Pocket Hole Joints: Is Glue Necessary?
George VondriskaDescription
There are a handful of topics and questions that pop up pretty regularly in the woodworking world. Most commonly: should I or shouldn’t I add glue to pocket hole joints? If you ask a room full of woodworkers you’ll probably get answers that fall on both sides of the fence. We decided to do a little experiment. Now we know that we didn’t take a hugely scientific approach to this, but it provides some results that are interesting.
The Experiment
We made up two pocket hole joints. One with glue in it, one without (The specific glue used was Titebond Quick and Thick). With one leg of the joint held in a vise, we yanked on the other leg, looking for a fracture. One measure was; how much force does it take to break the joint. The other was; what exactly does the joint look like after it’s been broken.
The Results
Well, we’re not going to give away the results of our experiment here. You’ll have to watch the video. But we can say you’re going to want to incorporate the results into your projects.
Applications for Pocket Hole Joints
There are so many places you can use pocket hole joints and screws. This is a such a versatile way of putting wood together. While most of us probably use it for face frames, or similar applications, pocket hole joinery can be used in lots of other applications.
Also Important…
Choosing the right joint for your project is important, and choosing the right glue is important too. Have a look at 4 Types of Glue You Can Stick With to make sure you’re using the best glue for your projects.
Let's discus a little woodworking controversy, and that is should one or should one not put glue into their pocket hole joints when they put them together? So I'll tell you a little bit of my story with this. My friend Charlie had a big cabinet shop where they were making face-frame-style cabinets all the time. Got kinda far behind on work, and he was so desperate for help, he asked me to help for a day. So I went over there and I was helping him put face frames together. And I'd put the parts together, rails and stiles, drive the screws, rails and stiles, drive the screws. And he noticed I was not putting glue in the joint. So he called me out on that, and I said, "Well, everybody knows it doesn't do any good to glue end grain 'cause it's so porous, it soaks it up, there's no real bond there." And he said, "I don't care what you think you know, we always put glue in the screw pocket joints." So I put glue in the pocket hole joints. As it turned out, I had one rail that I mislocated just a little bit, so I had to move it. So I took the screws back out and I grabbed that rail and I pulled on it and it didn't wanna move, and I pulled on it, and it didn't wanna move. And this was like, I don't know, between two and five minutes after I had put it in, so really close to assembly time. And in the end, when I pulled at it harder, long grain from the mating piece came with end grain from the rail. So that told me Charlie was probably right. Do not ever tell him I said that, but Charlie was probably right and glue is a good idea in these joints. So here's our experiment today. And I recognize this is not a 3M laboratory, this is my woodworking shop. However, we'll see what happens. On this pocket hole joint, there's glue in there. On this pocket hole joint, there's no glue in there. So what we're gonna do is put these in a vice, pull on 'em. Now, same species between the two joints, they're all red oak, the parts are all the same length, so I'm trying to make this a little bit scientific. So let's do the no-glue one first. Lotta people put their pocket holes together without any glue in the joint. Grab it in a vice. And then what I'm gonna do is try to just consistently grab this end of what would be a rail, pocket holes are going that way. Here's what I'm gonna do, I'm having a mind change. I'm gonna turn this around so you can see the pocket hole joint. All right. So I'm gonna try to just push in the same spot on both of 'em and we'll kinda see what happens here. All right, no glue, and what we did is, the screws held great, pulled 'em right through the end grain of the mating piece. Now glue, or eulg, I guess for you. All right, so I'm pushing harder now than I was on the first one. All right, now if you look, we've got the same thing going on. Those spots on the end grain are pieces of long grain that were pulled out of this piece, and it took quite a bit more tension to get this one to go than it did the first one. So, again, I'm the first to admit this is marginally scientific, but my lesson out of this is what does it take to add a little bit of glue to that joint? Not much. And I firmly believe that it adds a lotta strength to the joint, so it's worth doing, and, like I said, please don't tell Charlie I said so. So glue in the pocket hole joints, that's my vote.
As a relatively new woodworker, and from watching my dad who is a master at woodworking, I just thought it was a no-brainer to add glue to just about any kind of joint. For that reason, I've always used glue when using pocket holes. We can philosophize all week long about the forces at play, but at the end of the day, for the little bit of time it takes me to add some glue, I'm going to keep on doing it. It's just a little bit more insurance for the strength of the joint.
So how strong does a stile and rail joint really have to be? You're never going to be counter pressure on the joint and it will be secured to a cabinet box. So while glue makes it a stronger joint why does it need to be?
Noted that you did not use Kreg pocket hole screws. Kergs have a much larger washer head than the screws you used. Bet they would take a lot more force to pull out of the pocket.
A glued pocket hole joint which has cured is almost as strong without the screws as with. If it is a frame that will be glued and nailed to a carcass glue won't matter.
I watched your video regarding glue and pocket hole screws however, I was wondering how important you think it is to glue pocket holes where lateral force either forwards or backwards or even side to side is absent such as in the case of carcass construction? I do agree with your admission that adding glue like you showed in the pocket holes in your test is a good idea and something I would likely do in future projects where your example is applicable. Thanks for the tip!
"Video" ran with no video. Audio was very informative, however.
Here's the thing... maybe you don't need glue for pocket hole plywood casework, but I'm here to tell you I'd never assemble pocket hole face frames without it. Not because it's adding any great amount of structural strength - it obviously won't - it's an endgrain joint. But what it DOES do - and I've done 100s of these with and without so I know what I'm talking about - it does help to keep that joint from twisting and moving seasonally. It adds just enough resistance to a 2" wide joint to help stabilize it through seasonal changes - and therefore it WILL - not maybe - look better after 5-10 years than a face-frame that wasn't glued. I don't use pocket holes very much period - but when I need to do face-frames quickly they can be a useful tool -but after seeing how the seasons impact them I'll always glue them. The $.10 it costs and 5 seconds it takes is simply a non-issue when you want something to look good year after year.
How about we just use actual joinery? I get the speed of these pocket hole things, but I’ll never make something with them or buy anything made this way. I might as well go to ikea.
Thanks, I've wondered about this issue. I truely enjoy pocket hole joinery where appropriate, and knowing that Titebond will truely strengthen this joint is quite reassuring.
Hmmmmm. Who knew. Guess I'm gett'n the glue out next time.