Yanking screws out of wood to test for strength
ฝัง
- เผยแพร่เมื่อ 27 ต.ค. 2023
- Modifying my strength testing machine for pull (tensile) tests.
Then using the machine to test how well wood screws hold in wood against pull out.
Also testing head pull through force and effect of pilot hole size on how well the screw holds. - แนวปฏิบัติและการใช้ชีวิต
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I usually find these type of tests interesting but kind of useless until, a few months or so later, I run into an application where it matters and then I think "Darn, I'm glad Matthias ran that test so I don't have to." Thanks for doing the work and keep it up. I really do like these videos.
Similar. Apart from wood splitting, I've always questioned why my dad would randomly stop to drill a pilot hole when just throwing a screw at something and moving on seemed fine. I'd always assumed pilot holes had a greater negative impact, but seeing hold strength is nearly unaffected is pretty unexpected.
@@custos3249my pops taught me to drill an oversized hole (slightly larger than the thread diameter) in the first piece to prevent screw jacking and a pilot hole in the 2nd piece to prevent splitting.
An oversized hole comes in super handy when setting doors.
بالعكس هذا الاختبار مفيد جدا وخصوصا لأصحاب التخصص
I still think theyre useless
This is definitely NOT way more than I wanted to hear. This is the kind of experimental hands-on finding-out that we've come to expect from you. More? Yes, please, absolutely.
I was assigned a project at work to compare the holding power of screws Vs. rivets and roves in ship building. I searched for weeks for a published standard and mostly just found conflicting numbers published by screw manufacturers. I wasn’t quite at the bottom of the internet (but I could see it from there) when I found a study published by the Montana school of forestry for the construction industry that laid out pull strength of screws in wood. The interesting part of the study was that the moisture content of the wood played a huge factor in the screws holding power.
I really like how you spent almost half the video explaining the original need for this test. sometimes tests feel....disjointed from reality...so having this one start out with "I'm doin' a thing, and then had a question, and decided to test it to get more info. so this is why I"m yanking screws out and measuring the forces. "love your videos, Matthias."
i wish we could see all the math for that (including the math for even the reasoning and suggested ideas he gave)
I would love to see these tests performed in isotropic engineering materials like HDPE, nylon, or acetal plastic. Each plastic with a unique, known yield strength and ultimate strength. I've wondered if the results would be more consistent. Then, I'd also be very interested to see if the results from the engineering materials could be generalized for many different wood species, hardness levels, and grain directions.
I would agree, that would be a good one for the Mathias “bullsh*t detector” test 🤣
Plastics aren't super great for "unique, known half and ultimate strength" ... They can be a little tricky to pin down with creep and plastic deformation
I'd be quite interested to see the results for nails. Especially those cut or square nails that are supposed to get their hold by bending the fibres down sort of like a feather board
I'm an aerospace engineer whose knowledge of wood is practically limited to things I can remember from your videos. This was really fascinating to me, especially the bit at the end about how little additional threads changed the pull-out force and the negative trades that go along with driving it in the first place. I wish that had been a little more prominent in the video, honestly, to help reinforce it in my brain, but I'm glad you got it in there.
I just got tired of filming, so it was just a quickie test. And nothing overly interesting.
Woah that’s cool. Would you be so kind as to share some of the channels you find interesting? I work on transport refrigeration systems. There’s a little overlap between our fields. My background is in IT infrastructure. Thanks 😊
As a matter of fact, I think this information is very useful in meaningful and practical ways. Your videos of shown that many practices actually weaken projects. For example, threaded inserts failing before bolts or screws directly screwed in.
I'm a software engineer and practically never work with wood, but it's always interesting to watch your videos.
I found this very fascinating about the pilot hole size versus pull-out strength. With no pilot hole being not much stronger than minor thread diameter, I will be putting pilot holes in to prevent splitting even more than I had been. Thank you so much for sharing these strength test videos. Very informative!
This is great. I love this kind of testing because it helps me understand what's actually happening, not just the results. That's a far more useful tool to carry around in my head, since it is much more broadly applicable. Thanks, Matthias!
I think these sort of tests help with a general understanding, or feel, for how materials perform and can thus influence design of personal projects. So thanks Matthias.
Epic video! I don't know about most people in garage shops, but 90% of what I make are more or less experiments in engineering and reduction. But yours are much more comprehensive and structured.
Thanks for doing these tests. I usually eyeball drills to use for pilot holes. I try and get one the minor diameter or just slightly larger. One slightly larger will be easier to drive and lower the chances of splitting the wood. It's also interesting how the number of screw threads didn't impact pull force that much. Looking forward to seeing you test different fasteners.
drilling a pilot that is larger than the minor diameter will reduce the holding strength by a massive amount tho
That was fascinating, Matthias. I wonder about this every time I drill a pilot hole. Would be interesting to see you continue these experiments with sheer strength. I'm always wondering how well my drywall screws will hold up to side loads. Great video... Really enjoyed that!
Matthias, please keep doing your thing, it directly adds to the collective of all our living engineering knowledge!
I love the experiments that you run and how you share both your mental and the physical process. Thanks!!!
I LOVE THESE TESTS!!! I also super enjoyed that co-lab you did testing clamps. That was lots of fun! I cant wait for your next experiment!!
Thanks for taking the time to do these tests. Always interesting.
Mattias is a dispeller of unfounded notions, questioning and measuring and clarifying what the rest of us just gloss over with assumptions, presumptions, and "gut feel." As a retired engineer myself, I see the difference between real facts and imagined ones like the difference between bedrock and sandbank.
Glad to see there's so little difference, because that's something I've always eye balled. I try to make my pilot hole the size of the screw core, or slightly smaller.
And I've always prefered screws with less threads because they tend to strip less easilly when I drive them in. Especially in softwood.
Interesting test. However, I don’t think that just pulling on the screw is correct. You need to pull on the joint. It’s a bit complicated to explain in a comment but it has to do with compression of the clamped piece
these tests are great - i love seeing the evolution of your rig too! keep up the good stuff, Matthias!
Thank you for taking the extra time to film and share the experiments you run.
I love this kind of testing - you answer all of the questions that I wonder when I build things, but don't want to put in the effort to test. Thank you!
Fascinating results, Matthias! Thanks a bunch for the testing and comparison! 😃
Stay safe there with your family! 🖖😊
I do love it when one of your videos turns up in my feed. Its a rare occasion but i always watch.
Awesome. Loved this and am looking forward to some sort of series. Thank you for the videos you produce.
You're the best experimenter I've ever come across. Nice work!
I would be interested to see a video on the force required to sheer off a 16d and 8d nails. A lot of times in the trades you nail a cleat to a wall or something you want to move with a crane, and I have always considered a 16d to reliably hold around 200lbs in the sheer direction. Sheer paneling on modern engineered structures usually requires a very specific number of 8d common ("common" being a specific diameter) nails for a reason. Commerical or school wall framing requires 16d common nails for nailing studs, etc. I always prefered to use a smaller diameter nail because there is less splitting especially in dry lumber.
Always fascinating experiments when your testing machine comes out. I'm going to have a look for your video on building it.
Fantastic testing Matthias, and I appreciate this empirical information!
These tests are truly useful. In soft wood, I drill 1/64 smaller than the screw's inner diameter. That makes me feel better...
I find this all to be very useful.
Keep it going Matthias!
Thank you
I love your testing videos! Thanks ☺
Thank you for doing that test, I find your tests extremely helpful and I have actually won arguments with architects and engineers on jobsites using your videos as the only evidence
These tests are very interesting, keep them coming!
what i love about these channel is that it is most about the tools and the procedure of making them than the test itself. really loveit
Your contraption is a gift that keeps on giving.
i wonder if treating the holes with cyanoacrylate or wood glue will make a difference to the yield strength of the wood?
Would be cool to see. My prediction is that the glue actually makes the wood more brittle and will fail sooner.
@@F0XD1E You make an interesting point. You’ve got me thinking that there could also be a “sharp edge” between the CA glue and the unglued fibres which would lead to an additional failure point
@F0XD1E Interesting. I was thinking it would permeate into the wood and make a few mm of hardened wood around the hole. Hopefully our gracious host will see fit to try this for us on his testing apparatus and let us all know.
@@F0XD1E I'll stick my three ha'pence worth in.
The glue is fluid, and so soaks into the soft wood fibres. That forms a composite material that is hard and flexible. In addition the glue only sets fully under pressure, so the junction between the screw's hole and the clean wood is gradual. When the glue is fully dry, there's now a plug of the composite material maybe a half inch in diameter intimately bonded to the structure of the wood.
Hard wood? Meh, not so much. Time for an experiment, now I wonder who might be interested enough to do that?
Thoroughly interesting, thanks for taking the time to make this !!
As always, very informative content! Thank you. It would be interesting to see the difference between end grain and long grain, and also difference between long grain and long grain (by driving screw radially vs tangentially to the wood rings). And maybe something in between (45 degrees?).
I mainly watch your channel so I can watch your genius in action.
If you think this isn’t interesting, you are dead wrong. I love this sort of stuff! And now I know exactly what drill bit to grab! Thank you so much!
Very interesting, I like these videos. Nobody else would bother, and if they did, they probably wouldn't do it in a way that shows valid results like you.. Thanks for bringing this to us.
thanks for making this. looking forward to more! I found a load table for pullout force of various sized lag screws years ago, but other screws, too!?! that is so great
Thank guy, i whatched your channel for years! Almost videos
WOW! Those drywall comparison at the end was interesting AF
That was definitely not more that I wanted to hear about it! Thanks a lot for sharing these tests
You are the living definition of a mad genius. For years you’ve built countless machines, jigs and apparatus that have either proven or disproved a theory utilizing wood or wood products. And after all of this what have we learned? We’ve learned that wood varies in strength and hardware varies in strength. Use your talents to improve products that exist already and help the woodworking community and maybe even make a couple million bucks in the process. I for one would love to hear you’ve built a better mousetrap.
This was perfect, please do more of these.
Great DIY tensile testing machine!
Great video. I look forward to more tests!
The kind of stuff we never learned as trainees over 40 years ago, so very interesting. I'll be using smaller pilot holes from now on...!
I always made my pilot holes the same size as the minor diameter, now I know that a skosh larger won't matter that much. Thanks Matthias!
Great video! It would be interesting to see the effect of adding a washer and torquing the bolt with different values.
This was fascinating- thanks for another great video!
I don't think you're making a lot of money from these test videos... but I'm sure you're having fun doing them... Thank you very much Mathias
This is top notch work. Doesn't matter if it's for wood working screw strength measurements, Matthias' methodology is wonderful. I've seen less quality from a real life rocket engine analysis presentation.
I've been wondering about these exact things. Not kidding. Great video
Absolutely great and useful information. Thank you sir!
Pilot hole at minor thread diameter makes sense and easy to do with calipers and a good drill bit set. Thanks for doing this.
No, not way too much to know about pilot holes. Always wondered what the optimum pilot hole diameter was. Very interesting. This reminds me of Materials Testing class I had is college. Thanks!
actually, those tests are really interesting, helps a lot in trying to select which screw to use for which task. I usually go by gut, or try to follow some arbitrary recommendations, which were already proved wrong with your experiment on the thread count (although I suppose they are a bit stronger, but not by enough to be worth it)
This is so useful. I'm used to just using whatever is laying around, which is usually drywall screws, but whenever it's actually under some load I'm always wondering what are actually the right screws to be using here.
Since the beginning of watching all the force tests became a big fan of the screw jacks that are used in case of an emergency to change a tire on gm pickup trucks. Can really move alot with just finger strength.
Thank you for doing this. We need more hard data about this kind of thing.
Great and eye opening video. Thanks for sharing!
I love CNC kitchen and I love this kind of videos
I found this beyond interesting, I would love to see more
These test videos are the best.
As always cool video
Can’t wait for more on this topic
This was not at all more than I ever wanted to know about pilot hole size, but instead very interesting and informative.
Thanks for doing these tests
Actually, exactly what I wanted to know! Not too much! ha ha. I've always wondered about this exact subject, especially the effect of different pilot holes. Great video.
This kind of content is like wood science. I love it.
I love this type of content!
I really enjoy these tests. Especially the insights into minor pitch and pilot hold etc.
Would be great to see same/similar tests on hanger bolts and anchor screws (don’t know if they’re called something different overseas) considering the application claims behind their design.
Keep up the great work!
Glad you found the most common failure mode: the wood is collapsing. I suspect that's why no pilot hole showed a slight increase in one of your tests: that pre-loaded the wood fibers and the preload is what resisted failure for a little bit more.
we want more, this testing is gold :)
Very interesting to learn that what I assumed to be correct about pilot hole size is more or less correct. Thank you.
I just built a bike camper and was just thinking about this...also sheer strength between two pieces of wood screwed together. Perfect timing! This literally helps me decide how many screws are are actually necessary. I know the screws will usually break if you try to pull em out with a cat's claw or crow bar. So pull strength seems far greater than sheer strength, but I really dont know.
Intuitively I would think you’d get tear out way before actually shearing the screws themselves.
Would be fun to see it tested though!
Super cool testing.
I wonder how pull force is affected if you screw in, then screw out (like making the threads), and then screw in again the same screw and "tight it enough".
Also how much pull a regular bolt of same external diameter will hold compared to an screw.
I would be very interested to see what would happen if you squeezed a drop or two of epoxy into the pilot hole, before screwing the screw in and let it cure overnight, before pulling.
Very interesting experiments and test fixtures you come up with.
Let it cure for 3 days.
This is really interesting. I've genuinely wondered about pilot hole sizing for a while. It looks like the pilot hole should be the size of inner diameter of the threads, period. More samples would be great!
Hi Matthias, great post, as always! I work for the Dept. of Wood Science and Technology od MENDEL University (Brno) in Czech Republic. We carry out these standardized type of tests (on soft and hardwoods, wood-based panels, etc.) almost on daily basis on our Zwick (GER) universal testing machine with 50kN load cell. If you would be interested in comparing results, let me know!
It would be great to see smooth joinery vs. surfaces textured to retain some glue during assembly. I think this would be easiest to test regarding dowels, but I have seen some commentary that box joints are often glue-starved, so I'd be interested to see that sort of test too.
Those wood tapped threads holding it down like a champ! 🙌
Wood density is probably the main factor. Then all kinds of variables, hardness, stiffness, moisture content, etc. Holding power of pallet nails (spiral or ring shank) often surpasses the tensile strength of the steel. Screws can be even more tenacious, but sometimes less, because the threads being finer disrupt wood more. This is a well studied thing, because building codes and all kind of engineering depend on fastener strength.
My takeaway was: "do what you expect you should do an use a pilot hole at or just under the minor diameter to ensure secureness and prevent splitting" and potentially "flatter heads may actually be better at preventing pull through"
I just love this type of stuff; actual knowledge. Too bad it's not a view-winner, but please do note Matthias that even though you would get more viewers talking about vapid stuff like the Kardashians, this is the type of stuff that has real value and is highly appreciated by those who have the appetite for it.
When reading the title of the video, I thought it'd be about testing the difference between screws that had been screwed in, and screws that had been hammered in, like you did in your teenage years on roofing... I'd be really curious to see some hard data on that! Very interesting, though!
Really useful to know. Thanks Matthius
Ohh, there's so much more I'd like to know now (also there wasn't more about pilothole sizes than I wanted to know in the video 😉).
How much weaker is a screw into end grain?
What about machine screws compared to same outer diameter wood screws?
Does tapping the hole change anything?
Is there a difference between cutting the thread with a tap and a screw made into a "tap" by filing/grinding teeth into it? (I have accumulated a whole set of the latter over time, because taps create slightly oversize threads compared to screws on purpose, but for wood that's not needed and screws don't "wobble" in a thread cut with another screw)?
Come to think of it, yeah, what about all that?...
What a coincidence I just rewatched your old video testing drywall screws vs deck and wood screws.
Hello Matthias I like this kind of test very much make more of this test 😊👍👍
Thanks. You made a dry subject interesting, as usual.
There is the concept of the stiffness of the testing machine. As you apply load to the specimen and the specimen deforms, the testing machine also deforms. If the testing machine deforms a lot and the specimen fails suddenly, the testing machine will react like a spring and can recoil quite a bit. If the testing machine is very stiff it will not recoil very much.
I thought the pilot hole tests were very interesting. I drill pilot holes for most uses because it makes it practical to drive the screws. I'm always worried about what size pilot hole I should use, now I know.
If you do building construction out of wood you are only allowed relatively shallow notches in the end of beams or joists. When I saw the notch you created in the top beam I thought it would split relatively early but it didn't.
To be fair: his results seem to bear out the conventional wisdom on the matter: pilot hole should be equal to the minor diameter of the threads (the center "rod" of the screw, inside the threads.
This makes an enormous amount of sense: the threads are a helical inclined plane that taper to a cutting edge. This means that, by providing a pilot for the innermost cylinder, one provides a shaft for that innermost rod to live in. The outer threads _cut_ their own path, cumulatively, into the wood fibers. This means the maximum amount of thread penetration and contact with the minimum amount of lateral play.
One might go 1/64 smaller in central shaft size (pilot), in that the swarf from the threads' cutting should only get impacted around the screw, making the void that tiny bit stronger, but it WOULD be just that: a tiny bit.
In short: on this one we old guys are right: just use the minor diameter of the screw, maybe a hair smaller for softwoods.
Another interesting and useful video.
I would like to see this repeated for solid softwood, softwood plywood and Baltic birch ply; both into face and edge.
I love it, please more!
10:17 actually I could go for more pilot hole studies, love these force testing videos
Very useful, thanks for the effort.