How they are made !

After all the speculations I will tell You several ways to make a repeater gong.
All this informations are not speculations, this are the actual methods!

Materials:

1 - Todays gongs are made of fine steel like swedish steel.
2 - Old gongs are sometimes made of copper alloys like: german silver, bronze or similar.
3 - IWC made tests of making them out of sapphire or glass. (Sound is too fine)

How to make them:

1 - Soldering: most of todays gongs are piano wires soldered with silver soldering in holes of the gong feet.

2 - Rare gongs are first machined to a approximate form, then drawn to its final wire size and then bend to fit in the case. Like soft steel wire don't sounds, they needs a hardening, this means heating to about 800?C (cherry red) and droping them in oil at ambient temperature. Cleaning. Tempering at about 300?C for a half hour and polishing to remove the dirt of the heat treatment.

3 - Modern gongs, like in IWC repaters, are are laser welded piano wires on steel feets.

Note: the story about the urine of a horse is true.
Reason: Tempering in horse urine is like hardening in amoniac atmosphere and it results a nitrated steel.



Andreas Strehler, the Watchmaker