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journeyman carpenter
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Discussion Starter #1
i am making a modern bench using walnut and maple. it is basically a 2"x10"x50" walnut top with 2"x12"x20" maple legs with a mortise and tenon. another piece of walnut is fixed between the legs with a pegged tenon. i was planning to use a dowel through the overlap of the maple into the walnut, and another dowel through the end grain of the maple tenon into the peg. these dowels would lock everything together by themselves. so my question is; should i glue all of the joints or just glue or pressure fit the dowels? the joints and pegs are pretty darn tight.

here is my sketchup drawing:

bench.jpg
 

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Short answer... glue.

Wood moves. You have a lot of different grain directions going on in that design, not to mention the different expansion/contraction coefficients between the two species of wood. I made a table top years ago made of white oak with dovetailed walnut end caps. Everyone of the tails broke. Learned the hard way.

Even with glue things will eventually loosen up regardless of design. Nature of the beast. The glue will buy you time.
 

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journeyman carpenter
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Discussion Starter #3
thanks for the quick response. so where do you see the areas of concern regarding the expansion/contraction. i guess i am not too worried about things loosening up a little bit over the life. the design itself should keep things pretty much locked in place.

so how much difference is there between walnut and maple when it comes to expansion/contraction?
 

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recently retired
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Kerf the ends of your dowels & tenons, then drive wedges. Glue is fine but if the joinery is good and the wedges are properly done it won't become for decades, if ever.
 

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journeyman carpenter
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Discussion Starter #5
Kerf the ends of your dowels & tenons, then drive wedges. Glue is fine but if the joinery is good and the wedges are properly done it won't become for decades, if ever.
so what is the proper way to do the wedges? i have the grain running horizontally. or perpendicular to the main piece. is there a rule of thumb for orienting the grain with this type of joinery?
 

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Scotty D
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so what is the proper way to do the wedges? i have the grain running horizontally. or perpendicular to the main piece. is there a rule of thumb for orienting the grain with this type of joinery?

Your drawing, looks correct to me. :thumbsup:
 

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Short answer... glue.

Wood moves. You have a lot of different grain directions going on in that design, not to mention the different expansion/contraction coefficients between the two species of wood. I made a table top years ago made of white oak with dovetailed walnut end caps. Everyone of the tails broke. Learned the hard way.

Even with glue things will eventually loosen up regardless of design. Nature of the beast. The glue will buy you time.
I think your analysis of wood moving is good. Using that logic I would come up with the answer of no glue.

I believe that your dovetil example and this table are different.

George
 

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Old School
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I'm looking at how you configured the wood and the grain orientation. The bench top is long grain and will E&C (expand and contract) in it's width. The standing leg will also E&C in its width. With the fitment of the top of the leg in the bench top, you have two different species moving. The likelihood of the rectangular tenon at the top of the leg, will create a gap, or push against the Walnut enough to break the outer Maple stops. Or, mayhem could come from just the Walnut, in creating a gap, or breaking off the outer wings. Gluing won't stop that if it's movement is inevitable.

As for the doweled, pegged (wedged) stretcher with a tenon, I wouldn't dowel the wedge. If it's all fitted well, it would pull up tight.








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journeyman carpenter
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Discussion Starter #10 (Edited)
thanks everyone.

it was my original plan to use no glue. so that is what i will do. i feel like i do need the dowels in the top at least just to keep it secure. so i added the dowel (in my drawing) in the stretcher to give continuity. i have everything assembled now but am not 100% on using the dowels. what other options do you all see for securing the top? without glue..

oh, and in the drawing i was thinking i would use three woods. but ended up just using walnut for the wedge. so i planned on using a maple dowel there.
 

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iguana
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My bias would be to glue, but see that you shouldn't really need to. The thing to remember is that you can always glue later if needed, but it's hard to unglue. It's like adding salt or peppers to chili- you can always add spices, but can't get them out.
 

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Short answer... glue.

Wood moves. You have a lot of different grain directions going on in that design, not to mention the different expansion/contraction coefficients between the two species of wood..

That's exactly why I wouldn't want to use glue.

If you glue up parts with different expansion rate it will end in failure.

Accept the fact you have movement. Embrace it. Allow for it. :)
 

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where's my table saw?
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we know you made the bench

So what did you finally do.....glue or no glue? :blink: bill
 

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journeyman carpenter
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Discussion Starter #16
no glue

sorry woodnthings, missed this one.

i ended up using no glue at all. you can see the pics in the "modern bench" thread in the projects. i turned the dowels using cut-offs from the main pieces. the upper dowels go through the walnut into the maple tenon about 1". the lower dowels go through the wedge and back into the stretcher again about 1". i like the idea of the dowels keeping it "locked" in place. everything is still very tight today. though it has not had much use.
 
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