this is the problem with threaded inserts 

Even though yours is the top comment for some reason I'm watching to see if it's actually clickbait. Thanks for the warning though

This is a joke right? Witt is in the running for the king of clickbait titles! He has good videos though and I watch almost all of them.

@@ericb0422 just joking. Thanks for watching my stuff. And technically my titles aren’t clickbait. I deliver on the promise. Legitbait would be a better description. True clickbait is deceiving and lying.

I love how accurate this comment is 🤣

@@WoodcraftBySuman actually it was a good video with a full explanation of the difference between metal inserts and wood threads. To be honest it looks like wood threads will save both time money and reduce chance of failure

What style is that?

True, I would assume similar to screws, a hardwood insert would have finer/more threads while a softwood insert would have coarser/fewer threads. It appears the inserts he used were coarse thread and cherry is a hardwood.

Gotta say, this one is a tad bit too flawed as a test. For starters, threaded inserts are not there to be stronger than a traditional mechanical wood joints. They're there for reliability of disassembly over time, including against weather. Wood moves around it with it in place, so it comforms to the insert wether there is a bolt in it or not. It doesn't deform due to wood breathing humidity. So you can disassemble, store, transport, wood breaths, and the threads for the actual bolt are still unchanged. Wood threads without the bolt in it, specially in soft woods, are more prone to deforming when humidity changes And as you pointed, you use different inserts for different woods. Less dense woods move more and can't hold as many threads per inch (which matters a lot for the strength of the bolt), so you relly on fiber compression more, effectively make it locally more dense, strengthening the wood and reducing movement. Denser woods already cmpress less, move less, are already stronger, and already hold finer threads better, so you use inserts with more threads. So not much of a surprise the threads with higher tpi survived longer. Specially since it has not gone through cycles of humidity change with the fastener off, so none of that wood movement the inserts are fighting against was a factor.

Yeah, do this again in pine and see how they stack up. Most furniture isn't made from hardwood anymore.

Mine have held up for many years in both woods. DC of SB...

Also using #2 tap instead of #3 tap would be better, since there would be less wiggle or no wiggle at all. Maybe the problem would be the fact that #2 taps are for hand use mainly and so they are also ground at the end, on the other hand #3 are mostly machining taps, that have no taper at the end.

You are spot on! The length, diameter and number of threads makes a big difference to the outcome of this testing. He should have made the Insert and the bolt the same length and it would have been a more accurate test. Here are the numbers. At 0.6 inch the 1/4"20 has 10 threads engaged, but the shorter insert only has 3 threads engaged. That is a difference in square inch thread engagement area of: - 1/4" Bolt = 0.318 - Threaded Insert = 0.2478 That's a difference of -0.0702 Square inch of area or 22% weaker for the insert. If You had used the same length of insert as the 1/4" bolt then there would have been 4 insert threads engaged in the wood. that would make the difference of: - 1/4" Bolt = 0.318 - Threaded Insert = 0.334 That would be a difference of +0.016 or 4.9% stronger for the insert. 1/4"20 Bolt Area for one thread: 0.0318 square inches X 10 threads = 0.318 Insert Bolt Area for one thread: 0.0826 square inches X 3 threads = 0.2478 Insert Bolt Area for one thread: 0.0826 square inches X 4 threads = 0.3304 If a blind hole is not required then always use pronged captive T-nuts for wood. The are made of carbon steel and are far superior in strength and durability.

Great observation, I didn't realize how few threads those inserts have. And had no idea they made hardwood inserts! Now if you use hardwood inserts compared to wood threads in Hardwood, they will both have the weakest link (the wood) improved. But as for stripping out (or pull test) the thread depth would also be a large factor and I notice inserts are fairly short, so 1 advantage of wood threads is that you can make them quite a bit deeper (limited only by tap length).

I'm not sure what I'm missing here, but 1/4-20 thread is 1/4-20 thread with the same TPI no matter what material or medium it's in. TPI remains the same regardless of the engaged length. Yes? No?

The threaded insert nuts have just four spiral threads…if they were an inch long there would be about twelve…hence 12 TPI for the nuts. FWIW the bolts can only engage their threads for the internal threaded section of each nut…which isn’t much, but it is metal in metal. A bolt screwed full depth into threaded wood has its entire 20 threads of its one inch length engaged. Now if you had one inch long threaded nuts with a full twelve spiral threads cut into the wood…that would be strong.

@@contessa.adella OK...I think. I wasn't aware of this. I'll make a point to inspect one of these inserts at my next chance to get a better understanding of that. Many thanks for the reply....I learn something new every day!

@@donaldp9259 insert nuts are called 1/4-20, because they accept a 1/4-20 screw (metal to metal interface). The 1/4-20 nuts outter threads that interface with the wood are a non standard size with a thread pitch of roughly 12 TPI. So the weak part in a insert like this, is it's interface to the wood itself. A 1/4-20 threaded nut insert with 12TPI stacked up against a identical length 1/4-20 bolt alone, would always lose in a maximum or cyclical torque test.

@@HotSteel-kl9tb Thanks for that input. I've used these inserts in the past, but I really didn't realize that. So, I've learned something new this week....a good thing.

Would be even worst since they are softer woods, I have use this once on a table, and I regret forever. Dont use this for stressing areas of your projects! One thing missing on the test and actually hard to test is the movement, the stress, from using the product, for instance a table is allways being pushed and pulled so in a matter of days this metal inserts are loose and as soon as you try to tigh them.. they will loose the engagement on the wood.. Btw I would use use epoxy glue if I want to stick metal and wood.

The wood expansion would affect the inserts as well...I think wood screws exist because they work well in wood and can even stand up to reassembly.

Absolutely this. All the cheap wood or wood products would be very beneficial to know about. The three that you listed would be perfect.

I would also be interested to see tapped threads vs just driving the screw directly into a slightly undersized hole

@@MrNiceGuy442 I think the best bet would be epoxying in inserts tbh, the real value of inserts is for multiple re-assembly cycles.

Have you tried stabilizing the threads in MDF with some liquid CA glue? I wonder how that compares. Also if you're running from the back side anyway I would think a bolt and washer would be superior to any insert. I suppose an exception would be in a case where you couldn't insert the bolt from the back for some reason, and absolutely had to thread in from the front side. Even so, on that rare case you're probably better off cutting a couple shallow depressions and using a flange nut, as you can get a lot more surface area on the face of the board.

I completely agree. If it's done right it will last a long time. I have seen so many times though, especially in cheap particle board furniture, where it wasn't done right. The best ones are like you said, where it is pulled into the material. Then it's almost like having a nut on the other end. Even if it does become loose you may be able to get it to work by holding it while you tighten everything down. Of course, that also depends on where it is. You may have to use some CA glue to hold it in place until you get it tightened down. Other times you would do better just making another hole or using a different fastener.

Excellent point about applying force in the “wrong” direction so the top flange would provide additional resistance.

You thought you were making a case for threaded inserts, but really you just made a good case against using MDF in applications where frequent re-assembly is a factor...in fact, if something needed to be portable MDF or similar composites would not even be on my list of materials because while it is solid, it cannot take hits well, it's heavy, and causes high degrees of wear on your tools.

@@alphaforce6998 Well yeah, obviously MDF is the "cheap" alternative, which is why it's used in basically everything. Any woodworker would rather use anything else (except maybe big-box construction plywood) but the cost limits for a particular job might force otherwise.

😂😂 I love seeing all the other RU-vid woodworking folks sass each other

Ouch lol

Haha ouch Scott 😂

🔥

@walterwinnipeg Yer a friggin prince for pointing this out as clearly as you did, as are many other commentators who’ve educated far beyond the scope of author of this video. MANY THANKS!

That's not how it is with most cheap furniture..the threaded insert often comes out because it goes in on the same side as whatever is screwing into it.

T-nuts go on the far side but often the acorn nuts go on the bolt side because you're typically not using a through-hole.

@@brianwest2775 A threaded insert is not an acorn nut. An acorn nut is a domed cap nut.

The ones I use have no flange but looks exactly the same except for that so they are not directional and thruholes are not what a woodworker wants so this is a very coomon use whatsoever they where designed. Therefore this is an interesting video 🙂

The longer the set time the more wicking... It is liquid for longer

@@Anyone700 maybe? Super glue is thinner and acetone the solvent used In the glue can permeate into materials quickly.

Drill for the insert, apply the CA glue, let it wick in and dry. Repeat as needed until the CA glue doesn’t just wick in. Then install the insert.

Yes. Epoxy is the ticket. CA-glue is just horrid mess.

Wood (sic) the gel CA work better in this situation so it doesn't wick into the wood?

For your 3d printed parts a much better insert is the melt in type.

I bet it would be a similar trend, though maybe CA glue would be more helpful regarding durability of wood-tapped threads. Pine is pretty strong, and the logic of how tapped threads grab the end of the fibers is pretty similar almost regardless of wood species; I don't expect it would approach drywall-anchor type dynamics until we start considering like redwood, balsa, or paulownia.

I was literally going to comment the samething. Of course the wood will hold up better the harder it is. Inserts will hold up better on softer woods like pine

I think the outer threads on the inserts are just not coarse/deep enough. The inserts in the video look like they are meant for very hardwood. I think the wood used in this experiment is soft wood. It’s almost like using a bolt meant for metal in wood. As I mentioned earlier, using inserts is like using much bigger bolts. The threads need to be much coarser to compensate.

The inserts points is repeated disassembly over time. Wood moves. People move the furniture. And when you stick the screw back in, the metal thread catches it the same way every time. Wood thread or screws do not.

Crt or lcd?

Yer a friggin prince for pointing this out as clearly as you did, as are many other commentators who’ve educated far beyond the scope of author of this video. MANY THANKS!

Conversely, I've (improperly) used inserts to repair a hardwood office chair after the wood completely failed around the original screws. I cut 1/4-20 threaded rod to make studs and then torqued "furniture nuts" to somewhere in excess of 30 ft-lb. In one place I passed the rod entirely through the chair, with an insert on each side, to clamp the arms with said nuts. I used 35mm inserts with coarse, interrupted, deep threads - softwood inserts. Chair's still rock-solid after years of further abuse, although it desperately needs to be reupholstered again and the pedestal needs similar repair.

It's fine to use an electric driver as long as you use low torque settings (as he did) and are careful when you first get it started.

That doesn’t sound very idiot proof.

The lower clutch settings on a drill will torque the screws less than most people would with a hand tool

Too bad you likely left mis-informed because the test itself was setup for failure... RU-vidrs misinforming people 1 video at a time.

Shit... You're absolutely right. You're a fart smeller... And the stripping test. I read a few dozen comments and a bunch of engineers talked about thread and science bs ... You absolutely nailed the reason. Nobody else caught this, not even me. How could he fix the test? Place wood between the insert and the washer and bolt? You're the damn genius ... Whatcha got?

Use a bolt shorter then the insert.

I agree - oversinking them means tightening them will try to extract them. And in any case, overtightening them will cause cam out. On the other hand, if that's how he'd use them in real life, those are the results he should expect.

I’m also curious about the efficacy of wood tapped threads in end grain since the wood surrounding the threads would be less likely to fail over a large area, but perhaps more likely to fail nearest to the threads. As with any other wooden connection point, I think choosing your attachment-point grain can make a very large difference in the performance of the connection. Be nice to see this tested in a follow-up video.

It seems to boil down to the quality of the outer threads, of which the pilot hole size could be the dominant factor.

yes, I would like to see this tested also

25/64 is about 10mm

Americans and their freedom units :D

You would rather go for severe and probably unrepairable damage rather than replace some cheap inserts?

@@wernerviehhauser94you would need to plug the holes in both cases so they are both reparable

@@Timopeo you did not really pay attention when watching the video, did you? Check the tearout.

@@wernerviehhauser94 The tearout test was pretty extreme, and I think odd to happen with normal use, but still repairable. The most likely problem would be the insert stripping out completely, also a pretty easy fix.

Glad it helped! Thank you for letting me know

You can make your own by tapering the thread of a bolt. Use a longer bolt to make aligning easier.

Are the holes of same length in the test?

Not using superglue on impact loads AS AN ADHESIVE makes total sense. But in this case, the superglue is used to bond the wood threads together to make the wood matrix stiffer - not to bond the metal to the wood. And because the wood matrix significantly reinforces the cured superglue (similar to the way steel can reinforce concrete), the resulting wood-CA matrix is MUCH less brittle than cured CA would be on its own.

the inserts are wider diameter yes, but have fewer threads interacting with the wood. If you look at one of these inserts, the outer threads have fewer than 20 threads per inch.

If you're starting them by hand, like you should, you would definitely feel if you're started to cross thread in wood. I've actually tried this making tap handles. The metal inserts were a real pain in the butt and would always go in crooked. remembered I had a tap and dye set and tried it out. It was much easier and was plenty strong for a tap handle. I could also easily tell if I wasn't starting the thread right and just backed off without any problem.

I'll buy that wood-thread cross-threading idea. But also acknowledge that threaded inserts are a pain to install plumb. And if you get one started crooked you've just messed up the hole you drilled... in quite possibly the one spot where the hole needs to go.

He screwed and un-screwed the screws 100 times, and the metal ones didn't even make it to 40.

@@lexugax he didn't unscrew and screw them completely though. When leaving a little bit of the screw left in there, it ensures you won't cross thread. That's not how disassembly and reassembly works. The damage is done outside of this test parameters.

Excellent point, MANY THANKS! @@HotSteel-kl9tb

Yeah the wood threads looked much deeper than the insert.

Yeah I just can't believe people are watching this video and thinking it was a good test.. I guess it really highlights the different intelligence levels between people in the world... He picked one arbitrary threaded insert, using arbitrary bolts. Even in his video the BOLTS FAILED! He really should of tried a variation of different threaded inserts instead because ultimately a wooded insert with a larger diameter is going to have more surface friction to hold it in place assuming the threads are proper lengths. Instead he's using a threaded insert nut (in the wrong direction) that has a much wider thread gap that is effectively lowering the overall surface area. And because he installed it in the wrong direction, it's both trying to further thread the wood while pulling it at the same time.. This results in just destroying the entire thread very rapidly... I'm not even an engineer and I immediately can see how terrible this 'study' is..

I've found that the ones you describe are worse than the threaded inserts in pine as the knife edges rip through the wood fibres when torquing the screws up. Wherever possible I try to insert the threaded insert "upside down" so that the axial force is trying to pull the flange through the wood.

@@johnwatson8192 I fully agree that the inserts should be put in from the bottom of the board as much as possible, for just the reasons you describe. An even stronger option is to carve out a space in the bottom for a wingnut and epoxy it in place. That isn't going *ANYWHERE.*

🤣

Good point. It's an easy fix to plug a hole when a threaded insert fails. Worth putting some extra thought into it for sure.

@@applebutter4036 you can plugged the hole from a tapped hole also then. no?

@apple butter, based on the tests shown in the video, the wood thread is stronger and if it breaks, it will damage all the wood surrounding the hole which would require a major repair.

@@cyber2526 you can see in this video that there is a lot of damage when the wood threads failed. Be a tough fix compared to the threaded inserts

@@applebutter4036 the upwards pull yea, but you'd have to do something serious to put that much force on it, and homnestly, if that happens the table or whatever you made propably has more damage then just threads

Thanks Aaron! Great idea! I should consider going long term seasonal type tests and think ahead. I definitely have one in the pipeline on waterpoof and one on "oily" wood and glue performance. Taking some notes from your comment for possible future use. Appreciate you coming back to the channel! Great to hear from you

My pleasure!

Thanks Matt! Appreciate you watching.

Agreed. T nuts have unparalleled mechanical advantage because of the way it is shaped and use cases. But they're ugly as sin and perhaps I'm in the minority here but I've never used t-nuts for that purpose.

@@WoodcraftBySuman I drill from the back with a 3/4 inchForstner bit 1/4 inch deep, then after installing bolt from front, use a plug 1/8 inch thick or so & sand flush. Very similar to how pocket hole screws are concealed with plugs.

Much appreciated. Thank you. The next video is just as interesting. Finishing it up soon :)

Thank you for sharing your very sophisticated method. T-Nut on the back side I've done, but I never thought of "hiding" it by tapping the wood on the contact side to match the threads of the T-Nut. Very creative and cool idea. Thank you for sharing it.