# MDF for Workbench?



## socrbent (Mar 9, 2012)

Making a workbench with several layers of MDF for the top (77" x 31") with a final layer of hardboard. Should the MDF be glued, screwed or both to fasten together? If glued then how much to use (stripes, around border, full coverage, or something in between)? I plan to frame this with an red oak border. Your advise please?


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## builtinbkyn (Oct 29, 2015)

View on YouTube

I've thought of making one myself.


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## sawdustdad (Dec 23, 2015)

Doesn't matter how you glue it together, as there is little force trying to separate them. As long as the surface is well supported, I'd just screw the layers together, counter sinking the heads. But some glue won't hurt.


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## clin (Sep 3, 2015)

You do want those piece attached firmly. That way they will act like a piece 2X as thick. And that is much more rigid than 2X a single piece. But I agree it won't take that much to do that.

I'd glue it and shoot brads in from the bottom to hold it together until the glue sets. Screws of course would be really good, if a bit more work. Even screws about a foot apart is something close to 30 screws in a top that size.

As for how much glue, I'd glue it all. not so much because it needs it, but the glue won't magically spread out and it will have a thickness to it, so where there isn't glue would have a very small gap. Probably doesn't matter. Pour the glue and roll it or use a toothed trowel or something to spread evenly and fast.

I also agree it's just not that critical, but is there really a reason not to do it as well as can be done? It won't take much more timer, and it's not a crazy amount of glue.

Whatever you do. make sure it is flat when you do it. It's pretty much going to stay in whatever shape you have it when you attach it together. That's of course a good thing, but you need to start flat.

Don't assume your floor is flat. Though you could lay the first piece down, then run a straight edge all around on it and shim as needed to get it flat.


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## Lazyman (Aug 8, 2014)

If you do use screws just make sure you not only countersink the screw heads but also have relief for the other side as well. When joining MDF and plywood with screws, the material will often sort of erupt even with a pilot hole so it is a good idea to use your counter sink tool to make relief on the joint side as well so the pieces will stay flat.


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## richardchaos (May 12, 2017)

MDF. I hate and love MDF… It is cheap and rock solid stable. I hate that it weighs more than LEAD! One man can not lift/move a 4×8 3/4 inch sheet by himself.

A long time ago I had a gig where I needed to use MDF.

While cutting it on my bandsaw, once in awhile I would see a SPARK fly by/out where the cut was. So I looked very closely and could see a few tiny specks of metal in the MDF.

I must assume a lot of MDF is made with recycled wood. I must also assume that they try to remove old nails and such and do not get them all out then they send it to the GRINDER to process it.

Keep that in mind


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## bbasiaga (Dec 8, 2012)

You could consider covering the top with laminate from the home center. It will last forever that way.

Brian


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## builtinbkyn (Oct 29, 2015)

If I were to make the bench in Cosman's video, I would use contact cement to adhere the layers. No mechanical fasteners required. That would first require sealing the MDF with shellac. MDF is like a sponge and soaks up most any finish or glue. One or two coats of shellac will seal the surfaces to be bonded, thus needing less contact cement for the job. Then I'd seal the top with more shellac. Cosman used BLO. That seemed to be an odd choice, but I'm sure it works. Maybe it allows the surface to remain more rough than shellac. You could have that bench together in a day.


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## richardchaos (May 12, 2017)

Don't make my mistake do not make your bench top out of demential lumber such as 2×8s side by side. I left a tiny gap between them to allow for expansion and contraction.

When it is dry the gap is wide enough for small drill bits to fall through, screws to get caught in and solvents, paints and 12 year old scotch for fall through not the tolls stowed below


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## socrbent (Mar 9, 2012)

Thanks for all of your quick replies and advise. Let you know how it goes.


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## MrRon (Jul 9, 2009)

> You do want those piece attached firmly. That way they will act like a piece 2X as thick. And that is much more rigid than 2X a single piece. But I agree it won t take that much to do that.
> 
> I d glue it and shoot brads in from the bottom to hold it together until the glue sets. Screws of course would be really good, if a bit more work. Even screws about a foot apart is something close to 30 screws in a top that size.
> 
> ...


I second this post, but I wouldn't bother with fasteners except for a couple here and there to keep the sheets from sliding out of alignment. Depending on the type of work you plan to do, I would fasten a sacrifice sheet of hardboard that can be replaced if/when it gets nasty.


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## builtinbkyn (Oct 29, 2015)

The problem with using a PVA glue to adhere wide panels is not only the issue of having them slide about during glue-up, though it can be prevented thru various means or adjusted after the fact, is the problem that the layer of glue will not be consistent and will tend to migrate when the two surfaces are brought together, leaving a thicker layer of glue in one area vs another. This is why contact cement is used for adhering wide panels together such as laminates. The layer of adhesive is uniform and will not move or change when both surfaces are mated.

There will be no issues regarding the "shape" of the final product using contact cement. It goes on in a thin layer like paint and then dries before the pieces are mated. It won't move about or cause the MDF to swell especially if the MDF is sealed prior. MDF will absorb the moisture from PVA glues and may deform the surface, leaving it uneven. Using a PVA will also require clamping with cauls to ensure good adhesion across a wide panel. Contact cement adheres upon contact and doesn't require clamping - hence the name - and will not move after the components are placed together.

IMO no glue or nails needed for this. Just a cheap contact adhesive roller and some contact cement. Oh and a few sticks to lay down between the sheets of MDF before marrying them together. Then they'll never come apart and will remain as flat as they were before the process.


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## LesB (Dec 21, 2008)

I agree with the advise on contact cement.

I have made a couple of very sturdy benches using 1 1/8" sub-flooring ply wood topped with 3/4" MDF that I fasten together with screws. I like this combination because when the surface of the MDF gets dirty and scarred I can unscrew it, flip it over and use the other side. When that second surface is shot I just get a new piece of MDF. I have also had good success coating the surface of the MDF with a coat or two of Poly. It soaks in but also seals the top so dripped glue and other things come right off.


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## jimintx (Jan 23, 2014)

Bill, I need help to know what this sentence in your post #11 above meant. 
"Oh and a few sticks to lay down between the sheets of MDF before marrying them together. "

Could you explain that a little for me, please? 
Thanks.


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## pontic (Sep 25, 2016)

I have a different approach. I would not glue the top layer of mdf only screw it. That way when the face gets too chewed up you can take it off and flip it or replace it.


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## socrbent (Mar 9, 2012)

There will be 2 loose layers of hardboard on top of 5 layers of 3/4" MDF which can be flipped or exchanged as needed. First 3 MDF layers are now glued together. So far alignment has been good.

This will yield a 3 3/4" inch thick top which will work the eclipse vise I've had for 3 years. MDF and hardboard will be surrounded by a 4/4 red oak border to protect the MDF and hold the hardboard in place.


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## builtinbkyn (Oct 29, 2015)

> Bill, I need help to know what this sentence in your post #11 above meant.
> "Oh and a few sticks to lay down between the sheets of MDF before marrying them together. "
> 
> Could you explain that a little for me, please?
> ...


Ah, sorry I should have been more clear on that. Contact cement is applied to each surface then allowed to dry before placing them together. Once the two surfaces touch, they are bonded and there's no moving them. So in order to get good alignment, especially on something large like a table top, you would lay down some wood strips or sticks on one surface that has the contact cement. Then place the mating surface on the sticks, with the contact cement side down facing the other surface with contact cement. This allows you to position the two surfaces as you want them - presumably aligned - before they touch. For flexible material like laminate, one would start from the center, removing the wood strips and pressing down to adhere the two materials until you reach one end and then do the same for the other. Since the MDF will not flex, you would start at one end, removing the wood strips in succession until the two surfaces are together. I hope that's clear. If not I'm sure I can find a video of the process, online.





View on YouTube


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## BB1 (Jan 29, 2016)

I an new to woodworking (so limited experience on building shop benches!) but have added a couple benches that work for me. Glued mdf layers together and held them in place while the glue dried with some weight plates from our workout room plus clamps to maintain alignment. Trimmed it out with scrap wood I had left over. Used hardboard for a replaceable top on one. First picture is in progress and second is the final with my husband in the picture.


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## socrbent (Mar 9, 2012)

BB1 - your table looks great. Bet you find it very useful.

I was surprised by the dead sound when you thump on the top.


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## BB1 (Jan 29, 2016)

Love the work area…of course, rarely can see the top as typically both are covered with all the stuff that goes into a project!



> BB1 - your table looks great. Bet you find it very useful.
> 
> I was surprised by the dead sound when you thump on the top.
> 
> - socrbent


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