I've got NMTB 40 taper on my mill. It uses a threaded draw bar to pull the
tool in tight. The CAT taper has a pull stud on the end. So, they are not
interchangable even though the taper part is identical. I have modified a
few rare CAT 40 holders over to NMTB40. More work than its worth but doable.

The drive flange and V flange are two different ways to keep the holder from
slipping. The V flange also has the drive flange collar so they will
interchange if you use drive flange.

After using taper 40, I will never buy and R8 machine again. So much better.

Karl


"DeepDiver" wrote in message
...
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