Thread: How tight should mortise and tenon joints really be?

My take has always been that if they're an easy fit, not sloppy, or need to be tapped together then that's fine. The glue is going to make the timber in the joint swell a bit so if they slip together easily by hand the glue will do the job for you anyway. It probably makes a difference whether you cut your joints with a router or the more traditional methods too. Any mortise that has had some chisel work done on it is bound to have some irregularities in it so a tighter fit is likely to be OK whereas you wouldn't want too tight a fit with a routed mortise due to the potential for the joint to be starved of glue.

I'm using a mix of both power and hand at the moment so they are not exactly engineering tolerance mortises. I'll be pinning the joints eventually so I can probably afford to ease them a bit more than I have them at the moment.

Originally Posted by Fuzzie

I'm using a mix of both power and hand at the moment so they are not exactly engineering tolerance mortises. I'll be pinning the joints eventually so I can probably afford to ease them a bit more than I have them at the moment.

It doesn't sound like they're going to fall apart Fuzzie. Long grain to end grain can be a bit of a worry, but it sounds like you've even got that covered.

Actually thinking about questions around this stuff I asked many years ago, I'm now wondering if I'm brave enough to do it Woodwould style and assemble the cases without glue.

Trick for new players - compress the tenon slightly in the vise to get a nice easy assembly fit. Swells up again when glued for the final assembly.

That is some beautiful work, and exceptional finishing, by WW. I also learned something new about pegging and draw boring.

Fuzzie, I judge that a mortice-and-tenon is a correct fit when they slide together, and then you can up end the mortice without the tenon falling out.

Regards from Perth

Derek

Thanks Derek, WW certainly was a master of what he did. I think I'll try and finesse the joints on my current build with another pass or two of a shoulder plane to try and get that slip together with hand pressure only fit.

Something that i've learnt working in an environment that isn't climate controlled is that a perfectly fitting tenon on one day can be a loose/tight fitting tenon on another depending on the time of day/season/humidity when the original fit was made.

So i've concluded that somewhere between mild hand pressure and not slipping out under its own weight is ideal and the glue will fill the rest of the space.

Don't be overly concerned, as lets face it, the stuff from mass produced furniture stores are probably not built to the standard that you're working to and that stuff seems to survive for decades

He still does. His blog is Pegs and 'Tails | Seventeenth- and eighteenth-century English and Irish furniture &c.