Failed glue dado joint??

[Jerry Olexa]

Building a cabinet with poplar..Have dovetails on ends and dado openings for the shelves..Two of the dado joints on one side failed (maybe I didn't glue those properly)..
When I saw problem last night, I partially pried open the 2 joint to access and dripped in more Titebond and then heavily clamped..Will let it clamped for +24 hours.
My concern is, if my memory is correct, that Titebond will not adhere well to old Titebond,,,(Maybe I should have epoxied).
How would you guys handle this ? Thanks:confused:

[John Lankers]

I guess more details would help, maybe a picture. When you did the glue up how tight was your original joinery and how long did take to assemble, titebond has a 5 - 10 minute open time. I remove my clamps very often after 1 1/2 hours (mostly because they're needed elsewhere) and never had a failure - yet.
Edit: I don't apply severe stress to a fresh glue joint during the first 24 hours.

[Tom Trees]

I would like to know an application where you would want to glue a dado.
I thought the whole point of them was to allow for expansion and contraction.
Tom

[Lee Schierer]

I would like to know an application where you would want to glue a dado.
I thought the whole point of them was to allow for expansion and contraction.
Tom

Dado joints are used for strength when supporting shelves. They are generally glued in my experience, but since most of the surface is end grain it doesn't add a lot of strength, but it does serve to hold the pieces in place.

[Jerry Olexa]

Thanks for your comments. This is a small hanging tool cabinet I'm building..that's why the poplar,
I use dados regularly when building shelves to add some strength but primarily as a holding, positional device.
I normally use Titebond with the normal timing i.e., 30sec/1 hour and 24 hrs. for full strength.
In this case, I'm trying to correct a mistake and correct without having to dismanttle and reconstruck the whole carcass.
That's why my unusual gluing (correctional) behavior,,,
Still anxious for your advice, input. thank you. Soon the glue will be dry.

[Brian Holcombe]

It's less than ideal, but if you clamp them back in place, then drive long screw to hold it, likely it will stay in place. Use a long screw with coarse threads and it stands a good chance of staying tight.

[andy bessette]

Titebond is inferior for gluing dado joints, which require a gap filling glue. I use WEST epoxy to achieve extremely robust and 100% reliable glue joints, but admit it takes longer and requires much more special care to apply and to cleanup. My joints don't come apart.

[Jerry Olexa]

Titebond is inferior for gluing dado joints, which require a gap filling glue. I use WEST epoxy to achieve extremely robust and 100% reliable glue joints, but admit it takes longer and requires much more special care to apply and to cleanup. My joints don't come apart.

Andy, you are right..the gap filling feature is my concern..Although I love Titebond, it is not good at that.

[Lee Schierer]

Andy, you are right..the gap filling feature is my concern..Although I love Titebond, it is not good at that.

Good dado joints should not have significant gaps. But because there is exposed end grain, you need to be generous with the amount of glue you use as it will soak into the end grain and cause a glue shortage.

[Jerry Olexa]

There is joy in Mudville.....Happy ending....My crude, simple gluing and clamping did the job.
The clamps were removed and the joints are tight,
In retrospect, I probably did not apply glue to that portion of the dados...All 4 corners of cabinet were Dt'd but I wasn't pleased with that almost 1/4" gap in 2 of the joints on one side only.
Now, All is well..Thanks for your comments..
That's what happens when you glue in a hurry.:D

[Greg Works]

Perhaps add pocket screws underneath the shelves. That would hold them in place, but wouldn't help to solve the joint failure mystery. Without a doubt epoxy is stronger than wood glue, but I've used Titebond on MANY dado joints with no problems. Glue can go bad. I've also had projects where I was careless and didn't clamp tight enough and left a gap. That was user error.

[Lonnie Gallaher]

I use Loctite PL for my case construction. After doing some tests with it at work - gluing two non-porous items. And having tested it with plywood case construction - dados.

The following is from WoodWeb forum. More supporting tests by a professional.



From contributor B:
About fifteen years ago, when PL Premium polyurethane construction adhesive was introduced, I discovered that PL pretty much welds to melamine as well as any other porous joint, such as plywood edges to solid wood, covering most case joinery.
I embarked on a test. I made a bunch of 4" x 4" x 4" L-shaped sample joints in melamine and birch ply, to test in an arbor press with a weight scale to record the threshold weight the joint would hold at the point of breaking.Joints were dado, biscuits, and screws using Titebond, versus a set of joints that were simple butt joints glued with PL premium, and a set of butt joints with PL and a 3/4" x 3/4" cleat glued and pinned on (no clamps) for added glue surface area.
The results were as follows:
Melamine: The screw joints broke at around 30 lbs, same with the biscuits. The dados went to 37 lbs. Dados are far weaker than people think due to the fact that the cutting of the groove destroys the integrity of panel.
PL broke at around 45 lbs, ripping out the HDPB core, but no joint failure.
Here’s the real discovery:
The joint with the PL and glue cleat broke at 127 lbs!
Essentially the same results with the pressure tests on the plywood.
Conclusion:
My whole cabinet business was revolutionized, and all my case joinery utilizes PL premium butt joints and two "locator" nails to keep the joint from slipping during cure. I put a couple deep-throat clamps in the middle to aid in pressure till set. It’s hard to measure, but I figure I saved about 10 - 15% overall time by eliminating the time consuming joint cutting operations like insertion dowel, dado, etc.
For face frames I use PL all the way. I would use Titebond only for solid wood-to-solid wood.