Because of the brittle nature of chinese B20 I was rather hesitant, especially because the process would also involve cold-hammering a cup, which is always a risky procedure with B20 alloy.
But he insisted and was prepared to take full responsibility if anything went wrong.
Luckily it didn't.
The gong appeared to be not round, extremely irregular in thickness (yes, typically chinese), very lopsided and full of really deep "lathe chatter", so I had to get rid of all the thickness irregularities. This cannot be done on a lathe, so I actually had to grind down the whole gong to the thickness of its thinnest spot, so the whole gong would be of a uniform thickness. Just doing this took several hours.
First I hammered a cup, drilled a hole, did some initial bow hammering, then I grinded away all the thickness irregularities, hammered the bow in various sessions (with several lathing sessions in between the hammering sessions) and finished off with a patina-treatment and a little extra lathing.
The weight was reduced from over 1600 grams to roughly 1050 grams. It's now a 16" dark trashy crash.
Here's a BEFORE AND AFTER clip/
http://users.telenet.be/cymbzdrumz/RECR ... _Crash.mp3
Some pics of the process:
