Originally Posted by Health Nut
Good stuff. I like the lock mitre, I will definitly do that. Question: with a mitre (lock) cut, it looks like I will have to make the lengths of the cuts all
equal to the outer dimension of the box (unlike but ends where some cuts are shorter by the thickness of the wood... correct?
But wait, that seems to be good for ALL 4 WALLS, but how about the top and bottom??
How can you do a lock miter for the top and bottom once you have done all 4 of the walls??? do you have to make the top and bottom butt-end only?? (seems like you can do 4 out of 6 walls with this technique only...)
Cut the top and bottom of the sides flat on the table and all four edges of the top and bottom vertical against the fence. One pair of sides have their vertical edges cut against the table, the other against the fence.
Use a tall sub-fence.
Use double sided tape to stick a straight piece of scrap to the top of your work because the lock miter wastes the whole edge. Stick a sacrificial backing piece on to avoid blow-out. Use multiple passes.
Do not dry fit without having the driver hole cut-out because you won't get it apart to glue.
IMPORTANT: The lock miter joint is nearly air-tight and half end-grain in plywood. PVA sets up _real_ fast allegedly due to the moisture getting sucked right out in such situations. Even using a fresh bottle of Tite-Bond Extend. If each piece isn't square by the time you have all four sides together you'll be stuck.
I switched to epoxy after learning the hard way.
I never used EPOXY since it seems to be less 'rigid' upon drying.
It's plenty rigid and doesn't creep like PVA. The down sides are that you get bigger glue lines, it soaks in more than PVA (you need to use tape to keep squeeze out off), it takes solvents to clean up (white vinegar actually works), you need to wear gloves, and it's not inexpensive.
The big wins are that it's structural across large gaps, takes no clamping pressure to form a strong bond, and can be had in any open time you want for complex glue ups (T-88 is about 45 minutes).