I’m a big user of pocket hole screws. They’re easy to use, and real woodworking joints look time-consuming. But I kept hearing that wood glue is actually stronger than screws, so I decided to put it to the test with my own experiment. Here’s a quick summary of the results:
When applied between two pieces of wood, wood glue is stronger than screws. This is because screws only grip the wood in a specific location, while wood glue can grip the wood across the entire joint. The more surface area available for the wood glue to join, the stronger the joint will be.
Now lets take a look at my experiment, and find out the best way to use wood glue or screws on your project!
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Wood Glue Vs. Screws: Methodology
I tested four different types of joints:
- a butt joint, where one end of the wood was simply butted up against the other
- a miter joint, where the two ends were both mitered to 45 degrees
- a box joint, where each end had interlocking fingers
- and a pocket hole joint, where the two ends were arranged like a butt joint, but connected by pocket hole screws instead of wood glue
The butt joint, the miter joint, and the box joint were all connected by wood glue alone (this Titebond glue, to be exact,) and the pocket hole joint only contained screws. The idea was to test different glue joints against a screw joint to determine if/when wood glue or screws were stronger.
I’ll also mention that all four joints were made over a week before the experiment was performed, in able to give the glue plenty of time to cure.
To test the strength of the joint, each joint was placed on a scale, and pressure was slowly applied with a clamp to determine when the joint would break. If you’re interested in seeing the actual experiment happen, check out the video below!
My hypothesis was that the box joint would be the strongest, but the pocket hole screw joint would still carry more weight than the miter and butt joints.
Spoiler alert: I was wrong.
Wood Glue Joint 1: The Butt Joint
So, it’s pretty common knowledge in the woodworking community that a butt joint connected by wood glue alone is a weak way to join wood. The end grain of the wood, which features heavily in a butt joint, doesn’t take glue as well as the rest of the wood, leading to a weak glue connection.
Therefore, I expected this joint to be the weakest. I wasn’t wrong.
I actually started this experiment by applying weight with my hands only, and foregoing the clamp. Somehow, I thought my weight would be enough to break the joints. This joint was the only one my weight could break.
The wood glue on the butt joint failed at 60 lbs of weight. It was the only joint weaker than the screw joint.
Wood Glue Joint 2: The Miter Joint
The miter joint is made up of two boards joined at a 45 degree angle.
Frankly, my miter joints never turn out that well. They don’t line up right, and there are always gaps. And when things don’t line up right, that means there’s less surface area for the glue to hold together, which makes the joint weaker.
So I was expecting my miter joint to fail pretty quickly too. Turns out, it didn’t.
The miter joint held 140 lbs of weight before the wood glue failed and the joint fell apart.
Wood Glue Joint 3: The Box Joint
Now, full disclosure: This was the first time I’ve ever made a box joint. I watched a Youtube video, built a jig, and then went for it. I had low expectations, but my box joint actually turned out pretty well, I thought.
And once I’d made the jig, it was easy enough that I might actually use it again. Look at me, gaining skills.
Regardless, I expected this joint to be the strongest, since it had plenty of surface area for the glue to join the two piece of wood. Plus, the box joint was a pretty good friction fit, which obviously adds a little extra support.
When I tested the joint, it was able to hold 208 lbs of pressure before the wood glue failed. At that point, it didn’t just break apart like the other joints. Instead, it was still able to hold some weight (70-ish lbs) because of the friction joint.
This was by far the best result.
The Pocket Hole Screw Joint
From the outside, the pocket hole screw joint looks the same as the butt joint. However, instead of being joined with wood glue, the joint is connected by pocket hole screws.
If you’re not sure what pocket holes are, check out this post going into all the details.
This joint wasn’t worthless – it held almost double the wood glue-only butt joint. The pocket hole joint failed at 108 lbs.
I’ll also note that the joint didn’t just fall apart. Instead, it deformed under the pressure, and the screws began pulling out of the wood:
Results and Takeaways
So, just to make sure everything is in one place for you, here are the results of the experiment:
|Wood Glue or Screw?
|Pocket Hole Joint
Wood glue clearly CAN be stronger than screws, but only if it’s applied appropriately, in a way that allows it to reach its full potential. This means applying the glue on a large surface area, and not on the end grain where it will struggle to secure the wood.
That said, I will probably continue to use pocket hole joints. Here’s why: for a beginner woodworker, pocket hole joints are significantly easier to make and use properly than miter joints and box joints. Additionally, the strongest joint, a box joint, requires a router or table saw, which is an expensive investment for many beginners.
Plus, a pocket hole joint can be strengthened further with the addition of wood glue.
If you’re reading the article for another application (that’s not woodworking,) be aware that wood glue is at its strongest when joining two pieces of wood, and when it has a large surface area on those two pieces. If you’re not joining wood, I’d consider adding screws as well for extra strength.
Wood Glue Vs. Screws: Which Should You Use
Wood glue alone is only stronger than screws when the the following applies:
- You are joining two pieces of wood, AND
- You’ve created a specific joint that allows for significant surface area for the wood glue to work.
If these two conditions aren’t met, you’re going to need screws, nails, or a different type of adhesive, depending on the situation.
Also note that wood glue doesn’t always hold up under extreme temperatures. If your project is designed for an exterior application, you’re better off using screws or another type of glue.
There are a few other things you’ll want to keep in mind as well
- Screws are significantly more expensive than wood glue. This is why you see professional, high-volume woodworkers typically opting for wood glue-only joints.
- Screws allow easy disassembly, while wood glue doesn’t. If you expect you might want to disassemble your piece in the future, screws are your friend.
- While pocket holes can help hide screws, there’s still a hole to deal with afterward. Wood glue doesn’t leave any visible mark on your piece (given you didn’t use too much glue!) If you’re looking for flawless, wood glue is the way to go.
Wood Glue Vs. Screws: Other FAQs
Is wood glue stronger than nails?
In the right application, wood glue is stronger than screws, and screws are stronger than nails. Therefore, when applied properly, wood glue is stronger than nails.
How strong is wood glued together?
The strength of two glued pieces of wood depends on a number of factors, including the surface area of the connection and the direction the force is applied. During testing, a box joint connecting two pieces of wood at a 90 degree angle was able to withhold 208 lbs of force.
Is wood glue strong enough without screws?
Under certain circumstances, wood glue can be strong enough without screws. The wood glue needs to join two pieces of wood together with a significant amount of surface area, such as that provided by a box joint. Butting two pieces of wood together and only connecting them with wood glue is not very strong joint.
Do I need to clamp wood glue?
When using wood glue, the boards should be clamped together for at least an hour to assure they do not move during the drying process. Alternatively, the boards can be secured during the dry period with another fastener, such as nails or screws.