Saturday, September 20, 2008

Pneumatic Circle Clamp

Today some friend were visiting the shop and I had just finished clamping veneer lines onto the inner edge of the soundhole with a balloon. This technique is so simple, but it's also totally ideal for this situation. The pressure is finely adjustable, the "clamp" is extremely lightweight, the rubber is soft, it won't mar the veneer or distort the shape, the pressure is perfectly distributed around the circle, the clamp is almost free and disposable. I get a kick out of this technique every time I use it. But today I didn't get the last laugh. While my friends were in the shop I stepped out for a few minutes, but it was long enough for them to get into some mischief while I was gone. And that's what worried me. I never keep soundboards clamped in the open air like this when someone else is in the shop (or even when I'm in the shop, for that matter), so naturally I was thinking about the safety of the soundboard for those few moments, especially with half a dozen people milling around. So as I step back into the shop, I hear "what's happening with this balloon setup" followed by a loud pop and shreds of yellow rubber flying through the air. My heart skipped a beat, and an entire day of carefully fitting the rosette flashed in my mind. Once the raucous laughter settled down, I realized I'd been fooled, and then I started cracking up too. I'm still trying to figure out how they found another yellow balloon so fast.


  1. Wow, that's intriguing! I don't think I completely understand what you're clamping. In the second picture, the balloon doesn't have contact with the entire inlay.? Was that placed and glued first and what you're gluing is the most inner circle? How'd you keep it from slipping, Tape?

  2. The tiles are glued into a mortise along with one line of .025" wide walnut. Then the soundhole is cut out. To complete the rosette, I glue in another line of walnut to the inside of the rosette. This is the line that the balloon is clamping. If you click on the picture you can see some squeeze-out between the inside edge of the tiles and the line.


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