I tried the collar approach to Duo-Art Cross valve modification a while
ago without success.  Teflon is one of my favorite materials for all
sorts of uses.  I have at least four types of Teflon which I tried
using.  Unfortunately the types I tried did not lend themselves to a
press fit for a part this small.  Teflon is quite elastic, in most
grades, and is more likely to slip than stay pressed on.  The harder,
filled types are too brittle to use for a part this small.  Fluting
the valve shaft might help to hold the collar but this would be
difficult.

It was my thought that the problem is more a matter of finding the
right leather than worrying about rotation of the valve.  I have a well
playing cross valve piano now that had it valves redone quite a while
ago and they are showing little depression of the leather nap.  I would
like to replace these as they do leak a little but I could not find a
suitable leather in the right thickness.  I wanted to try kangaroo, due
to its toughness but it seems to be available only in relatively thin
hides.  If anyone has a source of the perfect leather for these valves
I would like to know what it is.

I have found some thinner leathers that seem suitable, a very nice
kangaroo and a velvety but firm kid skin.  I made a die for my punch
press that will punch washers of the two different cross valve sizes
and was planning on laminating this leather onto a .010" thick epoxy
board to make a thicker stiffer valve face that would not warp.
I have tested the process and it works well but I have not installed
these valve faces in a piano yet.

If anyone is interested in trying these leather/epoxy disks in a
Duo-Art, I will make a free set with your leather.  The glass
reinforced epoxy board is quite stiff and makes a good press fit to
the valve stem.  It might even be possible to make a fluted positioning
piece of a suitable material that can be glued on top of the leather to
prevent rotation of the valve.  I think that a tight grained hardwood
might be best.

I have been wanting to experiment with these ideas before my stack
needs rebuilding and would like to work with anyone who has similar
interests and ideas.

Spencer Chase
http://nt.mcn.org/spencer/