4

I'm building a cart to hold my 60 lbs mitre saw. I'm using 3/4" Sande plywood. I plan on building the box using glued, pocket hole butt joints illustrated below. Keep in mind that I do plan on adding a shelf about 2/3 up from the bottom of the base.

My question is, which is the better design for the cart, given the weight that it will hold. Originally, I was planning on Option 2. However, every video and plan I can find for similar carts uses option 1. To me, option 2 puts less force on the joints themselves and takes advantage of plywood's great compression strength qualities. Whereas, option 1 puts a lot of shear force on the joints. Maybe it simply doesn't matter and that's why I'm only finding examples of option 1. Either way, I want to make sure there's nothing I'm missing anything in either design.

enter image description here

|improve this question
  • 1
    Possible duplicate of 90 degree butt Versus Pocket screws for cabinet with legs – Graphus Oct 8 at 7:48
  • 1
    "Maybe it simply doesn't matter and that's why I'm only finding examples of option 1" One thing to (unfortunately) have to bear in mind is that many people building things don't know what they're doing. Most stuff online is made by amateurs or selfmade pros (i.e. no formal training). But saying that, sometimes strong enough is strong enough, and, the aesthetic decision to have no ply edge showing from the sides in 1 is one reason that would be picked. However, if you want to build for absolute strength your common sense thoughts are often to be trusted. – Graphus Oct 8 at 7:56
  • @Graphus, If HD's Sandeply is truly as void free as they're touting it to be, then sanding that exposed edge will make it reasonably pretty. Especially with a coat or two of poly or shellac. Option 2 is a better design. – Ring Oct 9 at 11:09
  • @Ring, I'm personally quite fond of ply used honestly as ply so any exposed edges show the lamination. Very much a matter of personal taste of course. And the standard of the ply matters a lot since cheaper stuff can look pretty nasty here and there. Voids I don't mind so much, I can fill those, but overlaps and inclusions are impossible or hard to deal with. – Graphus Oct 9 at 13:24
  • @Graphus, too, true. I've had mixed results with cabinet grade from HD and Lowes. I've been getting mine from a local lumberyard, instead. They take better care of their stock, too. – Ring Oct 9 at 18:56
6

Your initial thinking is correct. You're much better loading the sides directly than transferring the load through a joint in a shearing manner.

The first method of construction is more typical in cabinetry because the load isn't usually directly on the top sheet, it is on a countertop that spans the sides. This effectively transforms it into the situation in your second diagram, where the sides are directly loaded. If you are going to have "point" loads on the top you want the top to be over the sides.

Similarly, if you plan to have a heavy load on the shelf in the middle you'd be better off setting it in dadoes in the sides than using pocket holes. If this isn't an option then I'd use ledger boards over pocket holes or shelf pins. Though if you're gluing it in addition to pocket holes it'll probably be fine up to at least 100 lbs.

|improve this answer
  • 1
    OP I think this may be underestimating pocket screws, see What About Strength? here. From an independent perspective Bob Van Dyke has talked a bit about how strong he's found them to be in practice and I believe I'm quoting him, "sometimes stronger than mortise-and-tenon joints". – Graphus Oct 8 at 8:07

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.