Following the thread on metals used in Polyphon disks, at an auction
I purchased a portable 9" Polyphon along with a dozen disks which had
been nicely wrapped in paper and taped up securely.  The auctioneer
assured us there were 12 disks and they'd been wrapped for protection.
Can you see what's coming?

When I unwrapped the disks they had been stored flat -- under a steam
roller!  Most of the projections (tabs?) had been squashed flat or bent
over 180 degrees.  To make matters worse, they were brittle zinc disks.

To restore them I used a leather worker's sharp pointed probe to
carefully open up and reshape the tabs that could be saved.  A small
screwdriver with the end ground to a point and a thin knife blade,
etc., would have worked.

To get the triangular shape of the tabs right I used a small triangular
file of a convenient size under each tab and gently pressed and poked
them back into shape, matching the shape of the few good tabs.

Now, because the disks were zinc and quite brittle, I checked each tab
with a magnifying glass for any signs of cracks.  This restoration
method only worked for maybe half the tabs (and for 12 disks that's
still a lot of time and patience needed) and the rest of the tabs were
either missing, cracked and too far gone, or I broke them off anyway.

So, from a hobby shop I obtained a narrow strip of beryllium copper of
similar gauge to the zinc, and carefully filed the excess width down
until it was about the same width as the tabs.  I made up a V-shaped
die from a couple of pieces of 1/2" square steel.  I just filed a V
notch into one piece and a male V shape on the other.  The Vs had to be
a more acute angle than the tab because the copper strip tended to
spring back a little.

Like :

            |_ _|  Male top punch
              V
  --------------   strip
             _ _
            | V |  Female bottom punch

 [ This "ASCII art" must be viewed with a monospaced font such as
 [ Courier, or it won't look sensible!  ;-)  -- Robbie

I then just aligned the strip under the die and gave it a whack with a
small hammer.  Then I used jeweller's snips (small and sharp) to trim
the excess length of each new tab.

Once I had a few dozen little tabs, I soldered them onto the disks
where required.  I set up a piece of timber with a pin in it for the
disk to pivot on, upside down, and used the male V punch from underneath,
poking through the slot where a tab was missing.  I clamped the punch
in position to the timber support because I didn't have the hands of an
octopus.

For each note, I could rotate the disk to each location that needed a
new tab.  Then I could reposition the punch to a different radius
(musical note) and do it all again.  That made it much easier to align
the new tab and I could hold it down whilst soldering.  I used electrical
rosin core solder.  After everything was okay I washed any resin
residue off with a solvent.

I didn't lacquer the disks, which might have been a good idea to
forestall oxidation of the now clean surfaces, but I thought excess
lacquer may be scraped off during playing, into the mechanism.

The width of the tabs and exact shape are probably not critical but I
tried to ensure that the side of the tab that operates the Geneva wheel
was in the same position and angle as the originals so that the notes
sounded at the correct timing.

Now I have a small Polyphon and 12 useable disks to play on it.

And a lesson -- never trust an auctioneer!

Happy Christmas everyone,

Colin MacKinnon