Failed mortise & tennon glue joint need opinion

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Forum topic by Michigander posted 07-15-2015 06:42 PM 1029 views 0 times favorited 11 replies Add to Favorites Watch
View Michigander's profile


220 posts in 2417 days

07-15-2015 06:42 PM

Topic tags/keywords: trestle table failed mortice tenon glue joint

I am building a trestle table and have completed the base. See the pictures attached. The picture shows the base upside down. The tenon glue joints are the joints identified in the picture. These top stretchers have slots that accommodate wood pieces that hold the top to the base. The problem is the glue failed and when I released the clamps the joint popped, so there is no holding power there. I should have cut a groove for a wedge but didn’t as the middle main stretcher is glued and pegged, I can’t take apart the base to cut the wedge slot. So I was thinking of drilling a 1/4” hole through the joint from top to bottom and gluing a 1/4” maple dowel to hold the tenon in the mortise.
Am I right in thinking this will suffice or should I add additional pieces to secure the stretcher to the base legs? I hope I am clear. Your advice is appreciated!

11 replies so far

View chrisstef's profile


17385 posts in 3004 days

#1 posted 07-15-2015 07:26 PM

Id go a little larger on the dowel if you can but I don’t see why pegging it wouldn’t hold just fine. Unless that joint was super snug to start with I can see how it might fail. I think the table is very cool lookin.

-- Its not a crack, its a casting imperfection.

View RobS888's profile


2411 posts in 1843 days

#2 posted 07-15-2015 07:38 PM

Could you use a 3/8 draw bore on it? If you can remove the ends you could drill through the top (bottom in your first picture) of the end piece over the mortise and into the bottom (perpendicular to the tenon) then reassemble and mark the tenon using the drill bit. Then move the point 1/16 closer to the shoulder. Drill through the tenon, reassemble then drive the sharpened dowel down into and through the tenon. I used them on a bench and it is rock solid. I used glue, but I’ve read it isn’t necessary.

-- I always suspected many gun nuts were afraid of something, just never thought popcorn was on the list.

View Woodendeavor's profile


276 posts in 2604 days

#3 posted 07-15-2015 07:47 PM

from the picture it looks like mortise and tenon are not that tight. If there is any gap I would first try and make a wedge that I would glue and drive in there, then I would dowel the joint from the bottom

View b2rtch's profile


4861 posts in 3046 days

#4 posted 07-15-2015 07:51 PM

Peg them, they will never move

-- Bert

View HokieKen's profile


4998 posts in 1136 days

#5 posted 07-15-2015 08:01 PM

It looks like you might be able to sneak a pocket screw in the top of the stretchers into the leg assemblies? I know it isn’t pretty but it would be permanently hidden after the table top is attached. Pegging should work as well, I’m just thinking pocket screws would be easier and wouldn’t be visible.

If you do peg them, I’m with chrisstef, I’d go with a dowel larger than 1/4”. If the joint “popped” when you released the clamps there’s obviously some internal stresses that may increase with changes in humidity. If you’d rather not have the dowel end grain visible, you could peg down from the top rather than up from the bottom. Again, it’ll be hidden when the top goes on.

-- Kenny, SW VA, Go Hokies!!!

View bondogaposis's profile


4727 posts in 2349 days

#6 posted 07-15-2015 08:06 PM

I would wedge the gap first then peg the tenon.

-- Bondo Gaposis

View Michigander's profile


220 posts in 2417 days

#7 posted 07-15-2015 08:20 PM

RobS, I can’t disassemble the main stretcher so I have to fix it in place.
When I comment up or down I am referring to the pictures, not the way the base will sit when fully assembled.
Woodendeavor, Yes the one I took a picture is loose, but it isn’t as bad as it looks. (I tapered the holes inadvertently as I chopped everything by hand). My thought is that driving a peg in the base of the leg, the thin section (3/8” thick) above the tenon might break.
I checked the available room on each side of the tenon (think right and left) and looking at all 4 tenon, one has room for .030” wedge less than 1/32” and another has room for .050” wedge (less than 1/16”. My guess is the wedge would not go the full depth . The mortise was chopped from both sides so the hole is somewhat hourglass shaped.
Should I peg using a 3/8” dowel from the bottom, or would you go all the way thorough top to bottom. And stuff whatever wedge the hole will take?
Do you think I need corner brackets to connect the top stretcher to the base on the inside of the base? Remember when you move the table the stress on the top stretcher is towards the 3/8” web. (I know I put the mortise joint in the wrong place. )
Thanks for your help.

View Woodendeavor's profile


276 posts in 2604 days

#8 posted 07-16-2015 01:07 PM

John, any amount of wedge you can get in there I would to tighten up the tenon. 3/8 dowel may be a bit overkill in my opinion but what ever will make you sleep well at night. I would use what ever dowel I had in the shop, probably 1/4

View timbertailor's profile


1594 posts in 1422 days

#9 posted 07-16-2015 02:13 PM

from the picture it looks like mortise and tenon are not that tight. If there is any gap I would first try and make a wedge that I would glue and drive in there, then I would dowel the joint from the bottom

- Woodendeavor

Glue is not going to hold if it is not touching the wood.

I agree with your assessment.

-- Brad, Texas,

View Michigander's profile


220 posts in 2417 days

#10 posted 07-16-2015 02:19 PM

Thanks guys for the great advice. I’ll try to get some wedges stuffed in and then peg. Damn I wish I would have just cut wedge slots to begin with! Live and learn. I’m getting a mortise machine too so I can make straight sided holes!

View rwe2156's profile


2925 posts in 1478 days

#11 posted 07-16-2015 02:37 PM

Guide block should get you 90 degree walls.

Through mortices are not easy.
Don’t beat yourself up fixing a mistake well is part of good craftsmanship.
You’ve got a nice looking project there.

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

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