How Perfect for edge gluing?

[LFS19]

I was wondering how square two pieces of wood need to be for edge gluing?
I've been practicing my joints and using the plane, and in another thread I wrote, it was said that often the board doesn't always have to be absolutely, perfectly square to work.
This was certainly the case for recent applications - I made a simple box with boards that weren't bang on square but very close to, and when everything was glued up you certainly couldn't tell.

Of course, it depends on what you're using it for.
As someone said in the thread, some things do need to be bang on and if they aren't, you're out of luck when you come to assemble.

I was wondering, then, where edge gluing falls on that spectrum.
Do two pieces of wood have to be absolutely perfect to edge glue them together?
I've seen a couple of things online regarding the wood compressing as it glues, and actually sealing the tiny gaps if there are any..

Thanks allot.

 

[Droogs]

if you plane to 2 edges to be joined at the same time side by side, then they don't have to be perfectly true as they will compensate each other and the corresponding board will be flat once joined

 

[ED65]

In terms of squareness aim for either perfectly square or complementary angles as Droogs refers to above, e.g. 88° and 92°, which is the same as both being at 90. You won't always get there but this is what to aim for. If the edges are out of square or a bit off here and there you'll get a thicker glue line somewhere along the joint, or perhaps along one entire side of the joint, and this is not only ugly it's structurally weaker.

It's in straightness of the edge that you can get away with the most. You may deliberately create a very slightly hollow on one or both edges to make a sprung joint. You do want to carefully avoid the opposite case where the board ends are dubbed or the entire edge is slightly convex.

On boards under a certain length (sorry can't remember approximately what length this is) a sprung joint can be clamped with just one clamp placed centrally, as the edges will come together first more pressure will naturally be applied there as the central clamp is tightened up.

 

[LFS19]

if you plane to 2 edges to be joined at the same time side by side, then they don't have to be perfectly true as they will compensate each other and the corresponding board will be flat once joined

That makes sense, thanks.

 

[LFS19]

In terms of squareness aim for either perfectly square or complementary angles as Droogs refers to above, e.g. 88° and 92°, which is the same as both being at 90. You won't always get there but this is what to aim for. If the edges are out of square or a bit off here and there you'll get a thicker glue line somewhere along the joint, or perhaps along one entire side of the joint, and this is not only ugly it's structurally weaker.

It's in straightness of the edge that you can get away with the most. You may deliberately create a very slightly hollow on one or both edges to make a sprung joint. You do want to carefully avoid the opposite case where the board ends are dubbed or the entire edge is slightly convex.

On boards under a certain length (sorry can't remember approximately what length this is) a sprung joint can be clamped with just one clamp placed centrally, as the edges will come together first more pressure will naturally be applied there as the central clamp is tightened up.

I see, that makes sense,
And yeah I've heard about the sprung joint teqnique; I'll have to look into it.

Thanks!

 

[Jacob]

The main thing is to flood both surfaces with glue so that when you cramp up there will be a bead of glue along the whole length of the joint, both sides and ends. If not you haven't put enough glue in.

 

[deema]

Taking the ad use that's already been given and trying to expand upon it:

Take the two boards and place the two sides to be joined together as they will be when glued, now fold one board down so that the joined surfaces are exposed and clamp together. Plane the two surfaces at the same time, together. The planed surface must be straight, but not necessarily square. When you have them straight take one very fine shaving from about 1/4 in to 3/4 of the boards length.

Fold back up one of the boards and they will be perfectly matched, with a very slight gap in the middle that will close when clamped. As the boards aclimatise the ends of the boards will move more than the centre of the board, the slight spring that was made when joining them will stop the boards pulling themselves apart.

 

[rafezetter]

if you plane to 2 edges to be joined at the same time side by side, then they don't have to be perfectly true as they will compensate each other and the corresponding board will be flat once joined

Bear in mind that to make this work properly one of the boards after planing has to be flipped 180 deg, so the grain and or pattern might need to be taken into account.

 

[LFS19]

The main thing is to flood both surfaces with glue so that when you cramp up there will be a bead of glue along the whole length of the joint, both sides and ends. If not you haven't put enough glue in.

Thanks for the advice, I'll bare that in mind

 

[LFS19]

Taking the ad use that's already been given and trying to expand upon it:

Take the two boards and place the two sides to be joined together as they will be when glued, now fold one board down so that the joined surfaces are exposed and clamp together. Plane the two surfaces at the same time, together. The planed surface must be straight, but not necessarily square. When you have them straight take one very fine shaving from about 1/4 in to 3/4 of the boards length.

Fold back up one of the boards and they will be perfectly matched, with a very slight gap in the middle that will close when clamped. As the boards aclimatise the ends of the boards will move more than the centre of the board, the slight spring that was made when joining them will stop the boards pulling themselves apart.

Ahh, I see.
I actually thought that might work, but I hadn't heard anyone mention it until now.
Thanks for the info.

 

[LFS19]

if you plane to 2 edges to be joined at the same time side by side, then they don't have to be perfectly true as they will compensate each other and the corresponding board will be flat once joined

Bear in mind that to make this work properly one of the boards after planing has to be flipped 180 deg, so the grain and or pattern might need to be taken into account.

Understood; thanks.