From:  "Scott S. Logan" <ssl@l****.com>
Date:  Tue Aug 21, 2001  6:39 am
Subject:  RE: Spindle nose data.


The difference between the Logan Taper and the South Bend is NOT minute.
Here is a rundown:

Logan 9" and 10" Lathes and Montgomery Wards Lathes used a #3 Morse
Taper. There are a couple of exceptions, the Lathes that used the
push-type collets and bar-feed (Model 830 and 1830, I think that's all)
did not have an internal spindle taper. This taper is 0.60235" per foot,
with a gage line diameter of 0.9380"

Logan 11" Lathes prior to Serial Number 52576 used an internal taper of 3
degrees 45 minutes from center. That equates to 1.5730" per foot. The
gage line diameter was 1.6875". BTW, this would apply ONLY to 900 Series
Lathes. No other series would use this taper, and not all 900 Series
used this taper, refer to the Serial Number.

Logan 11" Lathes after Serial Number 52576 and all 12" and 14" Lathes
used an internal taper of 2 degrees from center. That equates to 0.8381"
per foot. The gage line for MOST of these lathes was 1.6250". Some 14"
Lathes had a gage line diameter of 2", and the Logan Chuckers had an
integral 5-C collet taper.

Some Powermatic Lathes had a different taper than any of the above.

South Bend Lathes (as far as I have found) used either a #3 Morse Taper
or a proprietary taper that was the same ANGLE as a #3 Morse. That taper
is 0.60235" per foot.

FWIW, I think South Bend had the better design in this situation. When
they developed the larger lathes, rather than coming up with a different
taper, they used the same taper setting, just made it larger. Makes for
MUCH simpler tooling and fixturing.

Keep in mind that during the production of these lathes, it was very
common for a manufacturer to use their own taper in the spindle.
Probably many reasons, including forced return sales, but also there was
no single, commonly used taper that would accommodate the other
requirements well. Those requirements being a through hole of at least
1-3/8" (to handle 5-C collets) and a 2-1/4-8 Threaded Spindle (a common
thread, and easily cut on the machines). No standard Morse Taper would
work (except for the uncommon 4-1/2 Morse), and other tapers were not in
common use.