One-Handed Cam Clamp

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Project by GnarlyErik posted 11-20-2012 03:10 AM 10882 views 53 times favorited 19 comments Add to Favorites Watch

Universal One-Handed Cam-Clamp Design

It is very handy to be able to clamp something with one hand while holding it with your other hand, mouth, leg, foot, etc. Old-style boat builders make many of their clamps, and some are very specialized, for ‘deep-reach’, single purpose, etc. Here is a one-handed version to share with those who like to make their own clamps. Most homebuilt clamps are made of wood, but other structural materials could be substituted. Wooden clamps do not usually generate the clamping power of a metal clamp.

This style is intended to make its initial ‘grab’ by cam action, then additional pressure can be applied by a wing nut on a threaded rod or modified bolt. Almost any size desired is possible, so long as some general parameters are followed. First and most obvious, the wood must be suitable – a sound hardwood like oak, ash, hickory or maple, with the grain parallel to the throat of the clamp is needed. Secondly, the width of the clamp arms should be at least 3 times the width of the broach (slot) needed for the threaded rod. The rod itself should be robust enough to handle the load – I use 5/16” -18 TPI or 3/8” – 16 TPI with appropriate sized wing nuts for my 3-6” throat clamps.

The rod anchor point should be about 5% (or more) past the centerline of the distance between the clamp hinge point and the jaws, towards the hinge point. The anchor pivot should be low down in the meat of the lower arm to avoid weakening in the arm. The radius of the curve for the cam section of the arm should be shorter than the length of the working part of the rod by 5% to 10% or so (the shorter in relation, the more jaw movement). The sketch shows the overall arrangement. Patterns from stiff cardboard are made to play around with to be sure everything works together properly before you commit to stock. Patterns are a must for making multiple copies in any case.

The hinge is anything that works. Leather tacked to each arm serves, as do actual cabinet hinges. There is little or no strain on the hinge as all the pressure is on the contact point of the two arms. Short pieces of steel flat bar with the ends radiused, and pinned to each piece will serve, but your must be careful on jaw alignment. The hinge should be centered on the desired jaw opening so that the jaws align with each other in action, both up and down and crosswise.

Arms are as long as you wish for deep throat clamps, by locating the rod further towards the hinge, but your leverage (jaw pressure) will be correspondingly reduced. The jaws may be fixed, or movable to align with irregular shapes. There are several ways to make them moveable, but watch to be sure they end up where you wish in action. (see photos). I am thinking of making myself clamps with hard rubber balls as jaws to use for delicate work for example – I just have to figure out how to hold the balls to the arms.

In use, the wing nut is roughly adjusted to close to the size needed. Then the clamp is applied to the work and the rod and wing nut pushed up the shoulder of the top arm of the clamp with the thumb. When the clamp has ‘grabbed’ sufficiently to hold things in place, the wing nut is then used to apply more pressure on the stock.

I usually put a little grab handle thingy on one arm of the clamp to hold on to in use, and this can be on either the upper or lower arm.

-- "Never let your dogma be run over by your karma!"

19 comments so far

View a1Jim's profile


118296 posts in 4860 days

#1 posted 11-20-2012 04:03 AM

These are way cool Erik,Great job.


View HillbillyShooter's profile


5811 posts in 3576 days

#2 posted 11-20-2012 04:44 AM

These are really neat! Thanks for sharing and for the great write up. Are the drawings available anywhere?

-- John C. -- "Firearms are second only to the Constitution in importance; they are the peoples' liberty's teeth." George Washington

View GnarlyErik's profile


366 posts in 3418 days

#3 posted 11-20-2012 05:07 AM

HillbillyShooter – see my sketch in photos section . . .

-- "Never let your dogma be run over by your karma!"

View dakremer's profile


2771 posts in 4375 days

#4 posted 11-20-2012 05:27 AM

I don’t quite get where the cam action is coming from…

Any chance of a video of it in action. I just don’t get how it clamps without screwing down the wingnut

-- Hey you dang woodchucks, quit chucking my wood!!!!

View Dennisgrosen's profile


10880 posts in 4398 days

#5 posted 11-20-2012 06:25 AM

nice to see a new design :-)
looking good .. and a great instrution
though I have to agree with Dakremer
how does it clamp with pressure with out using the wingnut

take care

View Oldtool's profile


3354 posts in 3474 days

#6 posted 11-20-2012 01:22 PM

I too, like Dakremer and dennisgrosen, couldn’t figure out the one hand operation, until I noticed the slot in the upper arm. Your good description led me to look for that. Perhaps a top photo would clear things up a bit.
Thanks for showing, these are cool.

-- "I am a firm believer in the people. If given the truth, they can be depended upon to meet any national crisis. The point is to bring them the real facts." - Abraham Lincoln

View balidoug's profile


535 posts in 3762 days

#7 posted 11-20-2012 02:24 PM

Many thanks for a great clamp, and many more for including the drawing.

-- From such crooked wood as that which man is made of, nothing straight can be fashioned. Immanuel Kant

View GnarlyErik's profile


366 posts in 3418 days

#8 posted 11-20-2012 03:15 PM

I apologize for not being more clear in my write up about the camming action. The rod with the wing nut rides in a slot cut in the upper armed (see drawing where it is labeled ‘broach area’ – last photo). The rod is swung back in the slot in the open position (photo 1) and pushed forward on the shoulder of the curve with the thumb to close the jaws (photo 2). So long as the radius of the curve on the arm’s shoulder (between the rod pivot point and the curve) is LESS than the length of the distance of the rod between its pivot point and the wing nut, the curved shoulder acts as a cam to close the jaws enough to grip, then the wing nut is tightened to apply additional pressure. In the example pictured, there is only about 3/8” – 1/2” cam distance, but more can be had by making the radius for the curve in the arm shorter. See text of the original write up.

It helps to note the difference in positions of the wing nut in the first two photos. I hope this helps to understand!

-- "Never let your dogma be run over by your karma!"

View Ken90712's profile


18081 posts in 4472 days

#9 posted 11-20-2012 04:31 PM

Great job, a really cool tool… Well done.

-- Ken, "Everyday above ground is a good day!"

View Mauricio's profile


7168 posts in 4435 days

#10 posted 11-20-2012 05:40 PM

Brilliant! I love shop made clamps. Thanks for sharing!

-- Mauricio - Woodstock, GA - "Confusion is the Womb of Learning, with utter conviction being it's Tomb" Prof. T.O. Nitsch

View OregonWoodRat's profile


174 posts in 3570 days

#11 posted 11-20-2012 06:33 PM

Thanks for the write up. Also thanks for explaning the cam action. It is much more clear now. I think I am going to try making some this weekend.

-- Peter, A man convinced against his will is of the same opinion still.

View Von's profile


238 posts in 3496 days

#12 posted 11-20-2012 08:35 PM

just the other day I was thinking about a very similar clamp design. but you have this nailed down already. I might just have to uh… borrow… your design here. hehe

View Dennisgrosen's profile


10880 posts in 4398 days

#13 posted 11-20-2012 09:47 PM

got it … thanks Erik

take care

View Ivan's profile


17049 posts in 4151 days

#14 posted 11-21-2012 06:45 AM

It’s always nice to see home made inspiration.

-- Ivan, Croatia, Wooddicted

View Dutchy's profile


4215 posts in 3452 days

#15 posted 11-21-2012 04:22 PM

Thank you for sharing. When there is time I am also making a couple.


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