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MDF for Workbench?

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Forum topic by socrbent posted 11-17-2017 12:09 AM 537 views 0 times favorited 19 replies Add to Favorites Watch
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socrbent

532 posts in 2102 days


11-17-2017 12:09 AM

Topic tags/keywords: question mdf joining

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?

-- socrbent Ohio


19 replies so far

View builtinbkyn's profile

builtinbkyn

1918 posts in 773 days


#1 posted 11-17-2017 12:19 AM


View on YouTube

I’ve thought of making one myself.

-- Bill, Yo!......in Brooklyn & Steel City :)

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sawdustdad

333 posts in 718 days


#2 posted 11-17-2017 04:04 AM

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.

-- Murphy's Carpentry Corollary #3: Half of all boards cut to a specific length will be too short.

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clin

750 posts in 829 days


#3 posted 11-17-2017 05:08 AM

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.

-- Clin

View Lazyman's profile

Lazyman

1493 posts in 1220 days


#4 posted 11-17-2017 05:18 AM

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.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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richardchaos

517 posts in 212 days


#5 posted 11-17-2017 11:28 AM

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

-- “In a time of universal deceit, telling the truth is a revolutionary act.” ― George Orwell

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bbasiaga

1003 posts in 1828 days


#6 posted 11-17-2017 02:46 PM

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

Brian

-- Part of engineering is to know when to put your calculator down and pick up your tools.

View builtinbkyn's profile

builtinbkyn

1918 posts in 773 days


#7 posted 11-17-2017 03:25 PM

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.

-- Bill, Yo!......in Brooklyn & Steel City :)

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richardchaos

517 posts in 212 days


#8 posted 11-17-2017 03:28 PM

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

-- “In a time of universal deceit, telling the truth is a revolutionary act.” ― George Orwell

View socrbent's profile

socrbent

532 posts in 2102 days


#9 posted 11-17-2017 04:08 PM

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

-- socrbent Ohio

View MrRon's profile

MrRon

4487 posts in 3076 days


#10 posted 11-17-2017 07:54 PM



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.

- clin


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

1918 posts in 773 days


#11 posted 11-17-2017 08:24 PM

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.

-- Bill, Yo!......in Brooklyn & Steel City :)

View LesB's profile

LesB

1348 posts in 3276 days


#12 posted 11-17-2017 08:30 PM

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.

-- Les B, Oregon

View jimintx's profile

jimintx

509 posts in 1417 days


#13 posted 11-17-2017 08:34 PM

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.

-- Jim, Houston, TX

View pontic's profile

pontic

500 posts in 441 days


#14 posted 11-17-2017 09:20 PM

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.

-- Illigitimii non carburundum sum

View socrbent's profile

socrbent

532 posts in 2102 days


#15 posted 11-17-2017 09:29 PM

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.

-- socrbent Ohio

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