Glue pocket holes?

[Cody Colston]

I glue because, why not?

Furthermore, the idea that end grain to long grain butt joints have no strength is simply one of those internet forum things that keep getting repeated but isn't exactly accurate. It's the same thing as saying "biscuits add no strength to a joint."

In the FWW joint strength test, the butt joint actually fared pretty well. It was stronger than both the cope & stick and the stub tenon and groove joint. BTW, biscuit joints were plenty strong, too, ranking just a few pounds below the Domino loose tenon.

The test was not perfect in some opinions but the results are more credible than just an opinion.

[Bruce Page]

The test was not perfect in some opinions but the results are more credible than just an opinion.

Excuse me? It was humble opinion.

A long time ago, long before the pocket joint came out, I made several simple mirror frames as gifts using glued butt joints. It wasn’t long before every one of them fell apart. Maybe it was the glue I used back then, maybe it was the wood. In any case, I don’t glue butt joints.

[Jim Dunn]

Jim, are you talking of gluing an end grain butt joint as in a stile/rail? If you are, there's absolutely no strength added to the joint by gluing, IMO.

Well I glued them and really screwed up the initial fit that I had.

I have to agree with Bruce as it is end grain not much holding power. That said the joints can be reinforced across the back with much more holding power than end grain glue or one screw in each piece.

As to the mortice and tennon suggestion I would like to be good enough, some time in the future, to do this type of joinery proficiently.

[Ray Newman]

Jim: I found that you really need to securely clamp the part the is receiving the screws for a good tight fit and a the joint doesn't really need a great deal of glue. Too much glue and things will shift.

In my experinece, the faster the screws and driven in and set, the better the fit. I use a corded drill or a portable drill with a freshly charged battery.

At first, I didn't securely clamp the work and the results were less than stellar. On a whim, I also tried screwing into end grain to determine if it would hold -- don't try it, trust me.

What I did do was rip and cross cut a few scraps a spent some time practicing. Finally the knack of doing it right set in.

[David Cefai]

About a year ago I made a 5 x 3 1/2 inch frame from 3/4" square pine to test a hand mitre saw I had just bought. (Dead on 90 and 45 degree cuts )

There are 2 mitre joints and 2 butt joints. I've just dug it out and applied a fair amount of force to the joints to no effect.

I wonder if the type of glue matters. Not just its comparative strength but its behaviour with end grain. (I use mostly Evostik white PVA).

"Everybody" says that end grain joints are inherently weak. Maybe it's time for a rigorous test. It could simply be that end grain joints usually have a smaller contact area than others and that there is no mechanical reinforcement to them.

[Joe Chritz]

A test of both cross grain and long grain joints was done by a wood magazine a couple years ago.

Basically a bunch of joints were made using the same amount of different types of glue and broken apart by machine. The results were interesting.

Yellow PVA glue has about 80% of its final strength in around 20 minutes and the cross grain joints are a lot weaker but still took a fair amount of force to break. At least a few broke the wood apart.

I will dig around and see if I can find that mag and post back some specifics.

Joe

[Tom Welch]

I'm in the no glue camp. The reason is two fold. First, speed, I use the pocket hole jointry because it is a fast way to put together faceframes. While I agree that adding glue does not take that long for one joint, but add up all the joints and you get the point. Besides Pocket screws alone will give all the holding power you need for a faceframe unless you intend to drive a tank over it. If I need more strength, then I use my domino or use mortise and tendon jointery. Second, and more important to me, is if I make a mistake (A frequent habit) I can move the joint a 1/8 or 1/16 of an inch real fast and I don't destroy the piece as if it was glued.
Anyway just my humble 2 cents.

[J.R. Rutter]

I glue because I think that the joint looks better. I try to get an even, light layer of glue at the front of the joint, and worry less about the back. If it is stain grade, an unglued joint is especially noticeable where the stain sinks into the end grain if there is no glue to seal it up. Even under a clear finish, the joint is less visible when there is glue at the surface to force wood movement to the back side.

[Glen Butler]

I glue because I think that the joint looks better. I try to get an even, light layer of glue at the front of the joint, and worry less about the back. If it is stain grade, an unglued joint is especially noticeable where the stain sinks into the end grain if there is no glue to seal it up. Even under a clear finish, the joint is less visible when there is glue at the surface to force wood movement to the back side.

I can agree with this and is the only reason I see for gluing face frames.

[Bobby Thistle]

Funny this should come up... I've been making doors for cabinets this past week using pocket holes. I do use glue. It may not offer a LOT of strength to the joint but anything is better than nothing in my view.
BTW... I got my Rockler Pocket Hole clamp this past week. When used with the Kreg clamp it is SWEET!!!

--Bobby

[Cody Colston]

A test of both cross grain and long grain joints was done by a wood magazine a couple years ago.

Basically a bunch of joints were made using the same amount of different types of glue and broken apart by machine. The results were interesting.

Yellow PVA glue has about 80% of its final strength in around 20 minutes and the cross grain joints are a lot weaker but still took a fair amount of force to break. At least a few broke the wood apart.

I will dig around and see if I can find that mag and post back some specifics.

Joe

Fine Woodworking #203

[James Morton]

Unfortunately, I was able to test the strength if a glued end grain to long grain pocket hole joint just today. Glued and screwed up a face frame, then about 2 hours later, I noticed that I made a mistake on that frame. I removed the screws and tried to get the joint apart by hand. I ended up having to use a clamp spreader to break the joint, and while the joint failed somewhat along the glue line, there was quite a bit of long grain wood still stuck to the end grain. So much so, that the stock is unusable and I will have to remake that whole face frame. I was using titebond 2.

[Bill Huber]

Unfortunately, I was able to test the strength if a glued end grain to long grain pocket hole joint just today. Glued and screwed up a face frame, then about 2 hours later, I noticed that I made a mistake on that frame. I removed the screws and tried to get the joint apart by hand. I ended up having to use a clamp spreader to break the joint, and while the joint failed somewhat along the glue line, there was quite a bit of long grain wood still stuck to the end grain. So much so, that the stock is unusable and I will have to remake that whole face frame. I was using titebond 2.

I have see the same results as you with end grain to long grain. I put glue on the end grain and let is soak in and then put another layer of glue on it before the finial glue up, like sizing wallpaper. I have found them to be very strong.

[mreza Salav]

Although end-grain-to-face grain glue is not as strong as face-to-face grain, contrary to common belief, it is still fairly strong. This was shown in several tests recently, one of which in FWW I think.
I use both glue and screw.

[Steve Griffin]

Although end-grain-to-face grain glue is not as strong as face-to-face grain, contrary to common belief, it is still fairly strong. This was shown in several tests recently, one of which in FWW I think.
I use both glue and screw.

Absolutely!

Even though it is end grain, glueing face frames adds significant strength. Some of you guys you don't like the idea of glueing really need to do some shop testing.

I think the reason end grain glueing is so successful in combination with pocket screws is that the screws provide attachment strength, while the glue provides sheer strength. This prevents shifting of the joint during use, transport or wood movement.

Another reason to glue is to seal up the end grain. If your cabinet gets wet, it is one less place water can get in and do damage. Water is evil stuff which can seep into fantastically tight joints.

-Steve