There are dozens of different ways to cut a tenon, from using a $10 handsaw to a twin-headed tenoner costing thousands of dollars. But most of us home woodworkers choose something somewhere in between. We want accuracy, of course, and speed would be nice, but we don’t want to have to spend a lot of money or be limited to a small range of sizes.
No jig is perfect for every kind of tenon under the sun, but there are some we can short-list for our consideration. Here are my criteria for choosing a tenon jig.
1. Length of tenon.
Any jig that cuts the tenon end on, vertically, such as the Leigh router jig or the Delta tablesaw jig will have the depth of cut of the machine as the limiting factor. For a 10″ tablesaw this means tenons up to 3″ long. On a router it is the length of exposed router cutter.
On a bandsaw there is no length limitation, just that the width of the workpiece be less than the height under the blade guard.
2. Thickness of tenon
If you use a jig which uses templates, then you are limited to the size of those templates. For new-build projects that probably won’t be a problem but may be if restoring an older piece. Most people in North America use inches as their unit of measurement, whereas most of the rest of the world works in millimeters. Being able to use either system is sometimes very advantageous.
3. Accuracy and consistency
Consider the way the jig itself actually operates. Are both cheek cuts references of one face, just as you would by hand, or do they reference of two different faces? The latter is common, where you have to turn the workpiece round to cut the second cheek, but this is inherently inaccurate. If your workpieces are even very slightly different in thickness, then you tenons will be, too. Some will be tight and some will be loose and require a lot of fettling to get right. Plus, the tenon will always be dead center, whether you want it to be or not.
4. Machine safety
Many tenon jigs, especially those designed for use on tablesaws, require the user to remove the riving knife, because it gets in the way. The riving knife usually supports the blade guard so the user is exposed to unnecessary risk. Make sure that you choose a jig which allows easy operation but which retains your personal safety.
If the jig you choose can be used for a variety of tasks in the workshop, then you will get added benefit from it. For example, will it also cut bridle or halving joints, or keyed miters perhaps? Can it deal with off-center tenons or twin tenons, or is it a one-trick pony?
6. Speed of set-up
Almost all tenon jigs can be relied upon to produce accurate tenons, but just how easy are they to set up? Some jigs take longer to set up than to actually use for a batch job. It is not just the fit of the tenon that needs to be considered, it is the position of it within the thickness of the workpiece, too. This is especially important when making face-frames. If the tenon is not in the right place, the maker will have to plane off the faces of all the rails and the backs of all the stiles in order to get everything flush. On some jigs, moving the tenon over, say, 1/32″ requires the repositioning of both tenon cheeks separately, so both fit and position become a matter of trial and error.
7. Speed in use
Once the jig is set up, how quickly does it cut the tenons? A jig that cuts the cheeks and shoulders with a single cut, rather than nibbling away 1/8″ at a time will be faster to use.
Once you have satisfied yourself of the above tenon jig issues and found one that ticks all the right boxes for you, then you need to decide whether you buy one off the shelf or build your own.
There are many plans on-line, some free, some not, but most of them, in my opinion at least, fall very short indeed, especially in the set-up speed and safety-in-use, departments.
And many off-the-shelf ones have serious limitations of capacity, as well as the setup and safety issues of most of the others.
It was with speed, safety, accuracy and versatility in mind that I developed the Ultimate Tablesaw Tenon Jig and, later, the Ultimate Bandsaw Tenon Jig. There is no unguarded tablesaw blade on which to risk your fingers and both jigs are quick to set up as well as to use. Furthermore, I am not restricted to having the tenon dead central, I can have it to match the mortice if that is not dead centre, and if the tenon is not quite in the right place I can move the whole jig over a precise and accurate amount so that it does become properly aligned, and do so without losing the fit of the tenon in the process.
I also found that it was easy to use it for twin tenons and halving joints as well, so it ticks all the boxes for me and others have said that they would never go back to their old cast-iron model, as well. Sure, buying one is quick, but making your own as a project in its own right is very satisfying, especially when the end result is so much better.
It does look complex when you first see it, but each part has a particular function and is quite simple in itself. If you find that too daunting, start by making one of the many free designs available on the net. But see if you can improve on the original design, bearing in mind some of the issues raised above.
So however you decide to cut your tenons, make sure that your jig cuts them Right First Time Every Time.