Have you ever built a seating bench or a chair using a Kreg Jig pocket hole system and wondered how much weight this bench can hold? When working on my DIY projects, that thought always crosses my mind. What if someone sits on that chair that I build, and that chair just crumples to the ground? That would be really embarrassing. So I did some research on how strong pocket hole screws are, and this is what I found.
According to a study conducted by the RADCO testing division, a common 90-degree pocket hole joint using a 2×4 rail that is attached to a 4×4 post could hold 1361 lbs before failing. However, using the same setup, if you apply pressure from the bottom of 2×4, the same side as the holes, this 2×4 holds only 410 lbs.
When it comes to woodworking, not all screws are created equal. The type of screws to use will depend on the situation, and some can be cheaper and easier to use than other types.
What are Pocket Hole Screws?
Pocket hole screws are specialized screws that are used in joinery. These screws have a wide, flat head that sits flush with the surface of the material being joined, and they have a sharp point that penetrates deeply into the wood. The threads on these screws are designed to grip both pieces of wood tightly together, creating a very strong joint. Pocket hole screws are commonly used in cabinetry and other woodworking projects where a strong, hidden joint is desired.
A pocket hole is, in a nutshell, a hole drilled at an angle that forms a “pocket” for the screw. The pocket hole is an advanced and precise toe-nailing that involves the pocket hole jig, which allows us to drill into the wood at an angle to produce the pocket to house the screw head.
There are a few things to keep in mind when using pocket hole screws. First, it is important to use the correct size screw for the thickness of the material being joined. Second, the pocket holes should be drilled at the correct angle and depth in order to create a strong joint. Finally, it is important to use a good quality wood glue in addition to the screws, as this will further strengthen the joint. With a little practice, pocket hole screws can be used to create strong, hidden joints that will last for years.
Why Use Pocket Hole Screws?
The pocket hole screw system is especially important in DIY projects because the pocket hole screws allow very strong joints, but the process of creating it is fairly simple. You don’t need any expensive tools or learn special skills for this: all you need is a Kreg jig you can use to drill angled holes in your wood to house the screws securely,
There are other techniques you can use to secure two different boards, from dovetails, half-lap joints, and biscuits, among others, but most of these other techniques are typically time-consuming and would require expensive tools to make.
If woodworking is not a full-time job, then using pocket hole screws is the easiest and the most cost-efficient method. Also, pocket hole screws are strong enough to hold the board together, and you won’t need to use clamps (which can be quite expensive).
How Strong Are Pocket Hole Screws?
Below, I include a chart to display the strength of pocket hole screws. This is based on the test using 4×4 (Post) and 2×4 (Rail) pieces. There are four different methods/joint types and three different screw positions for each method. This chart was based on a Kreg Jig Tool Company test conducted by the RADCO testing division.
As you can see from the image, there are four different joint types of pocket hole screws. Each joint was assembled as a Post (4×4) and Rail (2×4) system. Each configuration was tested with Cedar lumber as follows:
- Type 1: the Post and Rail form a 90-degree angle with two pocket holes. The short sides of the Rail sit flush to the sides of the Post.
- Top Pressure: force is applied to the long side of the Rail (opposite to the pocket holes), can hold 1,361 lbs of pressure
- Side Pressure: force is applied to the shorter side of the Rail, can hold 1,196 lbs of pressure
- Bottom pressure: force is applied in a similar way to the top pressure, but the force is applied to the same side as the hole, can only hold 410 lbs
- Type 2: the Post and Rail are positioned in a similar way to type 1, but the Rail is rotated 90 degrees lengthwise:
- Top Pressure: force is applied to the long side of the Rail (opposite to the pocket holes), can hold 1,325 lbs of pressure
- Side Pressure: force is applied to the shorter side of the Rail, can hold 1,025 lbs of pressure
- Bottom pressure: force is applied in a similar way to the top pressure, but the force is applied to the same side as the hole, can only hold 460 lbs
- Type 3: the Post and Rail form a T-shape with one pocket hole positioned on the opposite sides of the post.
- Side Pressure: force is applied to the short side of the Rail, just below the Post. Can hold 1,154 lbs
- Bottom Pressure: uplift force is applied to the Post from the bottom, can hold 1,025 lbs.
- Type 4: the Post and Rail form a T-Shape, with two pocket holes positioned on the opposite sides of the Post:
- Bottom Pressure: uplift force is applied to the Post from the bottom, can hold 1,961 lbs.
About Kreg Jig
Kreg Jig is a proprietary eponym or generic trademark to actually describes pocket hole jig because the brand Kreg makes the most popular jig on the market today. So, understand that when people say “Kreg jig”, it usually refers to the pocket hole jig.
A pocket hole jig, as briefly discussed above, is a tool that is used to create a pocket in a piece of wood where we can then attach a screw to join two boards together. The Kreg jig can guide your drill bit to the right angle and can be moved quickly from spot to spot, so they are very versatile.
Every Kreg Jig Contains at Least These Essential Components:
- A drilling guide: The drill guide holds a bit at a proper angle for drilling pocket holes.
- A stepped drill bit: A 3/8″ drill bit with narrower tip.
- Depth collar: The depth collar is used to set how deep you want the hole to be drilled
- Long drive bit: For screwing-in the screws
Using a Kreg jig, we can quickly drill and attach all hole joints faster than with other methods, in general, it would only require 30% of the time it would take using other methods like biscuits or dovetails. Also, Kreg jig allows us to attach the boards using pocket hole screws that are stronger than merely gluing the boards together (as discussed in the above section).
However, that’s not saying the pocket hole joinery using the Kreg jig doesn’t have any downside. First, they need specialized screws to fit the pocket hole, and the process will leave a hole on the boards that might not be aesthetically pleasing.
Different Types of Kreg Jigs
Kreg is, as mentioned, a brand that produces pocket hole jigs, and they actually offer several different Kreg jig products, namely:
- Kreg Jig Foreman: for small to large scale projects (up to 75+ pocket holes) with built-in clamping, storage, and high-speed pocket holes feature
- Kreg Jig K5: for small to large scale projects (25-50 pocket holes) with built-in clamping and storage
- Kreg Jig K4: for small to large projects (25-50 pocket holes)
- Kreg Jig R3: for small projects (10-25 pocket holes)
- Kreg Jig HD: for outdoor small-large projects (1-100 pocket holes)
Choosing The Right Pocket Hole Screws Length
You can use this chart below to choose the right screw length according to your board’s thickness:
- 3/4″ and 1″ screw lengths are for 1/2″ material thickness
- 1 1/4″ screw length is for 3/4″ material thickness
- 1 1/2″ screw length is for 1″ material thickness
- 2″ screw length is for 1 1/4″ material thickness
- 2 1/2″ screw length is for 1 1/2″ material thickness
When Not to Use Pocket Holes?
If you are working with a material that is too thin, pocket holes may not be the best option. The minimum thickness for a material to be used with pocket holes is 1/2″. If the wood board or plywood is any thinner than that, there is a risk of the material splitting or breaking when the screw is inserted.
Another time when you might not want to use pocket holes is if you are working on a project that will be visible from all sides. The pocket holes themselves are not very attractive, so they may not be the best choice for a project that will be on display.
Great article. Can any of these jigs be used to attach two 4″ posts together? Thank you.
Hi Simon, Yes the pocket holes could be used to attach 4″ posts. You’ll just need to figure out the best location for the pocket holes for maximum straight.
Hi I’m in the process off making some large boxes out of 3/4 plywood for making wardrobes and having wheel on base can you tell me what system I would use
Hi James, for 3/4″ plywood you would need to use 1 1/4″ pocket hole screws, but the placement of pocket holes depends on how you’re planning to assemble the boxes. Also the more screws you use the stronger the box will be.
I like ana White’s videos and like her I also glue my pocket hole joints, even end grain. Do you think this adds much strength?
Hi Robert, I also use wood glue with pocket holes, but the main reason why I use glue is to keep the boards from coming apart over time. Let’s say you made a chair with pocket holes, and you use it all the time. After heavy use, the joints might come loose, and the chair becomes squeaky. But if you use pocket holes with wood glue, those joints will not come apart.
James
Pocket hole jigs are a fine way to make furniture and other products but my problem is finding the screws that adjust to leagth of the project. Especially the size of the head of the screw plus leagth in finding those screws. Sometimes the head does not fit or is hidden unless you sand it down. So were do I find the proper screws.
Love the illustrations. Great article! Thank you. Is there an advantage to using glue as well?
Hi Joe, When I build wood projects, I try to use wood glue, especially on projects like a chair or a bench. Wood glue keeps the wood together and prevents pocket hole screws to come lose on furniture like a chair that is heavily used. When the screws come lose the chair will become squeaky. But let’s say some parts of the furniture will need to be disassembled later on, then I would not use wood glue.
Can drywall screws be used instead of pocket hole screws?
Hi Jeff, Pocket hole screws have a flat head, this makes the screws pull the boards together when driving them it. Drywall screws do not have a flat head, so they will rip open the pocket hole and mess up your boards. So I would not recommend using drywall screws in the pocket holes.
Hi I just use my kreg jig and my problem is the measurements for length of drill and screws is the wood your screwing into or the wood its going into . And I bought the pocket hole screw pack and they didn’t have 3/4 or 2 in screws and guess which ones i needed. I was using 1/4″ plywood for a table top and 1/2 cedar boards for the sides. Didnt know what would work so I had to do it on the other side and fill in the other holes.
Thank you for the information you provided it. It help me more how it work first time using it.
It wasn’t holding so I went to the next size and I bought 1/2 quarter rd mounding held that with Brad nails on 1/4ply turned it and made more holes and used 1/2 plus a little more on the bit and used 2 1/2 screws and glue. That worked but brad nails were a little long but I managed . This was a scrap wood project for a lego table for grandson came out ok. Next is a real furniture piece with instructions. Oh screw driver was to long to get screws in on the short end of table (angled table to fit space) what can you use in that case. Try square head screwdriver that slightly worked.
Great article, I just did a small base for my 180 gallon fish tank, I was using treated wood I had issue with the pocket screws doesn’t stop when driving in when the screw head are tight enough, I believe because of the wood being soft after treated, is there any specification on how much ft lb to be used or what setting to use on drill when driving the screws.
Are you using pocket hole screws with a flat head? If you’re using regular wood screws for pocket holes, it will not work, because regular wood screws do not have a flat head and it will split the wood. Using pocket hole screws on treated wood is perfectly fine. I’ve done it many times.
It must be noted that the RADCO Testing division results are for the Kreg Jig HD system only.
Knowing that flat head screws are a must for strong pocket hole joints, is there another more affordable brand screw that you’ve come across other than Kreg?
Can you use pocket screws with plywood?
Yes, I use pocket screws with plywood all the time.
I am building a storage bench with my son using 3/4″ veneered plywood and notice the workpiece shifts a little – approx 1/32″ when we tighten the screws. All settings are correct on the pocket depth and hole position (3/4″). An suggestions to eliminate (or compensate) for this shift?
Hi Chuck, I always clamp the boards together when driving in pocket hole screws. Otherwise, they will shift.
Hi,
Do you know if a Kerg HD or standard Kreg R3 jig was used in the joints in the strength test carried out on the cedar.
Can I substitute flat screws with a washer the same size as the pocket screws?
Are these measurements with the normal Kreg jig or the HD? What size screws are used?
This article is sorely lacking a basic fact and I wonder how a fairly lengthy article about pocket hole has no mention of the word “grain”. Pocket holes main purpose is not to hide screws but to do away with screwing towards the wood’s end grain. Therein lies the pocket hole strength when doing butt joints.
If you are attaching boards end grain to end grain it’s probably best to use draw bolts.
I am constructing a storage bench for the end of a queen size bed. The top will be 3 white pine 1×6 that are 50” long. When the boards are glued and kreg screwed together the lid will be 16.5” wide. The lid will overhang the bench box by 1/2”. Will this lid be safe for an adult to sit on?
Your article is the best I’ve seen. Thanks
Hi Joel, Yes I think a 16 1/2″ wide board will support an adult sitting on it. When attaching the boards together I would use pocket holes every 5 to 6 inches to make the seams stronger.
Thanks for your help.
How for away from the joint were those forces applied in the tests?
It was 2″ from the post/rail connection.
Where can I get 2 1/2″ fine thread kregg screws for 1 1/2″ material?
Jess, Pocket hole screws are very strong, but it depends on the design of the bed if it will support 300kg. You don’t want to pull all the weight on just few screws, you want to spread it out on many screws.
Hi,
I’m building a double loft bed (similar to american full size) – do you know what the bearing weight would be on a 2×4 on a 2×4 or an a 2×6 with 2×2 cleats? I was thinking of adding 2 additional lengthwise 2×4’s to support the bed and 2×4 ‘s for the slat system….is this overkill? The bed will also be just over 6ft total height.
https://www.ana-white.com/woodworking-projects/camp-loft-bed-stair-junior-height
In the tests above, when the joints fail, are the screws pulling out, or are shear stresses breaking the screw?
I’m having problems with 1-1/4” course thread screws breaking in hardwood Maple. Are the fine thread screws any stronger?
I’ve had the same problem, Ken. From what I understand, coarse thread screws are recommended for softwood because they have more surface area than fine thread screws do. I’ve read that fine threads are aimed specifically at hardwoods. Perhaps the extra surface area of the coarse thread is grabbing the hardwood with enough total friction that the force required to push it exceeds the shear strength.