Screw Advice Needed

[tim walker]

Hi all, I am building a base for an outfeed table and wanted your advice. Not to scale pic attached. All members are made of two laminated pieces of 3/4" ply. How would you recommend securing them to each other where the shorter members are perpendicular to the two long members? I have thought about pocket holes on either face (8 in total) and treat it like 3/4" single ply vs 1-1/2" ply and just use 1-1/4" pocket hole screws. My other thought was to just use 3" lag screws or deck screws from the front. Open to all recommendations. Second pic is scaled final configuration

Cross Member.jpg Actual.jpg

[Jim Becker]

Personally, I'd do butt joints with glue and 2" #8 square drive or torx screws in pre-drilled and countersunk holes.

[lowell holmes]

Make practice joints until you decide. I have a preference for phillips head screws.

[Phillip Mitchell]

I’m with Jim, though I might use 2 1/2” long T25 torx construction screws for 1”+ of screw embedment. If you clamp it together square then pre-drill/countersink it should go together smoothly with no splitting.

[Lee Schierer]

I would approach it slightly different. I would glue up all the center rib pieces to make them double thickness. Then I would attach one half of the long cross pieces to the end of each center rib making a bunch of H's with 2" long spax screws & glue through your 3/4" ply into the end of your center ribs. Then glue and clamp all the H's to each other one forming your the center fish bone. Attach one of the long side pieces on each side, again with 2" long spax screws & glue into the long rib gs of the H's. Finally glue on the remaining four side/end pieces with glue and 3" spax screws at the corners. Do all the glue up and assembly of the H's on a flat surface so they are assembled flat and parallel. You should end up with only the 3" screws showing at the four corners.

[Rich Engelhardt]

I built a portable flat surface (from a Shop Notes magazine article years ago) that was of similar construction.
I used pocket screws fr the first one.

For the 2nd one, just glue an #8 1 1/4" screws.

For the 3rd one - I used glue & dowels.

[Cary Falk]

Glue and pocket hole screws is what I woould do. Longer than 1-1/4" if you like but I don't think it is really necessary but won't hurt.

[johnny means]

I would do this with just glue and staples. I'd start with a series of "H" shapes, which would get stapled together, making the internal webbing. I'd then glue and staple the perimeter strips to the internal webbing. The outer fascia would get stapled on from the inside.

[Mike Stelts]

I'd pocket screw everything and add braces to the outside corners.

[Bill Dufour]

Biscuits and screws to hold it while the glue dries. The biscuits will help hold everything in place for assembley
Bill D

[Rich Engelhardt]

Biscuits and screws to hold it while the glue dries

Thanks Bill!
I keep forgetting I paid a fortune for that stupid PC biscuit joiner (thanks to Norm) that collects dust.
Next torsion boxy-thingy I make will get biscuits.

[Bill Dufour]

That many biscuits all at once will push you on being fast enough to get it all done before the biscuits swell and you can not pull it all together. Hence the screws to hold things while the glue dries.
Bill D.

[tim walker]

So on the use of pocket screws, would you do two on each side of the cross members at 1-1/4" length or two on one side treating it as a 1-1/2" thick member using 2" pocket screws?

[Kevin Jenness]

I'd omit the orange pieces in your second picture. They don't really add anything- a 3/4" top will be well supported with the spacing shown on the main cross-pieces. If you are actually making a torsion box with glued top and bottom skins the frame members don't need to be doubled up but you might consider a closer grid. In fact, the frames don't need to be doubled in any case unless you are parking a truck on it. Two or three #8 x2" screws at each joint plus glue will be reasonably stout.

[tim walker]

Thx Kevin, I am an engineer by degree so thus the overkill. Not really a torsion box per se. Here is what the final product will look like. Final.jpg