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butt joining oak

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Forum topic by Seanwood posted 06-19-2015 08:10 AM 973 views 0 times favorited 11 replies Add to Favorites Watch
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Seanwood

12 posts in 1465 days


06-19-2015 08:10 AM

I got 2 pieces of oak that i want to butt join together…i was thinking od biscuit joining them. But from my knowledge, if i use ordinary glue on the joinery the chemical reaction with the natural oils and resins of the oak will cause an unsightly black mark along the join.Is there a poly glue or epoxy glue that anyone can recommend that will do the job seemlessly?
Also what is the best way to glue and clamp up the two pieces together.i.e the positioning of the clamps ,where pressure is uniform by placing the clamp heads on opposite sides(see attached). And how do u prevent bowing or cupping…cause i noticed even thou i’m not putting too much pressure on the clamps that the piece when clamped together is not flat…...maybe the sides of each oak piece is not square perhaps and need to be planed….ohhh for a planer/thicknesser!


11 replies so far

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jdh122

879 posts in 2277 days


#1 posted 06-19-2015 09:36 AM

Biscuits will help with alignment but glue is strong enough by itself.
You need some way to joint the sides, that is to ensure that the two sides are straight and square (or if not square, at complementary angles). That will help with the bowing, but won’t make it go away entirely. Instead of having all your clamps on the same side of the boards when you glue up, alternate them. This way they’ll mostly cancel out the tendency to bow up and down. But not entirely – for that you should also use cauls, boards that are either flat or (better) slightly concave that you use with clamps along the top and bottom of the glueup to force everything straight.
I haven’t had problems with visible gluelines in oak (I have experience with North American red oak). Titebond 3 leaves a light brown glue line, which is pretty invisible. But if your boards are flat enough it shouldn’t matter much which yellow glue you use.
Hope this helps.

-- Jeremy, in the Acadian forests

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Kazooman

623 posts in 1412 days


#2 posted 06-19-2015 12:16 PM

I agree with Jeremy. You need to be certain that the edges of the boards are flat and perpendicular to the face. I don’t think that you will have any problem with a visible glue line with regular Titebond. Try a test piece to see for yourself in advance. Don’t overdo it with the amount of glue so that you end up with a lot of squeeze out. With a porous wood like oak the excess glue that squeezes out of the joint can fill some of the pores and you can see that in the final piece.

We all use clamps like the ones in your pictures, but they do have inherent problems. As you tighten the clamp the bar will bend. This results in the faces of the bearing surfaces splaying out and no longer being square to each other. Alternating clamps on opposite faces of the piece helps, as Jeremy suggested. Also resist the temptation to tighten the clamps too much.

Cauls are a great way to hold the piece flat. They should be conVEX not conCAVE. You want the center of the caul to apply pressure when you clamp down on the ends.

One final caution about potential staining. Keep the metal parts of the clamps away from making contact with the glue joint. Metals will react with the tannins in the wood to create a stain.

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jdh122

879 posts in 2277 days


#3 posted 06-19-2015 12:48 PM

Oops. I should have written convex rather than concave. Good catch kazooman.

-- Jeremy, in the Acadian forests

View chrisstef's profile

chrisstef

15656 posts in 2466 days


#4 posted 06-19-2015 01:11 PM

If youre going to butt joint things together id suggest a half lap so that you’ve got some glue surface.

-- rock, chalk, jayhawk

View Ghidrah's profile

Ghidrah

667 posts in 682 days


#5 posted 06-19-2015 02:15 PM

Or continuous spline

-- I meant to do that!

View jerryminer's profile

jerryminer

528 posts in 901 days


#6 posted 06-19-2015 04:02 PM


Metals will react with the tannins in the wood to create a stain. – Kazooman

Right—It’s the IRON and MOISTURE (from the glue) that causes dark stains in oak, not the glue. Regular wood glue is fine. Oak is glued all the time (in my shop and others) with regular wood glue. Just keep the clamps off the surface.

View jerryminer's profile

jerryminer

528 posts in 901 days


#7 posted 06-19-2015 04:06 PM

Alternate your clamps TOP and BOTTOM rather than FRONT and BACK

Good clean butt joints on long grain are fine—-as has been said, stronger than the “wood itself”—-meaning stronger than the lignin, the natural glue-like substance that joins the wood cells together.

View bonesbr549's profile

bonesbr549

1176 posts in 2527 days


#8 posted 06-19-2015 04:55 PM

end grain to end grain is not strong at all. My first question would be, is the final piece to be supported with a frame underneath? If not you got big problems.

If it’s just to get them together, then, I’d go with floating tenon at a minimum, or you could do a half lap with offsetting butt joints (like installing drywall or flooring).

Biscuits in end-grain ain’t worth much except for alignment.

Good luck.

-- Sooner or later Liberals run out of other people's money.

View Kazooman's profile

Kazooman

623 posts in 1412 days


#9 posted 06-19-2015 05:01 PM

I think the OP just used the term butt joint improperly. If you look at his pics it is edge gluing long grain to long grain. Should be just fine with no splines or tenons.

View jerryminer's profile

jerryminer

528 posts in 901 days


#10 posted 06-19-2015 05:11 PM



end grain to end grain is not strong at all. – bonesbr549

But we’re not talking about END GRAIN—we’re talking about LONG GRAIN BUTT JOINTS (see pic in OP’s post)

View OSU55's profile

OSU55

1056 posts in 1449 days


#11 posted 06-20-2015 01:11 AM

Edge to edge for well jointed boards is all that is needed, and clamping cauls will keep the boards from bowing when clamped. Regular wood glue will not cause oak to discolor.

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