Thread: Laminated plywood shelf bonding it to the uprights

Hi Corey

can you post a picture or drawing of your table?

my initial thoughts are that the shelf will need some sort of mechanical joint to hold the legs of your table together -- otherwise the shelf, even when glued, is at risk of falling out.

The attached photo is of the table still clamped,, as it was only glued up today.
if i do need a mechanical support, i suppose on the underside of the shelf would be the best spot, and in from the edges it would be not that visible.
suggestion?

Assuming you are using power tools and can work to precise dimensions, I'm inclined to recommend that the shelf be attached using a sliding dovetail joint -- preferably stopped to provide a clean front face.

Originally Posted by ian

Assuming you are using power tools and can work to precise dimensions, I'm inclined to recommend that the shelf be attached using a sliding dovetail joint -- preferably stopped to provide a clean front face.

That sounds great, but far to advanced for my skill set and power tool collection i'd say.
In hind sight, maybe i should have screwed the shelf in before the last layer or two of ply on top.
Is there is any other simple but maybe not as strong methid you could recommend?
Appreciate the feedback too 👏🏼

when you take the clamps off you should expect some spring back in the legs.

My suggestion is that you first clean up the front and rear edges of the laminate concentrating on getting the front and back parallel, then adjust the legs so the top is flat or at the angle you intend.

If you have a router, cutting a stopped sliding dovetail is not too difficult.

• The first step is to build a double sided jig to guide your router so you can cut straight trenches -- search for router dado jig -- adjust the jig by moving the bottom so that the slot which will guide the router is about 1mm wider at the rear compared to the front.
• using the jig and a straight bit, rout a trench starting at the rear to about 25mm from the front edge -- the diameter of the straight bit should be a bit smaller than the neck of your dovetail bit, and the depth of the trench about 1mm shallower than the length of your dovetail bit.

(turn the jig over to rout the other side).

• mount the dovetail bit and cut the dovetail slot -- again stopping about 25mm from the front edge.

have a look at the linked FWW video http://www.finewoodworking.com/how-t...-dovetail.aspx
which also covers how to cut the matching dovetail.

my preference is to cut a sliding dovetail with a slight taper to make the joint easier to assemble.

The main problem I can see is if the two legs ever 'flare out' the shelf will drop out.

From the pix you haven't trimmed the tops of the U's to length... will the front face of the shelf end up being flush with them?

If so, you might get away with a butterfly fastener or similar at each end of the shelf face, in effect making the front edge into a brace holding the curve in the U. (If you see what I mean?)

And then, possibly, a ply veneer to cover over the ends & face to conceal the fasteners and as a base for a final veneer.

Originally Posted by Skew ChiDAMN!!

The main problem I can see is if the two legs ever 'flare out' the shelf will drop out.

From the pix you haven't trimmed the tops of the U's to length... will the front face of the shelf end up being flush with them?

If so, you might get away with a butterfly fastener or similar at each end of the shelf face, in effect making the front edge into a brace holding the curve in the U. (If you see what I mean?)

And then, possibly, a ply veneer to cover over the ends & face to conceal the fasteners and as a base for a final veneer.

Once the glue has dried, i was planning to trim and sand the length, and all edges to size.

Thinking it may be more hassle to add a shelf.
Do you think 8 x 3mm layers would allow the uprights to be reasonably rigid as is, and not flair, unless someone sits on it of course?

if i tried the sliding dovetail, would the dovetail not hold the uprights in from speading?

Originally Posted by coreytroy

if i tried the sliding dovetail, would the dovetail not hold the uprights in from speading?

That'd be the better way of doing it by far.

Mine is more of a "Damn! I wish I'd put a sliding dovetail in when I could, now what can I do instead" type suggestion.

Originally Posted by coreytroy

Once the glue has dried, i was planning to trim and sand the length, and all edges to size.

Thinking it may be more hassle to add a shelf.
Do you think 8 x 3mm layers would allow the uprights to be reasonably rigid as is, and not flair, unless someone sits on it of course?

if i tried the sliding dovetail, would the dovetail not hold the uprights in from speading?

I suggest you leave the laminate in the clamping form for a minimum of two days to make sure the glue is fully cured before you release the clamps.

You should expect to observe some spring back, how much is hard to say.


The shelf
if it's a design element you really should persevere with it.
The laminating you've undertaken is pretty bold, so don't belittle your existing skill set. a good sliding dovetail just takes care in measuring and building the jig.

It is looking like i will give your suggestion of adovetail joint a go.
Can i assume, as with the link you posted about the join, being ply or laminated ply will not be any different to using normal timber?

in principle, the joint is the same in ply as it is in solid timber.
there will be little subtleties because ply has alternating long and cross grain, but these subtleties should only effect the amount of widening the joint will need so that it slides together easily and only locks over the last 10mm or so.


practice making the joint before cutting attempting on your table.

If you need help with a jig for cutting tapered trenches etc this might help.

https://www.woodworkforums.com/f44/ugly-34437

Originally Posted by coreytroy

It is looking like i will give your suggestion of adovetail joint a go.
Can i assume, as with the link you posted about the join, being ply or laminated ply will not be any different to using normal timber?

so how is the table and shelf progressing?

I tried a few test runs with a sliding dovetail joint, but was not confident enough to have a go on the table.
So at this stage, i have decided to have a shorter section of tasie oak (65/19)screwed to the underside of the shelf. The table legs screw into the 19mm thick edge of the oak so i could use 75mm long screws to ensure no chance of them pulling.
I do have 2 screw holes down low to have filled(have to live with that), but as the tassie oak is 20mm shorter in width than the shelf, it is not visible from the edges.
I have also decided to laminate ply onto the shelf to keep with the same 24mm thickness, where originally i was only going to have a 12mm ply sheet. Only for cosmetic purposes,, nothing to do with strength.
will post a completed pic when done.