Greetings,  I definitely agree that the best way to repair a stripped
screw is to replace the damaged section with a plug which is held in
place by more than glue, which can creep or fail.  In a fine or rare
instrument for which the cost of repair is of no concern this is what
should be done.

My suggestion of using longer or fatter screws assumed that clean
undamaged wood would be securing the new screw threads.  Cramming a
longer wood screw into cracked wood is only making the situation worse.
That is why I specified drilling a pilot hole for the new threads and
making sure that you know that the screw is going into wood.  It is not
going to be a permanent repair, but neither was the original design or
it would have lasted.  It is easy to blame careless rebuilders and
there certainly are plenty of them but a proper design will allow for
disassembly and repair without stripped screws.

The use of a fatter screw also requires a proper pilot hole that
removes the damaged wood.  If the wood is not cracked, then a larger
screw, when permitted, with a proper pilot hole, is just as strong as
if it were originally installed as a larger screw.  If there is not
enough room for a properly installed larger screw then this is not an
option.

I guess I made the mistake of assuming that a brief mention of a proper
pilot hole was enough.  What I should have said was: If it is possible
to remove the damaged wood by drilling it out with a drill that produces
a clean properly sized pilot hole for a new screw, of a different length
or diameter, then this is a reasonable alternative to replacing the
damaged wood with new wood or other material that will hold the original
screw.

Although not suitable for instruments which are to be restored to
pristine original condition, the use of sheet metal screws often makes
it feasible to provide at least a portion of a properly sized pilot
hole since the sheet metal screw does not have a substantial portion of
the hole wasted by the shank which does no holding.  Since the diameter
of the screw is not tapered, it is possible to have a larger portion of
the thread in undamaged wood.

In applications where parts are to be disassembled repeatedly, for
adjustment or maintenance, it is inexcusable to use wood screws.  If
this is the case, it was a bad design to begin with and the screws
should be replaced by machine screws and threaded inserts.  The
original use of wood screws was a cost savings measure for an
instrument that was not intended to survive indefinitely.  Today we
often have to either replace cheaply make parts or modify them.

I often wonder what the restorers of the future will have to do with
the things we make today.  I am sure that human cleverness will evolve
as it has so far and that people will be restoring, as treasures,
things that we consider to be disposable today.

Best regards,
Spencer Chase
Laytonville, Calif.
http://www.spencerserolls.com/