"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?

Ok, so I think I understand the differences now, thanks primarily to J
Gold's excellent link:

http://www.cox-internet.com/drspiff/...ets/tapers.htm

The most obvious difference is that the NMTB tapers have a pilot extension
at the small end of the taper, while the CAT tapers do not (in order to
accomodate a pull stud). The CAT tapers also have a grooved flange (which I
assume is for an automated tool changer).

One thing that's still not clear: in my Machinery Handbook, it shows that
the drawbar for NMTB tapers have two threaded portions at the toolholder
end: a larger threaded portion (what they call the "Large End"), followed by
a smaller threaded portion (what they call the "Small End"). Why is the
drawbar stepped in this fashion and how does it work with the NMTB taper
toolholder?

- Michael