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tim

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I have two work benches in my workshop.

One is due for a serious overhaul later this year , with at least the top being remade (it has a slight cup to it!!), new vices etc etc, courtesy of Ian's excellent article and plans.

The other is an MDF beast that is about 2m long and 1m wide. It doubles up as an outfeed table, but sits at 90 deg to the TS ie the width is the outfeed part. The structure of it is no different to a run of cabinets (although it is one unit) with the right hand side containing full ext 750mm drawer slides with the pullouts used for portable power tools. The other half has been commandeered by the dogs!

Anyway the top of this cabinet although supported in several places still isn't flat and the obvious solution to this is to build a torsion box top to replace it. There is only one snag - how do I build such a top when I don't have a guaranteed flat surface on which to build it? Everything I hvae ever learned (inc logic) is that the torsion box will pick up the topology of the surface on which its made.

edit: The MDF bench isn't really a bench in the strictest sense but more of an assembly table.

Any thoughts?

Cheers

Tim
 

tim

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Thanks Chris

I thought it might end up being shims and workhorses etc but the other info is really helpful as well.

Cheers

Tim
 

RogerS

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Tim

I was wondering whether a more hi-tech approach might save you some time.

Maybe if you assemble the two layers of thick MDF on trestles as per the earlier suggestions but don't worry too much about getting the supports planed parallel to each other..just reasonably close.

Then if you fixed white card to three sides of the MDF and then used one of those 360 degree laser beam devices, you could easily see where the MDF was out. Shim as appropriate.

Roger
 

tim

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Roger":3vyqxa2u said:
I was wondering whether a more hi-tech approach might save you some time.
Thanks Roger - might well do except for the time lost buying a 360 deg laser and the card!! :lol:

Cheers

Tim
 

AndyG

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Hi Tim,

I had this exact problem a while back. It's a real chicken and egg thing!! I ended up building the torsion box on it's side. This picture shows mid-construction:


I used a square to get the first two supports parallel, then clamped some 'straight' bars (the yellowish ones) to these and used them as guides for the other supports as a built upwards.

Unfortunatrly, I guess this approach might not be too practicle for a large table top area though.

Andy
 

Chris Knight

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A wild thought here.

You need to chat up someone who has access to or control over the pattern shop or design studio at an automaker or independent design consultancy. Even in the small auto company I worked for for a few years, we had a good number of cast iron surface plates around 6 metres by 3 in size.

I reckon if you chat up Price Waterhouse, you could get the ones at Rover for a song. Pay transport and build your entire workshop on top of a big one!

(They come in sections and putting them together accurately is a job for experts with all kinds of fancy gear - still for our woodworking purposes, a straight edge and a laser level would probably be quite good enough)

A not so wild thought..

Someone will be auctioning things like surface tables in due course (they are the size of a workbench but weigh a ton - literally) and will come from their precision measuring section (whatever they call it). Virtually zero resale value for their original purpose and too heavy by a mile for much else but great for anyone with the room and transport.
 

Chris Knight

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Andy,

That is an interesting approach - I wonder how big one could make it (albeit sectionally) and keep it accurate?
 

tim

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Chris":1ml68jzq said:
A not so wild thought..

Someone will be auctioning things like surface tables in due course (they are the size of a workbench but weigh a ton - literally) and will come from their precision measuring section (whatever they call it). Virtually zero resale value for their original purpose and too heavy by a mile for much else but great for anyone with the room and transport.
You are of course right, but the auction will be announced the day after I have finished it and no doubt will be more galling because of the free transport offer that will go with it!

Cheers

Tim
 

mrbmcg

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Roger Sinden":2rb8ytfd said:
I wonder how flat a billiard table is?
Exceptionally!

I use my mine to assemble anything (made of wood) which has 4 legs.

We might be moving soon and I can't take it with me! :cry:
 
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