My cello is making progress, even if rather slowly. I’ve just closed up the box, which is a step that requires a lot of clamps to hold everything in position while the glue sets.
And here’s the problem: where to find enough clamps. One solution is to buy or, cheaper, make spool clamps for the job. But these clamps are less than perfect because the force they exert operates at the edge of the plates rather than directly over the ribs. For clamps that put pressure in the right place, you have to buy a set of the dedicated cello clamps made by Herdim®, which, I’m told, are easy to use and work well. Unfortunately each of the Herdim® clamps costs about 15 Euros, so getting equipped with the 40 or so that are needed for a cello is quite expensive.
Partly out of meanness and partly because I enjoy making my own tools and jigs, I devised this alternative. The photographs make it fairly clear how the clamps are constructed and instructions are probably unnecessary. But perhaps a few details will be helpful. The clamping force is supplied by a wing-nut on 6mm studding. I made at least half of the clamping length out of aluminium tubing so that the clamps were as light as possible. It’s important that the aluminium tubing has an internal diameter only very slightly greater than the diameter of the studding so that the upper part of the clamp slides smoothly, but without play, over the lower part. The clamping pads are mahogany but, of course, any hardwood could be substituted. When making these pads, it’s a better idea to work a rebate into a length of cross grain mahogany and then saw it up than to craft each one individually. The pads are lined with cork that has been glued on in a profile that puts the pressure directly over the ribs. I used polyurethane glue to set the tubing into the clamping pads and to cement the studding into the aluminium tubing but I should think epoxy would work equally well.
The same principle also works for shorter clamps. The one below is designed for crack repairs. Shallow cleats are temporarily glued either side of the crack, which the jaws of this clamp can grip to close the gap.
Finely Strung 
10 Comments
That’s a great solution. I’m sure your clamps are equally good as the Herdim. Thanks for sharing the details.
tico
Hi! Would you be selling those Cello clamps you made?
No, I don’t make them for sale. The idea was to show how easy they are to make for yourself.
Hi –
Did you finish the cork at all?
Those are absolutely lovely!
I used the sort of cork composite that is sold for making gaskets, which has a fine even surface that requires no further finishing. I did however, use some sandpaper to round over the lip of cork that sits in the purfling groove. Hope that answers your query.
Thanks. I’m in the middle of making my own clamps for my first cello repair adventure. They’re nowhere near as intricate as yours, but I think they’ll do the trick.
For the cello clamps, do you think the aluminum tubing is necessary given the profile of the clamping pads? With that design, you wouldn’t be in any danger of the threads chewing up any edges, right?
Also with that diameter of threaded rod, do you notice any problems with flex?
Aluminium tubing was used to save weight. The clamps would work just as well if threaded studding was used for the entire length, but they’d be a lot heavier.
I’m not sure that I’ve fully understood your question about flex. Are you referring to distortion in the clamps, or in the ribs of the cello? But it’s not a problem either way. Only light pressure is required to keep the front (or back) of a cello in position over the rib structure while the glue dries and the clamps never done up more than finger tight.
Hi, your clamps are really amazing! Thanks for sharing! May I ask you about their dimensions? Thanks gianpi
Of course. What do you want to know? Email me at cm.finelystrung.com