Hello again, MMD.  While I'm in thanking mode, I should also
express my appreciation to those who gave me some useful clues about
preventing slippage of my Half D-A's control shaft.  Ironically,
as soon as I got some responses to my query, I discovered that
I had exerted enough torque to prevent the slippage.  Inevitably,
however, I will have to readjust the shaft position and that's when
I will try out the suggestions of a leather insert around the shaft
(Ken Vinen), or a copper insert (Malcolm McDonald).

I was going to finish by stating that all this MMD assistance has
prompted me to renew my MMD subscription but I can't immediately.
My wife, Beryl, has lost our credit cards and we are waiting for
replacements.  But in a couple of days that should be rectified;
and no, nobody picked up the cards and raided our bank account.

John Phillips