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Do angled tenons mean poor glue surfaces?

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fobos8

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Hi all

Please look at the angled tenon in this photo. It is of a rail joining to the front leg of a chair.



It occurred to me that as the loose tenon is not parallel to the grain in the rail (the dashed lines in the rail are the grain!) you will not get the usual strong bond of a long grain to long grain connection.

Is this a genuine concern or should I not worry about it?

The problem is not because I'm using loose tenons. If I opted for a normal mortise and tenon joint you'd get the same thing. The tenon wouldn't be cut parallel to the grain and so where its glued into the leg you wouldn't get long grain to long grain orientation.

Should I do this joint differently?

Cheers, Andrew
 

RogerP

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The grain angle does not define a long-grain to long-grain glue joint, think of a lap joint where the grains run at ninety degrees, it's still a long-grain to long-grain joint.
 

xy mosian

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If that were a tenon on the long rail, then the grain of the tenon would be short, not fully along the tenon. Chairs I have repaired have the tenon on that rail in line with the rail and into an angled mortice.

xy
 

Allylearm

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xy mosian":1tc8m6hf said:
If that were a tenon on the long rail, then the grain of the tenon would be short, not fully along the tenon. Chairs I have repaired have the tenon on that rail in line with the rail and into an angled mortice.

xy
Ditto
 

Jacob

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It's not the glue bond it's the cross grain in the tenon which would be the weakness as it and could break diagonally along the grain if under stress. Possibly even more so in a well glued joint. Tenons should go straight with the grain.
Xy is saying the same I think.

PS and Ally too.

Correction; With a loose tenon you'd have straight grain in the tenon but cross grain on each side of the mortice (in the rail). With a cut tenon the cross grain would be in the tenon. A weakness either way. Strongest of all would be a straight grained cut tenon.
 

fobos8

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Jacob":3fg8cei2 said:
It's not the glue bond it's the cross grain in the tenon which would be the weakness as it and could break diagonally along the grain if under stress.
Xy is saying the same I think.
.... so if I use a loose tenon as in the diagram it should be okay then as the grain will be straight?

Bye the way the angle is about 7 degrees off 90 degrees

Thanks for the replies

Andrew
 

Jacob

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fobos8":28ed5sxx said:
Jacob":28ed5sxx said:
It's not the glue bond it's the cross grain in the tenon which would be the weakness as it and could break diagonally along the grain if under stress.
Xy is saying the same I think.
.... so if I use a loose tenon as in the diagram it should be okay then as the grain will be straight?

Bye the way the angle is about 7 degrees off 90 degrees

Thanks for the replies

Andrew
Cross posted an edit see above.
 

Paul Chapman

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As I see it, you'll either have to go for an angled tenon or an angled mortice. I'd leave it as you have it in your drawing but with two slight changes. I'd move the loose tenon over to the right a little - that way you will be able to have a longer tenon into the side rail. I'd also cut the tenons at 45 degrees where they meet in the leg mortices.

Cheers :wink:

Paul

PS Make a couple of shallow saw cuts along the loose tenons so that when you clamp it up there is room for excess glue to escape.
 

fobos8

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Paul Chapman":18lstw0z said:
As I see it, you'll either have to go for an angled tenon or an angled mortice.
Many thanks to all for the advice.

All of the angled morise and tenon joints are in the Jeff Miller Chairmaking book are done will tenons at an angle to the rail and a straight mortise in the leg.

So a cross grain to long grain bond will be strong enough?

Andrew
 

Paul Chapman

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If you are worried about the strength and the design allows it, you could fit corner blocks as well, which would increase the strength considerably.

Cheers :wink:

Paul
 

fobos8

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Hi Paul

I definately plan to fit some corner blocks.

I was just curious why the book I bought on chairmaking and some of you experienced makers think that a cross grain to long grain joint will be strong enough for a chair.

From the limited knowledge I've gained over the last 3 years of woodworking I thought you should always go for long grain to long grain for a strong joint.

Cheers, Andrew
 

RogerP

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fobos8":cucsnxpm said:
Hi Paul
From the limited knowledge I've gained over the last 3 years of woodworking I thought you should always go for long grain to long grain for a strong joint.
Cheers, Andrew

I think you may be confusing terms.

Using a plank as an example: long grain is the sides and faces on a plank, whilst end grain is on the ends of the plank. Long grain surfaces glued together give a strong bond - the actual angle does not matter, you don't have to glue the surfaces with the wood grain running in the same direction. In contrast an end grain glue joint will be very weak.
 

fobos8

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RogerP":dp3fsyh0 said:
I think you may be confusing terms.

Using a plank as an example: long grain is the sides and faces on a plank, whilst end grain is on the ends of the plank. Long grain surfaces glued together give a strong bond - the actual angle does not matter, you don't have to glue the surfaces with the wood grain running in the same direction. In contrast an end grain glue joint will be very weak.
Maybe I am using confusing terms.

However........

with the angled tenon in the diagram in the original post you are gluing some long grain to end grain because you are cutting a mortise for the loose tenon accross the grain of the rail. Surely when you cut across the grain you expose end grain.

Similarly if you cut a conventional tenon at an angle to the grain direction you are exposing end grain --- so if you glue this to long grain you have an end grain to long grain joint.

Andrew
 

Paul Chapman

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You've only altered the angle of the mortice and tenon slightly - you haven't altered the direction of the grain. I think you're worrying about this too much :)

Cheers :wink:

Paul
 

Jacob

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fobos8":25gbadrs said:
.....

Similarly if you cut a conventional tenon at an angle to the grain direction you are exposing end grain --- .......
This isn't ever done - cross grain makes a weak tenon. There are near exceptions with angled details like stair strings where the tenon may be trimmed on one side in a triangular way, but even then the grain in the tenon and the string are straight and aligned.
The tenon in your drawing (cut or loose) needs to be turned to align with the grain in the rail, which means the mortice in the chair leg will be angled too. That's all there is to it, as several other posters have also said!
 

fobos8

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Jacob":2xtwrjm9 said:
The tenon in your drawing (cut or loose) needs to be turned to align with the grain in the rail, which means the mortice in the chair leg will be angled too. That's all there is to it, as several other posters have also said!
I agree that it will be stronger like that but several posters and the award winning Jeff Miller book say that a tenon at an angle to the grain and a straight mortise is okay?
 

Jacob

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fobos8":2xx70sn5 said:
Jacob":2xx70sn5 said:
The tenon in your drawing (cut or loose) needs to be turned to align with the grain in the rail, which means the mortice in the chair leg will be angled too. That's all there is to it, as several other posters have also said!
I agree that it will be stronger like that but several posters and the award winning Jeff Miller book say that a tenon at an angle to the grain and a straight mortise is okay?
Well they are wrong!
Can you do a photo of the J Miller relevant pages? He might have had something else in mind.
 

Steve Maskery

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In an ideal world, yes, you would make the mortice angled and have a straight tenon with angled shoulders. However, this is quite a lot more work and more difficult to do successfully. That's fine if you are a Master Craftman, but if you are like me, you might prefer to have a good joint cut with an angled tenon.
For an angle as small as that chair rail, the reduction of joint strength is, I suggest, not worth worrying about. Whether you use a trad tenon or a loose tenon, it will be plenty strong enough.
Of course, as the angle gets greater, the loss of strength becomes more serious, but at that level, I think you'd be fine. I'd certainly do it (indeed I have, with no ill-effects after several years). Just do whatever will be the cleanest joint.
S
 
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