Everyone needs to calm down. I like pocket holes, I use them all the time. But at no time did I think that they where stronger than mortise and tenon. Thank you for this really cool video and keep up the good work!
Hi Matthias, I've made 5 dining chairs from white wood and pocket holes. I would not do it again. After two to three years, the durability isn't there. However, I've found the ones with glue in the joints are faring much better (less wiggling when sitting) than the first couple I made without glue. My assumption here is that most of the forces the chair endures are actually below the breaking point of the butt glue joint, but still enough to cause compression around the screw threads and thus make the joint wiggle over time. These tests are great, but are only testing the ultimate joint failure, not long term real world forces. I have no idea how you would test the real world scenarios without simply building and testing the furniture as I have. Thanks for the well engineered videos and projects you produce.
Josh Garrisi That might be the case. But chairs are always a challenge for joinery. It's one thing to make a night stand, another thing to make something people sit on.
Agreed. I just wanted to point out that many times when people say that the glue makes pocket hole joints stronger, they really should be saying: "The glue makes the pocket hole joints more able to withstand small repetitive forces (under ~40lbs per your video), not large singular ones." Having learned the hard way, I would advise anyone against using pocket holes to make chairs, but if they want to keep the wiggle out of their nightstands, use the glue.
Glue does not make butt jointed pocket holes stronger. But. Pocket holes make butt-jointed glue joints stronger. This is because the screw adds a hundred pounds (?) or so of clamping force onto the joint. In order for the glue-joint to fail, you need to first remove this hundred pounds of clamping force and then apply enough tension to break the glue-joint. For chairs, you really care about 'force till joint separation' - this is because if the joint can separate, you get not only the load of someone sitting in it, but the load of someone sitting in it, combined with the joint wiggling, and coming to the end of the 'stop'. This can be much lower than the force needed to smash the chair if you jump on it, but can still make the chair wobble over the years.
Very few joints stand up to chair use and the screw style pocket hole joint would not work well in that application. However, if you did a drill through pocket hole with a dowel insert (it makes cool designs on the wood face) instead of a screw and glued them together, it would be as strong as a round mortise-tenon joint that is common in wood chairs with turned legs/supports. So the form of the pocket hole counts as well. These are rapid build joints that are used in low to no stress areas. You can make them pretty.
One of the most common and (IMO) best applications of pocket holes is for face frames. There is no issue with strength, and you can get a tight and square joint easily.
Hi @Matthias Wandel, I appreciate that the pocket hole is most likely going to be weaker in most situations than most wooden joints, however I think your (very) strong bias against them has made you miss some important factors. I am a finish carpenter. I deal mostly with basic trim and crown moulding. I do not work in a shop, I work in people’s homes. When trimming out a door or a window I find that the pocket hole is the perfect joint for the job. All I need it to do is pull two pieces of wood together tightly to let the glue set while holding the angle. In these situations there will never be any stresses on the joint. Ever. If I were to use a dowel joint I would need more tools, several clamps and at least 10 minutes to let the glue set before I could install the trim. To make a mortise and tenon joint I would need a shop and some expensive tools (or lots and lots of time) to get the joint right, not to mention the dry time. Furthermore these joints would be total overkill as there will not be any stress on the joint. With a pocket hole jig I can trim out a window or a door with invisible, tight joints that are more than strong enough for the job in about 6 or 7 minutes. Done. All I am saying is, I think your obviously negative opinions about the pocket hole joint come from the fact that you really don’t need one for the work that you do. You have a shop. You do not have customers breathing down your neck asking you when you will be out of their house. You have hundreds and hundreds of dollars worth of shop tools that enable you to get excellent, strong joints (all be it in a lot more time than it takes with a pocket hole jig). You are making things that need very strong joinery. The pocket hole is not meant for those types of projects, so please stop reviewing it like it is. It is a wonderful and unbeatable tool is many situations.
I have said it many times, but it needs repeating. If you ask a question, but have it set so no one can reply, no one WILL reply. What I do is I just delete the question.
Cabinet Carcasses with pocket holes work very well. Boxes, tables, and assemblies that are not sat on are ideal for pocket joinery. Also, design is the major difference in how well a pocket hole joint will work. Pocket holes work best when both sides of the wood on a side has pocket screws, such as in boxes or frames for pictures or mirrors. Maybe no one saw my post on the last video, but this testing method is clearly going to show the pocket hole as the weaker joint, as it could never compete in a strength test with a mortise and tenon or a dowel. Wood joinery science will always tell you the joint with the most wood surface that can be glued will make the strongest joints. So, this comparison was already at a foregone conclusion before it was even done. Some joints are just for convenience of the constructor. Pocket holes are such a joint. In making cabinets and drawers, pocket holes would work just as well as a box joint or even a dovetail. Pocket hole joinery is about ease of assembly on its surface, and design will make up strength deficiencies.
Out of all of these comments, did none of you notice the very awesome gear device made just to make this test? Always inspiring wood work from Matthias!
I've seen other joint tests that agree with your findings that there's no substitute for quality old school joinery, no matter how slick their advertising. Great work!
Nice test. As a n engineer and woodworker, I would definitely agree that mortise joints would be stronger. However 3 things to consider would be 1. A pocket screw jig can do holes much faster than cutting a mortise and tenon 2. If you were building a complete frame the sum of the joints frame would add to the strength. 3. Depending on what you're making it might be reinforced in other ways and the pocket screw may only act as a hold together, like the face frame of a cabinet body or something. Great videos though!!
Also the load testing he did does show that the pocket hole joints are weaker, but it doesn't reflect the reality of how the joints will be used. Any load borne by a pocket hole joint is going to be borne by at least two and probably four or more joints, and spread out, not in a single point of contact, meaning that there will not be the same leverage on the joint. A frame cabinet made of pocket hole joints is going to go out of fashion and get replaced at least a century before any of the joints are going to fail, unless it's getting repeatedly wet or something, and then tenons aren't going to save it.
Mind you... 1. Things built well only need to be built once. If you skimp when building something, what you build will probably fail, and fast. 2. This is true, but irrelevant to this video, or the comparison. 3. That isn't the application case being criticised.
What is the application case then? He says pocket holes aren't very strong, glue doesn't help, and leaves it at that. If strength of individual components was the only consideration here, then I'd say we're all wasting our time making things out of wood when we could have things made of high carbon steel. We have to consider the application - I named one where pocket holes are used frequently and are better than good enough. I can imagine all sorts of applications where they're not - for instance, I wouldn't build jungle gyms from pocket holes. But nobody is doing that, so I'm not sure why there's this frequent need to dump on pocket holes.
Right, I am not relying on one joint to hold my whole build together. If you've ever seen a house framed, as you build upward, everything is weak until subsequent layers are added. The floor joist are useless until the 3/4" decking is in place and the band boards are added. The walls are wobbly until the next floor or roof is added. Etc. Same principle.
@@seigeengine no it is not irrelevant the the video. That is the whole point of rather or not an average person will use a pocket hole for furniture etc. The full bearing weight etc without problems.
Thanks Matthias for going to extra distance to remove all doubt about the relative strength of these joints. I use pocket screw joinery occasionally, and probably still will, but its good to know more precisely how the strength compares to other options.
What I see, is that all of these joints are far stronger than they need to be. When I make face frames, all I ever subject them to is a cabinet door weighing just a couple of pounds. Very interesting to watch. Thanks a bunch for taking the time to do this.
In the end, it's all about application. With furniture building pocket holes have been a godsend, but it's not for every joint, and clearly not for the stress test you performed. Thanks for doing this regardless of the controversy.
My first wood project was to build a kitchen island. I got a quote of $900 just for the carcass and doors and I wasn't about to spend that. So for a $40 Kreg jig plus some clamps and screws, I was able to make the carcass and oak face frame for about $150. I had someone make the doors for me because they had to match existing cabinetry, plus I didn't have the router, table and bits to make the doors and that would have broke the bank. The drawer and cabinet doors cost me about $250. Add stain and poly and that was under $450, plus I learned something new and it looks great. Each project I will try to get a new tool to learn a new skill, but the pocket holes gave me the confidence to get started and continue. My next project I just finished and I used less pocket holes and used some rabbit joints. (An over sized oak jewelry box to match the current bedroom furniture.) On my third project which is a little work bench for my daughter and it still has pocket screws, but I try using what works for me and my current skill level.
This was a great test but the true symbol of brilliance is that the title of the video is not a question and is an accurate representation of what the video is about. Thank you.
As always I enjoy your videos. But I've got to say this isn't really a conclusive test since I have never seen a piece of furniture made with only one joint as in the test. This single point allows you to rack it the way you did which gave an unrealistic outcome. There is a million types of joints and double the amount of opinions but I just think tests like this are skewed and just make good "reality TV" type controversy. But I guess feeding the frenzy gets more views.
There are different thread screws for different woods do not forget this fact. Pocket holes do work and I have used them without glue and still have furniture I built 10 years ago in my home with them, rental house so until I find something I want to purchase nothing is going to be permanent. Either way I have 300+ lb people sitting on furniture that I used a combination of pocket holes as well as dowels to hold together. So I guess it is all how you use them since they vary with strength.
I keep seeing comments like "why would anyone use pocket holes". The reason these tests make pocket holes look so bad is because the pine is much weaker than the screw holding strength. The screw head either pulls through the pocket hole or the thread pulls out of the clamped part. Most applications of woodworking joinery (chairs,tables,face frames) utilize a hardwood. Try pulling a screw out of a maple board. That said, M&T joints are still stronger because they don't introduce stress risers. The wood always fails before the screws break, but the stronger the wood the stronger the joint. I like pocket holes for clamping other joints (like a combination of biscuit and pocket to join plywood carcasses) and really fast construction (with a dedicated machine). I have a Domino so I can make really fast M&T joints but you still have to clamp them. If someone wants to pay for M&T joints I am fine with that but they cost more.
This final test with glue answered my lingering questions on the subject. I wonder why I'm so fascinated by the subject but after reading through the debate I can see I'm not the only one. Your pressure application apparatus is a lot of fun too. Great series of very useful and entertaining videos. Thanks, Matthias!
I like your sample size. And also the curiosity on testing the lighter wood. Bravo. I will not be making anything that I am to sit on with pocket holes!
Thank You Matthias... for your videos... and all your labor... It is obvious...! screws... with heads... like wedges... and... in endgrain... will produce tearout... I'm very happy... you did this extra test... I am now certain... that no glue... or screws... will be used... in my pocket holes... I will instead... use needle and thread...! Ps: The planks... in the Early Vikingboats... were joined with roots... as is many kajaks... canoes... and other utensils... Tim Severin went ahead... and took on "Sct Brendans Voyage"... in an open leatherboat... Early Spring Greetings... from Denmark... Jakob.
I recently converted some lower kitchen cupboards into drawers. I added rails to the face frame using pocket holes. After watching this video I'll make sure not to stand on them.
I don't disagree with the author about his tests showing joints failing because we can see that with our own eyes. This is all about mechanical advantage and the lever mechanism employed in his test. The problem this is I rarely see a pocket hole joint stressed in the way that he does it in the test. I confident that if he made another table that (the one he only used a circular saw, drill, and his workmate) with pocket hole fasteners, it wouldn't yield any more when he jumped on it than the dowel joints. We've also seen his tests where nearly every time the wood fails, not the glue. I would like to see some type of a test bed where a long grain to long grain glue joint (think 2" wide 12" long in a "L" shape) is tested with and without pocket hole screws. For good measure, another could be down with dowels, the screw advance box joint jig, and just plain drywall screws. Pocket hole screws are a great invention when used in the proper application and fail miserably when they are not. A shear test of all of your joints would be an interesting read. Cheers!
I love your ingenuity Wendel; all your videos are captivating. I couldn't help but think when watching your joint strength tests that I would like to know the strength of one beam supported at both ends by the same type of joint. This info wouldn't tend to discourage woodworkers from using some of the various joints available.
I love that you appreciate the functional value of wood. Further, you enjoy design, you pay attention to detail, and so, I've a request. Please use cheap wood to prototype a puzzle box. Turn the video into a series. Maybe, one video per internal component mechanic, showing design, construction, and destructive testing at the end. If the video does well, takes orders for 20 hardwood boxes or similar. I hope your subscribers spam this request with an over-abundance of likes.
Great followup. Thank you for that. I did build an entertainment center out of 3/4" premium MDF (much denser) using pocket holes on each vertical butt joint. This gave me 4 connections per joint. I did not glue. I put on a back of 1/2" premium MDF attached with through holes and screws (no pocket holes). I made two doors with 1x2" lattices in them, also held with two pocket holes at each joint (40 pocket holes per door). In the two years since I have built this, the hinges on the doors have failed due to kids climbing doors but the joints holding the doors together have not budged. I have stood and walked on the entertainment center more than once and the joints are as strong as ever. I think pocket hole joints are usable and plenty strong depending on the application. I did not use mortise and tenon for a couple of reasons. 1. I knew I would move eventually and wanted to be able to flat pack it. 2. I work off saw horses in my driveway so hand tools are my primary tools. 3. I have never made a mortise and tenon and needed this built faster than I could learn to build them with what I had. As for those that say the holes are ugly, if you're taking it apart, it's obviously not fine furniture, or you can plug the holes if it's not being taken apart.
Can't we all just get along!? Pocket holes are weaker than a mortise and tenon, but they provide ease and speed for a something that may not require a lot of reinforcement. Each joint has a purpose. Matthias has even mentioned this himself in one of the comments. There's no need to divide into two camps and bicker over it! If you don't like pocket holes, then don't use them. Besides, a well engineered project is more important. If it wasn't, my house built with butt joints and nails wouldn't be standing right now.
I do agree with you and I also think Matthias doesn't mean pocket hole joinery is too weak to be used in any project. A well-designed project can have more than one joinery methods involved.
What is the price per tools for each method? The main reason I've been using pocket holes for most stuff is because I can do it for under $100. Pocket hole jig $20, screws $5, drill $50, bit $5. I assume dowel jointing is probably the cheapest. But I don't have the tools to do the other versions.
Great follow up. I appreciate you taking the time to test it. It's probably one of the most common joints many of us use. It's nice to see the tensile strength it has compared to the others you demonstrated! Can't wait to start seeing you use the pocket jig now that you bought one! Rofl!
Many people saying that they make furniture using pocket holes, and they have lasted very well and that's why they don't want to accept this conclusion. Well obviously the furniture will last pretty nicely, because they'll never experience this amount of direct force. The joints will loosen up in time, but they won't brake apart like this.
Love the wood gears. We use a somewhat similar structure to test wood samples, but we use a bottle jack on a bathroom scale. I only mention it since it might be slightly easier for some to manage.
Sorry if someone has already mentioned this, but while this is an interesting test I think it would be more interesting to test with a cross piece such as you would have on the legs of a table or desk rather than a single connection. It's obvious the pocket hole isn't as strong as other methods, however this isn't really a practical application. With the pocket holes connected on both sides I imagine you'd have to exert quite a bit of force. I have a 2x4 constructed desk with all pocket holes which easily holds over 400 pounds, which is far beyond what I would ever need. Mortise and tenon joints would have been superior but the extreme time needed to create them for an amount of strength that just isn't needed for this application seems pointless to me in this circumstance and many others. The point being, making mortise and tenon joints isn't always worth the time when you aren't building legacy furniture or don't need your coffee table to support the weight of a rhino. Pocket holes are quick and easy and more practical as long as you're using them for joints that don't need the strength of a mortise and tenon. It's obvious a mortise and tenon joint is superior, but I think pocket holes are great for applications that don't require that sort of strength. Dismissing them altogether seems hasty.
I 100% agree with you. But in Mathias' defense, most furniture joints fail when they are exposed to dynamic forces not static forces (ie - can support an entire book collection until you pick up one side of the bookcase). For me, I'm not making legacy furniture and I don't have a rhino either, so pocket joints are best for me in most applications. But I know where he's coming from.
The ShavingWood Workshop My father said similar stuff. One of my favorites was "since everyone makes mistakes, the difference between a good craftsman and a bad one is that the good craftsman knows how to fix his mistakes'. Memories...
6 Days (2017) w/Jamie Bell. The leader of a British strike team is complaining about the poor quality weapons they're forced to use, and his second in command tells him 'A Craftsman never blames his tools'
Matthias, a static one time test is not the full story. It's the stress and shock over the years that glue really makes the difference even if your test does not show much difference.
Hey Matthias, Great video. I always enjoy watching these testing videos, It gives me much more appreciation in spending the time to make traditional joints. Pocket holes do have their place.
I think the appropriate takeaway here is that pocket screws are a fast and easy low to medium strength system that has a really steep learning curve for beginning woodworkers. Any suggestion that it can replace traditional joinery in medium to high strength applications is probably mostly marketing.
Well I suppose if you want to stack 60 pounds or more on unsupported end of a 3/4 inch by 3 1/2 inch board, don't use pocket holes to hang the other end. . . They aren't bad joints or useless though. They have their place and if you use it properly it's a very handy joint, it just depends on the ANGLE of the forces you would expect to see placed on it. Good for repairs as well.
And I'd like to point out that I have never seen a piece of furniture fail under such a load. They tend to fail under imbalanced loads and lateral forces.
I appreciate the honest testing that you are doing. I myself am a "weekend" woodworker, (not an armchair woodworker) and frequently use pocket holes with glue. Explain to me (and im being sincere) why some companies rate them at over 600 lbs. This confuses me lol.
Many thanks Matthias. You saved me some monies because I was thinking of purchasing pocket holes because they were easier to join wood. Now however, I will spend a bit more time and use the more traditional mortise and tenon joints.
Matthias, Thanks for the videos. I find them informative, entertaining and motivating. I built the pantorouter from your plans just for the challenge and thoroughly enjoyed myself. I was amused at the prolific discussion following these two presentations on pocket holes. They have their uses as does glue as do tenons and dovetails. Keep em coming.
Another awesome video. I myself was one of the first to cry foul when you didn't use glue. In my personal experience glue always seems to sturdy up my joints. You have used science to prove my perspective as wrong. Thanks again and keep up the good work.
I guess I'd have to say that whenever I use pocket holes, it is for things that do not require a ton of holding pressure. Like an end table. Most understand they are not meant to hold a work bench together. :)
Peter, I was a viewer who wanted the test run with glue. Not to defend the sanctity of the pocket hole (which I use when appropriate), but for consistency in the testing process. And I'm glad Matthias followed up.
Shadetree Woodworking Why wouldn't pocket screws work on a work bench? Is it because it would distract for the idea of working on a stand that had pocket hole screws? If you are building a $5000 work bench where looks are more important than what you are going to do with the bench then by all means use the best jointery system available.
a more practical test would involve testing shear strength. no chair, or other piece of furniture for that matter would be designed to withstand that much leverage being applied to it. To test shear strength (and i'm sure you know this) you would want to fasten the piece at both sides. The old school joints would likely still be sturdier, but all joint types - including the pocket joint - would undoubtedly meet minimum strength requirements for any well designed piece of furniture.
Wow! Thanks for the test. Honestly, I expected pocket holes to perform better in your test. I've never used just two pocket holes on a stress point, and I won't in the future either. 👍
Matthias, thanks a lot for doing these tests. I'm always a big fan of your videos! One question: you always test these joints with only one end secured as opposed to having both ends of the wood secure (like a typical apron on a table). I wonder if pocket holes do as well as M&T joints when the force is distributed across both sides of the wood. In other words, maybe pocket holes aren't designed to work when only secured on one side, but are instead designed to work in more conventional furniture construction. I am not an engineer, so I don't have a good intuition of how the force would distribute differently, but it strikes me that I never build furniture with a piece hanging off like in your test.
Before I had much knowledge on building chairs. I built all my dining room chairs connecting them with pocket holes. All of them have had the wood pulled through the pocket hole, probably within 2 years.
I have used pocket holes on face frames ... which I know will be subjected to nearly no load. Cabinet bodies like base cabinets are also never subjected to this type of load. On the other hand a chair would certainly get these types of stresses. I don't see what all the fuss is about.
im a cabinet maker and using these to make kitchens is the easiest method. plus glue is a must! when the frame twists at the joints the glue helps it from splitting
At any point of the experiment, the Young's modulus of the composite must be equal to the sum of the moduli of each separate system (glue and screws), which of course varies. By the end of the experiment, the glue is almost totally cracked so its modulus is close to 0, adding nothing to the ultimate strength of the composite. At the beginning of the experiment, while we still have both systems performing, they do collaborate, so we should expect to see the glue cracking at a little bit higher stress. Thanks for the video, it was fun to watch and very instructive. :)
I still think we need to revisit the dry tenon test, and compare glue on one surface and on both surfaces, along with the simulation of sliding the joint together. I also think it'd be cool to see a comparison of different clamping forces, ranging from none to tons, rather than normal and tons.
As I said before. They make great clamps if you don't have any. I have used them in spots where I need to clamp a dowel or mortise and tenon joint and my clamps aren't long enough. I feel they are fine for face frames on cabinets because the face frame just needs to support a door that isn't all that heavy and I think the hinge will fail before the face frame will. I think the pocket hole infomercial is misleading building desks and bookcases. I guess they are comparing themselves on TV to particle board fast furniture.
This is essentially just measuring pull-out strength (the beam pivots around the top corner, acting as a lever to pull out the screws). Can you do a test where the other end of the beam is locked in place, or also fastened with pocket screws (which would be more representative of typical pocket screw use cases), so you're measuring shear strength rather than pull out strength?
Marco exactly what does any one build the 85 lbs will be put on one joint of the project? If one is building something that will have 85 lbs on each joint I would believe the person would use a material stronger than wood.
A test as such wouldn't really be testing the strength of the joint, but moreso the strength of the wood itself. Also, having it joined at both ends is more like a leverage system and isn't really a fair test focusing the force on the joint itself, but introducing more variables.
***** It's not like he didn't compare pocket hole to mortise and tenon in the same conditions. If M&T can withstand double the force in this setup, it also can in any other setup...
My very limited experience suggests that glue adds a lot of shear strength. Where I notice this is in torsion of the piece with the pocket holes in it. If I recall correctly, the wood blows out along the short grain. Pocket hole joints probably have very high shear strength linearly, especially if the test supports the wood around the screws that might otherwise split. The tests in this video show failure in tension which is probably a more fundamental mode of joint failure.
Great video. Still not giving up my Kreg Jig :) I made a bench out of 2x4 pine lumber using pocket holes and three people stood on it. Over 600 lbs total. That's strong enough for almost anything I will ever make. I'm surprised at how strong the dowel joints were. I honestly thought the pocket hole would beat the dowel.
If you set up your kreg jig properly you should never have screws poking through the wood like that. I think you would have significantly different results with a hardwood such as oak and the appropriate fine threaded screws along with a higher quality glue such as titebond iii. This is a very creative setup for testing. Keep up the good work.
I enjoyed watching these experiments. At first I thought glue would added substantial strength to the joint, but as you correctly pointed out the glued joint failed first, that is below breaking force of the screw joint. Therefore, it didn't add to the joint strength. So this really limits use of pocket hole joints, if considering safety and durability of the design. Thanks again.
Thanks so much for testing these joints! I've been curious about their strength since I got the jig. If you know how strong they are, you can make informed decisions about where and how to use them. :)
Great test, I am glad you added the glue for the pocket screw test. I use pocket screws successfully (without glue) for cabinet work. In particular any cabinet that gets mounted to a wall or a built in. Kitchen cabinets etc. If its a free standing unit I prefer traditional joinery methods.Its the racking of the case you need to account for.
I really enjoy your videos. In many cases, it seems that you are reinventing the wheel, but with really cool and imaginative solutions! Looks to me like the wheel could use some reinventing from time to time. Thanks for sharing your time and efforts and keep up the great work.
Very nice set of tests. I appreciate the experiments to back up your hypothesis. Good to know how strong the pocket screw is weaker.This is despite what Kreg has claimed.
Just noticing some of the responses about mortise and tenon verses pocket screws. I read an article a few years ago (maybe Popular Woodworking) about draw-bored mortise and tenon joints. According to the article, this joint lasts the longest over time and gave many examples with medieval furniture. Most of the time the joint never received any glue. How about a test, from a curiosity standpoint, to see just how strong a draw-bored mortise and tenon joint actually is? You could very it with one or two pins. Just a thought. Keep up the good work and keep the videos rolling.
We can all agree that pocket holes have their place. For instance, pocket holes make way more sense on picture frames. Tenons make more sense where strength is key. I wouldn't want to sit on a chair that was constructed with pocket holes (even though I use them as a primary joint). If I had the skills to pump out consistent mortise and tenons, id use them every time.
Did you notice he didn't actually build something such as a book case that would never reach 100 lbs against one small area I have built many items with pocket hole and have yet to have a failure. Hell he quit trying to move to the country. Another case where he failed to prove anything. Let him build a bookcase and fill it with books and see how long the joints last. I am betting he would quit trying before the joints break. When does someone put a jack into a book case and attempt to break the joints?
Every week brings an anxiously awaited video, but I love reading the comments... Yikes! The tests offer up information based on different joinery techniques. Yes, pocket holes are inferior if their marks are lowest. These things cannot be disputed. Use them for cabinet faces or low stress applications and put the box of tissues away. Thank you for the information, Matthias. Your new threaded jack is working well!
Thanks for another interesting and well conceived set of tests. I really enjoy seeing how you do these things. To those who want additional tests just for completeness, I suggest not going down that rabbit hole. A complete and rigorous analysis of pocket screw joint strength would be an enormous undertaking. These tests suggest that pocket joints, in that particular use case (short screws, at that angle, through a soft wood, tightened to that torque range, running through end grain and into edge grain, etc.) are a bad choice if you need high strength. They don't say anything about joining boards edge to edge, or working with harder woods, for example. As he says, there are a great many variables to control for.
Interesting experiment Matthias! I would have thought that a pocket hole joint would of done better. But I guess this proves that old school joinery is stronger
I appreciate your dedication to the scientific method, Matthias. Ultimately, every woodworker will use the joint he/she thinks is appropriate for a given application. It's great to see the glue test added to the pocket hole test. I was sure that the joint would be much stronger with glue. Your testing was unbiased and to the point. Thanks!
Every joining technique has its own strengths and weaknesses, it just depends on the situation which one to use. If strength is not crucial and you can hide the pockets, pocket screws are a perfect solution. It's quick, easy, cheap, safe and it pulls the wood together, so no clamping required. Not everyone has a CNC machine or pantorouter, if someone pays you by the hour, it's dishonest to spent hours creating mortise and tenons, when you can get the same result using pocket screws.
rutger houtdijk this is totally right. As my old boss would say, there is quick, fast and cheap at most you can have two. Are pocket holes the answer for every situation? No but they do have a place.
Greetings fellow CDN! Your videos are great, thanks for taking the time to make them! Testing the joints only in torsion, and not shear or tension only gives an incomplete picture of joint strength and intended application. Yes, I checked out your site. You're forgiven though, being a graduate of UW and all ;)
Matthias Wandel The mechanics of wood as a building material I believe are available here www.woodweb.com/knowledge_base/Wood_Handbook.html - hopefully the link still works. Cheers!
Rockwood Joe Hello to You Joe,thank You very much for the link,and yes it still works.I am only average d.i.y.er but had a quick look and it is very informative,will be very useful even to Me.subbed to Your site by the way,will have a good look tomorrow. Thanks again--Max.
I tend to think of these joints as having a combination of attributes. The glue gives the joint stiffness while the screws give the joint flexibility. These two attributes work together to make a more robust joint that can better withstand a range of stresses.
The problem with that reasoning is that the screws can't provide flexibility until the glue fails, and at loads under which the glue fails, the screw joints haven't really started yielding anyway, meaning the joint should be basically as stiff.
Terry Pullen I am saying exactly what I said, and not anything else.
9 лет назад
Matthias Wandel The fact that the glue breaks first would indicate that the job it does is exactly what it should be doing in a "real application", that is to try deal with any small rocking/twisting that would over time compromise the stability of the screwed joint, which would loosen, rock more and fall apart. Thoughts?
Thanks for the test! But another question comes to mind. Maybe screwing (pocket holes) are more depending on the wood type and still cannot be considered a weak joint per se
Ok, so I won't use pocket holes if I'm building a diving board. But what about in a practical application like a small table, weighted until failure? I love the idea of this test, but it doesn't really help me conclude that pocket holes aren't fine for quick / less-refined furniture, like a 4x4 kitchen table or something.
I'd be interested to see how John Heisz favorite; polyurethane construction adhesive fares in a test like this. Perhaps on a series of half lap joints. Because, you know there can never be too many joint test videos! Great work.
I would ask you to kindly test a butt joint with construction adhesive and screws from the outside. Also, I think the majority of the people don't seem to get that this is a test of how one joint breaks to compare them to eachother. This still doesn't mean that pocket holes can't be used or have no real world application - they do. But when added strength or movement is involved a different joint would be preferrable. I prefer to use dowels myself. Hoping to get better at finger joints and dovetails. I need more practice, though. Keep up the good work, Matthias Wandel :)
Great approach, and great videos! Pocket holes for some, mortise and tenon for others! However, folks should probably stop peddling rustic reclaimed pallet wood pocket-holed farmhouse tables on etsy (bench sold seperately). One thing we should mention is that you are presenting a shearing force. Maybe to test racking forces you could build a couple of tables, one with pocket holes and one with mortise and tenons, then using 2 hook-eye screws and rope create a force vector on the table top. Put some weight on top, block the legs and pull, attaching a sportman's scale. Pull the scale to a set force on all sides of the table, for each table, then increment the force. After the experiment, see which table is more wobbly by measuring the drift compared to a perpendicular plane on all sides of the table (unless one of the table completely collapses). Or go crazy and get two sportman's scales, build cogs with pegs that would pull a certain distance thus creating a defined force, and attach to the floor and have set the cogs in phase with one another to create an alternating pull/ pull force and let it go for an set time.
15 cm. Well, "Racking" is just a lamens word for a torsional force that is present in a structure, so I would have to disagree and state that what you crated here is an axial shear force creating an unbalanced moment about the joint- but add a new method of testing. Eyelets on opposite and opposing sides of the table and apply equal pulling forces causing the table top to rotate about it's center. Use this in conjunction with the test methods above, and afterwords, measure the overall shear strain of the table top (gamma) wrt the perpendicular plane from the ground. Many people are stating "sum of joints" etc, but seem to be forgetting about combination of stresses as well.
I used to use pocket holes for some quick and dirty shop cabinetry, and I still use it for annoying joints on similarly quick and dirty stuff. I'd guess that the only possible benefit of glued pockethole joints is that regular jostling/wiggling use might remain well below the breaking strength of a glued butt joint and keep the screws from wiggling and loosening over time. That said, I mostly abandoned pocket holes in favor of brad nails/glue/countersunk screws. It's faster and more accurate for the work that doesn't need to be pretty. Always hated how pocket holes misalign a joint unless it's clamped tightly.
Excellent unbiased test. I noticed that the wood under the pocket hole screws tended to pull out along the grain. I would have imagined that the screw would have pulled out in the thread area but alas, this was not the case. I wonder if you would get the same results from poplar or a harder wood? Although pocket hole joinery is not as strong as mortise and tenon, I'll still use them for projects not requiring a ton of strength (picture and face frames come to mind). Good video Matthias!
To qualify first, I'm not a professional woodworker but in my hobby shop I've build a variety of projects using M&T, Biscuits, Dowels, and Pocket Holes. Most projects I've done fair well On the pocket hole controversy I found the cabinets I built with them are holding up very well. One the Tree Surround Bench it dead fairly quickly. I thing it goes back to basic technique; choose your joinery method appropriate to the job.
Great video. Thank you for taking the time to test these out. I was looking at buying the pocket hole tools set or making my own. After seeing this I think I will try out working with dowels.
That's an interesting experiment. What it shows of course is that glue is useless in peel mode - such as you get in a butt joint. The glue must be working in shear mode, as you get with a mortis and tenon.
When taking bridges off 1920's guitars, I've noticed the old timers often scratched wood, like they took an awl or nail and zig-zagged. I've seen it on old furniture as well. I'd be interested to see that tested: smooth wood to wood vs scratched for strength?
It would also depend on the type of wood. More porous wood doesn't benefit much from a rougher surface, because it already has plenty of places for the glue to grip.
I love these joint strength test videos, and the new rig is really cool! It would be interesting to see if the new setup would change some of your previous results :).
