I am building a pantry cabinet with 3/4″ red oak plywood. I’ve seen a few plywood joinery techniques and no definitive answer as to which is best. I need to join top and bottom to sides, plus a single permanent shelf, and a middle vertical panel between that shelf and the bottom. A 1/4″ plywood back will be let in a rabbet around the perimeter and glued/screwed to the internal pieces.
For the vertical panel, I am thinking a 1/8″ deep dado is the way to go, glued up with no fasteners.
To join the horizontal members to the side panels, I’m not sure what to do. I saw in a FW book on carcase construction where someone really favored a dado with a rabbet instead of a plain dado – I guess more glue surface and a positive stop? Others have said go with a shallow dado, especially if you can use biscuits or screws from the outside – I suppose to maximize the strength of the vertical panel.
I don’t have a biscuit joiner, but as the pantry will be recessed into a wall, I can put plenty of screws in without having to plug holes. This should help reduce the # of clamps I’ll need for glue-up, too.
I know there are fancy router bits just for corner joinery on plywood, but I’ve already maxed out my budget for new equipment. I have a mediocre table saw with a Freud dado stack, and a router with a few straight dado cutters. I have parts for a router table but haven’t built the base yet.
Also, I am assuming it’s easier to do your edge banding (1/8″ oak strips) before the dados.
One last question: When using a router to rabbet the edge of a board, does it make any difference whether you use a rabbeting bit, or just a straight groove cutting bit?
Thanks,
proje
Replies
Since the ends will be hidden, I'd just rabbit the side members about 1/4" deep and use screws from the outside. I would pre-drill the screws to prevent splitting of the horizontal plywood. Run the screws in by hand. A rabbeting bit will made a cleaner cut, but I've used both. Put some masking tape centered on a the edges of the cut to help minimize tear out.
I would edge band after the carcass is assembled.
PlaneWood by Mike_in_Katy (maker of fine sawdust!)
PlaneWood
Regardless of what joinery method you choose (besides biscuits), use PL Premium polyurethane construction adhesive instead of wood glue. It is a superior glue for bonding end-grain and filling the voids and gaps of plywood. You will find that the whole case could just about survive a toss down a flight of stairs it will be so ridgid when done. Much stronger than drywall screws alone, much stronger than biscuits alone.
I've done tons of cases like this with just simple butt-joints glued with PL (clamping helps) with the addition of 1x2 glue cleats shot onto the underside of the shelf and bottoms. All that glue surface area LOCKED it up tight. Perfect glue for melamine too - will rip the melamine right off the surface - never a glue line failure.
I did arbor press tests of sample joints (dados, biscuits, screws etc) over a scale and found that PL'd butt joints broke under the highest load. With a glue cleat, the 4"x4" x4" PL joint held to 130 lbs before cracking.
"The furniture designer is an architect." - Maurice DuFrenes (French Art Deco furniture designer, contemporary of Ruhlmann)
http://www.pbase.com/dr_dichro http://www.johnblazydesigns.com
This forum post is now archived. Commenting has been disabled