Tony wrote:

During their later years of production, SB put vee belts on their
lathes. You would get one more set of ratios that way.


The V-belts are from the motor to the countershaft, not on the cone
pulleys. The reason for flat belts are to make it easier for the
operator to change speeds.


No.

South Bend used V belts for both the countershafts (single and two
speed ones), and, IIRC they used the vee pulley on the motor, and ran
the belt on a flat surface of the countershaft pulley(s).

They used a four speed set of Vee pulleys on the cone pulleys on their
later production small lathes. This gave you four cone pulley speeds,
vice 3.

The ease of changing speeds theory pretty much went away at the same
time a requirement for fast and loose pulleys on the overhead did.

Regardless of whether the belt is flat or vee, you have to stop the
lathe, slack the belt, and change it's position, before restarting.

Take a look at http://www.lathes.co.uk/southbend9-inch/page2.html and
admire the variety of both flat and vee pulleys in the various mixes. :-)

Cheers
Trevor Jones