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Mortise and Tennon Question

by Jsbeckton
posted 02-05-2017 04:07 AM

9 replies so far

View woodenwarrior's profile


255 posts in 2795 days

#1 posted 02-05-2017 04:29 AM

How long is the joint that you’re trying to make breadboard ends for?

-- Do or do not...there is no try - Master Yoda

View woodenwarrior's profile


255 posts in 2795 days

#2 posted 02-05-2017 04:33 AM

I ask because by making multiple tenons on a longer piece, you increase the strength and decrease the likelihood that the panel you’re making the ends for will cup.

-- Do or do not...there is no try - Master Yoda

View a1Jim's profile


117901 posts in 4178 days

#3 posted 02-05-2017 12:33 PM

It’s also a wood movement issue so smaller tenons will have several areas of tenons instead of one long one that will move more.


View TungOil's profile


1371 posts in 1095 days

#4 posted 02-05-2017 02:09 PM

The most recent breadboard ends I made were done with loose tenons. I routed a single long groove in the table end and the breadboard, cut a bunch of 1” wide tenons to length and glued each one into the tabletop. I left spaces between the tenons for screws to attach the breadboards. The key point is to glue only the center couple of inches of the tenon on the breadboard side and be sure the screw holes on the breadboard have enough clearance to allow for wood movement. The top will expand and contract with the weather but the breadboard will not.

-- The optimist says "the glass is half full". The pessimist says "the glass is half empty". The engineer says "the glass is twice as big as it needs to be"

View Jsbeckton's profile


10 posts in 1094 days

#5 posted 02-05-2017 03:32 PM

It will be for a 40” tabletop. I don’t understand how multiple shorts tennons is stronger than one long one? I would have expected the opposite.

View JBrow's profile


1368 posts in 1521 days

#6 posted 02-05-2017 04:18 PM


It seems to me that the long short tongue that fits into the groove in the breadboard functions to keep the breadboard flush with the surface of the top. The short tongue is oftentimes too short to pin the breadboard to the top with dowels. The longer tenons every so often and set into oversized (wider) mortises provide a place for dowels. The width-wise elongated holes in the longer tenons (that extend beyond the tongue) allow the dowels, which are only glued to the breadboard and not the tenon, to hold the breadboard in place and the top to expand and contract independent of the breadboard.

The longer tenons provide added strength required when the table is lifted by the ends, as when the table is moved from one location to another. The breadboard, which is mostly free-floating, would be less likely to break free and separate from the top with doweled in-place longer tenons.

If the tongue on the table top end is a longer tongue so that dowels could be used every so often to hold the breadboard in place I could foresee the potential problem of the breadboard cracking along its length. A lot of material would have to be plowed out of the breadboard to accept the longer tongue. This would leave the breadboard thinner and thus more susceptible to cracking along its length. It could crack when installing the breadboard if the top and/or breadboard are not perfectly flat. The breadboard could also crack should the top ever decide to cup. A shorter tongue along the length of the top with a few longer tenons would leave more material intact on the breadboard, making the breadboard stronger and more resistant to cracking.

View Jsbeckton's profile


10 posts in 1094 days

#7 posted 02-05-2017 11:05 PM

The tennon will be 1.5” whether it’s one long tennon or 4 separate tennons. I didn’t notice people saying that the one long tennon was really short and the separate tennons were longer. Just seemed Line people were doing both but why take extra steps to cut out individual tennons when you already have one big one? Maybe it’s because they are mortising in way that one long slot is not convienent?

View Robert's profile


3598 posts in 2081 days

#8 posted 02-06-2017 03:45 PM

It takes less time to make and also glue up easier, plus simply not necessary to have one deep tenon that long.

BTW, its tenon, with one “n”.

-- Everything is a prototype thats why its one of a kind!!

View Jsbeckton's profile


10 posts in 1094 days

#9 posted 02-06-2017 05:15 PM

Tenon, got it! I used a router to make the tennon and mortise. I think it would actually take longer to make 4 small mortises rather than just marking my fence for one long slot? And the tennon would just take extra time to notch out the individual tenons after I make the one long one. If it’s no harm I think I’ll still with one long 1.5” tenon because that seems easiest with my method and avalilable tools. Just wanted to make sure no harm in doing so.

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