Debunking Pocket Screws

DOWELMAX:

BLADES:

TOOLS:

BITS:

SUPPLIES

INSTAGRAM:

MUSIC:
Epidemic Sound
Use my referral link and start your free 30-day trial:

[WoodcraftBySuman]

None of these joints would fit in my pocket.

[georghofmann]

trick i learn some years ago .. use regular Screws with Glue to get stuff done fast, when the glue is dry/hardned, unscrew the screw and replace them with Dowels .. saves the Time for Clamps and you can go on with the work

[rpenm]

My biggest issue with pocket joints is it always moves as you tighten it up due to the angled screws. You have to remember to clamp everything down first.

[AaronGeller]

Scott, you’re probably one of the few people who can engage me on this topic for a full 13:46 minutes without me getting bored. It’s interesting how we just come to accept “common knowledge” as fact when testing often proves otherwise. I hope that by June of 2024, you’ll see 200k in subscribers 😊

[sam]

Your mini-split says it's 42 degrees in your workshop, and I can't figure out if it's really cold in there or really hot.

[DIYtechie]

This is exactly how to make a YouTube video. Informative and to the point. Keep up the good work!

[kwigbo]

Another way to stop cracking would be to not go full send and go in a bit, back it out and then go in. The screw itself can clear the hole. Just like in the metal threading example.

[ADBBuild]

A self drilling wood screw more closely resembles a spiral point tap instead of the hand tap you showed. You do not need to reverse to break the chip with this kind of tap as it pushes the chip forward out of the hole (for that reason, they shouldn't be used in a blind hole). However, your point about the screw not removing material is true, although the slot ground in the screw would hold some amount of material.

[jwthomas]

Changing woodworking lore and meta one video at a time. Great work as usual!

[ZackForester]

I love how the glue without the pocket screw scored the same as the 1-1/4" pocket screw meaning someone without any power tools could achieve a similar result to someone using power tools but not effectively using glue.

[ezde]

I had a job where I sometimes needed to add blocking on the back side of a cabinet face to have a 2.5" wide mounting position that wouldn't be visible. I didn't have a jig, specialty pocket screws, a pocket drill bit, or time to glue. And, I couldn't screw through the front of the cabinet. The stock wood I had was about 2.5" wide by 3/4" thick pine. So I found the best way to attach the blocking was pocket screws, but I had to figure out how to fashion my own pockets in the field using two different drill bits. It wasn't super pretty at first, but I was kind of proud of how consistent and quick I could make them after a while, and not terrible looking, but still obviously not a jig. The nice thing was because of how I made the pockets myself, I could customize the distance of the pocket from the joint based on the length of screw my company happened to make available to me. And I always pre drilled the cabinet part to receive the screw. I didn't see that as costing a significant amount of time, when compared to the idea of splitting a clients cabinet.

[keithmurray]

What I love about pocket hole joinery is how forgiving it is. If you have an alignment error when putting two boards together you’re committed with biscuits, dovetail, etc. With pockethole you just remove the screws from the original attempt, drill new pockets about 3/4” from the first attempts and tada… you’re in fresh wood and nobody’s the wiser assuming it’s a joint on the back or bottom of your project. For that reason alone I find using Kreg approach very user friendly and way faster than

[deucedeuce]

The finer threads on the screws helps prevent splitting by having thin, sharp threads that will more or less cut into the wood and not press it outward like a wedge. The very thin, sharp tips cut the fibers in half and split them forward and backwards more then the thicker threads, which create a lot more outward pressure. They're not perfect, but they definitely work. Like it was shown in the video though, they're not necessary if you drill a pilot hole, which is the only way to do it in my opinion. I'm not sure if they're stronger than the normal screws though after a pilot hole is drilled. I would bet that the regular screws are stronger, because they have a larger diameter (is the same side drill bit was used to drill the pilot hole)... so I've always thought the regular screws were the best option with a pilot hole. I'm not sure if it really makes a difference though. (Would love to see that tested, both with the same size pilot holes, but also with a slightly smaller pilot hole to match the shortened diameter of the finer thread screws. Would be cool in general to see if pilot hole size makes a big difference too).

[redlancer]

I just made my first nightstand with pocket screws and it turned out great!!

[JimBloggins]

This shows what has been common practice in every shop I've worked in over the years; pocket screw construction is used when no fastener should be seen and there is not time for joinery.

[papparocket]

As a researcher I love data, the more the merrier. But I also know that data from unrepresentative tests can unhelpful or even very misleading. So my continuing concern is testing the strength of joinery with a bending test since I can't think of many cases where in a finished piece only one end of a board is secured and it is subjected to repeated high loading.

The place where joint strength is a big issue is in drawers where loads are frequently applied to the joints. In the case of the joints in drawers nearly all of the forces generated are parallel to the joint line and so are generating shearing forces in the joint. This assumes that you make the sides of the drawer longer so they overlap the front and back. If the front/back of the drawer overlaps the sides, then the forces in the joint will be perpendicular to the joint and it will experience all pulling forces. So if made with the sides overlapping the front/back, it really shouldn't matter whether you screw through the side and into the end grain of the front/back or use pocket screws that go the opposite direction because the forces in the joint will be perpendicular to the screw and so the joint can only fail if the screw is sheared in half, or the wood fibers fail and the screw is pulled sideways through the wood. Plus the glue line will also be in shear, which should be its strongest direction.

Also the highest forces experienced by a drawer won't be the steady slow build up of forces until the drawer opens or you rip the front off the drawer. Rather the highest forces are likely to occur when something in the drawer jams against the frame and the drawer stops in a fraction of second. The whole F=ma thing then says that the high deceleration rate required to stop the drawer and all of its contents over a very short distance and time must be very high and as a result the force on the joints will also be very high. Further this force will go to this high level nearly instantaneously, but it will only last a fraction of a second. This is important because materials behave very differently when forces built to a peak at very different rates. Think about the difference if in when breaking a board in a karate demonstration if instead of a hitting the board with their hand already moving rapidly the person instead placed their hand on the board and then slowly pressed harder and harder until the board broke. When hitting it hard and fast, the board breaks and the person holding it feels a bit of a shock move their arms, but doesn't get pushed back. But if the pressure is applied slowly, the person holding the board will have to lean into the force or they will get pushed back.

I think that this is the joint configuration and load profile that should be replicated in any test of joint strength. One way to test the strength of joints in this way is to build a drawer without the back. Then solidly clamp the sides to a very stout test frame so that the sides won't move. Then to apply the load to the joint, an eye bolt is attached to the drawer front (likely good to sandwich the drawer front between two metal strips with the eye bolt through a hole in the middle so that the load is distributed across the drawer front. A rope with just a little bit of stretch to it is attached to the eye bolt on one end and a weight on the other. By allowing the weight to fall a short distance (say a meter to make the calculations easier) a force equal to that required to decelerate the weight to zero velocity over a very short distance will be placed on the drawer front the same sharp rise and short duration profile that a jammed drawer will experience. The heavier the mass, the higher the resulting force. While the applied force is not as easy to obtain as reading the number off of the digital display, the necessary formulas aren't that hard.

The velocity of the weight after accelerating at a constant rate over a given distance is equal given by v = (2 * a * y)^0.5 [ the square root of 2 times acceleration times distance]. In our case the acceleration is due to gravity, and so "a" is equal to 9.8 meter per second squared and y is the distance the weight falls before being stopped by the rope. So if we dropped a weight and allowed it to fall 1 meter, the velocity will be (2 * 9.8 * 1)^0.5 or 4.42 m/s. If the stretch in the rope is such that it stops the weight over the distance of 1 cm (0.01 m), then solving the above equation for acceleration, the deceleration required is v^2 / (2 * y). With v = 4.42 m/s and y = 0.01 m, a = 4.42^2 / (2 * 0.01) = 980 m/s^2. Then to get the force generated by a given weight, assume that the weight being dropped has a mass of 1 kilogram. The force is given by our old friend F = m * a. So the force equals 1 kg * 980 m/s^2 = 980 N. To put that in terms of old units, that is equal to 220 pounds force.

Because a rope with some give to it acts like a spring, the distance the rope stretches is proportional to the amount of weight being dropped. Without getting into determining the spring constant of the rope, the easiest way to determine the deceleration distance for each weight is to just measure how much the rope stretches for each weight and use that distance to determine the force generated by that given weight.

Sorry for the length of my comment, but I hope you find it at least interesting and perhaps thought provoking.

[audislowroad]

Switch your brain to think of pocket screws as permanently placed clamps. Use total wood glue coverage and the holding power of the screw is irrelevant. I have very often completely removed all the pocket screws from projects after the glue dried with zero problems. Screws are clamps. If you're not using wood glue there's great tips in the video to prevent splitting / increase holding power!

[Wordsnwood]

"I'll know if you don't".... 🤣🤣🤣 Okay Santa...
Seriously, some good points in this one.

[orazha]

Scott, Excellent video. I've got a pocket screw jig but don't remember using it. I don't generally use screws for furniture. When I do, I predrill and angle the screw from the opposite side. I've thought that woodworkers tend to over use pocket screws. You show that, many times, they do. But, I think most woodworkers, including me, have latched onto ways of doing things that don't make much sense when you think about it.

[davefoc]

Very amateur carpenter that has only used pocket screws for softwood face frames and softwood window trim here: Pocket screws are strong enough. For me the main point of pocket screws is to quickly make a serviceable joint. If I build furniture that I expect my grand child to inherit, then I'm not going to use pocket screws. I do enjoy these how strong is this joint videos, but as a very amateur carpenter they don't influence my very amateur carpenter ways.