Jon Elson wrote:


Mark Rand wrote:



Ch**st almighty! Fart and the change in floor loading would make it
move. Good
Gloat G



Heh! I got a Talyvel 3 on eBay about a year ago, and it is able to resolve
0.1 arc second, which works out to 5.8 microinches per foot. It is also
supposed to be able to hold a reference to absolute level of .2 arc second,
although I think mine isn't quite that good anymore. It was JUST the
thing to help in precision hand grinding a 6 foot lathe bed straight.
(It is hardened all the way through, no way to scrape it!)

Jon


Oh, yeah -- my point! If I walk from one end of the lathe to the other,
the Talyvel shows the whole concrete slab tilts one whole arc second.
The lathe has tilted 30 arc seconds since I put it in its final position,
so I have to relevel it. Hopefully, the floor has finished adjusting
to the weight of the machine.

Jon