference to 40 National Taper, 40 National Taper with Drive Flange,
and 40 National Taper with "V" Flange. What are the differences (and why)?
Can anyone provide a reference to the actual design specs for the various
National Tapers?

Finally, why are 40 National Taper spindles so rare in milling machines
sized for the small shop? It seems to be vastly superior (in strength,
concentricity, rigidity, and ability to accommodate larger-sized tooling) to
R8. Yet, even the 10"x54" class milling machines (costing $7,000+) are
fitted with wimpy R8 spindles. Not that I'm ready to buy such a machine...

- Michael