Thread: Best way to join plywood

Strongest - fillets of timber glued and screwed into the corners, but then they may be untidy, it depends on what the box is for as to wether or not this would be suitable.

Denn

Oddly enough that is what I did yesterday evening. Knocking up a dvd/digital recorder shelf. Its cold up here so glued and screwed the fillets to the carcass in the kitchen.

Will hide ply and fillets with beading at a later date.

Finger Joints. We don't get a lot of ply furniture here, but I kinda like the effect. If you keep your eyes open at Ikea you will see a few examples of finger jointed ply.

I guess it depends on how much stress will be on the joint...

woodbe

sorry, guess I should have pointed out that timber fillets are out for appearance reasons. Also, dont want the jointing method to be visible - which makes it hard I know.

Anyone tried a timber spline running the full length of the ply joint ? Perhaps on 45 degree joints, or maybe on simple butt joints.

regards
Arron

What are the stresses on your box?

Box joints?

woodbe

Any chance of rebates to house the plywood edges?

cheers
Wendy

The stresses are the normal ones on a cabinet carcase - racking when lent on, picked up roughly etc. Not great stresses really, I just dont want it falling apart.

What I'm looking at here is a free standing cabinet, really a cupboard. its going to be veneered in rather expensive veneer - over 15mm plywood. The design relies on clean lines. Obviously I cant do dovetails or finger joints etc because it will be veneered right up to the edges.

After doing a few searches, I'm leaning towards mitred corners with splines. I'm a bit worried about my ability to get perfect 45degree mitres along such long edges. My tablesaw is not accurate enough to do this.

Rebated corners (thanks Wendy) are something to think about as well. The ugly bit would be towards the rear or bottom, so maybe...

Arron

If you are going to veneer it right to the edges why does it matter what type of joint you use.
The joints will be covered by the veneer.

If you do a butt or finger joint using 15mm ply for the back of the cupboard will add rigidity.

Cheers, Jack

Rebated corners are probably best to hold alignment. Glued and screwed (countersunk). I'd rebate the top and bottom to house the sides, and the back all around. Face grain of the sides parallel to the screws so they'd engage the inner ply cross grain. Face grain of the top and bottom parallel to the back for the same reason. Screws from the back into the sides would engage the inner ply along the grain, but the top and bottom engagement should suffice to prevent racking.

For appearance, I suggest cutting the veneer face for the front edge of the sides on a mitre at each corner.

A compound rebate, with the face ply mitered, would provide better purchase for the veneer, but somewhat awkward within only 15mm total thickness.

Joe

You know, I reckon Joe's suggestion will serve you well here. Arron, what on earth is this cabinet for You've said it's to be strong enough to be picked up with a fantastic veneer, but what's it for??

Cheers
Wendy

You may not have the tools for it, but I have built all my cabinet carcases recently using loose tenons and glue and nought else. Very strong and just looks like butt joins, so clean lines.

The veneer will be applied by a pro veneering outfit here in Sydney. I dont have confidence in doing pieces this large myself. Clearly they must have flat stock to get it though their heat presses, so I will be giving them the unassembled sides, doors etc. When I get it back I'll assemble it. The ply can be edged with real matching timber on all visible sides, and the veneer laid right over the edging as well, giving a result that is very hard to tell from solid timber (except there is no end grain). I have had veneering done this way before and its been very successful - a little costly but hassle-free and its nice to be able to have total confidence that it isnt going to bubble years down the track.

In theory the resulting components can be worked just like real timber. In practise it isnt quite like that, and I've found that its best not to work the edges beyond straight planing and sanding - so dovetails and finger joints are out. Its probably best to use the same techniques as jointing plywood or any other man-made board which is why I posed the question this way. Mitres and rebates are a possibility. Loose tenons or biscuits are a possibility, as are splines running full length along the joints.

The thing is we want something completely, gaudily over-the-top and I'm thinking pomele sapele all round, though my wife is thinking birdseye maple.

What is the cabinet for? No idea. I usually make something then find a use for it.

As always, you guys have given me plenty to think about so thanks for the responses. Any more are welcome.

Jack you must be the only member from TI. What do you do there ?
Arron

Originally Posted by Arron

I'm a bit worried about my ability to get perfect 45degree mitres along such long edges. My tablesaw is not accurate enough to do this. Arron

Isn't there special router bits to do this with?

Originally Posted by Arron

a timber spline running the full length of the ply joint ?

That will be the best way.