On Thu, 08 Mar 2012 17:17:01 -0500, Bob S wrote:

Another possibliity exists to expand the available number of threading
possibilities by adding just one more change gear to the set, as a
number of machine users have done on machines which rely on a set of
gears to change thread pitches.

A slightly alternative approach is to get two gears which DO give you the
ratio you want and mount them outboard of existing change gears of
smaller diameter (turn a two-size mandrel, mount, drill & tap three
holes, then bore the new gears large enough to take the axle-fixing
screws). You may have to do some playing about to find a combination that
fits your existing gears and carrier travel.

It beats looking for that ratio in your particular pitch. For Minilathes
in particular, Sherline makes an affordable 127/100 combination.