Question About a Workbench Top

[Jon The Buddha]

The workbench plans I am about to build from has a couple of options for making the top. The one I decided to use calls for glueing up 3 layers of 3/4" plywood, followed by a fouth layer of 1/4" hardboard for a nice smooth top. The dimensions of each layer would be about 22" W x 58" L.

To do this, I would normally need two sheets of 48x96 plywood since all three layers could not be cut from a single sheet. However, there would be enough material left over from the first sheet (after cutting out the first two layers) to make the third layer by cutting two 'half' sections. I thought perhaps I could put a whole section for the bottom layer, then the two halves for the next layer, then the other full section for the third layer. It would end up looking something (vaguely ) like this...

_____________________ (hardboard layer)
_____________________ (plywood layer = full)
__________ __________ (plywood layer = halves)
_____________________ (plywood ayer = full)

Would this be viable, or would I be sacrificing too much of the integrity of the benchtop? I don't mind buying the second sheet of plywood if this isn't a good idea. Let me know what you guys think!

[LarryG]

Nuthin' wrong with that.

With good glue coverage over the full extent of all mating surfaces, that wouldn't scare me a bit. Two-layer countertops are made this way all the time; the top layer is one piece, the underside is pieced together. Your assembly will be better yet since you'll have a continuous piece both top and bottom.

EDIT: BTW, I presume you're making the hardboard layer removable, so you can replace it with a new piece as it wears? This is pretty much SOP for hardboard-topped workbenches.

[Raymonator]

I didn't realize that you would need so many sheets of 3/4" plywood to make a bench top. Do you have it ribbed/framed underneath too ? Sounds like you could sit an elephant on that thing once done. I'm just curious as to why you need such a thick counter top. I just asking to learn something, NOT to critisize your decision for making it like that.

[Jon The Buddha]

I didn't realize that you would need so many sheets of 3/4" plywood to make a bench top. Do you have it ribbed/framed underneath too ? Sounds like you could sit an elephant on that thing once done. I'm just curious as to why you need such a thick counter top. I just asking to learn something, NOT to critisize your decision for making it like that.

It's not a countertop... it's going to be the work top of the workbench I am going to build. That would be one helleva countertop, though!

[Tom Miller]

I didn't realize that you would need so many sheets of 3/4" plywood to make a bench top.

Three layers of ply really isn't over the top at all. It is plenty, but not too much. A lot of vises require (or at least assume) 2" inches minimum for attachment. Then, there's the issue of dogholes; again, 2 1/4" is nearly a minimum.

To OP: I agree with Larry; don't worry about the seam. With skins above and below, there's not going to be any appreciable extra flex. With that said, I was thinking you could cut the pieces smaller, and then stagger them, but you'd probably lose at least as much as you'd gain doing that. So, nevermind.

Regards,
Tom

[venkatbo]

Would using a solid-core door be a viable option ? I think Lowes/HD have one for ~$45-$50.

Assuming you are looking to add to your skillset, in the ply-layered option, 'am not sure if you would be learning anything other than cutting/gluing huge surfaces... imho using a solid core door should serve you well in that case.

However, if you go the route of using say 2x4s for the top, you may be learning to glue/bicuit-jointing/planing etc...

Also, not sure if even one non-flat sheet will contribute to a non-flat bench-top not matter how flat the other layers are... May warrant a careful check of the ply sheets.

Best,
/venkat

[Jon The Buddha]

Would using a solid-core door be a viable option ? I think Lowes/HD have one for ~$45-$50.

Actually, I had thought of that...but then I wouldn't have an excuse to buy lots of cool clamps!

Plus, I get more practice making cuts on my brand-spanking new BT3100! I have it all set up and aligned, now I'm ready to get to rippin'. I have not even plugged the power cord into the wall yet. She is still a virgin! Oh, I haven't waxed the tops yet, though. I still need to get some Johnson's.

[vaking]

Believe it or not workbench top can actually flex. My first top was 1" thick solid pine table top and I added 3/4" sheet of MDF on top as actual surface and for weight. Despite the combined thickness under prressure I had easily 1/8" sag in the center. I would add ribs under the top no matter the thickness.

[Raymonator]

Believe it or not workbench top can actually flex. My first top was 1" thick solid pine table top and I added 3/4" sheet of MDF on top as actual surface and for weight. Despite the combined thickness under prressure I had easily 1/8" sag in the center. I would add ribs under the top no matter the thickness.

That was my point too, to me 2x4 ribs spaced at about 12" centers and a couple of 3/4" sheets on top would make a workbench top quite strong IMO. With that said, what the heck do I know, I'm just a weekend newbie

[Tom Miller]

Believe it or not workbench top can actually flex. My first top was 1" thick solid pine table top and I added 3/4" sheet of MDF on top as actual surface and for weight. Despite the combined thickness under prressure I had easily 1/8" sag in the center. I would add ribs under the top no matter the thickness.

How did you combine the mdf and the solid pine? Unless they were glued across the entire face, then you're just adding weight to a pine top which will make it sag. Then again, if you did face glue them, the top will flex as the pine gains/loses moisture through the seasons, and the mdf does not.

Even with a thick top (mdf, ply, whatever), you still have to support it reasonably well, or even a 3-layer lamination will sag somewhat.

Like I said, there are more reasons for a thick top than merely maintaining flatness.

Regards,
Tom

[Tim Clark]

Jon,

The layers that you illustrated are the exact same thing I saw in a WB plan I'm getting ready to build. The only difference is that they called for MDF (and about six strong men to flip and position it). Minus the HB.

I'm going to use 3/4 ply instead with some Red Oak on top for stronger dog holes. I think it'll make a nice effect to have oak ply and solid RO for the top and trimmed in RO as well. The solid would have the lines of dog holes in it.

I have a source for RO at less than half what the BORG demands.