Epoxy for Cabinet Door Glue-up?

[tom cooper]

I have 20 cope & stick type cabinet doors in-process, all pieces cut and ready for glue-up. When checking fit in the coped end during setup, I missed seeing a very slight gap of about .010"-.012" between the stile profile cut (it is a cove style profile) and the rail mating surface (bead shaped cope). The gap follows the curved sufaces only. The tenon fit is perfect and the rail & stile top and bottom outside surfaces are perfect.

What to do about the gap? I am concerned that even though the tenon and all other features of the joints are perfect, that I will loose a fair amount of the strength that the joint would otherwise have due to the gap along the curved surfaces. The door panels are 3/4" MDF and the largest door (~20"x27") is kind of heavy. Titebond II or III can probably fill this gap but since this area will not experience clamp pressure during glue-up, strength will be lost.

What about epoxy? and in particular, System Three T-88. I was thinking that epoxy may not need clamp pressure to develop max joint strength, is this correct? And will I end up with an incredible mess?

Any and all thoughts are appreciated.
Thankyou

[Chris Padilla]

Tom,

That connection point is end-grain to long-grain...like the shoulder of a tenon when mated with its mortise. Nearly all the strength of this joint is from the cheeks of the tenon to the mortise sides: long-grain to long-grain (albeit perpendicular to each other).

I NEVER put glue on the shoulder of a M&T joint because:

(1) It is end-grain to long-grain
(2) It will require cleaning of glue squeeze-out, which I avoid like the plague whenever possible

[Les Heinen]

Tom

Just finished using epoxy on two exterior doors and while it will fill gaps and provide a strong joint, ANY squeeze out will effectively seal the wood and would in all probability affect the finishing.

I would be reluctant to use epoxy for this purpose if finish quality is an issue. I used West system on my project and was very satisfied with the product...haven't used System 3.

Les

[Jim Becker]

Can you shave a little off the end of the t&g tenon to snug it up? You really want to avoid epoxy for this due to the potential finishing issues that Les brings up. A snug fit with PVA glue will give you a better overall door construction.

[J. Z. Guest]

...or you could use poly glue on the tenon, and the foam-out will come out onto the shoulder and kind of fill the gap and give some strength there.

The problem with having a gap there is not that you're losing strength from glue surface area, but that the joint is more likely to break loose if the fit isn't tight. In other words, the other glue joints will experience more stress because of a gap there.

I like Jim's suggestion to trim the tenon a smidge to eliminate the gap.

[tom cooper]

Trimming would work but I will have to trim back along the long edges of the stiles as well. The long edges seat into and are in proper contact with their corresponding shoulder cuts on the rails.

I guess the stiles could be trimmed back with a quick light pass on the jointer. On the rail, the tenon and leading edge of the cope cut would also have to be trimmed back by a corresponding amount. This would take two setups as the tenon and leading edge of the cope cut are different lengths. I suppose this could only be done on a table saw. Boy, that is about 12 more opportunities per door for me to screw up!

The doors will be a paint finished. Maybe the best thing is to glue up as is and look for a different way to reinforce the joints on the inside of the larger heavier doors.

[Joe Chritz]

Was that caused by the stick cut being a bit short on depth? If so you could most likely rerun the profile to get it correct. I'm trying to visualize how that happened.

As mentioned that section supplies virtually no strength and mine gets very little glue if any at all. I use the squeeze and pray method of gluing on those.

As long as they look good when done I don't see any problem. Any cope/stick joint I have tried to break apart took a good amount of force to do. Unless it is dropped on one corner they are pretty resilient to breaking.

Joe

[tom cooper]

For Joe-
I am sure that my explanation and description of the problem could use improvement, but if you happen to have a CMT catalog or a Sommerfeld catalog, there is always a page in there that describes "fine tuning for rail & style bits". If you look at "Problem #4" you would see exactly what I am talking about. The solution is to place shims between the kerf cutting blades and the cope cutting blades. Unfortunately I am using Freuds insert cutters which have no way of shimming to remove these clearances. I have talked with Freud and their only guess is that any one (or more) of the four inserts may be out of tolerance.

For all,
I am beginning to agree with the folks that mentioned that the long/short fibers in the coped area add little effective strength. Although I may still go for a drop of epoxy here and TBIII the tenons as normal.

Thankyou for your time and the suggestions.
Regards.

[Jim Becker]

...or you could use poly glue on the tenon, and the foam-out will come out onto the shoulder and kind of fill the gap and give some strength there.

The foam from the poly glue has no effective strength. It is likely, however, that the glue joint would still be strong since the tenon seats well by the OP's description. That said, given he's painting, I'd go with epoxy because once sanded, it will give a better joint surface than the foam from the poly glue.

[Chris Padilla]

Tom,

I was beginning to wonder if my post was only viewable by myself!

Since you are painting these doors, your options open up for dealing with the open joint:

(1) Wood putty
(2) Spackle
(3) Paintable caulk
(4) Sliver of wood glued in

Frankly, I'd go with either (1) or (2) because you can apply it nice 'n smooth with your finger and they'll dry the fastest and are easily sandable unlike (3). (4) sounds like a TON of work cutting small strips, glue in, sanding...blech.

[Wayne Cannon]

Aside from the squeeze-out/finishing issues, System Three does not recommend straight epoxy (including T-88) for wood joinery because of its inability to deal with the expansion and contraction. I can't find the info right away on-line, but their literature (possibly the ir"Epoxy Book") suggests either using a filler or using their "SilverTip GelMagic" which is factory formulated for woodworking joints.

A recent test showed very little strength advantage to epoxy over PVA. I used epoxy for exterior M&T'd gates, but that was before I learned that Titebond III's ANSI Type I "water resistant" is tested by multiple 4-hour boiling in water and baking cycles that my gates will never see.

[Mike Cutler]

Tom

System Three T-88 is an excellent epoxy. It already has the thixotropic (sp.) agent in it to act as a gap filler. I've used it many times, and in fact, epoxy is my adhesive of choice almost exclusively.
Depending on the finish, you may, or may not see the epoxy. The T-88 will appear a milky white when mixed, but will dry clear.

Apply the epoxy just as chris suggests, don't purposefully coat the shoulders, let the epoxy squeeze out. If you are painting these doors, I highly doubt you will see the epoxy.

System Three makes an excellent product, and the T-88 is actually a little more forgiving than their traditional epoxy products.

[Alan Trout]

I am going to stick with Chris on this one. What I have used to fill small gaps on painted base and trim that works better than latex caulk. is DAP tub and tile sealant. It is pretty thin goes on very smooth with the finger and even acts to some extent as an adhesive. I know is sounds kind of crazy. A professional painter friend of mine turned me on to this about 20 years ago. Be sure to prime first and then use th DAP.

Good Luck

Alan

[Jim Becker]

Wayne, the reason that some of us recommended the epoxy was more about filling the gap than adding extra strength. But as I think at this point and given this will be a painted piece, I'd probably do the glue-up with PVA and then use a filler, such as non-shrinking spackle prior to priming and painting.

[Chris Padilla]

I recently (well, still doing it) trimmed out my entire living room with 100' of baseboard and 7 door casings. My 15-minute drying time squeeze tube of spackle will get HEAVY use for pathcing nail holes and outside miter gaps as well as inside coped joints. I did the best I could but I didn't fuss with it too much since it is all painted. "Spackle, sandpaper, spackle, sandpaper-->touch-up paint" will be the jingle this weekend.