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One-Handed Cam Clamp

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Project by GnarlyErik posted 617 days ago 3938 views 48 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.

-- Candy is dandy and rum may be fun, but wood working is the best high for me!





19 comments so far

View a1Jim's profile

a1Jim

112001 posts in 2180 days


#1 posted 617 days ago

These are way cool Erik,Great job.

-- http://artisticwoodstudio.com Custom furniture

View HillbillyShooter's profile (online now)

HillbillyShooter

4367 posts in 895 days


#2 posted 617 days ago

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

GnarlyErik

179 posts in 737 days


#3 posted 617 days ago

HillbillyShooter – see my sketch in photos section . . .

-- Candy is dandy and rum may be fun, but wood working is the best high for me!

View dakremer's profile

dakremer

2448 posts in 1694 days


#4 posted 617 days ago

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

Dennisgrosen

10850 posts in 1718 days


#5 posted 617 days ago

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
Dennis

View Oldtool's profile

Oldtool

1750 posts in 794 days


#6 posted 617 days ago

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

balidoug

363 posts in 1081 days


#7 posted 617 days ago

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

GnarlyErik

179 posts in 737 days


#8 posted 616 days ago

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!

-- Candy is dandy and rum may be fun, but wood working is the best high for me!

View Ken90712's profile

Ken90712

14830 posts in 1792 days


#9 posted 616 days ago

Great job, a really cool tool… Well done.

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

View Mauricio's profile

Mauricio

6749 posts in 1754 days


#10 posted 616 days ago

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

OregonWoodRat

114 posts in 890 days


#11 posted 616 days ago

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

Von

184 posts in 816 days


#12 posted 616 days ago

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

Dennisgrosen

10850 posts in 1718 days


#13 posted 616 days ago

got it … thanks Erik

take care
Dennis

View majuvla's profile

majuvla

3262 posts in 1470 days


#14 posted 616 days ago

It’s always nice to see home made inspiration.

-- Ivan, Croatia, Wooddicted

View Dutchy's profile

Dutchy

432 posts in 771 days


#15 posted 615 days ago

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

-- My englisch is bad but how is your dutch?

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