Mark Washek asks about worm gear shafts for a Duo-Art expression box 
in MMD 17.12.26.  The fragile design of these can lead to damage by
those unaware (or unobservant) of the proper adjustment procedures.

A technique I have used with success is to use a thin hacksaw blade
to cut a cross slot in the end of the shaft so that it can be engaged
by a short (stubby) or right-angle screwdriver.  In this case it may be
helpful to go ahead and purposefully strip any remaining cusp threads
off of the (softer) shaft so as to not impede turning it against the
(harder) adjusting screw threads.

I think I also replaced the locking screw with a hex socket cap screw
that enables tightening with a pure torque force that minimizes turning
the shaft inadvertently once the proper position is achieved.  This is
useful even for worms that are still functional as designed.

John Grant