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Box Joint Trivets

Or: Making Your Box Joint Jig Do Things For Which It Was NOT Designed...

 

This all started when I saw a post by Glenn Bradley over on the Familywoodworking.org forum about using his iBox boxjoint jig to make long pieces of fingerjointed wood and then interlocking them to make trivets.

I thought that was a cool idea, and set about copying him down in my shop. I built the woodgears.ca boxjoint jig less than a year ago, and so I set it up on my saw ready to go.

But then my jig let me down.

Box joint jigs are designed cut finger joints in the ENDS of boards, not the FACE of boards. It was designed to clamp the board standing vertically on end.

See the gap there between the base and the sliding part? What I wanted to do, was to lay a board down flat on it's face, and then make a series of box joints in the face of it. But with that gap, there is no way to clamp it.

I later found out that Glenn had also run into a somewhat similar design limitation on his jig, and had to jury-rig up a method to hold his strips.

Well, I kept thinking about this, and came up with a way to trick my jig into working with boards laying on their faces.

First, I went to my pile of short boards and found some likely pieces, resawed them down and planed them to a half-inch in thickness. I ended up with a some cherry and ash boards, like this.

Then, I glued them together in pairs like this, making L-shaped pieces.

Note that you don't want big boards here. My jig can really only handle boards that are up to around 12" long by about 7-8" wide. Other jigs will have other size limitations. It also depends on what size of trivet you are trying to make.

I could now clamp these properly in my jig. The vertical part of the L-shaped assembly could be clamped to the back of my jig. The horizontal part lay flat on the bottom, for cutting. I also took care to hold it flat at all times, as extra insurance.

I then proceeded to cut a whole series of 1/2" wide box joints in the face of the board.

Don't lose count! On my jig you move the jig by turning the crank. However since the board is face down you really can't see the cuts. So it is important to count carefully when advancing the jig. I was using a 1/4" blade, so it required making a cut, advancing 1/4" and making another cut, and then advancing 3/4" before starting over. Those alternating sizes of moves can throw you off.

Here is what I think is the clever part -- once done, I could then flip the board around so that the vertical part was now laying flat, and the face was now standing vertical, and then cut box joints on the other face as well!

Check out the results...

The two boards are later separated, so it does not really matter at all if the box joints line up between the two sides.
Next, you break the two boards apart and proceed to rip them all into half-inch wide strips.

Take care when setting up the table saw. The width of the strips that you cut must exactly match the size of the box joints that you cut.

Here is the result.
Then comes the fun of assembly into trivets. You might first want to touch up the sides with a sander, especially if you have any saw marks. Use a light touch, as you don't want to affect the width of these strips much!
Then it is on to the glue-up. This is actually rather tedious, since you want to just put a small dab into each joint. With all of the holes that you will be getting, cleaning up glue squeeze-out will not be easy.

Full disclosure: I had trouble with not putting enough glue on several joints, and had to deal with some joint separation later, and the resulting mess of trying to pry things open and slip in more glue. THAT is why it is a good idea to practise with making a few before you start setting up a whole production line!

I clamped mine between scrap pieces of plywood, to try and evenly distribute the pressure over the projects.
After it dried, I cut them up into individual trivets and sanded the edges and faces. A belt sander makes sanding the edges a snap, but you probably want a Random-Orbit sader for sanding the faces.
And here is the results of my first test run, sanded and ready for your choice of finish.

This was in a sense just a test, so I did not worry a whole lot about board sizes. The round one was just a fun experiment with some leftover scrap pieces. The rectangular one was a result of running out of strips.

I think the ideal size for a trivet is probably around 6"x6". So you should start out with boards that are either 7" long or 13" (to cut in half).

 

Thanks for reading!