Reimagining the C-clamp

The C-clamp is to the job shop as silverware is to dinner. The tool has worked the same way forever. It’s just there, an unchanging and almost timeless part of the workbench, and it works well enough. But for Mike Costen, it didn’t.

“I’ve been a structural analyst for 30 years, working on aerospace products ranging from rockets and satellites to aircraft,” he said. “Engineering is my passion. Designing things and getting things made has always been part of my DNA.”

It’s that DNA that led him to question the age-old clamp in that quintessential laboratory of good manufacturing ideas: his garage. He was building a lightweight tabletop, made of wooden boards salvaged from skids. It was a wedding gift for his son, and he had trouble lining up the edges after all the boards were planed to the same thickness. Traditional C-clamps just didn’t do the trick; they didn’t have the clamping power he needed nor the reach. There had to be a better way.

At first he developed a kind of “press clamp,” with two long clamping mechanisms that extended several feet from the screws, giving him the reach he needed to hold down the board. The long-reach clamp sparked an idea: The market for such specialized clamping was far too small, but would this “reach” design apply to the standard C-clamp, a product with an extremely broad market?

Being a tinkerer, Costen was always having parts made in and around Milford, Conn., so he knew a lot of the local machine shops. “Everybody at these machine shops seemed to complain about these little handles [on C-clamps] and the fact they could never get them tight enough. And sometimes it was painful when they tightened these clamps manually.”

As Costen saw it, the C-clamp has two fundamental flaws. First, its very shape works against the goal of actually clamping something. Its stress and load characteristics basically make physics work against you. Second, the screwing mechanism is inefficient; the screw moves down only in one direction, and the small handle makes turning the screw a bear. You don’t have much leverage.

“The screw is guided at only one point,” Costen said, “and if you start loading it up under too much load, it goes off-center and then bends. And the frame of the C-clamp could also be done better. It’s fine for low loads and cases where time is not that important. Opening and closing a C-clamp is time-consuming.”

Being a structural analyst, he relied on, well, analysis—specifically, finite element analysis. “I made a computer model of the clamp. It applied force [virtually] just like it would be applied in the real world. The software showed me where the stresses are high,” Costen said. “So basically, I added material where the stresses were high, and the shape evolved based upon that, while paying attention to reach, grip, and clearance.”

What he ended up with was a product that morphed from a C-shape into a clamshell, combined with a central, double-seated screwing mechanism. The screw-assembly design at first incorporated a ratchet-driven turnbuckle with two threads—a good idea, but manufacturing a ratchet into every clamp would be costly. So ultimately Costen decided on using a simple hex, which could be turned with a ratchet or any driver, including breaker bars, torque wrenches, and impact wrenches.

The screw closes from both directions, like a clamshell snapping shut—though this clam happens to exert more than 5,000 pounds of force. Costen added that the screw, being in the center of the clamp instead of at the edge, also helps give the clamp better reach.

The clamp’s enclosure is sheet metal that can be stamped and welded, while other components are cold-headed and riveted. “Stamping is an old process, but it’s very time-competitive,” Costen said. “The amount of time it takes to stamp out just one part is minimal. All these processes are very fast and very proven.”

As of this writing, Costen’s new company, Dimide Clamps, has produced fabricated prototypes in low volumes. The clamps also have been tried and tested at various job shops. “Its load capability and endurance have all been verified,” Costen said.

As of November, the company is using Kickstarter to obtain funding that will put the clamp into production and bring it to market. The campaign was set to launch Nov. 16.

So why does the clamshell shape work so well? As Costen put it, that’s where the FEA model showed how he could attain the most clamping force with the least amount of time and effort.

Is it pure coincidence that it looks a little like a clam? Not really. “Mother Nature has had billions of years to optimize things,” Costen said, “and she’s done it. With the finite element analysis, we’re able to figure out that shape too, and we came to the same conclusion Mother Nature came to.”

Dimide Clamps, 203-745-6496, www.dimideclamps.com