Gareth Magennis wrote in message
...

"Gareth Magennis" wrote in message
...

"N_Cook" wrote in message
...
2 of the keys are sticking, because the plastic has warped with time or
temperature. Instead of internal dimension of 18.7mm the underside open
width is now about 18.3mm where it abuts the static pillar and rubs
against
it. Any recognised safe method of locally heating or something that
will
accurately realign the plastic and retain reformed shape? the throw on
one
side is likely different to the other side so needs taking into
account.




I have tried heating deformed keys with a hot air gun, and found it very
difficult. If you are very careful you can just about pull things into
a
different shape if it is fouling something, but I found heating of a
large
area often reults in the plastic shrinking and the key becoming too
short
to fit/work at all. Different plastics may have different properties
though, these were old Roland keys no longer available.

Also there seems to be a fine tolerance between getting the plastic
pliable enough to remould, and so pliable it runs into a goo, which you
have no hope of moulding back to shape. A temperature controlled oven
is
probably your best bet,k and you will need a lot of practice on
something
disposible first.



Gareth.




Oh, and boiling water is not hot enough unfortunately.



Gareth.



Just short

Using my ceramic block method, melting point around 105 to 120 degree C.
Opened up one side about .1mm and worse sticking although the "correct" side
to compensate , but more convincing now a rotation problem along the key
axis. I'd just allowed the key to rotate more. Hopefully such slight melting
will be recoverable now real reason of failure found.
I'd noticed these keys removed and replaced easier , and didn't seat well,
than the good keys so now assumed a wear problem at the pivot end. Found
some ball bearings to take measurements from good and bad key recesses with
Vernier callipers. Cleaning off the grease inside , a part of the pivot end
housing broke away. I've previously repaired Yamaha keys on a different
piano that had been kicked over - moulding repacement sections as original
flaked off parts missing in the original incident.
This one must have been cracked but holding together enough to use /remove/
replace but not locally clean. The other one on very close inspection a
short crack visible and stressing remainder opened up more of the crack.
Will capilliary superglue and reinforce with "hot melt soldering" in the non
contact areas of both key breaks.
Crack on one face allowing the key to rotate on the pivot slightly, then
rubbing action at the play end.