Thread: dovetail and finger joints using plywood

Using good birch 9mm ply on the Incra Ultra, even with a pair backing boards, there was splintering and a little delamination. Manufacturers of ply boxes must stack lots of sheets together and sort out the poor ones, MDF works well.

The reason for the question is that I have a friend wanting to make some 300hx300wx470l lidded boxes to hold up to around 20kg of gear. Looking to keep the weight of the box down but obviously build some strength into it? Ply or MDF to keep the cost down.
Would MDF be fine for this or any other suggestions?

The boxes I made for my daughter were much bigger and incorporated a lid. I glued up the box, added top and bottom, then sawed 2" down from the top and added 4 strips inside the lid to fit into the box. The boxes are really strong, even in 6mm MDF with 3/8" finger/box joints.

I've made a couple of boxes out of ply.
They're a bit smaller and more ornimental. Very sturdy however.

https://www.woodworkforums.com/f87/box-using-plywood-41438

If you clamp a piece of scrap where the router bit would exit the work piece this should prevent tear out.

Regards,
Nick

Nice box Jack. 2 other negatives about routing ply. Sorry. It will blunt your tools more so than other woods, due to the resin glue it is laminated together with. You must take care not to sand through the top layer when cleaning up after assembly, and whist polishing.

I've done dovetails in A/C plywood (for drawers), but found a sandwich of MDF to be necessary to prevent tearout or breakout. Another problem not mentioned is the occasional void in an inner ply layer. Also, the smaller bits are a no-go for me - too great a probability of failure. Birch ply might be a better bet all around.