Dado depth?

[farmerbw]

I currently re-started working on a play table for the kids and am sort of hung on my assembly method.

The table is pretty simple, it's got a 3/4"x35"x50" BB top and I'm using 13/16"x5" Poplar for the sides. I was planning to have the sides be flush with the top and to attach them via pocket screws. I then decided that there needed to be a lip/edge to keep toys and what not from rolling off which sort of complicated the attachment of the sides. I'm decided on 3/4" for the lip.

I've now decided that it would make assembly a little easier if I were to dado the sides. I was playing around with some scrap to get my width right for the metric BB plywood and have finally gotten a fit that I'm happy with. The point I'm stuck at now is how deep should I make the dado?

Since I'm really only using it to index the sides and make them easier to install, although I guess it will also give me more strength and make it easier to glue. The test cuts I made were at 1/4" but looking at them now they seem a bit deep. Think I could get away with 1/8" depth, or go ahead with 1/4", or am I putting too much thought into this? I'm still planning on attaching via pocket screws and glue, but will just have to rethink my screw length and drill set up.

TIA,
Brian.

 

[ScottM]

I believe the standard rule of thumb is 1/3 the tightness. So in the case of 3/4 stock the dado would be 1/4" deep.

 

[DaveO]

Brian, it's very easy to use pocket screws and have a reveal on your edge banding. Place your ply top up side down on spacers that match the reveal (¾" in this case) and then clamp your side banding to the top, flush with the bench-top. Drive home the pocket screws bored into the ply top and you will have a nice ¾" reveal/exposure all around.
I generally do structural dadoes (for example book shelves) at half the thickness of the stock, or 3/8" in 3/4 stock. That gives the balance between holding the joining member and not making the side to weak. But in your application the dado is primarily being used for registration and not so much for mechanical support I would go with ¼" depth.


MTCW,
Dave

 

[farmerbw]

Scott and Dave thanks for the responses. I'll stick with the 1/4" depth and move on.

Dave, I think we'd discussed the spacer option and it's draw backs at the Kreg raffle drawing lunch. The top is fairly large and I don't currently have a trustworthy flat/level surface that's big enough for me to be comfortable trying it on. My worktable is presently a construction site salvaged partial sheet of 3/4 OSB on saw horses, so it's not a real flat surface and doing it on the concrete garage floor is out as well. :eusa_naug

That's why I decided to use a dado for registration in the hopes that it would lessen my need for a "true" level surface and give me better results and I guess it will give me a little more structural support as well.

Thanks again guys for the good advice. It'll be next week sometime before I can get back to working on the table since it's my weekend to work, but I'll keep everyone posted on my progress.

Brian.