Assembly clamps

[Rich]

Does anyone use this type of clamp for glueing? What are the pros and cons? Which are the best and/or fastest?

www.stewmac.com/shop/Tools/Special_tools_for:Violin/Violin_Clamps.html

[Michael Darnton]

Two things: Often you have to use local pressure on a rib to get it to stay, or to push it around to precise position, and second, not all violins are as flat as the clamps. The result is that if you're lucky, these work, but they don't provide the necessary adjustment needed in many situations. A set of spool clamps will cost about the same, and be much more useful.

[Rich]

Are those Herdim clamps actually worth the extra money? Are they that much better?

[Andres Sender]

I imagine they would be, but I can't justify the cost. I hate to admit it but I've used spring clamps with little pads in my time.

I think the shop-made clamps shown at Michael's site (the viola-making sequence) are the way to go.

[DelDuca]

The last time I was in Germany I brought back a set of the Herdim clamps. I love them and wouldn't use anything else. They were worth the money to me.

[Singingmaple]

I know that Dov was trying to get some of those Shop made clamps made to sell Cheap. I don't know if he has yet.

[Michael Darnton]

The Herdim clamps are great. Mine are the same thing, only lighter, which is even better.

[John_Jesseph]

Michael, how did you go about making the clamps? I will be ready for some in the next few weeks, and thought about making some. I have a lead on some used Herdim clamps, but might make some like yours if I can figure out a way to easily rout the shapes. I thought about making curved pieces and routing the rabbet and groove, then cutting off the individual parts. If I get the Herdims, then I can postpone for a while, although at some point I would make some lighter wooden ones...

[Brad Dorsey]

"Are those Herdim clamps actually worth the extra money? Are they that much better?"

I think the answer to this question could depend on whether you're primarily making new instruments or repairing old ones. The big advantage to this type of clamp is that it bears directly over the rib, rather than at the high point of the edge which is usually outside the rib. In making, the wood is fresh and strong, and it can probably withstand the clamping force being exerted a little outside the glue joint. But in repairing old violins, the wood is often old and weak, with repaired cracks and edge replacements, and it would be a lot more important to have the clamping force bearing directly on the ribs. The Weisshaar book says spool-type clamps "exert pressure on the ridge of the edge: this can pull the edge down over the rib, break the edge loose from the purfling and even cause deformity of the arching near the edge."

When I was starting out, the Herdim clamps seemed like a huge extravagence, so I made the set I am still using from acrylic (Plexiglas). It took me three days.

[DougP]

You can make a large number of spool clamps cheaply in the shop with a little effort. Buy a 1 in. dowel at the home center, as many 1/4 in. diameter 4 in. long bolts as you need, and wing nuts and washers to fit. Cut the dowel off at 1/2 in. intervals, round the edges glue on a circle of cork gasket, and drill the holes. The dowels come in lengths of 36 inches, so one dowel will make a bunch of clamps. Total cost is 10-15 dollars.

[Michael Darnton]

I didn't make my clamps: a friend did. He made them on a large lathe, cutting the appropriate series of grooves and rings, and then cut apart the individual pieces, but you could also use a router and trammel point to do the same thing. He set up a bunch of jigs, and made four or five sets all at once.

[Regis]

I've made and bought spool clamps but after reading Brad's post, I would do a little different. I would drill off-center for one thing. Then, I would saw or sand (belt sander) a step on each spool so the clamp could reach over to the rib. Wouldn't take much longer. And I may just re-do some of mine if I have enough room from the bolt.

Regis

[Rich]

Would you mind sharing a clear picture of several of your clamps, Michael? Or better yet, some dimensions?

[Michael Darnton]

I can post a photo later, but this shows everything you need to know, I think:

I just read a cool tip for making spool clamps: cutting them out of a board with a holesaw. I think I'd put the cork on one side of the board, first, too. One step, then thread them on bolts. I like it.

[Rich]

How many different radius's do you use? or are they all the same for the outside radius and all the same for the inside?

[Michael Darnton]

Yes, there are three types: outside, inside, corners. In each type, there's only one radius. My friend also made a couple of shortie outside ones, for extra pressure inlittle areas, or filling gaps.

[Michael Darnton]

I just found a huge bump in my webpage stats, and tracked it down to a request for figuring out the various pieces of these clamps, so I'd better explain them better.

The lower part is bored so the threaded rod screws into it. There's a larger counterbore that's a slip-fit for the brass rod, which is then glued in place in the counterbore. On the top, the small hole is larger, so the threaded rod can slide through, and there's a similar counterbore with the tubing glued in. The tubing is to keep the threads from damaging the violin edges. So there are four things: wood blocks, appropriately grooved to fit the edges, with leather on the gripping part, tubing that's a snug, non-binding, slip fit over the threaded rod, threaded rod, and the nuts on top.

All the metal is hardware store standard stuff--tubing, threaded rod, and nuts, though these exact nuts might be difficult to find.

[Brad Dorsey]

The clamps I made are just like yours, except I made the heads out of acrylic rather than wood. I put bushings made from brass tubing in the movable heads so the holes wouldn't wear bigger, and I used flat head screws instead of threaded rod. All the stuff is available at hardware stores. The nuts are called thumb nuts, and they were the hardest thing to find. Each store I went to had a few, so I had to go to several stores to get all I needed.

[John_Jesseph]

Sorry! It's a pretty busy site, probably got a few hundred hits from it. I hate to bother with simple questions...

[Michael Darnton]

In a perfect world all the woodworkers on that site would backtrack the picture, find my site, and all buy violins from me. :-)

[John_Jesseph]

I backtracked the pig, never did figure out what it had to do with the host site...

Thanks again for sharing the clamp info!

[jackc]

I haven't been able to find those knurled nuts in my little burg of William. I tried Jenks Hardware in DC, but they've been reduced to a shadow of their former selves.

Lee Valley sells an interesting variation, with an oversized, slightly off vertical hole. The nut will slide on the threaded rod until is bumps up against the clamp head, then as it's forced to vertical it starts to grip the thread. Sort of a speed nut.

I've bought four of the Herdim clamps, expecting to slowly build up to the required number, but now they are really expensive, so I'm going to buy a pile of the speed nuts and get busy on the lathe.

What's the wood in yours, Michael? It looks dark like mahogany, but that wouldn't seem very strong...

[Michael Darnton]

I didn't make them. I think it might be cherry.

For the nuts, check http://www.mcmaster.com for "knurled nut".