Flat as a pancake

[PerranOak]

I bought a rather expensive Sjoberg workbench two years ago.

As I put in the last screw (self-assembly) I noticed a label saying that it had been stored in an environment of 40% humidity!

Here in Cornwall the only place humidity is ever that low is in a pasty oven!

Sure enough, the doors now only fit in the winter as I had to shave so much off them so that they close at all. In the summer there is a one inch gap ... I kid not!

What really bothers me is the top. It is NOT as flat as a pancake: it's more like the top of a loaf. I had hoped that it would "settle" or at least be usable in the summer when I do most of my "work". No such luck as it remains a dome all year round.

Is there any way I can level the top? it is glued beech blocks with the grain running side-to-side.

Any suggestions gratefully received. Cheers.

 

[JJ1]

Here's a link to one method http://www.thewoodwhisperer.com/vid...uter/?as=flattening workbench&mode=posts&ap=1

 

[mouppe]

Well the good news is that it's convex not concave. That makes your flattening job a lot easier. Secondly I wouldn't overly fret about flattening the whole top. The most important area is around the front vice and in the front centre.

I would go at the high spots with a jack plane cross-grain and finish plane it lengthwise with a #7.

Its amazing how fast you can level it with a hand plane.

Here in Canada we go from extreme aridity in the winter to high humidity in the summer. My workbench width changes by about 1/4" over a 24" span. I level my workbench annually but it only takes 1/2 hour or so. And there is less to do each time. My bench is ten years old now.

 

[Steve Maskery]

And there is less to do each time.

That is interesting, Mouppe, do you have an explanation?

 

[mouppe]

Yes, I didn't do a very good job the first time!

Maybe the wood is more seasoned now? I also planed away the oil finish after a few years and have left it raw ever since so both top and bottom are the same.

 

[PerranOak]

Cheers for that. It's good to know mine isn't an unusual problem.
I've never seen such movement, is beech particularly prone to this?

 

[sdjp]

I've never seen such movement, is beech particularly prone to this?

The Wood Database lists it as having 'a large amount of movement in service'; the important numbers being

Shrinkage: Radial: 5.7%, Tangential: 11.6%, Volumetric: 17.3%, T/R Ratio: 2.0

Oak clocks in with 13.6% volumetric, with a T/R ratio of 1.8; so beech is a bit more than others.

It's the T/R ratio thats responsible for the uneven movement - 2 is mostly typical; lowest I can find for a native wood is 1.4 for Walnut… although I suspect making a bench out of that would encounter … other considerations!

Quarter sawn wood is more stable, as you separate the uneven change neatly into height and width shifts. I suspect your bench is _not_ all quarter sawn blocks - rather: not all identically orientated quarter sawn blocks?

(For a wooden plane, it's make out of a single bit of wood, which means the effects of the movement are mostly limited to changes in size, which are not really important, provided the wedge doesn't get stuck!).

I'm afraid coastal areas (just about all of Cornwall qualifies on that count…) are always going to have a harder time of it than inland… I keep toying with the idea of using plywood when I get round to making a bench, purely to address the wood movement problems - although that does present a set of other issues, of course.