How to make a tenon

Accurately sized tenons without a tenoner. September 25, 2002

I'm making some basic furniture using mortise and tenon construction. The mortise is no problem - I use a plunge router and it works well. The tenons are another matter, though. It's tough to get them the right width and round the edges so they fit the mortise tightly. Short of buying a $5000 tenoner, what's the best way to do this?

Forum Responses
Sounds like making 4 to 6 cuts with the table saw and rounding the corners with a rasp is where you're headed. A good tenon jig will help on the stand up cuts, and a square crosscut jig and fence will do the other cuts. Get good at it and you can even put a very slight bevel to the cheeks so the tenon tightens up as it pulls up. It works - I've done it for 30 years.

There are two table saw techniques:
1) Using your miter gauge with the stock flat on the table, set the blade height right to nibble off the cheeks by repeated passes. Use an auxiliary stop against the rip fence to assure the correct tenon length. *Do not use the fence as the depth stop, as it will cause binding and dangerous kickback!* Then reset the blade height to nibble off the edge of the tenons.

2) Buy the Delta tenon jig and follow their directions.

Round the tenons to fit with a rasp. I like the Nickelson 'Four in One' as it has the rough and smooth cuts on the same tool, saving time switching between two tools.

I use the same method as above. Plunge router for mortises, then table saw the tenons. For the table saw, any one of a number of methods will work just fine. As for the rounding, I am up in the air on that one, but have gravitated towards finishing out the mortise with a chisel. It really doesn't take very long once you've already removed all the material with the router. Then you've got the real thing.

You can avoid the need to round the tenon by squaring the mortise with a chisel. If you lack the power tools to cut a nice tenon, you can always do it the old fashioned way: use a backsaw or dovetail saw. Otherwise, the tenon can be cut by making several passes with a radial arm saw (set to the correct depth), breaking off the remaining wood slivers, and cleaning up the tenon with a rabbet plane.

The Delta tenon jig. Best $99 I ever spent.

I'm sure the Delta jig is nice, but you can easily make a jig that slides over your rip fence from scraps.

I don’t mean to propose woodworking heresy, but why bother rounding the tenons at all?

True, a rounded tenon will give a superior mechanical advantage (provided it is fitted perfectly), but offers no additional glue surface advantage since the rounded portion of the mortise is mostly end grain.

I use this method for my face frames and feel quite sanguine about the integrity of my joints (especially when you consider the fact that most guys out there “screw” their face frames together).

To answer the question directly, I prefer two straight cutters stacked in the shaper, separated with the appropriately sized spacer.

I round my tenons because I do not necessarily use a 'standard' size thickness. So there aren't any mortising chisels to square up the ends easily. Also, many times I use through tenons with wedges so the round tenons look nicer.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
Just a thought: since you have the mortise down, you might try making two mortises and use a floating tenon pinned with a dowel. You can then round over the edges on a router table before assembly.

Comment from contributor B:
I use a mortise plunge chisel on a designated press for the mortise; works great. I then use a table saw mitre slide (squared) for the tennons, rounding over the edges. To secure the joint I like to pre-drill holes into the joint to set in dowel pins, cutting flush with dowel saw. Takes longer but creates a perfect look and hand done touch.

Comment from contributor C:
When I used to use a router for mortise and tenons, I cut the tenons on the router table, then rather than round the tenons or square the mortise, just chopped the corners off the tenons with a chisel. Your goal is to remove enough of the corner so that it won't bind against the rounded mortise. There will still be enough of the top and bottom of the tenon left to make the joint fit snugly, and you still retain virtually all of the useful gluing area. And chopping the corners off takes seconds. Obviously this is only an option for hidden tenons, which I assume is what you're making.

Comment from contributor D:
Regarding tenons, I always ease (round over) the edges at least a little bit. A crisp, sharp edge is more likely to cause a split because it can place more force on the inside corner of the mortise, which is a potential weak point. It will do this especially if the tenon is slightly larger.

Comment from contributor E:
I can make all my M/T joints for a kitchen table in a few minutes. I also use a jig and plunge router to make the mortises. I use a spiral downcutter and it does an awesome job (no rip out). I have a homemade table that is flat with a 90 degree riser (fence) that is permanently fixed and I put two dedicated routers with spiral upcut bits in them. They are mounted so the bits cut the faces individually (upper and lower), and then the top and bottom can be run through the lower bit so I get all four sides.

Comment from contributor S:
So many of you are making the tenon the hard way. Use a router table and fence. A three-cutter wing bit with the bearing reversed on the spindle so that it is beneath the cutter and rides on the center of the wood will work with two passes over the table. Accurate adjustments are critical, and clipping the tenon is still necessary, but making the tenon is an absolute snap.

Comment from contributor L:
To make a tenon I first make an x to find the center of the piece. The I take a hole saw that fits the drill and drill the piece. Then I make the mortise by drilling to the required depth and pop out the wood with a chisel, and I have a glove fit.