Gluing face frame joints

      Is the added glue necessary? August 13, 2002

Question
I recently purchased a pocket cutter for face frame construction. Do you need to glue the joints or not? I used to mortise and tennon the joints and we always glued them.

Forum Responses
You probably don't have to glue, but I think it adds a lot of stability to the joint for a small amount of effort.



From contributor L:
We always glue. I totally agree with the above on the stability issue.


From contributor B:
Glue on a mortise and tennon makes good sense. Glue on a butt joint does not.


From contributor L:
Contributor B, I strongly disagree. I think glue on most types of joints makes good sense. We butt joint our standard drawer box carcasses using 9-ply birch. We glue and staple the joint. Without any doubt, the joint strength is greatly enhanced by the application of glue. Also, when we make a mistake, after removing the screws, the glued up face frame joint has to be pounded apart with a rubber mallet. The easiest way for the questioner to make up his own mind is to run a test. Join a face frame with screws and glue, give it a couple minutes, remove the screws and see how easy the joint is to separate.


From contributor D:
I used to install factory cabinets. On one job, the lady was home when I brought the cabinets in. I would unbox the cabinets and we would look them over for problems.

She asked why have them built when it is cheaper to order them and they look the same. About then I came to a 4-drawer 18" wide cabinet. As I unboxed it and she looked it over, I grabbed it and lifted it by the top rail. The joint failed and I was left standing with a broken rail in my hand. Upon inspection I realized that the machine that did the gluing didn't get any glue on the joint. Closer inspection revealed 3 of 5 rails didn't have glue.

So now all of a sudden the expensive cabinet guy was valuable because he was able to take the cabinet back to his shop, knock off the face frame and build another face frame (biscuits and clamps), stain it, spray it and have it back the next morning.



From contributor O:
I would probably glue the face frame joint - for its "gap filling" properties more than anything - even though it's not adding enough strength to really make a difference (being an end grain to face grain joint).

Contributor L's example of his butt jointed 9-ply drawer box is not the same. There will be some face grain to face grain surface area on that joint, so the glue is certainly serving a purpose.

I wonder if stapled and butt jointed drawer boxes are considered the "very finest" everywhere, or just CA?



From contributor L:
"Very finest" defined as the finest the customer can afford. We offer 9-ply (Baltic birch only), dovetailed and doweled drawer construction in all species. We also offer Blum standard slides, tandem and Accuride (standard on large drawers and pullouts). I have often thought of using a lock mitre joint on the 9-ply. Anyone here do that or ever try it?
I would never ever in a million years do that white vinyl wrapped particleboard junk.


From contributor O:
Contributor L, at least you offer choices in drawer boxes. In our area, most of our competition provides a stapled, butt jointed box made from junk plywood with voids. We provide either Baltic birch or solid maple sides, dovetailed using Accuride slides.


It really does make a difference to glue the joints. Build two face frames, glue and screw one together, then only screw the other one together. Then unscrew both of them. One will be parts and the other one will be a face frame. Then to take the glued face frame apart, you need to slam a hammer on the joint. If you're lucky, both sides will come apart fairly clean - often the end grain side will rip wood off from the other side. There are textbook answers, and there are real world conditions. I say glue the joints.


From the original questioner:
I think I will glue them. After testing a few frames, I found that gluing them takes all the play out of the joint.


From contributor O:
Like I said, I would use glue as well. But I'm not kidding myself into thinking that it's doing much. If it's holding as much as you say, why even use pocket screws? Just glue and clamp them up and let them go!

I do think the glue adds enough strength with the pocket screws. In addition to filling in any small voids in the cut, it will keep the joint in place. A dry joint with just pocket screws would probably "creep" over time.



Here's your chance to use the Hi-Pur hot glues - this is a perfect application for that. I've been using them for lots of different applications. They dry very quickly and are the strongest stuff I've used.


From contributor D:
Contributor O, the reason for the screws is to speed assembly of the piece and keep it lined up until the glue dries. The strength of the joint is provided by the glue, which forms a bond stronger than the wood fibers themselves. If done properly, the joint will not fail cleanly.

The factory cabinet companies use the screws so that the frame is instantly assembled and ready for the next step. They need to produce a cabinet in about 2 minutes to make money.

I always use clamps because I feel I get a stronger joint than I can with screws.

The biggest asset of the mortise and tenon joint, widely regarded as the premium joint for face frames, is that the design gives an incredibly high amount of surface area for gluing. Without glue it isn't that strong.

As far as filling voids, if your equipment is set up right and if you clamp sufficiently, there should be no voids and if there are, the joint is compromised.



From contributor L:
Contributor O, have you seen the new Accurides? They are a smaller full-x with a 75# rating made more for standard type drawers instead of the heavy-duty 3832's. I ordered 3 cases and they must be popular because they were back ordered 3 weeks. I have been using Blum slides for years and Accuride for heavy applications but I think I will give these a try - at least offer them to clients as an option.


From contributor O:
Contributor D, an end grain to face grain joint does not provide "a bond stronger than the wood fibers themselves". This only occurs when you're gluing edge to edge or face to face. That is why the mortise and tenon is used (to provide more face grain to face grain surface area). The screws act as dowels in a way, but also need the glue to maintain the alignment.

As far as voids, I'm talking small voids, not 1/16" gaps. If every joint you cut on every job is perfect, that's great. We're not as good. We have some minor imperfections from time to time in the edge of the stiles, or end of rails.



From contributor M:
Does anyone think that gluing along with pocket screws will help reduce wood movement on poplar face frames? I am getting ready to do an all-white kitchen and I am concerned about the cracks that develop at the joints.


From contributor S:
Contributor M, make sure you explain to your customer that you will get some cracks at the joints on painted face frames no matter what you do and glue is a must. Also, I found paint grade soft maple to be more stable than poplar.


Contributors M and S, the glue is a good idea. Splitting is not necessary, however. Have you tried the Quickcutter screws from S&G?


From contributor L:
We glue our face frames with pocket screws and also glue them to the cabinet carcass (I am not talking about a dot of glue - we keep a damp rag handy and glue our joints liberally with Titebond yellow glue). I also did a PG job using poplar face frames 2 years ago and to date, none of the face frame joints have cracked.


From contributor O:
You might also consider the finish as a culprit of the cracking at the joints. Some finishes are more flexible than others.


From contributor M:
Contributor O, the finish I will use is SW white undercoat and SW white cab acrylic topcoat. How does that rate on the "flexibility" scale?


Is the cracking the finish or the wood?


From contributor M:
I am sure it is due to wood movement, as the cracks show up at the intersections of the rails and stiles.


Fact: using glue minimizes or eliminates cracks at the joints and adds strength in most applications. Even butt joints.

Fact: Using glue is better than not.

Fact: Pocket screws allow faster assembly until the glue dries and are a substitute for the clamping process. (If you have ever clamped frames the old fashioned way, you understand.)

Fact: If you're not concerned about joint flex, cracking or strength, don't glue.

Fact: Most modular cabinetry frames are not glued because they are not concerned about joint flex.

Fact: If you are building really nice cabinetry, the added time to squirt a little glue in the joint is minimal.

Fact: A good clean joint, even with end grain, has good holding power when glued and clamped. (Pocket screws are a substitute for the clamping process.)

Fact: This doesn't apply to face frames only.

Fact: Wood putty is made for filling gaps and cracks, not glue

Use the proper glue for the application for best results.



From contributor O:
A couple of the above facts are wrong.

"Fact: A good clean joint, even with end grain, has good holding power when glued and clamped. (Pocket screws are a substitute for the clamping process.)"

Pocket screws add much more strength to this butt joint than the glue. If you build these joints with no pocket screws, mortise and tenon, etc., and only glue, the joint will fail and is unacceptable. It's that simple.

What is your definition of "good" holding power? Take an edge to edge butt joint, glued and clamped - that is the best holding power - and bust it over your bench top and the wood will fail. Take an end grain butt joint and the joint will fail.



From contributor L:
Contributor O, I think that the pocket screws being a "substitute for clamps" says it all. If I just used glue and clamps and didn't remove the clamps, that would make for a pretty strong joint ;-)

I got those cases of the new Accurides in and they look pretty cool. The Accuride product # is C3732.



From contributor O:
Contributor L, we have used them before, but we use the 3832 as a standard "box" slide. We actually prefer the progressive action slides, but they don't make one in a smaller slide (just for file drawers and heavier applications).


From contributor A:
To make end grain butt joints a bit stronger, I use a watered down Titebond (50% water), which I apply to the end grain and let it soak in and dry. The glue tends to soak about 1/8" into the grain and seal the end, forming a sort of non-porous surface. If the cut is clean, the surface is more able to adhere to the face grain. This adds an increase of about 50% in the joints holding power, as compared to face grain bonding. I ran dozens of tests on this application and came up with this data.

I have even used this process while making a bar for a local pub. I used biscuits and glue to bond different angles in the bar top, forming an elongated octagon shape. Three years and many beers later, it is still strong and tight.

I was shown this by my granddad, a German woodworker who did this with hide glue.



From contributor B:
I must confess, after I saw all the posts here I did my own field tests and the glue adds a surprising amount of strength to the joint. I stand corrected. Also, the above post on soaking the end grain makes good sense.


Regarding the end grain versus edge grain joint strength issue... Is the wood structure weaker than the glue joint on the edge glued joint causing the wood to fail before the joint? Is the wood structure stronger than the glue joint on end grain joints, which would cause it to break at the joint first? Could it be that the joint strength is nearly as strong in both applications, but the failure comes as a result of the wood failure and not the glue joint? If you glue and clamp a piece of end grain to a piece of edge grain and bust it over your bench, which will fail - end, edge or glue? You all know that to maximize your joint strength, clamping must be involved with most wood glues. As woodworkers we seldom glue end to end unless it is an unusual situation, so this is rarely encountered. I have had to modify face frame openings by removing a rail and have had the edge grain tear loose, only to be hanging tightly to the end grain of the rail at the glue joint (after removing the pocket screws). Just a thought to whittle on.


From contributor A:
In my experience, the edge grain is going to fail before you will pull any grain from the end of the piece. For the most part, this is because of the joint conditions prior to gluing. I have found, with proper prep, the joint will almost always have failure due to the material rather than bond.

I have seen poorly prepped joints fall apart with little or no force applied. Almost always, the joint is a clean break at the glue line, with some edge grain from bonded piece still adhered to the end grain, but only a very little. I have seen end grain removed only when there is a defect in the wood within the first 1/8 inch of the joint in the piece where the end grain is glued.

If the joint is prepped the way I spoke of in my earlier reply, it will almost always fail due to material conditions and not the bond. I still use clamps and screws to hold the joint while drying and leave the screws in place when dry. This will give you a nearly movement-free joint. I also glue the entire face frame to the case for added strength. I have never had an open joint other than when a cabinet is dropped off the truck by one of the delivery/installers and totally destroyed.

I used mortis and tennon for years and now the later method is all I use.



From contributor D:
Since this is such a hot topic, I decided to test, too. I glued up 10 face to edge joints of 5/4 x 2 walnut 10" long. The only bonding done was Titebond II and clamps.

After a day of drying, I broke them apart with a hammer. 10 of 10 failed by having grain tear-out from the edge glued side. None failed at the joint. This was with no other reinforcement like biscuits, dowels or screws.

I clamp everything and although it is more time consuming, I don't have joint failure.



From contributor O:
Contributor D, did you test face to edge joints, or face to end grain?


From contributor D:
I guess it is end to edge, as in how you assemble the face frame. I don't know if I used the right terms in that one.


The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor C:
We make only high-end cabinetry, and one way to remove any doubt as to joint failure is to share any load on the joint(s) across as much of the surface as possible. To accomplish this, we also use the glue and pocket screw method (yes, we are total believers in gluing). Then, like others, we also glue the face frame onto the cabinet, however, with a twist... We also dado the face frame on the left and right stile 3/16", then extend the box panels on the left/right the same, and then glue the dado and face frame all-around prior to attaching the face frame to the carcass. Prior to assembly, we also pocket-hole the cabinet carcass all the way around the front (sides, bottom, and I-bar on top), and as with the face frame, screw the glued joint together. The load capacity on any one joint is dramatically increased, and the stress shared/decreased.

Sound likes a lot, doesn't it? Well, our philosophy is "when it leaves the shop, we never want to see it again" (except maybe in a magazine, whoo-hoo!). There are many ways of doing everything in this business and we are after the fastest, best way, because we are in this business to make money, as well as add to the craft.

Besides, in reality, it adds approximately 10-15 minutes per cabinet, provides easier installs, and speeds assembly (as with the face frame, no need for clamps after initial assembly). Does it pay for itself over time? Well, we warranty our work for 20 years, and although this may be hard to believe for some of you, we have never had a callback for joint failure on a face-frame, no matter the finish. Oh, sure, we've had the call-backs where a customer claims a door panel failed, but it turns out their German shephard slid across the floor, slamming its head into the panel and splitting it... It's amazing what some people think are warranty items.



Comment from contributor E:
I keep hearing glue, wait five, then remove the screws. When do you remove screws from the face frame in reality? Then why remove them at all? Try this: Glue a frame... no screws, just clamps, wait till the next day. Then, take a frame and pocket it... no glue, wait till the next day (no reason). See which is stronger. The small amount the glue is doing isn't worth the time it takes to put it on, clean it up, or the cost of the glue. As far as the rail breaking off the bank of drawers, the builders may have put the screw in too far, which causes the rail to split down the middle where the screw went in. Besides, woods like hickory split as soon as the screw enters the end grain. What kind of wood was it?

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