Smoothness of Mortise walls and Tenon faces

[Todd Burch]

In my 23+ years of woodworking, I've made a few mortise and tenon joints, but it's not something I incorporate into every project (obviously).

I've cut them several ways:

totally by hand via chopping (no drilling)
drilling and chopping
square chisel mortiser
router, leaving round tenons
router and chopping

Every time I make one, I question myself "how smooth should the insides of the mortise and the faces of the tenon be?" (I think that is poor grammar...)

When using a router, the mortise cheeks and tenon faces are always perfectly smooth. (well, "perfect" is relative)

When using a tablesaw to cut the tenon cheeks, they are "saw blade rough". Occasionally, I'll trim faces or edges with a chisel, small plane or file if the fit is too tight.

When chopping mortises (or corners) by hand, I always get ragged cheeks (and corners). Pine seems to be the worst. Poplar not as bad. By "ragged" I mean divots in the side walls due to grain tearing out or non-perfect movements of the chisel, or crushed grain, or, who knows what.

Even the machine cut square chisel mortiser leaves a rougher finish. (By rougher, I mean "way" rougher than I would accept for edge glueing two boards that would be used for a tabletop.)

So, I get them to what I consider is "good enough" (tight fit) and glue (yellow) them up. I've never, ever, had a mortise and tenon joint fail. I don't pin most of the M&T joints I make, but I have pinned some I deemed more critical. No failures provides the feedback to me that what I'm doing is good enough.

What's the word on this? What do you do? How finicky are you? Would I fail a fine furniture building contest? Am I considered a hack when it comes to mortise and tenon joinery?

Thanks, Todd

[carl zietz]

Todd,
I have been doing it exactly theway you describe, and witht the same results. and since my tenons have shoulders, no one can see my dirty little secret that the joints are not smooth as glass. If you are considered a Hack, I am also in the club.

[Steve Peterson]

Count me as a hack also. :)

I figure that there is still a lot of good surface areas touching even with rough cutting. The tennon will probably break off before the glue fails.

If you have one that you consider critical, then deliberately leave it rough and use epoxy.

Steve

[pat warner]

I cut my tenons (http://patwarner.com/images/index_tenon.jpg) and mortices (http://patwarner.com/images/508_a.jpg) with a router. My goal is a close fit; x default the surfaces are smooth & enjoy each other.
Glue does its max. duty whence the assembly is in close proximity and intimate. Routing works; I'm fixtured for it and it's quick, why not?

[Pat Barry]

I think if the strength question is in shear mode then it doesn't matter so much, but if the stress is to pull the joint apart in tension the cheek surfaces should be a close match to get the most benefit from the glue joint.

[glenn bradley]

Depends on the glue as well. Epoxy likes something to grab onto. PVA likes smooth surfaces mating as closely as possible. In generally I always make the tenons a bit fat and plane to fit routed mortises (mortisi?)..

[Mike Wilkins]

Common wisdom dictates the smoother the walls of the mortice and faces of the tenons, the better and stronger the glue joint will be. Wood should be in close contact with the other surface with enough room for the glue for a strong joint. That said, my mortice/tenon joints are usually of the hack variety, even with a morticing machine. Still have to clean up the walls of the mortice even after sharpening the chisels.

[Brent Ring]

Hack Style - Nothing broken or come apart so far - including thru mortises.

[Jim Neeley]

If you start with a precisely square board for the tenon, I get the best fit by cutting close with a tenon saw and fine tuning using a sharp router plane, referenced off of each side, to make the tenons perfectly flat, coplanar with the sides, and even in thickness... of course, only enough for it to fit the mortise correctly. <g>