Might be a neat idea to test dowells of various lengths. See where the benefit of longer dowells, if it exists, meets diminishing returns.

You’re slowly creating a wonderfully valuable database that I’m sure will end up being cross-referenced exponentially over time

Thank you, Matthias! I use quite a few bamboo dowels because I have them and they are cheap. One thing I have noticed, some of them have a burnished almost waxy surface feel to them. I don't know if it is a substance in the bamboo or a result of the dowel-making process or both, but I feel it may hinder the glue from fully penetrating the surface of the dowel, on those, I give the full-length dowel a light sanding with 220 paper before cutting them to length, I don't know if this helps though.

While one method may be marginally stronger than another, all of these tests demonstrate to me that any of them are adequate for my needs.

This is my favorite type of Matthias video. Full of real data about real world building strategies. Super valuable stuff!

I have been using small bamboo skewers - the ones you can get at a grocery store - as dowels in small projects for a long time. I find them useful especially when joining thin pieces of wood side by side. They work well for me. But I don't have all of the quantitative test equipment that you do, so I have no actual data to share.

The endgrain VS longgrain screw holding power is as surprising as the endgrain to endgrain glue strenght in one of your earlier test😉

very interesting bonus test at the end... I didn't expect the endgrain to do so well. thanks!

Great video. It would be interesting to see a "stress-strain", actually force-displacement, diagram for each joint. Then you could get a sense of the failure mode of each, at least from a brittle/plastic mode.

Thanks for teaching me not to shy away from screws in endgrain anymore, l never would have expected that to work so well

As a bonus, flush-sanded bamboo skewer dowels look brilliant

I'm here to say I really appreciated the short intro to action. 26 seconds on a 9 minute video is impressive.

Hello Matthias, thanks for video, Super video with stats, it blows my mind the things you able to do, either machine building or testing. Thank you, very informative. Regards

i like this. simple, direct, and conclusive. worth the time dealing with clamps and jigs and boring holes...

Being no engineer, I can't comment on your test methodology, but based on videos of yours I watched a long time ago, I have been using wood-dowel joinery on most of my simple projects, and these have all held up way better than I would have expected, given my clumsy techniques and the crappy pallet or salvage wood I tend to use. This video only reinforces what you have been showing your viewers for ages. One obvious point: Few people make their own screws, but anybody can make their own dowels, using scraps that normally would just be thrown away.

My experience with repairing wood windows: 1. Two inch long fluted dowels about thirty years old. Mostly the glue from 1976 had failed long before I was working on the windows. 2. Miscellaneous kludge screws to try to fix the failed dowel joints: The dry wall screws were rusted through (the windows were at the ocean) and the zinc plated screws didn't do much better. I also thought that there was a failure mode where the rail/stile joint failed from the screw working against the wood over time from wind loading. 3. 7/16 inch dowels through the stiles into the rails from the outside with titebond glue: As near as I could tell this was a permanent fix in the sense that something else was probably going to fail in the window before the rail/stile joint. I saw no reason for the fanciness of hiding the dowels inside the joint I just drilled a hole through the stile into the rail with the window clamped together. For awhile I was concerned that I wasn't using a fluted dowel. I doubt that was an issue. I put glue on the dowel and into the hole (I used an acid brush to make sure the inside of the dowel hole was thoroughly coated). As an aside I thought about doing the kind of testing that was done in this video. I never did but I thought the testing in this video vindicated my choice of window repair method. One thing though, I could just pull the old windows apart because the original joints had failed. I don't think the guy who tries to repair the windows I fixed will be able to tear the joints apart in 30 years.

Thank you so much for this! This is exactly the additional testing I wanted to see after your last tests!!

Very interesting results Matthias, thank you for sharing. I enjoyed this one 🙌💕👍

I'd imagine the fluting adds a good amount of surface area without increasing the radius, which seems especially important bc the dowels seem to pull out rather than fail themselves

Back in the old days, when we were adding a wall to a concrete slab (such as when changing an open carport into an enclosed garage or additional family room), we would use a hand chisel type star drill to put a hole in the concrete and then pound a peg of wood into the hole. We would then drill pilot hole into it and use that the mark the location of the hole for the 2x4 baseplate for the wall. Then we would use a lag screw to attach the baseplate to the peg and thus to the concrete. Later on, we started using lead and/or zinc inserts into the holes, but still lag screws. It would be interesting to see how the strength of those old solutions compare to the modern concrete fasteners.

This is good information. I would have never guessed that dowels would perform this well. And I like using dowels over screws for a lot of projects, but not all.

Mattias's hatred of pocket holes will never die. I can't say I blame him. I hardly use them.

I always love seeing these methodical tests.

Thank you for this video. I always find your activities fascinating.

Thanks Matthias. This was a really great test to see!

Greetings from the BIG SKY. A good analysis of screwing around.

Thanks for the video, always enjoy watching!

BEAUTIFUL jig, man! Excellent job!

Great video. I love the scientific evidence vs. hearsay.

I would like to know, how much would putting a suitable sized washer beneath the screw head prevent the screw head from sinking in and such increasing the strength of the joint. The result of end grain versus cross grain was indeed somewhat surprising.

The instant you have visual separation could be considered the yield point. In the case of the screw heads the wood beneath the seat is yielding to the load. Up to that point the wood is probably elastic, after that point the screw hole undergoes plastic deformation. Interestingly, a lot of people think in terms of ultimate strength when the component is often no longer useful after yield. The beauty of ultimate strength is that it provides a little margin after yield and before ultimate is achieved. That provides an opportunity to avoid sudden catastrophic failure. Interesting set of tests.

These videos are always so great!

Awesome! Thank you for all the hard work

Would be interesting to see if the relationship between screw strength in end gain vs cross grain stays about the same across different types of wood. Also would be interesting to quantify that comparison in plywood since I'd expect screwing into the side of plywood to be significantly weaker than the other direction.

I really enjoyed this video. I enjoy dowels, but sometimes had the thought that they weren’t as strong holding as screws, for whatever reason. This really did provide some useful data for me. Thanks!

Lovely bedtime story! Thanks Matthias.

An additional parameter of interest could be the rigidity of each joint, which, depending on the application, might be even more important than the tensile strength.

Mathias, I am really enjoying all the new vids!

I'm loving this stuff. I feel like it's building towards something that would make for a catchy thumbnail "proven: best furniture ever made"

These are so nifty! Thanks for making these!

I went in thinking that- of course screws would win. These tests were quite a surprise! I absolutely love a good experiment!

Thankyou very much for an very informative and useful video. I am really enjoying those videos. Thanks Matthias, Best to you and your family from Denmark

Thank you, this is useful! No legends and fairytales - just raw tests and analysis.

Perhaps it's time to buy a clip-on displacement gauge allowing you to plot force vs displacement. It would be nice to track the drops in force and jumps in displacement, you can then associate them with what you see and hear during your tests. Some other nice data to be had from such graphs, work done etc. A bit of extra nerdy fun.

It's impressive that the simplest dowel held up longer, and that the screw instead gave a lot of "heads up" that it _is_ going to fail, but failed completely different instead.

That is why dowel joints can be repaired and screws make such a huge mess when they fail or get overstressed

I love watching you break stuff 😊

Matthias' pull out game is crazy

Your experiment and testing are inspiring to engineering students.

Very solid experimentation with large sample sizes. Very good Science sir.

This makes me wonder about angles! Toenailing in actual nails at 30°. Or even skew(er)ing the skewers and dowels at angles so they are not in-line with the pulling force.

Moisture cycling should hurt the strength of crossgrain screws more than that of endgrain screws, since expansion and contraction should stress some threads more than others. Into endgrain screws can be as long as you like. Hoadley specifies half the pullout strength per length of screw into endgrain vs sidegrain. I wonder if the difference with your results is hardwood vs softwood.

Love these tests, I’m always telling my brother that screws hold better than you’d believe they would. Many a house is built with screws and nails, not everything has to be proper joinery if your in a rush.

This was a good video and answered a lot of questions

This would be interesting to see with different types of screws. The wedge shape of many seems like a point of potential compromise to me, so, in appropriate applications, like butt joints, i use countersunk cabinet screws, which have an integral washer. While my preference is generally dowel joints, i am convinced that an appropriate screw style can be technically superior in some applications.

I love these tests... lots or woodworking (and construction for that matter) is based on folklore... I often wonder which type of force is more typical on furniture fails... sheer, torque, pullout, etc...

I love these tests, thanks. Great information, I’d like to see a comparison with cross wise pressures, but that may be more of a measure of the wood and not the medium of attachment.

Up next: multiple dowels/screws. This is invaluable testing. Thanks for sharing.

Some time ago I switched to using 3/8 inch dowels for shop furniture joinery (benches and such). I don’t find screws any easier to use than dowels. Just clamp up your assembly, drill your holes, pound in your dowels, trim them down when the glue is dry. Simple. And apparently plenty strong. The practice of putting screws deep into counterbores and then covering the heads with dowels for cosmetic purposes mystifies me: why not just use dowels in the first place?

Very nice analysis! Thanks

I would’ve liked to have seen you test the pocket hole screws in the same orientation as the other wood screws, as I don’t think the heads would’ve pulled in as far and maybe held just as well or better.

This was like my old strength of materials labs..without having to write my own lab reports. Loved it.

Interesting results!

Now you just need to make a pocket hole bamboo skewer jig to get 100% test coverage ;-) And in a stroke, Matthias wipes out the pocket hole industry in a single video.

I would do a scatter plot rather than a bar chat. I think its easier to read, distinguish between the different tests, and see trends.

I wonder how 2 or 3 bamboo skewers would compare to one 3/8 dowel pin, if you space the skewers tightly so they do not take up a lot more volume than the dowel pins.

I saw a video recently where someone said that the commercial dowel pins are compressed, so that when you add glue and assemble, the moisture in the glue causes them to re-expand a bit, locking them in the hole tighter. I’d never heard that before, and have no idea if it’s true. I don’t have any on hand, but I guess you could test it by lightly wetting one and seeing if it did expand.

Ya finally splurged and got the TB III. Love that green cap stuff.

These are great videos

Used to be you could get spiral-fluted dowels at most builder's supply places. These days they're all straight fluted. I'm sure the spiral type is still available...and probably makes for a stronger glue joint.

I always wanted to know how large the difference between screws crossgrain and endgrain is. If I had to guess, I would have said endgrain has half the holding strength (not measured anything, just had a feeling that endgrain fails proportionally more often). Good to see that they are way closer than I thought. So the endgrain failures were more likely due to where they were used (butt joints, which pretty much always are like a lever) than the strength of the connection itself. Also good to see that drywall screws work almost as well as wood screws (and are even more consistent over grain directions). They are cheap and I have a lot of them left from building drywalls during a renovation.

I use drywall screws for lots of quick projects. They are cheap as chips, and very strong.

I like how this whole testing is all about showing, that pocket holes suck. :D

Wonderful as always. So takeaways for me is: use two screws instead of one dowel and screw in endgrain work!

Interesting results. I like using dowels instead of screws, but they take a little more work to use for joining, and I actually assumed screws were stronger. I wonder what the results would be with a more sheering force on the fastener; turning your test pieces sideways and applying opposing forces on each piece being joined.

Thanks for the good testing/video, I always enjoy finding out what works best. I have seen dozens of KZfaqs for making your own dowels, but there was one I really liked. You just use a thread cutting die and spin the prepared stock through it. With a complete die set you can make any size dowel you want, and they come out with good gluing surfaces. I wonder how they would work in you test jig?

Thanks for this. Clearly, dowels don't get the respect they deserve these days.

Thank you for doing this. I would love to see how lag bolts or construction screws would hold up (thinking GRK fasteners). I’ve considered using them and then covering the hole with a dowel for an easy joint.

Would be interesting to test two screws at different angles, that way pulling out doesn't rely on the screw heads as much. And pilot holes vs no pilot holes.

I wish you could test my favorite: 2.5mm "bamboo nails" (bbq skewers). They are a really easy method of reinforcing rabbet joined boxes for example. But I'm not sure how much they provide strength, especially if the rabbet is already glued.

The amount deformation before the failure can also be a data point

Thanks for looking at this often asked question. Very appreciated! Can you address pocket hole screws with the various common wood glues? (Titebond, Elmer's, maybe a 5 minute epoxy, etc?) Can you show us how your test platform is set up?

I've seen a lot of these ultimate joint strength videos recently on KZfaq but I really question the validity. What I think is more is more relevant to furniture is cyclical loading, or fatigue of the joints. For example, in this test it showed that the screws especially started separating before the joint ultimately failed. Imagine you made a small shaker style side table with no stretchers between the legs- and you only had the top rails directly under the table top. The normal load this will see under daily use is if it's bumped, and the table slides across the floor. This would be especially bad on carpet where the narrow feet sink in. The loads on on the joints would loosen those pocket screws and the table would get really wobbly really quick and drive you insane, and you'd throw it away long before it ultimately failed. If this was made with mortise and tenon joins, and maybe with draw bored tenons, it might not be any stronger in ultimate strength, but it would last a LOT longer, maybe even for centuries before the joints came loose and the table got wobbly.

All these years of watching your videos, my main takeaway is to not use pocket holes. My biggest reason for not get the setup is that it costs too much. Looks like there are better ways regardless. I'm finally starting to actually build stuff, so I'll be getting a dowel jig first. It's cheaper anyways...

Makes one wonder how screws and dowels would fair using hardwood. I also suspect pan head (or round head) screws, especially with a washer would do. Not tested, Domino style or floating tenon type joint. Then you could go completely around the bend and test other glues (Titebond type glue has a fair amount of creep) like Plastic resin glue, epoxy, and resorcinol glue. Your average woodworker likely would only consider epoxy or urethane. After seeing some tests in Fine Woodworking I'm typically OK with Titebond. Good stuff! Thanks for doing this!

Would be interesting to plot the force curve over time for each sample, and then maybe overlay them all together. That would help show the different failure modes. Not sure if you’re logging that data.

A load x time graph would be nice. Even better if you could add a displacement x time, so we can see when the joint fails.

Excellent video. I'd love to see the addition of glue to the screws in your testing, as glue and screws each give a different type of mechanical hold. Also, the same results with a harder wood might result in the screws performing better than they do when they can just deform the wood as they pull through (at this point you're testing the hardness of the wood instead of just the holding power). Thanks!

Thank you for doing all this testing and video-making. This information is invaluable to the carpenter and woodworker. I wonder if you might be able to do some testing with hardwoods? I feel that the hardwoods (walnut, hard maple, cherry, hickory, oak) might be able to withstand the head pulling through better than softwoods. The other consideration is that furniture typically isn't made with softwoods. To be honest, most fine furniture is made with loose tennons or dowels instead of screws, but that's a whole other thing. I really am curious to see how hardwoods can resist pulling the head of the screw through them. I can send you some sample hickory and walnut. I might be able to send some cherry as well. I don't really have any oak or hard maple though.

I use 3/4" through bolts for all joinery work 👍

I’d like to see sheering strength test with dowels, joinery, nails nails and those common gold screws from the big box stores

excellent content and presentation. I would like to see the bamboo in shear when it is used as a scroll pin. i use this method where i don't want metal fasteners or i want the pin to pull a joint together using a taper.

Very very good.

For screws in endgrain you'll have brittle failure, whilst you'll have more ductile failure in cross grain (as shown in the experiment). This coupled with potential cyclic loading, variation in moisture and cracks developing over time along the grain. I would be careful with utilising them more than 50% of your numbers for critical connections. Especially for short screws.

These tests are awesome. I enjoy seeing how different methods behave. I am curious what the failure modes are for real world furniture and what the thresholds of force on them are. I suspect short peaks through racking are a big one and that degrading materials from time and moisture changes are the bigger ones. My suspicion is that in real use for most furniture builds you hit diminishing returns well before getting to optimal raw strength of the fastening methods

I love dowels. They provide great strength in any direction. Any screw with perpendicular force is so weak compared to a dowel. Dowels are great for alignment also. The only problem is jigs for aligning dowel positions is not that great. Someone needs to come up with a great doweling jig!

I always watch till the end... And always learn something new but more importantly, something _useful_!

Did you try screws with glue? What glue and metal combo would work best I wonder? In the end, these tests often ignore the importance of what the application actually calls for, but they are still fun and informative.

Wendel, as thorough as you always are I am surprised you didn’t test a biscuit joint or two. Great video.

Applying a shear force might be even more relevant in many cases.. or a bending force..