Fatten up tenons for tighter fit before glue-up?

[Doug Dawson]

I have some tenons with a little slop* in them, and I’d like to add a few thousandths to the cheeks to snug them up before final glue-up. Is this wise? feasible? Would paper work? How about gluing some 2 or 3 thou shavings to the cheeks? The scale is a 12 x 24 x 42 cherry cabinet with 3/8” x 1.5” x 1.25” deep tenons on 7/8” thick rails into 1.75” x 1.75” stiles/corners.

*By “slop” I mean most of the tenons would slide out if I hung them from the stiles.

Just draw-bore them. That wouldn't even need glue for structural integrity, in many cases. It doesn't have to be a suction-tight fit. That was never a requirement, except for NASA or the Navy (padding the bill.)

[Jim Koepke]

Looking ahead, I need to refine my tenon technique to avoid the annoyance of this rookie mistake. It's something I haven't studied enough yet. I had used a dado set to cut these tenons. I see now that that method lacks precision. At the moment I like the looks of Philip Morley's "band saw" tenon, for which he makes a shim exactly equal to the mortise thickness plus the kerf width. We'll see...

The bandsaw method sounds like an easy way to go.

For hand work one way that worked for me was to make a test tenon. This was as much for a depth check as it was for fit. Then the mortises would be cut, checked and fitted against the test mortise. If the test tenon was loose in the mortise the mortise would be marked to let me know to cut the tenon a little fat. The mortises were all cut with the same Narex 1/4" mortise chisel so there wasn't really much variation to be a worry.

It might be easier to read about it:

https://sawmillcreek.org/showthread.php?262272

The articulated gate used 24 mortise and tenon joints.

jtk

[David Eisenhauer]

Using a shim to the thickness of the desired tenon thickness to create the second face of a tenon from a fence is a good way to go regardless of which machine is used if going the power-tool tenon fab route. Using scrap squares with wax paper (or similar) glued to them are useful to have for adding plane shaves or veneer shims to tenon faces with the squeeze-type clamps. I have a few of those in a coffee can for use as required. Due to the size of a typical furniture-sized tenon, I can't say that it will matter whether or not the direction of the grain run on a tenon shim will matter, but I could not make myself glue one on crosswise. Your tenons can, however, be shimmed anyway you want. I venture to say that your skill in fabbing tenons will increase with experience, but you (as most of us) may never be completely free of a loose tenon from time to time in the future. When David Charles chimes in on how to fix a loose tenon, it says something. "Hey, DC read about it somewhere, never had one himself". OK. Main thing is to enjoy the process Bob Jones number five thousand four hundred and forty three .

[Bob Jones 5443]

Nice mind-read, David. I have been using little squares of parchment paper on these finicky little glue-ups. They're getting prettier. Here are the latest two rail-ends after truing up with the No. 71:

tenon fix.jpgtenon fix 2.jpg


Both now fit snugly! What fun. Two rails down, nine to go (unless some of the tenons already fit, which at this point would surprise me).

My No. 71 is a wonderful tool, but the Old Timer is a bit primitive because it lacks the screw height adjuster. But no matter: once the 0.025" veneer chips dried onto the tenon cheeks, I just zeroed out the No. 71 on the new chip, and then crept down to final dimension using little square shims of –– parchment paper. This allowed me to take the finest shavings, controlling the process. In the end I needed only two parchments' thicknesses to reach snugness. So that tells you how skinny the tenons were!

Next time I make tenons, I'll still aim for high precision à la the Morley shim/band saw method, but now I think I'll intentionally make them just a few thou proud so I can ease up on the final size with the No. 71. I can now clearly see it's better to start fat than too skinny.

Why are so many of my tenons skinny? I suspect it's from drying. I cut them ages ago (over a year?), and I'm sure they were not so pathetically undersized at first. They have since lived in our dry house interior for many months, recently through the dry DRY DRY California summer/autumn. (Heard about it on the news?) Could the tenons have lost dimension as they dried? Makes some intuitive sense. What do the experts here surmise? If there's any truth to this, it suggests that any M & T joint could suffer that fate after a while, even after it's been glued up. I might just give draw boring a try.

[Edward Dyas]

I have some tenons with a little slop* in them, and I’d like to add a few thousandths to the cheeks to snug them up before final glue-up. Is this wise? feasible? Would paper work? How about gluing some 2 or 3 thou shavings to the cheeks? The scale is a 12 x 24 x 42 cherry cabinet with 3/8” x 1.5” x 1.25” deep tenons on 7/8” thick rails into 1.75” x 1.75” stiles/corners.

*By “slop” I mean most of the tenons would slide out if I hung them from the stiles.

If it were me I would just glue the joint with epoxy. It would be thick enough to take up the slack.

[Bob Jones 5443]

Jim, I've just taken a tour of your articulated gate story line. Very informative. You mentioned a few blowouts with the draw bore technique. Did you consider using a draw bore pin to check each M/T pair for fit with the offset bores? Maybe it's less of an issue with hardwood.

[Doug Dawson]

Jim, I've just taken a tour of your articulated gate story line. Very informative. You mentioned a few blowouts with the draw bore technique. Did you consider using a draw bore pin to check each M/T pair for fit with the offset bores? Maybe it's less of an issue with hardwood.

Don't overthink it. Play around with the dowel stock to get a feel for how it's going to react, and then go to town. You'll understand what to do.

[Jim Koepke]

Jim, I've just taken a tour of your articulated gate story line. Very informative. You mentioned a few blowouts with the draw bore technique. Did you consider using a draw bore pin to check each M/T pair for fit with the offset bores? Maybe it's less of an issue with hardwood.

My biggest error was not planning to draw bore before starting. Since the tenon was a bit short for draw boring the dowel pin was a bit close to the edge on the mortised rail.

My second error was in getting the offset correct. My first ones had too much offset, combined with how close it was to the top of the mortise caused the blowouts. Lessening the offset a little took care of the blowout.

Checking the gate panels was easier to do by clamping it together to make sure all the shoulder to rail joints closed all the way. With draw bore pins it could have take six of them to check properly.

jtk

[Bob Jones 5443]

Well, I've been through all 22 tenons now. I'd say about 8 or 9 were on the skinny side. After a couple of tries, I got the veneer-and-trim process down to a science. One or two were actually a little fat. Again, love that router plane! The others just needed the edges eased. So, the whole genesis of this thread has reached a resolution, and I'm on to the next operations.

I'll build the door after the cabinet is assembled to ensure a tight fit. The door will have six tenons of its own, so I can see if I've learned my lesson from making sloppy tenons. It will be time for me to try the band saw method discussed above, in hopes of avoiding these problems altogether. I'm looking forward to taking another skill on board.

Then after that, someone will make me aware of a better way to make tenons.