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Gluing end grain is stronger than you think.

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Rorschach

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What we all really need to know is long grain vs end grain vs face grain glue joints on MDF.
 

sometimewoodworker

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In recent years we have started to C24 structural softwood timbers with finger joints coming from Germany. Admittedly in sizes like 7 x 3 and 8 x 3in, not the biggest stuff we use, and only graded for interior use, but I think that does indicate something about modern glues used in a controlled environment
Finger joints are closer to long grain joints and it’s been pretty conclusively proved that that kind of joint, even with a humble PVA is stronger than the wood itself. Using those kind of joints will give you solid wood sheet goods. I have 2440 x 1200 panels of pine and rubber wood. They are an excellent alternative to plywood, this is an example
2D7264A9-3FDF-4910-A6B7-877B7E685D4F.jpeg

it happens to be pine
 

robgul

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It seems that lots of YouTube chaps have had something to say on the subject - including Stumpy Nubs, Steve Ramsey and Colin Knecht?
 

GerryT

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Finger joints are closer to long grain joints and it’s been pretty conclusively proved that that kind of joint, even with a humble PVA is stronger than the wood itself. Using those kind of joints will give you solid wood sheet goods. I have 2440 x 1200 panels of pine and rubber wood. They are an excellent alternative to plywood, this is an example
View attachment 118060
it happens to be pine
Yes it is very strong, but very little of the gluing surface is true end grain to end grain.
Most of the glue surfaces on finger/comb joints are cross grain to cross grain which is why it’s so strong.
Only the tips of the fingers are truly end grain to end grain.
 

AESamuel

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What is the point of the video?
To show that long grain joints fail in the wood because wood is weaker in that direction, not because the glue joint is inherently stronger than end to end grain joints

No one is suggesting you start lengthening pieces of wood end grain to end grain, just dispelling a myth.
 

TheTiddles

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There’s no myth.
You normally don’t glue endgrain to endgrain as a continuous piece of wood is better.
You do glue edge to edge as the glue is usually as strong as the wood, so you have not created a weakness.
To describe that as a myth would be like describing the myth that everyone should eat yellow snow, I’m looking forward to his test of that in the next video.
 

AESamuel

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There’s no myth.
You normally don’t glue endgrain to endgrain as a continuous piece of wood is better.
You do glue edge to edge as the glue is usually as strong as the wood, so you have not created a weakness.
To describe that as a myth would be like describing the myth that everyone should eat yellow snow, I’m looking forward to his test of that in the next video.
Myth: "widely held but false belief or idea" It's the literal definition.

The myth is that long grain glue joints must be stronger because the wood breaks before the glue. But it's the wood that's weak, not the joint that's strong.

How we use glue joints doesn't factor in to this teat. Pointing out that a continuous piece is stronger than end grain to end grain just shows you still don't really get the concept on display here.
 

TheTiddles

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Myth: "widely held but false belief or idea" It's the literal definition.

The myth is that long grain glue joints must be stronger because the wood breaks before the glue. But it's the wood that's weak, not the joint that's strong.

How we use glue joints doesn't factor in to this teat. Pointing out that a continuous piece is stronger than end grain to end grain just shows you still don't really get the concept on display here.
That’s not a myth, that’s a lack of understanding
 

TRITON

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Oh-Oh, better move this over to the 'controversial topics' it's beginning to get heated...
 

Sachakins

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To save you fast forwarding that vid, here's Steve Ramsey 1 minute vid of same.
(Myth/belief/thought/idea whatever you like to call it)
 

TRITON

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You do glue edge to edge as the glue is usually as strong as the wood, so you have not created a weakness.
The glue is stronger than the wood.
Parallel to the grain the wood breaks because the bond in the lignin is less than the glue strength.

Its very easy to snap a piece of timber along the grain even with your fingers, but take the same dimension timber and try to snap it lengthways you cannot, in fact as per original vid, you'd need to use both hands and place a knee behind it.
 
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sometimewoodworker

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Yes it is very strong, but very little of the gluing surface is true end grain to end grain.
Most of the glue surfaces on finger/comb joints are cross grain to cross grain which is why it’s so strong.
Only the tips of the fingers are truly end grain to end grain.
That was exactly what I said, though phrased very slightly differently so what was the point of the reply?
 

GerryT

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That was exactly what I said, though phrased very slightly differently so what was the point of the reply?
It’s no big deal, I was just commenting on your first line of your post which said :

“Finger joints are closer to long grain joints and it’s been pretty conclusively proved that that kind of joint…”

I was just trying to point out that they are aren’t really closer to end grain joints at all as they rely on the surface of the cross grain for their strength .
Maybe I’ve misunderstood your post and thought you were referring to finger joints as end grain joints.
I apologise if I have but I was simply making a reply to the point of the thread without no attempt at contradicting you.
 

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