Violin Bow Maker’s Cam Clamp
I built this clamp for a violin bowmaker who had lost the use of his left hand and could no longer hold a blank against the force of a plane or scraper.
The clamp had to quickly grab and release different size blanks anywhere along their lengths and let the bowmaker rotate the work to put one or another surface up. The clamp body also had to rotate to allow the bowmaker to position the work wherever he needed it along the workbench.
I made a prototype cam clamp in a couple of hours and verified the idea with a luthier friend. It took 2 weeks to work out the design details and build. It’s mostly made of glued up and machined MDF that I soaked with varnish and sanded several times.
The cam is held by a block with a threaded insert that rides on a screw to change the distance between the cam and clamp block.
You can see the underside of the cam below the block and part of an interrupted circular groove that limits how far the cam can rotate in either direction.
I made the adjusting knob from an old knurling wheel I had.
The resistance the clamp assembly offers to rotation is controlled by the pressure applied by a screw and spring against a leather covered brake shoe.
Both the cam and clamp block have leather faces that are dusted with violin bow rosin to improve their holding power.
The clamp worked well but the bowmaker I made it for only used it for a short time before stopping work. Now it’s back in my shop, waiting.