Will the joint fail?

[zelk]

I have two pieces of timber that I would like to glue endgrain to endgrain. Each piece is 300 by 55 by 30 mm and is constructed from Kauri Pine floorboards. If I glue the pieces, as shown in photo 3, will the joint eventually fail over a period of time?

Zelk

[HazzaB]

Hey Zelk,

First a Question what are you making,?

The answer will have a bearing on how to do it.
I would probably use a PVA probably TiteBond, but if there is any load I would probably go for an Epoxy, and a couple of Biscuits or even Dowls

HazzaB

[Ron Dunn]

I've not tried butt-jointing timber like that, because every piece of advice I've seen advises against it. It MIGHT work - apparently there are glues which love end-grain - but I wouldn't take the risk.

If there is just no alternative to joining the timber this way, perhaps you could strengthen the joint using some loose tenons ... or perhaps a scarf joint (using an angle like 45 rather than joining at 90) would be stronger.

My other concern will be finishing. This will look UGLY.

[joe greiner]

If it remains supported as shown for the rest of your life, it will not fail.

Otherwise, it depends on everything else, and your definition of "fail."

I generally rely on glue to hold things in position, while other mechanical contrivances provide structural resistance. Endgrain to endgrain is pretty much the weakest attachment possible. A midline board, spanning the joint, would allow sidegrain contact amongst the pieces, and should be quite robust.

Cheers,
Joe

[ian]

as others have hinted, what load does the joint need to carry?

I'd be inclinded to reinforce the joint with a loose tongue, think two breadboard ends without a pesky table top in between



ian

[Rattrap]

Loose tenons would be my first choice for joining end grain to end grain. As has already been said, end grain to end grain is the weakest joint of all. Glue up some scrap pieces & leave them for a few days then put a bit of a load on it, u'll find it breaks pretty easy.

[mat]

If you partially seal the end grain first with a weak water/glue mixture before you glue you will increase the strength. By how much - don't know but one of the reasons end grain glue joints are weak is that the glue gets sucked away from the joint.

[Bloss]

That's a big surface area to join and I can't see a use that would put a sufficient load on either piece that would break a plain glued joint using and good woodworking adhesive eg PVA. The joint will not 'fail over time' if what you mean is does the glue weaken. Depends on the glue, but any modern glue will likely outlive your use of the piece.

As has been said if there is some great load the will apply shear or twisting forces along the two pieces that would tend to have them come apart then you'll need to add some mechanical fastening as other have said - biscuits, dowells or some screws. In any case it is a simple job to drill, countersink and insert two or three screws and then there is not concern on any load (so far as the joint goes). :2tsup:

[ian]

snip...
In any case it is a simple job to drill, countersink and insert two or three screws and then there is not concern on any load (so far as the joint goes). :2tsup:not having a go...

using screws to reinforce the joint would require the screws be driven into end grain.
screws into end grain don't hold near as well as screws into long grain


ian

[Lumber Bunker]

yes it will fail... eventually.
add some interlocking messure... biscuts, dowels etc, and it'll help.

Good luck.

[rrich]

The joint (end grain to end grain) will not be as strong as some other joints. It would help if you made it a lap joint, even with just a 12 MM over lap.

I have made end grain to edge grain joints with TiteBond III that were surprisingly strong. If the final application is not in a high stress application, you may want to try TB III.

[zelk]

Thank you for your replies.

Lets, for the moment, forget about where such a joint would be used. We all know that endgrain to endgrain is a weak attachment.

Lets assume that the pieces are glued to another without reinforcing, allowed to sit indoors as shown in photo 3, exposed to the natural variations in humidity and occasional sunlight and under no load for 5, 10, 20, 50 or even 100 years.

Keeping in mind that the timber will expand and contract, will the joint fail, as it is endgrain to endgrain?

Zelk

[Zed]

half lap the joint with at least the depth of the thickness to provide some bond strength on the long grain. or as they say - loose tenon...

[silentC]

I wouldn't expect much of an end grain to end grain joint.

The normal thing to do is a scarf joint. Any reason you don't want to do that?

[zelk]

half lap the joint with at least the depth of the thickness to provide some bond strength on the long grain. or as they say - loose tenon...

Thanks Zed, you're back!

as mentioned, NO reinforcing.

Zelk

[silentC]

Actually, scratch that. I didn't look at your photos properly. You are gluing what looks like thin off-cuts, presumably for some sort of art piece or something. I don't believe it will fall apart, but probably depends what glue you use.

[Zed]

ive never been away... just keeping my mouth shut!

[Bloss]

Thank you for your replies.

Lets, for the moment, forget about where such a joint would be used. We all know that endgrain to endgrain is a weak attachment.

Lets assume that the pieces are glued to another without reinforcing, allowed to sit indoors as shown in photo 3, exposed to the natural variations in humidity and occasional sunlight and under no load for 5, 10, 20, 50 or even 100 years.

Keeping in mind that the timber will expand and contract, will the joint fail, as it is endgrain to endgrain?

Zelk

Depending on the glue and it's expected life, no IMO - if no loads other than expansion & contraction indoors. I have various simple end grain to end grain jointed pieces in my home that were joined using animal glues and are still together after more than 250 years including being used with small loads. But happy to wait around for 100 years to see how it goes . . .:D And if it is simply a theoretical question rather than a genuine need to sole a problem I'm outa here . . . :(

[Bloss]

not having a go...
ian

Well yes you are . . . :rolleyes: I know how to suck eggs too (well blow actually) and yes, screws into end grain do not hold as well as screws into other faces, but in the piece as described with no loads it would add considerable security. Depending on screw design/ type and method of use they can be very secure even into end grain (but depends how deep, timber characteristics, nature of loads and so on). This thread seems to be about theory and some sort of p**sing competition not practical application so I'm on me bike . . . :wink:

[bsrlee]

Its not entirely clear from the photos, but if the pieces are different lengths just make sure that the long and short bits don't line up, so the joint will match the rest of the joints in a brick wall pattern. If you do that, then it should hold for years, at least until some kids get hold of it, then all bets are off :B

[zelk]

As Bloss pointed out, I am more interested in the theory of endgrain to endgrain glueing, but it does concern a practical application.

I FEEL that gluing endgrain to endgrain will create a thin film of glue between the adjoining surfaces. One assumes that the glue will move with the expansion and contraction of timber, if it doesn't then there will be a shearing affect at some point in time.

I would imagine that some glues may be more successful than others, as Bloss hinted, hide glue may be preferable for this gluing application.

Feel free to trash this theory of mine.

Zelk

[Zed]

i read an article in AWR where the compared modern glues with other modern glues - the comeupance was that they are all pretty much the same. get the cheap crap and off you go... maybe a difference if u use a high oil timber and need to glue up with some foamy glue... otherwise meh....

I reckon your gunna get a failre if you glue end to end grain at some point - especially if you stress the joint somehow.

diff stresses in individual lengths within the joint (end to end grain that is) will eventually weaken the joint.

I tell ya - lap or loose tenon is the way to go. or as my first girlfriend ended up ; disappointed, broken and sore :D

[ian]

As Bloss pointed out, I am more interested in the theory of endgrain to endgrain glueing, but it does concern a practical application.

I FEEL that gluing endgrain to endgrain will create a thin film of glue between the adjoining surfaces. One assumes that the glue will move with the expansion and contraction of timber, if it doesn't then there will be a shearing affect at some point in time.

I would imagine that some glues may be more successful than others, as Bloss hinted, hide glue may be preferable for this gluing application.

Feel free to trash this theory of mine.

ZelkMore like some of the glue will migrate partway into the end of the vessells and then link with itself in vessells on the other side of the joint.

if this is theory, why not make a joint let it cure and then see how easy it is to break it.
do the same with a scarf, loose tennon, and half lap joints.


ian

[zelk]

More like some of the glue will migrate partway into the end of the vessells and then link with itself in vessells on the other side of the joint.

if this is theory, why not make a joint let it cure and then see how easy it is to break it.
do the same with a scarf, loose tennon, and half lap joints.


ian

Hi Ian,

As mentioned before, it's not about how to make the joint stronger using the methods you outlined, there is no load.

As someone has said sealing the endgrain before gluing will avoid starvation of glue at the joint surface and thereby improve the bond, but is that enough to ensure the life the bond, allowing for the natural movements in wood?

In this case, I'd like to get peoples view on whether the joint will fail irrespective of the type of glue used and secondly, will the choice of glue influence the life of the joint?

Zelk

[Ron Dunn]

Why don't you just tell us what you're trying to make? It would help A LOT with the discussion.

[Wongo]

Thank you for your replies.

Lets, for the moment, forget about where such a joint would be used. We all know that endgrain to endgrain is a weak attachment.

Lets assume that the pieces are glued to another without reinforcing, allowed to sit indoors as shown in photo 3, exposed to the natural variations in humidity and occasional sunlight and under no load for 5, 10, 20, 50 or even 100 years.

Keeping in mind that the timber will expand and contract, will the joint fail, as it is endgrain to endgrain?

Zelk

I vote no. It will not fail.

[zelk]

I vote no. It will not fail.


Thank you Wongo.

Zelk

[Ron Dunn]

I'm going to push this one more time, because the silly bugger might be going to do something like turn it. If this was true, it would be an explosion just looking for place to occur.

Zelk, what are you doing with the timber?

[zelk]

I'm going to push this one more time, because the silly bugger might be going to do something like turn it. If this was true, it would be an explosion just looking for place to occur.

Zelk, what are you doing with the timber?

Not telling you:D. Thank you for considering my safety, you'll be happy to know that I"m not turning anything.

Ron, it's purely a theoretically matter. In one of my threads http://www.woodworkforums.com/showthread.php?t=79836&highlight=shaping, (http://www.woodworkforums.com/showthread.php?t=79836&highlight=shaping) reluctantly, I need to build up timber in an area that requires endgrain to endgrain gluing. I have a few ways that I can reinforce the joint, but I was curious as to how long the 'load free' joint would survive without reinforcement. I wanted to go about finding this out in the least complicated way, I failed!


Zelk

[Christos]

I wanted to go about finding this out in the least complicated way, I failed!

That ante the half of it. You have created a monster.

[Christos]

I think it will fail

[echnidna]

If the grain is in perfect alignment it will last.

If you are joining different grains it will fail

[ian]

Hi Ian,

As mentioned before, it's not about how to make the joint stronger using the methods you outlined, there is no load.

As someone has said sealing the endgrain before gluing will avoid starvation of glue at the joint surface and thereby improve the bond, but is that enough to ensure the life the bond, allowing for the natural movements in wood?

In this case, I'd like to get peoples view on whether the joint will fail irrespective of the type of glue used and secondly, will the choice of glue influence the life of the joint?

ZelkZelk, try to stay with me with this one

go grab a bundle of drinking straws. Tap the ends on a table so that they are all aligned.
These straws represent timber end grain.
You can see that there is almost no material at the very end of each straw. To glue two bundles of straws together end-to-end, you either have to get perfect alignment of the tiny amount (mere microns) of the "flat" at the end of each straw in one bundle with the end of a corresponding straw in the other bundle – a not very likely occurence, I'm sure you will agree,
or
you have to get a bit of glue into the open end of each straw to link with a bit of glue inside the open end of a straw on the other side of the joint. Something that is much easier to do.
(Glue starvation in an end grain face occurs when the glue runs down the straws leaving no (or not enough) glue at the end)

now staying with the straws, imagine the straws are arranged into arcs of a circle (like growth rings are), you can see that there will be a difference in alignment across a joint depending on how the growth rings are orientated either side of the joint – in broad terms the options are:
this ( (
or this ) (
the first orientation will result in both sides of the joint moving the same way as the timber expands and contracts with moisture changes, while the second will result in parts of the joint moving in opposite directions due to moisture changes.

the second orientation will place more stress on the glue linkages across the joint, which form the bond, and will result in earlier joint failure.


Now some glues are better at forming links between the inside of the straws either side of the joint line than others, so these will be "stronger"
some glues are flexible enough to accomodate differential movement either side of the joint

The "best" glue is probably rubber cement



ian

[Wongo]

It is not quite the same if the straws are thinner than hair, is it?

With no external stress, I just don’t see why the glue wouldn’t hold the pieces together.

I just made up 2 joints. 1 uses with Titebond I and the other uses 2 part epoxy. They are now sitting in the shed. Will let you know they fall apart.

[echnidna]

Over a period of time the timber will move in relation to humidity.
So if the grain is not perfectly aligned the movement will eventually cause a glueline failure.

If for example one piece is backsawn and the other quartersawn you will have maximum differential movement so that join must fail due to changes in humidity.

[ian]

Wongo, the principle still applies

If yiu can align all the straws, the joint will be stronger than if you can't


ian

[joe greiner]

How many angels can dance on the head of a pin? When reduced to nothing but theory, the joint has already failed.

Cheers,
Joe

[Wongo]

Yes, thank you I understand.

I will let you know when my experiment fails. :)

[zelk]

Halleluja, the thread is going in the direction that I would like it to.

It's agreed that the joint will last providing the majority of the microtubules are aligned, which is pretty well impossible.

If the majority of the microtubules are not aligned then what whatever glue exists in the joint, will be subject to the shearing affect of timber movement. How long before it fails will be determined by the elasticity of the glue.

So to cut it short, the bond will eventually fail, but how long it takes to fail, is anybodies guess.

[Wongo]

I will let you know.:cool:

:D:D:D

[zelk]

I will let you know.:cool:

:D:D:D

Thanks Wongo,

go to bed now.

Zelk

[Wongo]

How long before it fails will be determined by the elasticity of the glue.

Exactly! Also, don't forget that the movement in the 2 joined pieces are in the same direction.

My bet is the joint will not fail. It might not be a strong bond but it won't just seperate. Only time will tell.

OK I will go to bed now.:D

[Waldo]

Are you in bed yet Wongo?

I just wanted to know, so that if you're not, to see if you could go down to the garage and see if the joint has failed yet? :U

[Wongo]

I will check them out tomorrow.:2tsup:

[Waldo]

But it's tomorrow now. Well it was yesterday when I asked. :D

[Wongo]

OK listen up, this is way I did.

I glued up 2 joints, end grain to end grain. The wood is Tas. Blackwood. I used Titebond I for one joint and 2 part epoxy for the other.

The joints are holding up nicely, I couldn’t separate them. I placed them on top of my tool cabinet, we will see what happens in a year or 2.:roll:

[zelk]

Mr dear Wongo,
while you were experimenting in your shed last night, way across the other side of Sydney, I was doing my endgrain to endgrain gluing. Below shows what was being glued, a piece of timber glued to the underside of a table surround. As I am about to shape the underside of the table surround, I needed the extra width. I didn't want to delve too much on what I was doing, as the technique used is in desperation, not in anyway traditional and very embarrassing.
Zelk

[old pete]

Hi Zelk,

Must be an easy life over there in Sydney. Here is Tassie life is so hard I don't know anyone who would wan to make it even harder by attempting that sort of joining process. What's the end game? what's it going to be made into? I'm inbtrigued.

Cheers Old Pete

[zelk]

Hi Zelk,

Must be an easy life over there in Sydney. Here is Tassie life is so hard I don't know anyone who would wan to make it even harder by attempting that sort of joining process. What's the end game? what's it going to be made into? I'm inbtrigued.

Cheers Old Pete

Hi Old Pete,

I know it's puzzling, but the link in post 29 will give you some perspective.

Zelk

[ian]

Zelk

I don't follow

Photo 1 look awfully like long grain to long grain, butting up against a bit of end grain

ergo a long grain to long grain glue up



ian

[zelk]

Zelk

I don't follow

Photo 1 look awfully like long grain to long grain, butting up against a bit of end grain

ergo a long grain to long grain glue up



ian


Ian,

I know, it's hard to make sense of it, as mentioned, in post 29 there is a link to explain it all.

Zelk

[ian]

Zelk

I've looked at your link and I still don't follow.
I would describe what you are doing on the table as brick-laid-construction — small pieces of wood are glued together to form a 3-dimensional shape.
this is very common with turners, and as far as I know, glueing end grain to end grain is more a matter of convience during assembly than a necessity. The strength comes from the long grain to long grain bond between the brick-laid layers. Provided the end grain joint has no gaps, it needs no glue



ian

[zelk]

Zelk

I've looked at your link and I still don't follow.
I would describe what you are doing on the table as brick-laid-construction — small pieces of wood are glued together to form a 3-dimensional shape.
this is very common with turners, and as far as I know, glueing end grain to end grain is more a matter of convience during assembly than a necessity. The strength comes from the long grain to long grain bond between the brick-laid layers. Provided the end grain joint has no gaps, it needs no glue



ian

It may not be obvious from the initial photo but the piece that I am holding is the piece that was glued to the endgrain of the table edge surround. At that point there is no long grain to longrain gluing.

Zelk

[ian]

It may not be obvious from the initial photo but the piece that I am holding is the piece that was glued to the endgrain of the table edge surround. At that point there is no long grain to longrain gluing.

Zelknow I get it, but unless that little bit of timber was the absolute last piece of wood in Sydney, I'd would have backed it up with brick-laid pieces from the underside of the top. The stuff stuck to the underside of the top and ultimately hidden by the piece you are holding could be any species you like — if you were worried about differential movement the "bricks" could be 2" long with 1/4 gaps between them

glueing unsupported onto the end grain is creating a significant lever which will likely fail the second or third time someone leans on it



ian

[zelk]

now I get it, but unless that little bit of timber was the absolute last piece of wood in Sydney, I'd would have backed it up with brick-laid pieces from the underside of the top. The stuff stuck to the underside of the top and ultimately hidden by the piece you are holding could be any species you like — if you were worried about differential movement the "bricks" could be 2" long with 1/4 gaps between them

glueing unsupported onto the end grain is creating a significant lever which will likely fail the second or third time someone leans on it



ian

Hi Ian,
That little bit of timber consists of eight smaller pieces.

You may have noticed the aluminium angle used for support the top, hopefully it will work and the small added piece will stay on.

The way I see it, the glue line is a barrier between the endgrain surfaces. Now if the barrier can expand and contract with the timber movement, the piece will stay there for ever providing there is no load.

What I realised later, was that the barrier mentioned is not the only one. As I have laminated the table surround, I have created continous barriers within the lamination, ie, between the layers. This table surround construction is inconsistent with the table top itself and there may also be possibility that the glue line holding the surround to the top may fail, in the distant future.

Wood turners may glue endgrain to endgrain, but the span is short.

Zelk

[Wongo]

Will the joint fail?

Well, not just yet. The bond is as strong as the day I put pieces together.

See you again in 2 years time. :D

[zelk]

Will the joint fail?

Well, not just yet. The bond is as strong as the day I put pieces together.

See you again in 2 years time. :D

How do you know? The only way you could tell is by breaking it:;
Zelk

[Wongo]

If you need to break it, it means the joint has not failed. The fact is the glue has been holding the 2 pieces together since day 1.

They are either together or seperated. It is as simple as that. :D

[Wongo]

Since I made 4 of them so I suppose I can sacrifice 1 in the name of woodwork. Just for you Zelk. :D

[zelk]

Since I made 4 of them so I suppose I can sacrifice 1 in the name of woodwork. Just for you Zelk. :D

You're so sweet.:;

[Wongo]

Any time bro, any time. :D

[Wongo]

Thank you for your replies.

Lets, for the moment, forget about where such a joint would be used. We all know that endgrain to endgrain is a weak attachment.

Lets assume that the pieces are glued to another without reinforcing, allowed to sit indoors as shown in photo 3, exposed to the natural variations in humidity and occasional sunlight and under no load for 5, 10, 20, 50 or even 100 years.

Keeping in mind that the timber will expand and contract, will the joint fail, as it is endgrain to endgrain?
Zelk

Let me remind you what this thread is all about. :;

[Wongo]

Here I have a 4.5kg weight hanging on a horizontal bar 90 degree to the glueline. We'll use the weaker titebond I for this exercise.

At 0.1m from glueline passed
At 0.2m from glueline passed
At 0.3m from glueline passed

There is no need to go any further. The results are beyond doubt. :D

So is it fair to say round 1 goes to the optimists? Look forward to seeing you again in 2012. Round 2 Ding Ding :D

[Artesano]

Wongo - why not accelerate time a bit? :; - wanna know what happens in 50 years?
Soak them all in water for 2 weeks , then put them in the sun to dry....:D

[Wongo]

That is clever, Carlos. :D

[zelk]

Wongo - why not accelerate time a bit? :; - wanna know what happens in 50 years?
Soak them all in water for 2 weeks , then put them in the sun to dry....:D

I like that.
Good way to test a piece of furniture:D

[NCArcher]

I think a few Qld'ers are testing their furniture as we speak. The submerge it part anyway.

[Artesano]

I like that.
Good way to test a piece of furniture:D

No , I suppose :wink: you won't do that to a piece of furniture. You just get all the seasonal movement of the next 50 years in 2 weeks. IMO , the joint will fail.

[Christos]

Then you just have to rebuild it.

[Wongo]

No , I suppose :wink: you won't do that to a piece of furniture. You just get all the seasonal movement of the next 50 years in 2 weeks. IMO , the joint will fail.


You do that to any joint, it will fail. :U



BTW, how did you work out that soaking a joint in water for 2 weeks and drying it in the sun is equal to 50 years of wood movement?:;

:D

[Lignum]

Im positive I read from Titebond that the number three glue apart from being water resistant, was also designed for stronger end grain to end grain gluing.

Wongo, I know you do not want to ruin your test joins, but it would be good to somehow do a test to measure when each one fails under pressure.

[Wongo]

Lignum,

Although my experiment is not about how strong the joint is, but I can sacrifice 1 joint because I always respect your opinion.

You know what I think? I think the whole thing is BS, it is a myth that people just believe. I think end grain to end grain is not weak at all.

We will find out this evening. :D

[Lignum]

One for you Wongo or anyone else… When do you think end grain becomes long grain? I had a highly respected timber lecturer (RIP Fitzy from Freo) who insisted a mitre was long grain. It would be fascinating to hear others opinion on that.

[silentC]

I think end grain to end grain is not weak at all
That depends on the glue. To be thorough, you really should have a joint glued with ordinary PVA and another with hide glue. Also different widths of wood. Do you reckon a 200mm wide board glued end grain to end grain would last long?

I don't think it's a myth. It's based on the fact that a good gluing surface should be smooth and flat which end grain is not. Nobody ever said you shouldn't glue end grain, but it's never going to be as strong as long grain, so you should work it so that there is some long grain in the joint if possible.

Otherwise, you could just throw your domino away :)

[Wongo]

My domino will strengthen the joint though. :;

Nobody said end grain is as strong as long grain, but end grain is not weak.

Strong weak weak strong, oh bloody hell I'll give up. :D :D

[silentC]

One for you Wongo or anyone else… When do you think end grain becomes long grain? I had a highly respected timber lecturer (RIP Fitzy from Freo) who insisted a mitre was long grain. It would be fascinating to hear others opinion on that.
If it was a perfect world, it would be 100% end grain. But if you go microscopic, I bet there is some long grain in there. I wouldn't go as far as calling it long grain though. And they're notoriously sh*thouse joints without reinforcement.

[silentC]

My domino will strengthen the joint though. :;

Nobody said end grain is as strong as long grain, but end grain is not weak.

Strong weak weak strong, oh bloody hell I'll give up. :D :D
But if end grain is as strong as long grain, why does it need strengthening? Why not just butt join your frames like you do your panels?

[Wongo]

I agree with you.:U

[Wongo]

Pic 1: 9kg weight 40cm from the glueline. Metal bar weights approx. 3kg. Joint didn't break. At 50cm, didn't break.

Pic 2: distance between end supports = 1.4m. I, 80kg, stood on it. It sagged and touched the ground but Joint didn't break.

Pic 4: distance between 2 end supports = 0.9m. This time the stress was on the short side of the glue surface (20mm X 80mm). I stood on the middle. Joint broke.

Discuss....

[Artesano]

You do that to any joint, it will fail. :U

BTW, how did you work out that soaking a joint in water for 2 weeks and drying it in the sun is equal to 50 years of wood movement?:;

:D

Somebody posted (can't remember if it was on this forum) a test where timber glued with epoxy was kept underwater (sea water , too!) for 6 months , and then broke not at glue line , it was wood that failed. How much years of interior seasonal movement is that worth?:D
BTW , I did some experiment , too - as a pro woodworker , I know what to expect from endgrain joints and PVA - generaly , they fail if under presure- so I used UF resin. I had to hit the b..tard with a hammer.:oo: Twice. :DIt broke , and I admit it was a hard blow , the second one , but in a year it would fail all by itself - IMO.

[zelk]

Somebody posted (can't remember if it was on this forum) a test where timber glued with epoxy was kept underwater (sea water , too!) for 6 months , and then broke not at glue line , it was wood that failed. How much years of interior seasonal movement is that worth?:D
BTW , I did some experiment , too - as a pro woodworker , I know what to expect from endgrain joints and PVA - generaly , they fail if under presure- so I used UF resin. I had to hit the b..tard with a hammer.:oo: Twice. :DIt broke , and I admit it was a hard blow , the second one , but in a year it would fail all by itself - IMO.

In the underwater test, did it involve an endgrain to endgrain joint?

Let us not forget my initial question. If the two pieces were glued endgrain to endgrain and left alone without any applied external forces, would the seasonal timber movement cause bond failure in future. I am wondering whether the timber movement creates a shearing effect at the glue line, enough to make the joint adhesion fail in time.
Zelk

[Lignum]

I gotta have a go at this :rolleyes::) I cut a 100mm x 22mm bit of Vic Ash in half and re-joined it using Titebond 111. I rubbed the glue on both surface nice and brisk getting it right down in the pores. I will leave it 8 hours and check out the strength and post the pics and results later tonight.

[Wongo]

Under the condition you described, my bet is my 3 bits of wood in the shed will remain intact in 50 years time.

Will report back when I turn 90.:U

[Lignum]

Not gunna do my break test tonight, because I had another idea.

To the left of my original cut, I have another cross cut using a basic budget quality “rip” blade. My theory is, the rip blade will hack the fibres leaving them very rough, their for the fibres will have a greater chance to intertwine and bond with far better structural integrity (structural integrity - the most poncy word in woodworking) My Linbide combo blade is the best mid priced blade I have ever used, and cuts superb. Im thinking it’s probably too good, and the ends of the fibres are to clean and smooth to bond properly.

Will be interesting when I put weights (in between the two glue lines) to see which fails first. My hunch is the combo cut.

[Artesano]

In the underwater test, did it involve an endgrain to endgrain joint?

Let us not forget my initial question. If the two pieces were glued endgrain to endgrain and left alone without any applied external forces, would the seasonal timber movement cause bond failure in future. I am wondering whether the timber movement creates a shearing effect at the glue line, enough to make the joint adhesion fail in time.
Zelk

No ,I don't think there was end grain to end grain joint. I think the timber seasonal movement is a force all by itself , and it will break the joint in due time. BTW , we make things in the worksop where such joint are used - to be exact , it's end grain - to - long grain , with screws , brads or staples , in works where quality is not important
(it was bird cages last time I did it :D ) - it holds OK , until you drop it to the floor - even with 2 screws , glue line breaks , as this joint doesn't stand sharp knocks.

re. Lignum's question: mitter joint is stronger than end -to-end , but weaker than long grain to long grain. If hit with a hammer , it breaks at glue line . IMO , if a joint is not strong enough for exterior woodwork , it will fail in interior as well - only it takes longer

[Lignum]

re. Lignum's question: mitter joint is stronger than end -to-end , but weaker than long grain to long grain. If hit with a hammer , it breaks at glue line . IMO , if a joint is not strong enough for exterior woodwork , it will fail in interior as well - only it takes longer

I think i feel another test coming on:)

[GraemeCook]

Years ago, I was advised by a shipwright that when doing end grain joints with epoxy, to put two soaking coats of epoxy on the end grain first, a third coat if the surface still looked dry. This was to fill the pores and is consistent with Ian's straws analogy. For the actual gluing coat thicken the epoxy to a clag consistency, squiggle the surfaces together to get good bonding and no air bubbles, and then do not over-clamp as this just forces the glue out, distorts the wood and builds up internal tensions.

I have used a lot of epoxy over the years and this advise has yet to be disproven.

Water is never a problem on cured epoxy, but sunlight is - it hates UV.

Cheers

Graeme

PS: He also advised a single soaking coat on long grain joints.