Make a Set of Cam Clamps
Easy and inexpensive to make, these quickly adjusting clamps with non-marring jaws are ideal for a wide range of light duty clamping jobs.
The traditional clamp for luthiers, cam clamps are ideal for holding things in place, particularly where you don’t need to apply a lot of clamping pressure. I find they are much quicker to adjust than bar or fast-acting clamps. They are very effective when gluing up narrow stock, mouldings, edge trim, and small parts, and they excel at holding jigs and fixtures in place. I also like that their padded jaws don’t mar stock.
You can purchase commercially made cam clamps for about $20 each, or make your own for a quarter of the cost. You can easily make a dozen of these on a weekend afternoon, and you’ll find they are super-durable. I still use the first set I made over a decade ago.
If you’re making more than one cam clamp, a drilling fixture is strongly recommended, as it speeds production and increases accuracy. A plywood pattern with a side and end block glued to it, and holes drilled in the plywood works great (above). With the fixture made, you can position the jaw in the fixture, flip it over and position it against the clamped fence, then drill the necessary holes (below). You will need to make separate fixtures for the fixed and adjustable jaws.
A simple piece of plywood, with two stop blocks fixed to its face that capture the jaw, is all that’s needed. This jig will increase safety and accuracy when machining the grooves in the ends of the jaws.
Yet another simple jig, this time for a router table, will keep you safe during repeated cuts. You could forgo this jig altogether if you wanted to cut the notches on the bandsaw.
After drilling a hole in the adjustable jaws to protect against splitting, bandsaw a cut that ends at that hole.
Cam Lever Groove
A groove centered on the movable jaws' edge will house the cam lever. Cut this groove on a table saw, with a stop block to limit the cut. A simple jig can be created to assist you in machining these parts, and keep your hands away from the blade.
Protect the Workpiece
Leather, or in this case cork pads, will protect future work from getting marred by these cam clamps. Adhere the cork or leather to both fixed and adjustable jaws.
Hammer the Pins Home
With all the machining complete, Duguay aligns the jaw and metal bar and hammers in the pins. The adjustable jaw doesn’t have to be fitted over the bar during this step, but the bar does allow you to control the jaw while hammering. This jaw will slide down the bar before the fixed jaw is pinned in place.
It’s just as quick to make half a dozen of these clamps as it is to make one. Don’t get stuck on the materials or dimensions that I’ve used, as nothing much is overly critical here except the placement of the hole for the cam. If you don’t like aluminum, use steel. If 1″ bar stock seems too narrow, use a wider bar. Want a greater jaw depth? Increase the length of the jaws. If you can’t find spring pins, use nails (cut to length and preened over with a hammer) or rivets.
Drill the pin holes
The fixed and adjustable jaws are mirror images of each other, so mill them all at the same time. While you can use whatever wood you have laying around the shop, a straight-grained hardwood is preferable. I make a spare adjustable jaw that I use to test the settings on the table saw when cutting the slot for the cam.
To speed up drilling the holes for the spring pins, I make two holders out of scrap wood – one for the fixed jaw and one for the adjustable jaw. Load a blank into the holder and drill the holes free- hand or at the drill press. Make sure you use a drill bit that is ever-so-slightly smaller than the diameter of the spring pins you’ll be using. Drill a few test holes and check that you can hammer the pins in place without splitting the wood.
Cut the end slots
I cut the slots on the back end of the jaws on the table saw, using a 1/8″ blade to match the thickness of the aluminum bar stock. Aim to center the cut on the stock, but it doesn’t matter if you’re slightly off-center. Use a tenoning jig if you have one. Otherwise cobble together a simple sled to hold the jaws; don’t attempt this freehand. When cutting the slots, aim to have about 1/2″ of material extending beyond the back of the bar, so that it doesn’t split when you drive the outside spring pin home.
You want the fixed jaw to fit nice and tight in the slot. If the adjustable jaw doesn’t slide freely along the bar, run a file or a strip of sandpaper glued to a 1/8″ thick scrap of wood, along the slot to widen it. If you don’t have a table saw, you can cut the slot at the bandsaw. Cut, test, cut.
Drill holes in the metal bar
At this time I drill the two holes in the top of the bar stock, and one hole at the bottom. Chuck a length of bar into the slot of the fixed jaw, check that they are at 90° to each other, then drill the holes. Aluminum is pretty soft to drill through.
Shape a nice curve
You have a couple of options for cutting the recess on the inside of the jaws – router table or bandsaw. I’ve tried both methods and either produces good results. If you cut the recess on the router table you’ll definitely want to use a jig with hold-downs to secure the jaws. Don’t hog out the waste at one go; take two or three passes.
If you’re getting a bit sweaty with the thought of routing the recess, head over to the bandsaw. Using a cardboard template draw out the recess on all the pieces, and then bandsaw to the line. I find a 1/4″ blade works best. There’s no need to sand the curves other than to make the clamps look pretty.
Rip the adjustable jaw
Once you’ve cut the recess, it’s over to the bandsaw with all the adjustable jaws. Using the thinnest blade you have, rip the top part of the jaw up to the 1/8″ hole you previously drilled into the jaw. This cut enables the top part of the jaw to flex as the cam is activated. That 1/8″ hole will help to keep the jaw from splitting in use.
Cut a slot for the cam lever
The cam lever needs to be housed in a curved channel in the adjustable jaw. The easiest way to do this is on the table saw. You can make multiple cuts with a 1/8″ saw blade or, better yet, use a dado blade.
Set the dado blade height so that it’s even with the bandsaw kerf you previously cut. Limit the length of the cut by clamping a stop block to the rip fence. You will need to have at least 1″ of clear area so when the cam lever is rotated it comes into contact with the thinner portion of the adjustable jaw.
Using the spare adjustable jaw, make a test cut. If needed, adjust the height of the dado blade and the position of the stop. Then go for it. I feed the stock freehand, but if you feel uncomfortable dong this, make up a carrier for the jaws.
Shape the cams
Here again, it’s handy to make a template (cardboard or wood) of the cam, and use it to lay out the cams on your stock. Rough out the cams on the bandsaw, and clean them up on a disc sander, with a file, or freehand with sandpaper. I also use the template to locate the position of the hole for the spring pin. Having a spare cam comes in handy for testing the hole location. Pin the cam to one of the adjustable jaws, and if all is copacetic you’re good to go. Otherwise, you’ll need to make a slight adjustment to the cam pin hole location.
Bring it all together
Before assembling the clamps, I attach a piece of cork to the face of each jaw. I use CA glue, but any adhesive will work. If you don’t have cork, use leather.
Pin the cams to the adjustable jaws. Before you do, make sure that the cams move freely in the slots.
Slip the bars onto the fixed jaws, and then hammer the spring pins home. Next, slip on the adjustable jaws and hammer in more pins. Cut some pins to about 3/8″ long, and hammer them into the bottom holes on the bars – these keep the adjustable jaw from dropping off the bar. If the pins are proud of the face of the jaws, sand them flush on a disc or belt sander.
If, for some reason, you find that a cam pushes up too tightly against the end of the curved slot in the jaw, simply use a 3/8″ chisel to chop out a bit of material – you’ll need to knock out the spring pin to remove the cam in order to do this.
Carl Duguay - [email protected]
Carl is a Victoria-based furniture maker and the web editor at Canadian Woodworking & Home Improvement.