Another bench top ?

[Foggy]

Planning a workbench/enlarged saw table. Which top?
One layer of 3/4" plywood with tempered hardboard face  or  two layers of 1/2" plywood with tempered hardboard face?
Which glue? Titebond, contact cement, liquid nails, or ?

[Handplanesandmore]

Is it going to be an assembly table or a workbench for use with holdfasts, etc.?

Assuming you'll have a strong frame underneath to support the top (what size?), 3/4" ply + hardboard would be my choice (one that I had made and used for over a decade before the whole thing was replaced). I used screws to attach the top which I replaced when worn out.

Simon

[Hank Knight]

I added another layer of 3/4" MDF on top of the 3/4" plywood with a sheet of 1/4" tempered masonite on top. The MDF is dead flat and adds considerable heft to the top. The plywood bottom layer gives you something to screw into since MDF doesn't hold screws very well. I didn't glue the layers together. Instead I fastened the MDF to the plywood with several rows of countersunk flathead screws. I put an oak border around the assembly wide enough for a 1/4" lip at the top to capture the masonite. A couple of screws on the edge of the masonite keeps it flat and in place. It's easy to change when it gets ratty looking.

EDIT:

Foggy, this is the bench top I posted about above. It is the top for my radial saw bench. It lives directly behind my regular workbench so it doubles as a workbench all the time and it has held up very well. I think John is right about gluing the layers together and removing the screws when the glue sets. I don't anticipate drilling into mine, but if I did, it would be aggravating to drill into a screw.

Version 2 by Hank Knight, on Flickr

[adamcherubini]

Planning a workbench/enlarged saw table. Which top?
One layer of 3/4" plywood with tempered hardboard face  or  two layers of 1/2" plywood with tempered hardboard face?
Which glue? Titebond, contact cement, liquid nails, or ?

If the 2 layers of plywood aren't glued or screwed together, they act (bend) independently making them less stiff than the 3/4" ply. If you can glue them together such that they are effectively 1" thick, they will be stiffer than the 3/4". Stiffness is probably more important than strength for this application. Remember that stiffness increases as a cube of the thickness.

Titebond is strong, but as I recently posted, it doesn't generate properties when its not clamped. If you could vacuum bag the 2 plywood sheets together, you would get 14.7psi of bondline pressure which is rough 10% of the pressure Titebond needs to develop strength. So I think Titebond is out. I think I'd be inclined to assume the hardboard is doing nothing for you structurally. I'd make a good stiff sub surface, and hold the hardboard on with 4 screws so you can easily replace it in the future. Get a single, thick, good quality birch plywood sheet, and support it from the underside with stiffening aprons until its what you want.

[Foggy]

Under structure will be 2x4's with enough top overhang for clamps. I usually tend to overbuild for strength but I don't think that it is possible to overbuild a bench [unless I want to move it later]

[jteneyck]

Thicker and heavier is better in every way.  I wouldn't want anything thinner than 1-1/2" and 2-1/4" or more would be better.  How about a layer of 3/4" plywood in the middle, a layer of 3/4" particle board on each side, and a layer of 1/8" Masonite on the top.  Glue and screw the three thick layers together.  Titebond is fine IMHO; never had a problem with the bench tops I've made.  When the glue has set remove the screws so you don't have to worry about drilling into them in the future.  Then tack or staple on the layer of Masonite, which is easily replaced when it gets chewed up. 


John