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Workbench top - which sheet material(s)?

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skiskool

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Hello, I'm new to woodworking, but have been reading as much as I can from these forums since I stumbled across them whilst researching workbench designs.  I'd like to offer a huge thanks to everyone who has contributed posts in the past, the sheer quantity and quality of informative and inspirational material is incredible. 

My workshop is going to be our garage, which is a nasty 1970s prefabricated concrete post/panel box with a corrugated asbestos roof. It has an aluminium up-and-over door and no windows.  I've managed to get permission from the wife for exclusive use of the space, which up until now hasn't been used for anything but gardening equipment storage and cobweb construction. So now I've evicted the spiders, added strip lights and IP65 sockets, and whitewashed the walls and floor (to seal the decaying surface of the concrete floor). There is no heating or insulation of any kind, so it gets cold and often feels damp in there. In the summer it's in the sun for most of the day, and feels like an oven. 

My first question is about the materials that I'm going to use for my workbench top. Ultimately I'd like to build something along the lines of a Roubo, but for now I'm going to settle for a top made of sheets of ?? sitting on a frame made of lots of 2x4s.  I've also got a Record 10.5" vice that will be mounted on one side, which must weigh the best part of 20kgs.   I was thinking to use a 4 part sandwich of 25mm MR MDF with a topping of 3mm hardboard, but a recent post on a similar topic suggested adding ply in there to stiffen up an MDF top.  So just how moisture resistant is MR MDF?  Is it stable when continually exposed to damp night air in the winter, and roasting temperatures in the summer? How much difference will using ply make? And if I incorporate plywood into this, should I go for marine ply or ordinary stuff? 

Finally, if I do go for an MDF-ply composite, what would be the best ordering of the layers? 

Cheers
Ste
 

WoodMangler

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My own work-bench tops are 3/4"x6" sawn planks, whizzed over with a power-plane for rough levellling after nailing to the frame (drive the nails deep to miss the planer blade), topped with screwed-down 3/4" flooring grade chipboard, topped with pinned-down oil-tempered hardboard - which can be replaced when it gets messy. If you're feeling posh you can edge the whole thing with a strip of softwood, I didn't bother.

Another thing to try for is placing the vice directly over a leg, so hammer-shocks are absorbed by the floor and not by the bench frame.
 

Benchwayze

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Hi Skiscool,

In my neck of the woods 18mm MDF is about £20.00 a sheet.

Two sheets cut and glued, would provide a top of 8 foot by 2 foot and 72mm thick. If you are using 4 x 2 for the frame that should do you fine, Again use a sacrificial piece of 6mm stuff for the top, even if it's just a piece you throw onto the bench for painting, and glue-ups. The surface would be as flat as you will get anywhere. In fact, you could get used to that bench and never feel the need for anything else. I think Paul C would agree.

If your shop is damp, then use the moisture resistant MDF (The greenish coloured variety!) is a good choice.
For a bit more cash you could use moisture resistant plywood in the same way.

Whatever you use, a throwaway sheet is always a good idea to protect the work surface.

HTH :)

John
 

bugbear

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skiskool":1adaj46j said:
My first question is about the materials that I'm going to use for my workbench top. Ultimately I'd like to build something along the lines of a Roubo, but for now I'm going to settle for a top made of sheets of ?? sitting on a frame made of lots of 2x4s.  I've also got a Record 10.5" vice that will be mounted on one side, which must weigh the best part of 20kgs.   I was thinking to use a 4 part sandwich of 25mm MR MDF with a topping of 3mm hardboard, but a recent post on a similar topic suggested adding ply in there to stiffen up an MDF top.  So just how moisture resistant is MR MDF?  Is it stable when continually exposed to damp night air in the winter, and roasting temperatures in the summer? How much difference will using ply make? And if I incorporate plywood into this, should I go for marine ply or ordinary stuff? 

Finally, if I do go for an MDF-ply composite, what would be the best ordering of the layers? 

Cheers
Ste
Presuming you're aiming at hand plane stock prep, your top needs to (nearly) flat. Be wary, as you glue up your layers, of laminating in a curve.

BugBear
 

skiskool

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Thanks chaps. I intend to glue them up on the floor to keep them as flat as I can, what's the best way to stick the sheets together, ensuring a good bond all over? Will this happen under their own weight or do I need to throw every heavy thing that I own at them? I'm assuming that something like Titebond III would be good enough for the damp environment.

Ste
 

Steve Maskery

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By far the best way of clamping large areas uniformly is in a vacuum clamp. Now a proper bag and pump is a lot of money, but there are bags for storing clothing available for little cost.
I can imagine a DIY setup, using the valve from such a bag, a large sheet of plastic and a tube or two of silicone sealant to make a bag that can be evacuated with a domestic vacuum cleaner.
This won't create the same pressure that a pro system will, but I strongly suspect that it will quite adequate. No bending is required, so it's just a question of getting the air pockets out.
S
 

Paul Chapman

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skiskool":1vase2rz said:
what's the best way to stick the sheets together, ensuring a good bond all over?
I made my bench from three layers of 18mm MDF. This was how it looked after about 10 years of heavy use



When I glued the top together I found the best way was to lip the individual sheets first. I then glued the sheets with PVA using lots of G cramps and curved cauls to ensure that the pressure was applied right across the boards. It ended up dead flat and has stayed that way.

Cheers :wink:

Paul
 

Benchwayze

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Benchwayze":1sb57zn2 said:
Hi Skiscool,

The surface would be as flat as you will get anywhere. In fact, you could get used to that bench and never feel the need for anything else. I think Paul C would agree.

HTH :)

John
I am glad my memory was good Paul! Thanks for the confirmation.

John :)
 

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