Edge-Joining Plywood to Hardwood

[TJ61]

Upon finishing I'd like it to be seamless.

Not sure exactly what you mean by "seamless", but it's very unlikely that the ply and hardwood are going to take a finish the same.  I think you will see the two species.  For this reason, I'd put equal widths of hardwood on either side, and make it look like a design feature.

I think a simple edge joint would be sufficient, strength-wise.  But biscuits or splines or the like sure make glue-up less hectic.

[D_Harris]

Thanks everyone.

I like what Alan said about ripping the hardwood and then gluing strips of plywood in the center, so I'll do that.

I'm hoping that lay the all adjoining pieces across a makeshift MDF table I have will when the glue is drying will result in a flush seamless fit at least on the outside when I do the eyes closed/touch test.  

I'm assuming that the addition of shelves between both sides will increase strength/support.

Thanks.

Darren Harris
Staten Island, New York.

[Stwood_]

Just joint both edges square and glue them up, leaving the uneven thickness to the inside.

[Cooler]

joint the glue edge of the hardwood square.  Use a reinforcing technique to hold the hardwood to the plywood.  I would use biscuits.  You could use a spline or dowels or a lap joint.

I would use a lap joint.  A 4" or 5" lap will make a strong joint.  I would mill down the plywood first to get approximately to half thickness making sure that I end up on some face grain ply and not on a glue line.

Then I would mill the salvage wood until it fits flush.  

Plenty of glue and some short screws underneath to keep it clamped.  With all that gluing area the OP will end up with a very strong extension.

[Steve N]

Alan, I didn't have the problem you are having with adding the plywood to do what the OP said he wanted to do.

He said

I'm building a cabinet from some scrap and hardwood and I need to extend the width of the boards, which will serve as cabinet sides, from 20" to 25".

Couldn't the added on plywood go on the back side of the hardwood, as easily as it could the face side? I'm not sure about you, but I'd guess 90% of woodworkers don't fuss about the backside look of a cabinet, unless it is in the center of a room, which I'll go out on a limb, and wager it will not be out from a wall more than an inch or so. If you are concerned, the edge treatments already mentioned are quick, easy, and most of all cheap. I think rather than worry about the look at the back side of the cabinet I'd be more concerned with a stain, dye, or natural finish that the ply is going to look just like ply, while the solid boards will look different. Now if the piece were to be painted, it would go a long way to mend a lot of potential problems. Movement could still be an issue, but not from separation of the join. I think if the panel is attached as you would a complete solid wood panel, you will be ok. Some manner of floating it between the solid framework. Think door panel, just on a larger scale.

[D_Harris]

Alan, I didn't have the problem you are having with adding the plywood to do what the OP said he wanted to do.

I assumed Alan's suggestion was geared toward making it easier by not having to square the wood edge first. I would increase the width by ripping both piece's down the center, and  then gluing them back together with the plywood in the middle.

Darren Harris
Staten Island, New York.

[Steve N]

Gotcha......

What I was responding to was Alan said

"If I read the OP correctly, he is asking about adding a plywood edge to widen hardwood, while most answers refer to the much more common adding a hardwood edge to plywood. That's because plywood edges tend to be unsightly and easily damaged. If you have enough solid wood, using that to add width would be preferred."

I had already talked about the first part in my original answer, and while a smaller solid piece is the norm, doesn't mean it has to be that orientation. In terms of connection, larger pieces would work the same way, given a clean joint, and properly glued. In the second part, about unsightly plywood edges, where edge covering them had already been discussed, and even if you chose not to, if oriented toward the back of the cabinet would essentially be invisible to most observers if the piece were against a wall. I'm still going to hold that if the piece isn't painted, even an untrained eye will see the ply, and then also see the solid boards, and know something is different there, so Alan's thought you should use solid wood is correct, but in my case for different reasons. I am not a good writer, and often fail to convey my thought, it's why I so often add pics/videos.

[D_Harris]

OK. Aesthetics is not what I'm concerned about. I just need the cabinet to be deeper than the hardwood I plan to use for the sides presently are.

I'll paint when I'm finished.

Thanks a lot.

Darren Harris
Staten Island, New York.