Home Made Cam Clamps - by Sam Howe

Home Made Cam Clamps
By Sam Howe
October 2006

A cam clamp is real quick and easy to use. Slide the bottom jaw into contact with your workpiece and flip the cam lever.

I can get over 200 lbs of pressure with mine, measured by clamping it on the bathroom scale.

For the jaws and cam, I used maple.

The bar is steel, mine is 1/4 by 3/4. I bought it in 20 foot lengths and cut it to size.

The most used size is a 12" bar.

I also made a few at 18", 24", and 36". The 36" ones are pushing the limit of the bar. The deflection of the bar reduces the clamping force available, but they are still useful.

The roll pins are 3/16 by 1-1/2" long. Some hardware stores carry them. Another good source is McMaster-Carr (see Q&A at end).

It takes 5 roll pins for each clamp.

Start off by cutting the top jaws. These are also used as the blank for the bottom jaws, so

make sure you cut two for every clamp.

Here's the dimensions of mine. Most of the dimensions are far from critical, but these have worked good on mine.

You want the mortise in the top jaws to be a tight fit on the steel bar.

Take half of the jaws you have just made and start turning them into bottom jaws by

cutting the cam slot with a dado blade on the table saw.

Featherboards, stop blocks, and paying attention is recommended,

this is a stop dado and you have to back the part away from the blade after cutting the slot.

Also, enlarge the bar mortise so the jaw slides freely on the bar.

Next,

drill the stop hole and cut the tongue free.

The tongue thickness is one of the critical parts, it needs to be thin enough to flex and not break when the cam lever is thrown.

Cut out the cams next.

Make the thickness fit into the cam slot in the bottom jaw where it moves freely.

Now,

hold the cam in place in the slot in the bottom jaw and drill the pin hole thru both as an assembly.

Use a sharp drill bit and proceed carefully.

Don't try to drill the holes separately, match drilling ensures minimum play of the cam against the bottom of the tongue.

OK, now comes the fussiest part.

Drilling the holes for the pins in the bottom jaw that lock onto the bar when the clamp is used.

Actually, about any spacing that allows the bar to go thru the jaw will lock in place, but

you want the jaw to be perpendicular to the bar when tightened down.

Making a couple of extra jaws for setup purposes helps, as well as

using stop blocks on a drill press.

Now,

after cutting your bar to the desired length,

insert it in the top jaw and match drill the holes thru the jaw and bar together.

Slide the bottom jaw on and go find something to clamp.

I left mine unfinished. An oil and / or wax finish would work fine if you want to finish them. Some of the commercial ones have cork applied to the clamping portion of the jaws. I didn't use any, and haven't noticed any problems with marking what I'm clamping against.

I've been using mine for over twenty years now.

A few times, I've had a cam split when really cranking down on them.

Just knock out the pin, cut a new cam and drill it while holding it in position.

Insert the pin again, and it's back in business.

Go ahead and make a batch, you won't regret it.

Sam

Questions & Answers...

Q. Would it be OK with you if I saved your post information to my web site... http://woodworkstuff.net/ under Jigs & Tools?
Joe Lyddon

A. Joe:
Go ahead. I'd like to see someone get some use out of it.
Sam Howe

Q. I guess you squeeze the cam inward toward the clamp to spread and clamp?

A. You slide the bottom jaw against your workpiece, then pivot the cam lever away from the steel bar. This applies the clamping force.

Q. Have you ever broken the wood from too much clamping pressure being applied?

A. I have broken a couple over the years, but have succesfully glued the jaws back together or replaced the cam as I mentioned.

Q. Where do you get that kind of steel bar? Approximate cost? Being 20' long, I think I'd have to cut it into about 3 pieces to get it home! :-)

A. I picked up the steel bar stock art a local steel supplier in Reno. Cold rolled bar would be preferable due to the better finish. The bar I got back when I made mine was hot rolled. Works fine, just isn't as nice a finish on the steel. It came in 20' lengths. It probably would be a good idea to get the steel ahead of time and then make the mortise in the jaws to fit. Mine are 1/4 by 3/4, but anything close to that would work also.

This place: http://www.onlinemetals.com has 0.25 x 0.75 flat bar stock.

I don't know too much about steel prices, they have cold roll for ~$1.50 a foot and hot roll for <$1 per foot.

Q. Sam, the roll pins
I go to mcmasters http://www.mcmaster.com/
Search for 'roll pins' and get them...
Click on diameter 3/16"
Click on 1-1/2" length and get:

Spring Pin Type
Steel
Plain
Slotted 98296A914 $11.68 per Pack of 250
Standard-Duty Coiled 91598A362 14.60 per Pack of 100
Heavy-Duty Coiled 95755A331 12.34 per Pack of 50

Zinc-Plated
Slotted 90692A728 $6.74 per Pack of 100

Stainless Steel
Plain
Slotted 92373A261 $10.01 per Pack of 50
Slotted 92383A734 12.91 per Pack of 100
Standard-Duty Coiled 93740A324 11.37 per Pack of 25
Heavy-Duty Coiled 95765A422 6.77 per Pack of 10

Now, which one would you suggest?

Thank you

A. I used the coiled ones. They fit a wider range of hole diameters since they have a large amount of "spring" to them. I'd recommend the
"Standard-Duty Coiled 91598A362 14.60 per Pack of 100"

Some people use solid pins made from heavy welding rod but I find the roll pins work the best for me.

Hope this helps.

PS: post some pictures of your clamps when you're done with them!

Sam Howe

Q. When you say 'tightened down' do you mean after the roll pins are in place?
(like the jaw wants to be square to the bar when the holes are drilled)

or after the clamp is 'tightened down' in clamping pressure?

A. You want the jaw to be perpendicular to the bar when the two roll pins are in contact wih the bar. The jaw is stiff enough, I've never noticed any deflection in it while clamping loads are applied. The clamp will work if the jaw is at something other than 90*, but it looks better if you try to get it close to square.

Neat thing about these clamps is that nothing is really that critical. Get anywhere close, and they will work just fine.