Shopnotes Workbench Top

[Jeremy Kargas]

I am working on designing a workbench and have a question about a top that I saw in one of the first Shopnotes issues. It was the workbench with three layers of mdf with a top layer of 3/4" hardwood that was glued with construction adhesive to the mdf. I can't remember which issue it was, but it looked kind of intriguing. I was more concerned how flexible the construction adhesive was and if the top held up without cracking.

Have any of you built this top and if so, how did it hold up?

[Bob Ross]

The one I built (commissioned) was, I think, in a later issue. It was 3-4 layers of MDF with a wood banding and a construction lumber base. Heavy sucker!!

If I was doing it for myself, I would increase the increase the width of the banding to incorporate a piece of 1/4" tempered masonite (hard board). Using some two-sided tape would make it easily replaceable.

[Gary Herrmann]

My lathe benchtop is 3 layers of MDF glued up with Gorilla Glue. That has lasted several years without any problems at all. Can't speak to construction adhesive, sorry.

[Greg Cole]

I dunno about the construction adhesive for a bench top either, suspect it'd be fine.
The MDF layered top I made was glued with epoxy and topped with hardboard. The egde banding captures it in place and a couple of brad nails for good measure.

Greg

[Robert Goodwin]

I am working on designing a workbench and have a question about a top that I saw in one of the first Shopnotes issues. It was the workbench with three layers of mdf with a top layer of 3/4" hardwood that was glued with construction adhesive to the mdf. I can't remember which issue it was, but it looked kind of intriguing. I was more concerned how flexible the construction adhesive was and if the top held up without cracking.

Have any of you built this top and if so, how did it hold up?

Seems like the 3/4" hardwood would want to expand and contract. The MDF would not. Seems like a battle that would only result in cracking and bowing.

-Rob

[Howard Acheson]

Rob has identified the primary issue. Solid wood will want to expand and contract with changes in relative humidity and affixing it to a substrate that does not expand/contract will present a problem.

Are you sure the article called for hardwood or "hardboard"? I've seen some plans for multiple layers of MDF with top layer of 1/4" masonite or hardboard. Generally the masonite fits into a hardwood rim so it can be removed and replaced when it gets damaged.

[Lon LeBlanc]

I just built a shopnotes design. A later issue. Called for MDF, but I just used a solid core door and put a 1/4 layer of hardboard on it, and then banded it with ripped 2x4. I can't even begin to tell you how solid and heavy this sucker is....nice and flat and stable.

With the surge protector and two wood vises, I think my total for this bench, using mostly scrap material, was about $150. Pics here

http://www.sawmillcreek.org/showthread.php?p=916429#poststop


Lon

[Jim Becker]

I'm very much in favor of the multi-layer MDF core, but not the solid stock glued on top. There have been a number of other similar designs in the mags that build it with several thicknesses of MDF, a solid wood apron that is proud of the MDF and a removable 1/4" thick hardboard ("Masonite" or similar) topper that is captured by the apron. If I ever build another bench, that will likely be the top design I'll use for it. A piece of plywood or solid stock embedded in the middle layer of the MDF sandwich at the location(s) for any vise attachment takes care of a secure material for lag screws or bolts to chew into.

[Robert Chapman]

I used three layers of MDF glued together with yellow glue and topped with a piece of tempered 1/4" masonite glued on with contact cement. I've been using it for about 10 years with no problems. It's heavy and flat.

[Jeremy Kargas]

Thanks for all your replies so far. The top layer shown in that Shopnotes was definitely hardwood (not hardboard). They said they used a flexible construction adhesive so that the wood could expand and contract. The reason I liked this over the hardboard option is that it would be a heck of a lot more durable than hardboard (and look prettier too). I was just curious whether anyone had built it and how it turned out.

Since we are on the subject... What if a guy were to drill slots in the mdf and screw the hardwood from the bottom side, not completely tightening of course, similar to a table top? Thoughts...

[Shawn Walker]

Has anyone drilled 3/4 in. holes in the mdf, hardwood topped bench for various types of benchdogs?
Just wondering if the holes would hold up.

I like Jims idea of sandwiching the plywood in between the mdf.

[Brent Ring]

What are the advantages of the MDF sandwich (I like Jim's idea as well) versus a torsion box? Maybe I am just going to answer my own question, because most people use torsion boxes for assembly only, and not for a work bench top. Is that right? Could one serve both purposes for those with limited workspace?

I don't want to hijack the thread, but it seems like the right place to ask. I like the sandwich idea, and it seems quick and easy to make...

[Greg Hines, MD]

My workbench top is made of 4 layers of 3/4" plywood, glued together with Titebond 2. It has 2x4 banding, glued on around the perimeter. It has held up exceptionally well, holds dog holes and is heavy enough to not walk around on me no matter what I am doing with it.

Doc

[Greg Hines, MD]

What are the advantages of the MDF sandwich (I like Jim's idea as well) versus a torsion box? Maybe I am just going to answer my own question, because most people use torsion boxes for assembly only, and not for a work bench top. Is that right? Could one serve both purposes for those with limited workspace?

I don't want to hijack the thread, but it seems like the right place to ask. I like the sandwich idea, and it seems quick and easy to make...

Torsion boxes are good at staying flat, and being strong for their weight. However, in a workbench where you may very well want bench dog holes in it, a torsion box would definitely not be the right idea. Same thing for plowing out grooves for t-tracks as seen in some workbenches, because the strength of the design needs the full thickness of the skins to keep its strength.

Someone else asked about bench dog holes in a solid MDF top. I would imagine that it would do ok, but eventually you would expect the MDF to wear and your dog holes would become loose.

Doc

[Jim O'Dell]

What if you did the best of both worlds...make a torsion box for the flatness, then add several layers of something on top of that for holding power? I'm guessing adding the additional layers to one side could cause it to move differently and therefore cup or bow. Yes, I answer myself often. But sometimes I don't like the answers I get.:eek:
Another question is what if you lined/filled the inside of the webbing with something more substantial, like plywood, or even hardwood? Would this pose any problems with the torsion box? If not, it might allow a better structure for dog holes and vises. I suppose if you could get a tight enough fit, you wouldn't have to secure it to the skins so that it might still "float" a little, but stay in place for the dog holes to line up. Maybe secure to the webbing only? I'll leave these for you to answer.:p Jim.

[John Townsend]

Here's what I'm working on that's similar and it might give some insight into the costs and design concerns, particularly the in terms of the bench top.
I've nearly finished a design of this bench. See my post in:

http://www.sawmillcreek.org/showthread.php?p=1267030#post1267030

[Mac McQuinn]

I built the bench on cover of SN's #24 and as advised in the issue, I used contact adhesive to glue the layers of MDF. This was a mistake because even after allowing the top to sit on a level surface to set up for 3 days, once placed on the base the edges slowly drooped about 1/8". My thoughts are the contact adhesive has a bit of squirm to it, especially with very heavy MDF. I gave the bench to my wife for stain glass work. I'll put a torsion box top on it one of these days.

Mac



I am working on designing a workbench and have a question about a top that I saw in one of the first Shopnotes issues. It was the workbench with three layers of mdf with a top layer of 3/4" hardwood that was glued with construction adhesive to the mdf. I can't remember which issue it was, but it looked kind of intriguing. I was more concerned how flexible the construction adhesive was and if the top held up without cracking.

Have any of you built this top and if so, how did it hold up?

[Mac McQuinn]

Has anyone drilled 3/4 in. holes in the mdf, hardwood topped bench for various types of benchdogs?
Just wondering if the holes would hold up.

I like Jims idea of sandwiching the plywood in between the mdf.

Shawn,
I drilled my holes w/ a forstner bit on a drill press, Takes a long time to drill through 4 layers of MDF. Holes want to tear out on bottom side. You really have to man-handle things moving a 3" thick MDF bench top around a drill press table:(. Lots of weight there. Need adjustable supports and patience.

Mac