What's the best way to connect a solid workbench top to plywood sides?

[Alan Lightstone]

I know variants of this topic come up every once in a while, but I wanted a fresh take on it.

I need to attach a 2" thick hard maple butcher block top to my carcase full of drawers. This will be my assembly table / workbench.

The carcase is 3/4" plywood on 3 sides. At this point, there are no battens on the top of the carcase, as there are drawers there. My present top is 3/4" plywood, attached with multiple screws and L-brackets. I know this is a non-starter for a solid wood top.

The top will be heavy (about 140 lbs or so). It will also have multiple dog holes, and an end vice.

I'd love some good suggestions on how to attach the workbench top to the carcase, while accounting for wood movement as the top should have some, but not the plywood sides and back.

[Wes Grass]

How about a typical cleat? But instead of grooving the plywood, cut slots through to make it look like a mortise/tenon joint. And you could get artsy with it if you wanted to. Make them out of walnut, contour the ends ...

[Andrew Seemann]

If you elongate/enlarge the screw holes in your current setup, that probably would work fine. Actually the L brackets might have enough give to use as is. Otherwise, glue & screw a cleat to the top of the plywood edges and put elongated holes in it for screws into the top. Pilot drill the screws in the maple top so you don't snap off the screw heads. Use round or pan head screws with washers so the can be relatively tight but still slide with seasonal movement. You are in a pretty mild/stable climate humidity wise, so it probably won't move much seasonally.

[Jamie Buxton]

Look into figure-8 fasteners along the cabinet sides. They pivot to allow the top to expand and contract across the grain. They'll also be trying to hold that 2"-thick top flat, even it if feels like cupping. So I'd use a whole bunch of the fasteners.

[Jim Becker]

I agree with Jamie...figure 8s. That top is going to move across its width and this method allows it to float nicely even with the screws snug to keep things level. My kitchen island top, which is a similar construction, was fastened on that way and it's been solid since the early 2000s

[Alan Lightstone]

One method I hadn’t thought of before that I saw was using bullet dowels in the middle of the width one on each side.

Seems like that wouldn’t keep it fastened, but I guess the weight must have a lot to do with that. Has anyone tried that?

[Andrew Seemann]

One method I hadn’t thought of before that I saw was using bullet dowels in the middle of the width one on each side.

Seems like that wouldn’t keep it fastened, but I guess the weight must have a lot to do with that. Has anyone tried that?

You could try it, but I myself would not. Not with the way I abuse a bench. You could also get cupping/dishing of the top with the seasons if you just use gravity to hold it down. Supposedly Klausz uses that method for his cabinetmaker bench, but it isn't too wide, and the top is massive heavy.

[Jim Becker]

THe dowels to keep it centered combined with a few figure eights to keep it down might be a good combination, especially since you're setup is mobile, if I'm remembering correctly. The dowels will help support things laterally when and iff you need to wheel it around.

[Gary Ragatz]

If the existing plywood top is sound, and it's solidly connected to the existing carcase, I think I'd attach the solid top to the plywood top with lag screws. Tight screws along the mid-line and screws with elongated holes through the plywood toward the front and back to allow for movement in the solid top, as others have suggested.

[Alan Lightstone]

If the existing plywood top is sound, and it's solidly connected to the existing carcase, I think I'd attach the solid top to the plywood top with lag screws. Tight screws along the mid-line and screws with elongated holes through the plywood toward the front and back to allow for movement in the solid top, as others have suggested.

I would love to do that, but that will make the workbench too tall, and could become dangerous when crosscutting wide pieces.

[Andrew Seemann]

Hi Alan,
Any chance you could post some pics of the bench & top and some details on it, like does the top overhang the sides? Those would help us come up with more directly applicable solutions

[Alan Lightstone]

Here you go, Andrew. And thanks in advance for the help.

IMG_5284.jpg
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The top is 74" L x 34" W x 2" Thick

There is a 3" overlap left and right sides. Not sure what overlap I'll choose for the front / back. Enough to not make the top drawers useless in front, and some room to place clamps in back.

[Andrew Seemann]

That is quite the top I would probably screw cleats to either the insides (if there is clearance with the drawers) or the outsides of the plywood (if there isn't clearance). Whatever hardwood you have lying around should work fine, something about 1 1/2 x 3/4 would work. The wide part goes against the top and the narrow side against the carcass. Then do the screws in elongated holes though the cleats into the maple top.

Putting the cleats on the inside means they won't get in the way of clamping on the overhangs, but that assumes there is clearance for the drawers, and that you want to climb into the carcass to put the screws in.

Ideally you would run a board across the top front to tie the partitions together and keep them from shifting, but I don't know if your drawers would allow clearance. Figure 8s would possibly work, the concern is that you wouldn't get good purchase on the screw going into the end grain of the plywood. They also might allow enough movement that the drawers guides could develop attitude problems.


An alternative might be to cover the whole thing with a piece of 1/4 or 1/2 plywood glued and screwed to the top, and screw through that with elongated holes. That would definteily hold the carcass together much better, and if you put the holes near the sides and partitions, that would be plenty strong. If height is an issue, you could take the equivalent amount off the feet to offset it. This is probably the best solution if you can make it work.

[Alan Lightstone]

Thanks, Andrew.

I was thinking cleats on the inside on the left. I've also been worrying about figure 8's getting good purchase on the end grain of the plywood. I could clamp before drilling and epoxy or super glue the area, but still likely not the strongest approach. They will have to keep out of the way of the end vise, so perhaps a cleat front and back on the left. The drawer on the left side I've removed and will make a dummy front as I need the interior space for the vise. The right cleat may or may not still be on the inside. It won't get in the way of the drawer slide placement. Just will make some some decreased drawer contents height. A minor thing.

Running a board across the top front is a very interesting idea. There is no question that there is some play in the front of the vertical dividers. I can't raise the table any higher, due to the table saw height. I may make some 1/4" or 1/2" hardwood boards that attach between the dividers in front.

Or how about chiseling out a small recess on the top of the front dividers and epoxying that to a metal strip or angle iron that goes the entire length of the cabinet? I would think either way would physically prevent movement in those dividers. The metal strip would take up less height.

Also the drawers on their slides should help a lot with that. They certainly seemed to do the job before the big workbench top.

I can't take any more height off the legs, though I agree it seems the simplest approach. I don't have the ability to flip the table, and I have epoxied and screwed the legs to the plywood carcass. I wanted those to be very solid. I guess in theory I could plane them, but I think expecting identical measurements without rocking on 6 legs by using a plane is definitely above my skill set.

[Jim Becker]

Looking at those photos, particularly the one from below showing the inside of the cabinet, I'd just make some "l brackets" from aluminum angle that have slots cross-grain to the laminated top. The will keep the sides square because there's no play in that direction, but allow for seasonal wood movement otherwise while keeping the top down on the cabinet securely. I'd make the connection "fixed" at the back...the side toward the saw...and allow the front of the top to float seasonally. You are not required to use "commercially available hardware" to make things work...which is why I'd make my own from the aluminum angle as described. Easy and fit-for-purpose. (you could use angle iron, too, if that floats your boat...but it's harder to work with than aluminum)