I have subscribed to Fine Woodworking for many years but this is the first time I have posted a topic on one of your forums.
I’m wondering if any of your members has ever tried, or know of anyone who has tried to use a section of billiard table slate instead of a torsion box to build a very flat assembly table. I know new slate is expensive and can probably only be bought in a package of three pieces, but three woodworkers who want torsion boxes could share the cost. On the other hand there are many companies who buy, sell, install, and disassemble billiard tables. They might be able to provide a section of used slate for considerably less than a new one. I realize that the material cost to build a torsion box is not very high, but there is a considerable amount of care and labor involved, and a section of billiard table slate must surely be flatter than a torsion box.
I would be interested to hear your members’ thoughts on this topic.
Replies
Tell us more please
I am picturing a slab of slate ( which I have here by the way; an old chalk board from a school that was being torn down ) that still needs to have a structure , a fairly accurately made structure, under it to support it. If not fully supported it would crack/break.
Also, not to poo poo your idea but , if one is still using any cutting tools at the assembly table the torsion box will be more forgiving if one drops an edge tool on it.
And finally
I must say my slab of slate is all I can handle to barely move it and it is only 1/2" to 3/4" thick. The torsion box would probably be easier to move and would not care in the least of it fell or I dropped it. The slate . . . one little misjudgment in handling and it would break in half and probably take my shins and a broken foot in the bargain.
I just don't know . . .
PS: here are photos of my hunk of slate.
Torsion Box Alternative
Hi Dusty,
In response to your question, yes, it would be my intention to use this as a very flat assembly table, for woodworking, wherever you would normally use a torsion box. But at this point it's still in the thinking stage and I was just wondering what other forum members thought of the idea.
True it would require a support structure but then so does a torsion box.. It would be supported the same way billiard table slate is. It's a relatively simple structure and does not have to be extremely precise. The precision is in the flatness of the slate surface.
I visualize something like this:- One section of the three pieces of slate required to build a 4-1/2' x 9' table. This would be a piece of slate 1" thick, about 3' x 5'. It's weight would be about 180 pounds (the density of solid slate is abot 168 pounds per cubic foot ). It would have it's own place in the workshop and would not have to be moved.
I doubt if just any piece of slate would do, but if you check the specifications for billiard table slate you will see that the surface flatness tolerances are beyond what you could hope to achieve with a torsion box. When not being used as an assembly table it could be covered with any one of various materials to protect the surface and serve for light srorage.
Two thoughts just occurred
Dropping heavy steel/cast iron clamps on it won't do the slate any good.
Why the extreme flatness ? The bench where the parts are made and panels planed flat yes but the floor the final work will be installed on won't be any where near flat so close enough is good enough for assembly.
I said two but here is another. How much does the slate sag under it's own weight ? Most surface plates are very thick so they are strong and stable. ( ope another opportunity to show off my little pride and joy ) .
PS: the king of the torsion box work bench, Ian Kirby, would use cauls across the bench and clamp directly down to the table to control the parts. That would surely crack the slate.
https://www.finewoodworking.com/Workshop/WorkshopPDF.aspx?id=2072
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