Messages Archive

Subject:
A discussion of panel clamps *PIC*

Bill Tindall, E.Tn.
A discussion of panel clamps

With the exception of pipe clamps, I don’t expect anyone to junk the panel clamps they are using. Hence, the purpose of this discussion is to inform someone new to clamping needs the merits of the choices available. If what you got works for your needs, and you got all the clamps you need, read no further.

Panel clamps are used for gluing up pieces of lumber to achieve more width, a table top for example as shown in Picture 1. Franklin, maker of Titebond, recommends 100-200 psi on the joint, depending on the wood species, for optimum joint assembly.

This large span of this same kind of clamp is also used in assembling case work, as shown in PIC 2.

Or they may be pressed into service when it is all hands on deck and the supply of F-style is insufficient, PIC 3.

There are at least 4 styles of panel clamps- steel I-beam, aluminum channel, parallel jaw Bessy type and pipe. When I began woodworking in the 70’s they only panel clamp you would find in professional shops were the Hargrave I-beam clamps made by Cincinnati Tool Works., shown on the left in Picture 4. They remain stiff even under maximum pressure which is something more than 2000 psi. A 2’ clamp weighs 7 pounds, a substantial disadvantage when using them for case assembly, but not a factor when assembling panels, the task they were designed for. Unfortunately, they are no longer made, but because of the vast numbers that were made they show up in used tool markets.

There are numerous aluminum channel clamps available ranging from the cheap in-every-way Harbor Freight clamps to the industrial quality clamps originally made by Universal Tool Company, the clamps shown on the right in Picture 4. These clamps were designed to hold up in industrial woodworking environments. I was told by the company owner that his industrial customers tightened them with air wrenches just like they did on panel assembly clamp stations, but probably not at the same air pressure. The rights to manufacturer these clamps was transferred to the Dubuque Company after Universal lost their casting operation that made the heads. At one time I could buy these clamps from Dubuque if I ordered them in case lots of 10 clamps. I bought dozens for club members. This wholesale price was about half retail. Lee Valley sells this clamp, but not in all the sizes available from Dubuque.

Rated at 1000 psi they are adequate for panel gluing 4/4 lumber. They are nimble to handle. It is easy to grab 4 at a time from the clamp rack. Where they excel is in case assembly operations. At ¼ the weight of I-beam clamps their weight doesn’t distort what is being clamped into squarness nor add so much weight that moving the result is difficult. The fact that these lightweight clamps can be manipulate while holding just the screw end is advantageous when clamping up drawers and the like. These are my go-to panel clamps.

Probably the most popular clamp is the parallel jaw Bessy style clamp. I own two of this kind of clamp (Jorgensen) and almost never use them because I have not found any advantage they have over the I-beam or channel clamps. In my hands his clamp is substantially more difficult to adjust to length. It would seem that their smooth, large parallel jaws are their primary advantage. This feature could be advantageous in some case assembly. It offers no significant advantage in panel assembly. These clamps weigh about 4X the weight of the aluminum channel clamps making them substantially less nimble, especially in case and drawer assembly. They have about half the load rating of steel I-beam clamps, making them marginal for assembling 8/4 and thicker panels. On the other hand the tightening handle enables them to be positioned close to one another to accumulate adequate pressure.

The least expensive, and least useful, panel clamp is the pipe clamp. They are difficult to adjust and the pipe will flex under load well short of proper panel assembly pressures. They are heavy for case and drawer assembly.

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