In response to John Tuttle's question about MDF, I am guessing that
there will be a lot of replies.  I use MDF in the construction of
my vacuum electrification kits and have found that there are wide
variances in the quality of the material.

I have bought dozens of sheets of MDF from the 'big box' lumber
stores and it seems each time I purchase it, the material is different.
Sometimes it has a yellowish look to it and others it is a pinkish
brown.  It must have to do with the type of wood they grind up to make
it, but it affects the strength to a great degree.

MDF is very dense, and is great for making the suction boxes as it
deadens sound better than any other material.  But as far as strength
for putting screws into, it is not much better than cardboard.

Gluing material to the edges would be nearly impossible as it is so
porous that almost all glues would soak in before you could put the
pneumatic cloth on.  I cannot imagine that one could successfully glue
cloth to it.  Since the MDF de-laminates so easily, it seems as though
cloth would pull it apart.

To try to use MDF for pumping bellows would be a disaster, too, since
the screws that hold the pedal assemblies would eventually work their
way free.  I have to be very careful when I build the suction boxes
as the screws strip out so easily.

Plywood is so much better suited -- it holds wood screws well and glue
sticks to it.  MDF sometimes costs more, so I can't see any reason to
use it in restoration work of pump assemblies.

Respectfully submitted,
Eric Bergstrom - PianoPro Service
Grand Haven, Michigan
http://www.pianoproservice.com/