Projects & Related Things: Cam Clamp

In 2005 when I was making an acoustic guitar, I borrowed a truckload of these wooden bodied cam actuated clamps from a friend as I only had four of them. Here is what the guitar body looked like when I was gluing the back to the sides with all those clamps.

I had always wanted more of them but at that time they ran about $25 each which is more than I wanted to spend for a specialty type seldom used clamp. That all changed when I recently found a plan for them that used a 1” wide by 1/8” thick aluminum bar for the clamp’s spine. By coincidence I have two pieces of aluminum bar just the size needed. They are left from when I made the Dining/Game Table for my son. The photo below on the left is one of my original clamps and the rendering on the right is what my SketchUp drawn plan looks like. If these work as well as the store-bought ones then I might make some more.

My first step in making the clamps is to create three templates. Having ready-made templates on hand will certainly speed things up. Here is the template drawing that I glued to a piece of ¼” plywood using some spray adhesive used for mounting photos.

First step in cutting out the templates is to drill the various holes around the perimeter of the piece. I use the drill press setting the depth stop so that only the point of the bit comes through the piece. Here is what that looks like. That’s done to eliminate any possible blow out on the back side when the drill breaks through there.

The hole is finished up by turning the piece over, aligning the bit point with the hole on the backside and drilling through meeting the hole drilled on the front. This photo shows the drilling completed with a thin piece just setting in the hole. It is pushed out giving me a hole with nice smooth edges.

This is the template with all the perimeter holes drilled. On one of the holes I applied a little too much pressure when starting and the bit grabbed the paper tearing out a little. That’s not a problem as all I needed to do was extend the base line in pencil. There are still six holes that need to be marked but those will be addressed later.

After ripping the templates to width on the table saw and cutting them to length on the chop saw I used the band saw to cut close to the lines that delineated the inset area between previously drilled holes. In order to smooth the bandsaw cut and bring the opening right to the line that was left from bandsawing I used the oscillating sander. Below are the two setups used. The only difference is the size of the sanding rod used. Its size is determined by the depth of the recess.

The last bit in these templates is working with the last six holes mentioned earlier. Of them there are three that really need to be located very accurately. Two are for pins that lock the top jaw in place on the aluminum bar when the locking cam is used. The third is for a pin that the locking cam rotates about also located in the top jaw. The remaining three holes locations are not quite as critical. One in the top jaw is at the end of a bandsaw cut to reduce the chance of the jaw splitting when the locking cam rotates and two are for pins that lock the aluminum bar to the bottom jaw.

If I drill the holes in the template and use it along with a bit to drill to make the holes in the jaws then over time the drill will chew up the template impacting the accuracy. Not a problem for most of the holes but I can see it being one for the three described above. To avoid this the template will be used to punch a centering mark in the jaws with a pointed pin. That mark will then be used locate the holes.

The process starts by making the pointed pin from a 4-penny finishing nail. The nail head is cut off then mounted in the lathe where the cut is filed smooth and the edges beveled. Next the pin is flipped and the nail’s faceted cut point is filed to a smooth conical point. That’s what is shown below.