Steel can shift during welding process but of course is stable afterwards.
In solid wood construction you will never see a tabletop for example made
from one piece, many slats are glued together to equalize shifting. If a
piece of uncoated wood is left uncovered with the top exposed to
air/sunlight, it can warp because the topside will shrink as the moisture
becomes less than the bottom side. MDF is very stable (just don't get it
wet) followed by other sheet goods.
Regardless of whether wood or steel is used and not taking into account any
possible shifting of wood if wood is used, a good sturdy box with sheeting
on sides using proper construction methods shouldn't have much if any give.
So back to my original question, if I make a box instead of the pedestal
design and adjusting the levelers doesn't affect the twist, should the
twist then be adjusted by shimming between the box and the lathe bed
instead? And in this case should dampening material be placed between
machine and stand instead of under levelers?
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On September 17, 2017 8:11:03 AM Erik Christiansen
<[email protected]> wrote:
On 16.09.17 16:37, John Bald wrote:
Have a few options for used stands and cart that I might be able to modify
that could work for the mill, but haven't found anything that could be made
to work for the lathe. Used to buy used steel from local scrap yards for
projects a lot, but they won't sell it any more because of liability
concerns.
Cross-grain wood movement with changing humidity has always been a
concern of mine w.r.t. a lathe base. My Taiwanese "Toolroom quality" 3/4
tonne lathe had massive bed twist (something like 0.4mm/200mm IIRC) when
first plonked on the concrete floor. Very fine adjustments of the
jacking screws included in the twin pedestal base, with a machine level
on the cross-slide, fixed that. But the ease with which 0.1mm/m of twist
can be inflicted, admittedly using the pedestals as levers, makes me shy
away from wood as a base.
OK, wood generally doesn't move much lengthwise, so wooden legs wouldn't
be a big worry, but I'd run them through any connecting planking, so loads
are only on end-grain to the floor. Then I'd check regularly with the
machine level, at least for the first four seasons, adjusting the
jacking screws as necessary.
Erik
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