Workbench top support

[Tom Porter]

I'm planning on building a new workbench (actually I was planning on this a few years ago and got sidetracked but we won't talk about that right now). It's a based on a couple of simple designs but essentially, I was planning on trestle legs with upper and lower stretchers, using mortise and tenons on all the joints. I've decided to forgo my original plan of laminated top and use 3 or 4 layers of MDF with a hardboard top for a variety of reasons. I plan to band it, though I haven't decided with what yet. However, since I'm planning on making it 8 feet long, I figure the MDF will likely sag in the middle. So what's the best way to support it along it's length?

[Andy Giddings]

Torsion box made out of MDF would prevent the sag - lots of videos on You Tube covering how to make them, You don't need 3-4 layers of MDF, just a sandwich of 3/4 MDF top and bottom with 1/2 MDF for the ribs. Would recommend 3 inch high ribs. Just made one myself, rock solid, dead flat. Banded mine on the front face only with hard Maple and used the same for a built in Moxon Vice. If you really want to go to town you can drill the top as an MFT lookalike.

[Doug Hepler]

356245Tom, this was my design for a simple workbench. I would not choose trestle support because I do not think it will be durable enough. This answers your question. Let me know if you want more detail.

Doug

[Mike Nolan]

I suggest a torsion box design. That is have one, or more, of your mdf layers below some wood and then one or mdf layers at the top. The wood in between needs to have uniform width and square sides before you stand it on its sides. THe wood can be thin as long as it will stand on its edges, that is very thin if you hold it in place somehow. You need wood lengthwise and crosswise. The pieces don't have to touch just be close to each other. The lengthwise pieces don't have to be continuous. I like the ones on the outside to look good but the ones in the interior can be any odds and ends that you never got around to throwing away. I would make the wood 1.5 to 3 inches tall. With 3/4 mdf skins I would have wood at least every 8 inches. I have a couple hundred lbs on a 6 foot shelf with 3/8 plywood skins. It is straight edge flat. I have a bandsaw so I resaw the wood to about 3/8 thick.

[glenn bradley]

Like you I find that laminated surfaces work well for me. On my latest bench I used 2 layers of 13-ply plywood with 2 layers of MDF instead of the 4 layers of MDF on the previous build. Shown upside down here . . .

356258

The previous build required supporting ribs. The current bench has done fine on just four posts but, is smaller than what you describe. I actually went smaller than the previous design to allow more room to work in the shop.

356257

The aprons are maple that is splined along the length of the edges or the layer cake top. the top is held in place by a large dowel "pin" at each leg position.

356259356260

[Robert Engel]

I would stick with your plan to laminate. This will give a denser top with better use for dogs and hooks.

I would simply install a couple beefy stretchers between the two supports that should eliminate sagging.

Installing laminate on both sides of sheet goods creates an extremely stable top, too.

[Tom Porter]

I like the torsion box idea except Robert is right about dog holes. I figured I could block out the section where I want the vise but that doesn't seem practical with a row of dog holes.

Just to make sure I'm on the same page, when I said laminated top, I meant glue up strips (it seems like that was what you thought but want to be clear). I'd prefer that type of top but frankly, it would take me til doomsday to make it.

Thanks for the suggestions thus far.

[Andy Giddings]

I can understand the concern about dog holes in 3/4 thick material. I wouldn't recommend it for a Gramercy Holdfast for example, but for drop in round dogs or clamps there is plenty of support using 3/4 top on a torsion box. And its a lot quicker/cheaper in materials to make a torsion box than a laminated top :)