Throughout our vast known woodworking history, many forms of clamping devices have been in use to clamp two boards together. Ancient Egyptians used to clamp by placing two boards vertically weighted down by a heavier object. Wedges were another form of clamping method used.
Today we have many clamping devices available to us. In fact, there is a large variety of them in all shapes and sizes ranging from the highest quality Bessey
clamps, to the lower quality Craftright. There are even lower quality no name brands you can find for a couple of dollars. I would highly recommend you steer away from those cheap types no matter how tempting they are. They are just downright atrocious and should be outlawed, the manufacturer imprisoned and whipped with the cat of nine tails.
Bessey being my ultimate most expensive favourite brand is sturdy built, and the head slides smoothly up and down the bar.
Prior to turning amateur, most of my work involved in making clocks. Rarely did I need clamps larger than 800mm (31 1/2”). Now I have the freedom to build what-ever I fancy and larger clamps will be needed soon enough. However, Bessey clamps as good as they are, are cost prohibitive and not within my financial reach. So, instead, I shall make myself a copy of the Bessey clamp and God willing, it will be just as good as Bessey. I will leave this for another article.
A new clamp for me is the cam clamp. Cam clamps are so versatile that I end up reaching for them often. Cam clamps are lightweight, non-marring and offer just the right amount of pressure needed for light duty work like building boxes or instruments. Instrument makers are common users of these types of clamps and they’re easy and fun to build.
Large clamping force is seldom needed if your boards are flat and out of twist. Sometimes boards cup and a little more pressure is needed. You would choose the right clamp for the job at hand. For light work cam clamps are the perfect choice.
Since I’ve been concentrating on making moulding planes, cam clamps are all I need. If you’re wondering why I need to clamp moulding planes, it’s because I’m using the French build method they once used in the 18th Century. The British frowned upon this build method, but there are pros and cons in both methods. They’re not so heavy on the pocket either. You can use any hardwood to build yourself a set. I wouldn’t recommend using softwoods like pine. Pine is too soft, and the force applied from the bar and pins will dig into pinewood and render the clamp useless. Therefore, I would recommend using hardwoods like maple, black walnut will hold up, ironwood is very strong, New Guinean rosewood looks beautiful and is perfect for them.
I already have a few cam clamps lying around but for the sake of this article, I will add one more to the growing set, besides I like making them.
So, I rummaged through my offcuts bin and found black walnut. It’s always good to keep your offcuts no matter how small or thin they may be, you never know when you will reach out for it for another project. Wood is expensive in Australia and just like our predecessors you can’t afford wastage, so I hoard as much as I can to use later.
The bar I will use is aluminium, you can use iron or timber, but the aluminium is lightweight and sturdier than timber, and it won’t warp through seasonal changes. The bar length I have on hand is
23 9/16” x ¾” x 1/8” (600mm x 19mm x 3mm). I will use half that length for two reasons: I’ll get two clamps out of one bar and it’s the right size for my moulding planes. The pins will be from a brass rod 1/8” in diameter. The rod needn’t be of any great length as the pins will be cut to just a little over an inch in length.
Cam jaws dimensions are 6” x 1 ½” x 1”. You will need to cut two; the upper and lower portion. The upper portion is called a fixed jaw. The lower portion is called a sliding jaw. The aluminium bar is called a bar. The lever is called a cam lever.
Crosscut the aluminium bar in half with a hacksaw.
Your bar can be of any length desired. There is no need for me to provide any specific length measurements as everyone’s need is different.
Aluminium bars are soft and easy to cut. Scribed lines are visible. Wouldn’t it be nice if all metal was this easy?
Once cut to length, file the cut end to a smooth square. Making it square isn’t necessary, but it’s good training. Working with a quality file is a joy to use.
After it is smooth and square, prepare your stock.
Note: Apply the following steps to both jaws to save on build time.
• Length, width and thickness
• Through Mortise
Rip and crosscut a little oversized by 1/8”, this is a precautionary method if you’re not a very good sawyer, otherwise 1/16” will suffice.
Surface plane both stocks flat and true five sides. Both faces and edges parallel.
Thickness both to 1”. Make them flush to each other.
If your stock is already 1” a little under won’t hurt.
Crosscut and chute to final length of 6”.
Determine which will be the fixed jaw.
Layout all your dimensions now rather than as you go along.
We will layout the dimensions for the position of the arch which will be at the underside of the fixed jaw.
From one end of the fixed jaw, measure in 1 ¼” on the edge (31.75mm).
Now on the opposite end, measure in 2 1/8” (54mm), what’s left in between will be the arch. The arch’s height is ¼” (6mm). Pencil a line between the two arch points. To draw the arch, I used ¼ of the size of a 5c coin. If you wish you can use a circle template, a compass or draw it freehand.
Shape the arch with a chisel or saw it with a coping saw or a scroll saw. Clean up the chisel marks or saw marks with a rasp, file, scraper or sandpaper.
Lay out the through mortise and chop it out. The bar will be inserted into the through mortise and fixed with two pins. The mortise is ¾” x 1/8”
From one end (refer to the drawing which end), top edge of the fixed jaw, measure in 7/8” and pencil it in. With a square, square the line around the work piece. Now, measure from the same side 1 5/8” and square the line around all four sides. We’ve now established the length of the mortise.
Now we need to establish the width being 1/8”.
Measure from both sides 9/16” to get 1/8” width, provided your stock is thicknessed to 1”.
If it isn’t, set the pins on a mortise gauge to 1/8”. Move the head of the marking gauge so that the pins are approximately in the centre of the stock and pinprick the stock. Flip the gauge to the opposite side and pin prick again. The difference in between the pinpricks is the centre of a 1/8” wide mortise. Repeat the same on the underside of your stock.
Chop out the mortise. You can drill using a drill bit narrower than 1/8” or chop it with a 1/8” mortising or bench chisel.
I’ve discovered a simple way to centre a mortise with pinpoint accuracy. This method will eliminate the need of having a mortise gauge and that’s one less tool in your tool box.
If you don’t own a marking gauge to mark out mortises, you can use a single cut-ting gauge with accuracy. To do so, take half the width of your stock add half the width of your chisel, then add that dimension to the half width of your stock.
For example; let’s say the width of the stock is 7/8”, take half of that which is
7/16”. The width of the mortise is 1/8”, half of that is 1/16”. Add the two, 7/16” + 1/16” = 1/2”. 1/2” is what I’ll be setting my marking gauge too, and scribe on both sides. Your mortise will be smack in the middle. Clever, eh. I think this method is much more accurate than making a gazillion scribes from both ends trying to potluck the centre.
In this final step we will insert the bar through the mortise of the fixed jaw and pin it in place to render it immovable.
Check that the bar is square to the jaw and apply glue inside the mortise and on the bar. (Refer to the list of glues below). Insert the bar into the mortise and allow the glue to dry at least a half hour before drilling through it.
Mark the hole locations at a diagonal on the stock/bar. Then drill straight through both. I used a 1/8” brad point drill bit as my brass rods are 1/8” in diameter.
Saw the rods/pins a little longer than the thickness of the fixed jaw. Apply glue to the pins and hammer them in place. Let the glue set. Saw the pins off as close as flush as possible. Then draw it out by hammering the pins towards the outer perimeter. This method is called peening. This is an age-old metal working trick to make the pins irremovable. Finish it by sanding the pins flush.
As for the glue that will glue metal to wood, any of the glues below will work.
• Fish glue
• Loctite AA330
Making the Sliding Jaw
The first thing we need to do is rip a narrow kerf so the clamp pad can flex when pressure from the cam lever is applied.
Pencil a line freehand ¼” up beginning from the clamp pad and ending at 3 7/8”. Drill a 1/8” stop hole at the end of the 3 7/8” line.
This will help prevent a potential split beyond the stop hole.
The drawings display a screw inserted from the bottom. I have omitted this screw as I don’t see the reasons for it.
Rip down the narrow kerf.
The width of the stopped slot is 3/8”. Using the same method for marking out the mortise in step 8, we shall mark out for the cam lever stopped slot.
Working from the top first, measure and mark the length from the right side 2 3/4″ (70mm). Then from the face side on the kerf measure and mark 1 1/8”. Pencil in a line connecting the two marks, this will give you the angle to aim to when sawing and chopping out the stopped slot.
Drill two holes for the pins. These through pins need to be placed next to the mortise wall, ¼” down from the top and 3/8” up from the bottom. If the pins protrude into the mortise, then the sliding jaw won’t slide up and down. If the pins are further away from the mortise wall, then your clamp will be ineffective.
Use a tenon saw to kerf the slot.
Insert a small thin shim in the kerf between the clamp pad and the stopped slot to avoid chiselling into the clamp pad.
Chop out the stopped slot referring to the angled guideline you pencilled in earlier.
Trace the lever from the drawings onto the timber and with a coping saw or scroll saw cut the shape. Clean the saw marks with rasps, files or sandpaper.
Insert the cam lever into the slot with the large rounded part of the lever in a downward position inside the slot and rest the cam lever flat on the angle. Position the cam lever so it protrudes into the saw kerf.
With the cam lever positioned in the sliding jaw, place both parts into the vice. Eye ball or measure in 5/8” from the right side of the sliding jaw and about 3/8” up from the kerf and drill a 1/8” hole.
Use a brad point tip to stop any wandering of the bit as you begin to drill.
Insert the pin dry (don’t glue it in). Use the same metal working trick to peen the end as described previously.
At this stage, you may be disappointed as the cam lever isn’t holding its position when activated. The problem lies in the pin hole location. I’ve experimented with different hole locations and haven’t yet resolved this phenomenal problem. To date 3/8” seems to be the better candidate.
If you drill your hole close to the kerf, the lever won’t swing very far and it won’t clamp at all. If you drill a hole above 3/8” then the cam lever won’t grab or stay put when activated. Even at the 3/8” mark the lever still doesn’t perform well.
My only solution to this is to insert a piece of leather with the suede facing up in between the saw kerf and the lever and glue it in place. If you like, use a quick setting PVA glue. It will set in 2 minutes and cure within 4 hours. You’ll notice that the clamp will now holding better.
In this final step of the build and only if you used metal bar, you will need to file a row of grooves on the back of the bar so that the sliding jaw will grab when you clamp. Use a triangular file and eye ball the spacings.
I glued cork to the clamp pads to provide better grip and more clamping power. I’m not sure how that works, but it does.
You can use any finish you like. Minwax Antique Oil is great, so is shellac. Just be careful that you don’t get the finish on the leather. It could seep in between the glue line and break the bond.