Sealing and flattening your MDF bench

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Forum topic by hiswillus posted 04-29-2013 02:34 PM 7164 views 0 times favorited 51 replies Add to Favorites Watch
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70 posts in 1971 days

04-29-2013 02:34 PM

So I was advised against MDF as a bench top after it was to late. I’m concerned with loosing the flatness of my bench as it wears and can’t really be planed flat again. I wondering if there is some sort of finish or lacker that can be applied that can mabe be sanded flat after to strengthen the top.

Thanks in advance, love this place!


51 replies so far

View redSLED's profile


790 posts in 1915 days

#1 posted 04-29-2013 03:19 PM


I really don’t think any finish can “strengthen” a top. Are you talking about “losing the flatness” in terms of 1/1000 of an inch? The same would apply to a solid wood or plywood top. Unless I’m misunderstanding your situation.

-- Perfection is the difference between too much and not enough.

View TobyC's profile


580 posts in 1898 days

#2 posted 04-29-2013 03:20 PM

Lacquer based sanding sealer.


View brtech's profile


1029 posts in 2945 days

#3 posted 04-29-2013 04:32 PM

There is flat, and then there is flat.

You don’t want a smooth surface, you want a “dead flat” surface. That’s a few thousands of an inch if you can get it, but I think those who hand plane their top probably are happy with 1/32”, which is a few hundredths.

The MDF is flat, period, if it’s supported. It may gouge, but it will stay flat if it doesn’t warp, but it won’t warp if you keep it dry and support it well. Any coating on the top isn’t going to affect the flatness, and short of a poly build up like a bar top, it won’t stop any tool from gouging. Sometimes, you put a piece of hardboard on top of the MDF, which you can replace when you need to.

How thick is the MDF, and what is underneath it?

Don’t second guess yourself too much – plenty of beginning jocks have MDF bench tops to start. It’s an inexpensive way to get a flat surface.

View ksSlim's profile


1276 posts in 2913 days

#4 posted 04-29-2013 06:36 PM

I put a piece of Masonite on top of mine years ago. When it get too rough and gouged up, I replace it.

-- Sawdust and shavings are therapeutic

View byerbyer's profile


241 posts in 1995 days

#5 posted 04-29-2013 06:50 PM

I applied (2) heavy coats of Johnson’s paste wax to my MDF bench top. Glue and finish will scrape off (easily) after curing and you can always re-apply as it wears. The only draw back I’ve seen is the surface becomes rather slick, so when you’re sanding small parts with a ROS you’ll need some tool box / rubber shelf liner to keep parts from skittering about.

-- Byer-- "Comparison is the thief of joy" -- T.R. Roosevelt

View SCOTSMAN's profile


5849 posts in 3608 days

#6 posted 04-29-2013 06:58 PM

mdf is about (,so they tell me) as flat as it gets don’t worry about the future just enjoy.Alistair

-- excuse my typing as I have a form of parkinsons disease

View hiswillus's profile


70 posts in 1971 days

#7 posted 04-29-2013 08:43 PM

Thanks to all of you for your input. One of my major concerns is that I’m a heavy water drinker and tend to slop it about quite a bit. I’ve seen what happens when it gets wet and it’s not easy to get it back to flat again without tearing it up. I actually have 3 layers laminated together on top of an old metal desk frame I found in the basement. The bench is about 5 feet long and has two metal cross bars supporting it. I don’t think we have to worry about support.

Oh I’m not real concerned with 1000th’s of an inch, just looking to keep a decent reference surface. So I guess it’s either put something over it or the wax idea which I liked for my particular concern. Unfortunately I was dumb and laminated all 3 pieces together to the frame as well, so I can’t really see any easy way to peel and replace.

Thanks again guys and any other input is appreciated by me and probably any others in a similar situation.



View brtech's profile


1029 posts in 2945 days

#8 posted 04-29-2013 08:51 PM

I’d probably seal it with shellac and/or poly. Take the faces off if you can and seal the edges of the MDF. If you can raise the edges 1/8”, then I’d probably drop the hardboard on there, and seal that the same way. I might even put something in the poly to give the surface some grip. I think wax is not such a great idea on a benchtop – you don’t want things sliding on it. There are folks that “tooth” their bench surface to get more grip.

View BurtC's profile


103 posts in 3153 days

#9 posted 04-29-2013 09:02 PM

I just brushed on a couple coats of Danish Oil on my MDF bench top. Do not sand the MDF. How is your bench top going to loose flatness?

View hiswillus's profile


70 posts in 1971 days

#10 posted 04-29-2013 09:06 PM

Drops of water cause the MDF to swell and deform…

Man, am I really that bad of a communicator. I can not disassemble any of the current top without destroying it. It is glued into one solid piece I think the MDF was about 3/4 inch x 3 leaving the frame a little lip on the bottom to hold the top from sliding side to side in any direction. I can lift the whole thing up and remove it all as one solid piece and that’s about it.

View bondogaposis's profile


4755 posts in 2374 days

#11 posted 04-29-2013 09:43 PM

I like to thin out spar varnish 50/50 with mineral spirits and apply it to MDF. It really drinks it in and provides some good protection I think. Give it a couple of coats.

-- Bondo Gaposis

View Tedstor's profile


1643 posts in 2656 days

#12 posted 04-29-2013 10:06 PM

Ever considered gluing a piece of formica laminate on the top?? It would make it waterproof. They even make laminate that has a wood-like pattern.

View Viktor's profile


464 posts in 3441 days

#13 posted 04-29-2013 10:15 PM

View Cosmicsniper's profile


2202 posts in 3181 days

#14 posted 04-29-2013 10:16 PM

Jeff, can you disassemble any of the current top without destroying it? :) jk

MDF is fine. Makes for a great work bench top. It takes a lot of water to really deform the MDF. Do you slobber like a camel? ;)

If you are concerned about it (like for spills), I’d seal it off with oil-based poly and then affix hardboard to the top.

I think you have a very fine workbench…and I think many people around here have a false sense of what is truly needed in a workbench. Having an heirloom workbench is somewhat of a rite of passage, but it’s not a necessity.

-- jay,

View hiswillus's profile


70 posts in 1971 days

#15 posted 04-29-2013 10:45 PM

Cos, that was hilarious!!! And yes I do slobber like a camel sometimes…lol What is “hard board” do you mean Masonite or an actual piece of hard wood? Here is a pic of my water “jug” for your entertainment. If that tipped I think that would be considered a camels slobber ;)

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