My first glimpse of a Bessey K-body clamp was on PBS's "The New Yankee Workshop." Like many viewers, I said: "I need some of those!" A few phone calls later, we were well on our way to populating the Popular Woodworking shop with our new-found loves.

That was about six years ago, and we've been surprised that there's been little competition in this category. Then, last year, Gross Stabil introduced an improved version of its parallel-jaw clamp, and Jorgensen introduced a new line of this same style. Both are aimed at Bessey. With three different parallel-jaw clamps in stores, we decided it was time to put 'em all in the shop to see how they stacked up.

Why Buy These Clamps?

First, what's a parallel-jaw clamp? Unlike traditional bar or pipe clamps, the parallel-jaw clamp has a flat and wide jaw surface that exerts even pressure along the length of the jaw. The even pressure starts all the way at the back of the jaw, against the bar, and continues out to the end of the jaw mouth. This makes gluing up flat panels a cinch. You can rest the panel on the bar, providing a flat, supported glue-up surface. It also means you can glue up a box and put even pressure along the edge of the joint, rather than at just one point.

Another advantage of all these clamps is they rest flat on your assembly table as you glue up a panel — no rolling or tipping. And once your panel is clamped, you can set the whole thing on end, and your glue-up will stand upright on the outside edge of the jaw. This frees up space on your assembly bench and allows you to keep working.

Details of the Test

To test the clamps, we simply put them to use. You may note that while we've included the reported clamping pressure for each clamp, we haven't compared or discussed this feature in the individual comments. Truth be told, too much clamping pressure will starve a glue joint. Suffice to say that all three of the models have more than enough pressure to perform any clamping task.

Our first clamping test was gluing up a simple, two-piece flat panel. The pieces were positioned to the inside of the jaws, lying on the bar. We looked for flex in the bars, as well as bowing in the panels during this test.

Next, we glued-up similar flat panels with the pieces lifted off the bar, held at the very tips of the jaws, unsupported by the bar. We used this test to look for bowing in the panel, and for any gapping at the joint caused by out-of-parallel pressure.

For a third glue-up, we cut two 1/2"-thick x 3" x 8" pieces of wood and clamped them end-to-end with the width of the pieces running the length of the jaws. We again checked for bowing and gapping at the glue joint.

One last test concerned durability. We dropped the clamps three times from workbench height to see if any damage occurred to the jaws. Finally, to test the durability in extreme shop conditions (or compressing years of use into a few minutes) we struck the most vulnerable corners of each jaw with an 18 oz. hammer three times with mixed results.

Gross Stabil PC2 Clamp

Also made in Germany, the Gross Stabil PC2 clamp is the company's second (and more successful) introduction into the parallel-jaw clamp category. The PC2 clamp uses a high-tempered steel I-beam bar that looks a lot like the Bessey's; but on the PC2, the teeth on the bar are on only the leading edge of the bar, not on all three faceted edges. The jaws on the PC2 are essentially injection-molded high-density plastic forms that are reinforced internally with 1/4"-thick steel bars. The jaws have softer plastic, slip-on pads that are easily removable and replaceable.

The PC2's head can be removed and turned around so you can use the clamp as a spreader. This requires using the outside surface of the top jaw and it isn't all that easy to do. Gross Stabil officials say that a next-generation design will have a fast-release mechanism and a lip on the top jaw so you can move the protective pad to the outside.

The locking mechanism on the PC2 uses slip pressure from the malleable iron lower arm against the toothed bar. The handle on the PC2 is wood, measuring 1 1/8" x 4 3/4", with a spindle length of 2 1/2". The PC2 is available in nine lengths from 12" to 100". The maximum clamping pressure reported by the company is 1,100 pounds. The jaw face measures 1 3/4" x 3 1/2", and a 48" clamps sells for about $45.

The clamp performed well in all three of our clamping tests, exhibiting similar bar-flex in the end-of-jaw position as on the Bessey clamp. The jaw moved easily with little assistance, and it caught quickly when we allowed it to free fall — indicating quick operation with less chance of pinching your hand.

The Gross Stabil performed best of all three competitors for durability. The drop test showed no significant damage. During the hammer test we knocked the corner off one of the protective pads, but when we removed the pad and continued to abuse the jaw we were able to knock off just an 1/8" piece of lip, leaving the clamp in good shape and operable. This clamp is tough.

Bessey K-Body Clamp

The K-body clamp was introduced in 1985 and has experienced only minor changes since then. Made in Germany, the clamp consists of a bar that is a hardened I-beam, a head made from sheet steel and jaw mechanisms made from cast steel. The jaws are covered with a high-density plastic. The clutch mechanism (which provides the pressure for clamping) uses the binding pressure of the jaw body against the bar. This is supplemented by teeth on three facets on both long edges of the bar and replaceable hardened steel screws mounted to the inside surface of the jaw body. The wooden handles measure 1 1/8" x 4 1/2", with about 1 1/4" of spindle length. The K-body is available in eight lengths from 12" to 98". The stated maximum clamping pressure is 1,100 pounds. The jaw faces measure 1 1/2" x 3 3/8" each, and a 50" clamp costs about $44.

The Bessey offered good performance in all three clamping positions. It showed less bar flex in the end-of-jaw clamping position than any of the other clamps in the test. However, the K-body's short spindle travel makes it necessary to readjust the clamp position more frequently.

The K-body held up without flaw to the drop test. In the hammer test we cracked both high-density plastic covers after three whacks, but the cracks occurred along the sides of the covers, not on the jaw face. So the clamp was still usable.

When we let the clamp head free-slide down the bar, it moved rapidly before stopping. This poses a potential for pinching your hands. In moving the head along the length of the bar, the teeth affected the smoothness of the travel, but this is a trade off for the quick grabbing capability of this well-made clamp.

The damage from the hammer blow is obvious on both jaws (right). Again, while I probably wouldn't continue using this clamp, the jaw faces still are intact.

Adjustable Clamp's Cabinet Master Clamp

This is the newest entry into the parallel-jaw arena. Made in the United States by Adjustable Clamping Co. under the Jorgensen name, the bar appeared to be of softer steel than the other two clamps, formed into a figure-eight shaped cross-section. No teeth are cut into the bar. The heads are stamped steel pieces covered in plastic covers, which are peened in position on the underlying steel structure. The locking mechanism works similar to that found in the traditional Pony clamps from Adjustable, with four individual stamped steel plates angled against the bar and held in position by a piece of spring steel. When clamped tightly, the steel plates bite into the bar, making its own teeth. The handle on the Jorgensen Cabinet Master is maple, measures 1 3/8" x 4 1/4" and has a spindle length of 1 3/4". The clamp is available in six lengths from 12" to 48". The maximum clamping pressure reported by the company is 1,000 pounds. The jaw measures 1 7/8" x 4", and a 48" clamp sells for about $41.

There is a quick-release mechanism at the end of the bar to allow the sliding jaw to be turned around to use the clamp as a spreader. An additional (and planned) benefit of the quick-release mechanism allows it to be used as a "kick stand" at the end of the clamp. This keeps the clamp from tipping when using longer clamps for a shorter application, where the weight of the bars lifts one jaw off the table.

As with the other clamps, the Cabinet Master handled the clamping tests well. The bar flexed more than its competitors in the end-of-jaw clamping procedure, but this still didn't gap the glue joint.

The heads moved smoothly during clamping, but reinstalling the head after removal for spreader functions required careful alignment. The clamp performed well during the free-fall test, protecting your hand.

The Cabinet Master didn't fare so well for durability. The plastic covers on the jaw mechanisms are brittle, and while they showed no damage during the drop test, both jaws shattered dramatically when struck once with a hammer, revealing the internal steel and making the clamp unusable.

Conclusion

During our real-world testing, all three of the clamps performed well for routine clamping procedures. The softer, non-toothed bar on the Jorgensen Cabinet Master holds well, despite material differences, but long-term testing will determine if this causes any problems. Though we had some minor concerns on the wear potential in the Gross Stabil's lower arm, this basic clamp design has been used by the company successfully for years. The Bessey's clamping mechanism is well-designed with good materials and has already stood the test of time in our shop.

As for the durability factor, we were disappointed in the Jorgensen clamp. While the abuse applied during testing was a little unusual, it wasn't outside the realm of possibility in a workshop. The Bessey clamp's cracked plastic also was somewhat disappointing, but it didn't make the clamps unusable, and in fact we continue to use similarly damaged clamps in our shop years after the damage. The Gross Stabil performance was impressive. Not only did the replaceable pad hold up fairly well, but the nearly indestructible performance on the inner jaw was very comforting.

The clamps all are priced very similarly (within $4 of one another), so price isn't a factor in announcing a winner. Because of durability factors, we're unable to give honors to Jorgensen. Between the Gross Stabil and Bessey, we consider the Gross Stabil to be a well-made clamp with more features than the Bessey. Both perform well, and if you can find one brand a few dollars cheaper than the other, buy the less expensive one. But in an even price match, the nod goes to the Gross Stabil for durability, versatility and features. PW

Contact Information

Bessey K-body Clamps

800-828-1004 or www.jamesmorton.com

Gross Stabil PC2 Clamps

517-279-8040 or www.grossstabil.com

Adjustable Clamp's Cabinet Master Clamps

312-666-0640 or www.adjustableclamp.com