John Phillips had the same technique I have often used, myself to
fix damaged wood screws. But I also have a few more I'll chip in.

   A really slick way to fix threads that are weakening but will still
hold to a degree is to first spray the screw with mold release. Next,
soak the screw hole with Hot Stuff. That's an alpha-Cyanacrylate super
glue. Then while the hole is still damp, screw down the screw and leave
it a moment. remove it, and you have a screw hole that's as strong as
iron.

   Another slick trick when a screw hole goes all the way through a
thin piece of wood, is to use hot hide glue and a loop of thread or
string. Poke the loop through the hole after gloping it in some hide
glue, then screw the screw back into it, holding the end of the thread.
Cut off the remainder. No mold release is necessary.

   When you're trying to mount the pedals on some of these Aeolian
grands whose pedal screws have stripped out, Use a good, hard epoxy and
steel wool. Lube up the screws and screw them into your matted epoxy/
steel wool, with the fibers of the steel wool running with the hole.
Screw them up into the holes about 1/4" deeper than you'll need them to
go, but no firther than that, and just let it cure for 24 hours. Get
really hard. That stuff is as good as steel inserts for machine bolts.
Makes perfect threads. By the way, coat the hole first with epoxy, then
smush the epoxy through your steel wool, and then start forming the
matted steel/epoxy over a smaller dowel that is able to stick the whole
mess up into the holes in one plunge. After the screws have taken a
good grip and you have enough to be sure of a strong, tight bushing,
spread the excess matted wool out over the keybed and chop it off flush
before it dries hard.

   Another way I fill small screw holes is by using the flat
toothpicks. Find the depth of a hole first by sticking a toothpick down
into it. Where your thumbnail is, from that point on the toothpick,
subtract the thickness of whatever board you are screwing down, so your
stuffing will be below its sealing surface. Dip the toothpick into hot
hide glue, stick it down into the hole, push it the rest of the way
with the screw, and tighten it down. This way, when you remove the
screw again, your filler doesn't fall out with it.  The glue also
unites with the wood dust in the hole and makes a very good, tight
hole. Make sure you have enough glue and it is thin enough to do that.

Craig B.