Sunday, May 25, 2014

Tenon Work

Jig in Test Mode

In Nov 2009 (I know because I wrote the date on the assembly instruction papers) I purchased the beautifully machined tenoning jig above. I'd have to go back in time to see what it was I was building then that made this purchase so "urgent", but whatever it was it turned out that I never actually put it together or used it. In fact, all this time the box has been in near pristine condition under my bench gathering dust. With the recent purchase of my mortising machine however it became clear that tenons to match only make sense, so it was finally time to break the assembly embargo and put this thing together. And doing so turned out to be a perfect rainy Saturday afternoon project.

I had a minor bit of trouble however. The miter slot runner was installed by the factory in a location that made it impossible to move the main fence all the way to my saw blade. So it needed to be relocated to an adjacent position.  Unfortunately the allen screws that secured it were frozen tight! I almost got to the point of drilling them out before finding a couple suggestions online about how to free bolts like this. One idea I would have never thought of involved using a torx head screw. But the method I eventually used (all ideas included penetrating oil and a good deal of hammering) was using a hex key in a ratchet wrench. When an allen screw is in really tight a little "L" shaped wrench isn't going to get it out. The extra leverage of a wrench however is much better. Once I got them out (without stripping no less!) it was a simple task to move the slot runner and proceed with setup.

Handle locations keep the operator safe

The key setup checks for any tenoning jig are to make sure that, (1) the main fence is perpendicular to the table saw table; (2) the support fence behind the workpiece is perpendicular to the table; and (3) the entire assembly moves parallel to the saw blade. For most typical, right angle joints, these relationships are critical to a perfect joint.  A custom jig like this also allows for more complicated angled cuts.

There are a variety of ways of creating a tenon. The simple way, and the way I've made them in the past, is to use a dado stack on the table saw. But this has a couple of disadvantages. Mainly it's quite slow, and if you have a lot of tenons to cut it gets a bit tiring. But a more important reason has to do with quality. Dado cuts can produce a rough surface on the cheek of the tenon and to get that cheek smooth means more time and work. Cutting tenon cheeks on the table saw however produces a smooth cheek with little need for added dressing. So using a dedicated jig increases both productivity and accuracy, and throws in high quality as a bonus.

Operator's view.  Shows the relocated miter slot runner.

Using a jig for tenon cuts also makes the process very safe. The handles guarantee that the user's hands will be well behind, above, and to the left of the cut and any flying pieces. And the supports and clamp ensure the work piece remains secure. Once the jig is set up to create a good fit numerous pieces can be prepared with confidence.

I have a fair bit of mortise and tenon work to do on my office work stool project, and on a printer table to follow that. Considering that I like making Shaker and Mission style furniture the new machine and this jig will probably see a lot of use in the future. Like anything in this craft there's a learning curve whenever you start doing things a new way.  These two new pieces of equipment are capable of producing superb results, and my tests today proved that I can get them.  There will be a few more things to be figured out yet, and probably a few mistakes.  But I'm looking forward to getting up and running.  Mistakes and all.  :)


  1. There was a time in my life that I really wanted one of these but I knew I would never have the time or the money for all the tools so I went with using dowels. I know we will be seeing some really quality work in the future! Congrats on getting it out of the box! You must have have a busy day all the setting up and the photo blog!

  2. Dowels are often a perfect choice for a joint. They're much stronger than biscuits or pocket hole screws. Dowels are simply a form of loose tenon, and a much less expensive solution than using a multi-router or something like the new Festool Domino. I plan on using dowels myself on the upcoming office stool. But where exactly is still a secret. :)