How well do screws hold in wood?

[@lewisbyerly9831]

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.

[@custos3249]

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.

[@jeffpower6473]

@@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.

[@عبداللهعلي-ع8ت5ح]

بالعكس هذا الاختبار مفيد جدا وخصوصا لأصحاب التخصص

[@smashyrashy]

I still think theyre useless

[@TizonaAmanthia]

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."

[@ChristopherBotelho3052]

i wish we could see all the math for that (including the math for even the reasoning and suggested ideas he gave)

[@leifhietala8074]

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.

[@Name-vu1kn]

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.

[@CDP135Z]

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!

[@Squibbleses]

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

[@fxm5715]

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!

[@deanrambler9006]

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!

[@antraxxslingshots]

Your contraption is a gift that keeps on giving.

[@ErinJayEldridge]

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.

[@matthiaswandel]

I just got tired of filming, so it was just a quickie test. And nothing overly interesting.

[@markm0000]

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 😊

[@EvgenyPakhomov]

I'm a software engineer and practically never work with wood, but it's always interesting to watch your videos.

[@nobodycares85]

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.

[@jeffcostello6747]

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.

[@Xtian982]

I would agree, that would be a good one for the Mathias “bullsh*t detector” test 🤣

[@MordecaiV]

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

[@chrisoddshoes]

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.

[@mspacone]

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!

[@oskimac]

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

[@IvoTichelaar]

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.

[@OneManBandWoodworks]

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

[@Xeroxorex]

Matthias, please keep doing your thing, it directly adds to the collective of all our living engineering knowledge!

[@andyandnancy]

I love the experiments that you run and how you share both your mental and the physical process. Thanks!!!

[@jamisonlm3]

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.

[@hazza2247]

drilling a pilot that is larger than the minor diameter will reduce the holding strength by a massive amount tho

[@JPWack]

WOW! Those drywall comparison at the end was interesting AF

[@JayBates]

Thanks for taking the time to do these tests. Always interesting.

[@gericstewart]

Thank you for taking the extra time to film and share the experiments you run.

[@bobd5119]

These tests are truly useful. In soft wood, I drill 1/64 smaller than the screw's inner diameter. That makes me feel better...

[@wholesomeengraving]

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.

[@tf1354]

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

[@freedomofmotion]

I do love it when one of your videos turns up in my feed. Its a rare occasion but i always watch.

[@DonMohle]

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.

[@TgWags69]

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.

[@tracybowling1156]

I mainly watch your channel so I can watch your genius in action.

[@zoharflax6363]

You're the best experimenter I've ever come across. Nice work!

[@davidt8438]

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.

[@MCsCreations]

Fascinating results, Matthias! Thanks a bunch for the testing and comparison! 😃 Stay safe there with your family! 🖖😊

[@Bob_Adkins]

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!

[@javbw]

I love your testing videos! Thanks ☺

[@MiniLuv-1984]

i wonder if treating the holes with cyanoacrylate or wood glue will make a difference to the yield strength of the wood?

[@F0XD1E]

Would be cool to see. My prediction is that the glue actually makes the wood more brittle and will fail sooner.

[@JB-fh1bb]

@@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

[@MiniLuv-1984]

@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.

[@nicktecky55]

@@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?

[@AaronHendu]

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.

[@nasonguy]

Intuitively I would think you’d get tear out way before actually shearing the screws themselves. Would be fun to see it tested though!

[@DJRockinRob]

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!!

[@akiriwas]

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.

[@hdwoodshop]

Pilot hole at minor thread diameter makes sense and easy to do with calipers and a good drill bit set. Thanks for doing this.

[@jmig1021]

I find this all to be very useful. Keep it going Matthias! Thank you

[@HenryKamp]

these tests are great - i love seeing the evolution of your rig too! keep up the good stuff, Matthias!

[@truckguy6666]

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.

[@Sludgepump]

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!

[@esepecesito]

That was definitely not more that I wanted to hear about it! Thanks a lot for sharing these tests

[@Lucas_sGarage]

I love CNC kitchen and I love this kind of videos

[@nealkonneker6084]

Thank you for doing this. We need more hard data about this kind of thing.

[@TheAxecutioner]

Thoroughly interesting, thanks for taking the time to make this !!

[@JeremyMcMahan]

Fantastic testing Matthias, and I appreciate this empirical information!

[@simonhopkins3867]

Always fascinating experiments when your testing machine comes out. I'm going to have a look for your video on building it.

[@tomdenny8507]

Awesome. Loved this and am looking forward to some sort of series. Thank you for the videos you produce.

[@celivalg]

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)

[@Lizlodude]

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.

[@WoodcraftBySuman]

Those wood tapped threads holding it down like a champ! 🙌

[@thecasualcitizen492]

Very interesting to learn that what I assumed to be correct about pilot hole size is more or less correct. Thank you.

[@markm0000]

This kind of content is like wood science. I love it.

[@jinto_reedwine]

These tests are very interesting, keep them coming!

[@billj5645]

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.

[@grumblycurmudgeon]

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.

[@PeteLewisWoodwork]

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...!

[@carfreak201047]

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.

[@messaoudkrioua5002]

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

[@MrThetaphi]

Great DIY tensile testing machine!

[@JonnyDIY]

So we ahould drill our pilots the size of the smooth part of the shank of screw for best results? 🤔

[@ScramblerUSA]

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?).

[@YouPlague]

This was perfect, please do more of these.

[@alanheady7982]

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!

[@kylehadden7294]

I found this beyond interesting, I would love to see more

[@Kevin.L_]

Absolutely great and useful information. Thank you sir!

[@ChristopherBotelho3052]

i wish we could see all of the math of every event and every suggestion. and every thing done here.

[@ChristopherBotelho3052]

(including the math for even the reasoning and suggested ideas he gave)

[@ChristopherBotelho3052]

i believe chatGPT would be able to show the math, if you are able to explain to it what you are suggesting and looking for.

[@ChristopherBotelho3052]

realize moisture, temperature, would also play a part in these tests.

[@jackle7913]

Thank guy, i whatched your channel for years! Almost videos

[@jshet]

These test videos are the best.

[@naher1277]

This was not at all more than I ever wanted to know about pilot hole size, but instead very interesting and informative.

[@superdau]

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)?

[@deanrambler9006]

Come to think of it, yeah, what about all that?...

[@jdl3408]

Great video. I look forward to more tests!

[@Itslvle]

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.

[@amielgiloni7302]

Great video! It would be interesting to see the effect of adding a washer and torquing the bolt with different values.

[@GERntleMAN]

Basically that's exactly what I someone's want to see. Real in depth information, not what most people can in depth information

[@jcr723]

I've been wondering about these exact things. Not kidding. Great video

[@MrLiveEra]

Very interesting, Lots of scope in this kind of testing, Reisser make some great screws , They are touted as high performance and I can vouch for that, they are the best screws I have used,

[@mahmoudomara5421]

Great and eye opening video. Thanks for sharing!

[@Dcvmnaturalist]

This was fascinating- thanks for another great video!

[@Indievors]

I don't even know what he's doing but I can't stop watching!

[@davidboman6224]

I love it! I would like to see a test where you look at pilot holes vs wood splitting. My gut feeling has always been to use a pilot hole close to the minor dia. But should it be larger if I really like to avoid having the wood split on me?

[@1pcfred]

Wood being a natural material with a lot of variability to it there's no guarantees. But certain practices will increase your odds of not getting a split. To that end any pilot hole is going to help you out. There's still other factors to consider though. Like distance from the edge. Which growth ring you go in. Summer vs winter.

[@ikocheratcr]

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.

[@mxadema]

This screw jack is really worth its weight in video.

[@nicholasgeorge7825]

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.

[@LukeTheJoker]

Awesome! Only thing I think you missed was the final test of fine vs coarse threading was only done in soft wood, I would be curious if it makes any difference in a harder sample.

[@PatrickKQ4HBD]

Yes. I thought it was course threads for SPF, fine threads for hardwoods?

[@LukeTheJoker]

@@PatrickKQ4HBD Yeah, just thought it would be good to see it proven.

[@TimothyJesser]

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.

[@TheVoidSinger]

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"

[@piconano]

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.

[@mckenziekeith7434]

Let it cure for 3 days.

[@arcrad]

What a coincidence I just rewatched your old video testing drywall screws vs deck and wood screws.

[@rodsilva80]

Thanks for doing these tests

[@jcortese3300]

That countersink screw's going to have some epic war stories.

[@riba2233]

we want more, this testing is gold :)

[@Samtagri]

This is actually very interesting. I always like dry wall screws. I always thought their big thread gives them a good advantage. Also their black color just looks way cooler than the boring silver screws.

[@hazza2247]

in aus we have gold drywall screws

[@joelhollingsworth2374]

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.

[@johnfreiler6017]

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.

[@paulsmyers203]

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!

[@SeanHodgins]

Are you telling me I could've been using a single screw to hold my drywall to the ceiling this whole time?!

[@joerosburns5639]

Thank you Mr. Wizard!

[@DaveChurchill]

It would be really cool if you could use this to test different types of drywall anchor!