View Full Version : Seismic activity and machine accuracy....

12-20-2006, 11:27 PM
In the wake of a very minor earthquake , I discovered that my lathe was cutting a taper. Comparing notes with some other machinists in the area, I found one other guy whose machinery had been affected as well. Just a heads up for those of you in areas prone to earthquakes.

12-20-2006, 11:41 PM
Sounds like one unlucky shop layout - the headstock end is on one tectonic plate and the tailstock end on another. But there's probably some lucky guy out there who was too lazy to set his tailstock right, and now his machine is running dead on. Ya can't win!

Spin Doctor
12-20-2006, 11:43 PM
All the more reason for an isolated foundation

Paul Alciatore
12-20-2006, 11:56 PM
I would suspect that it is a good idea to check the level of your lathes from time to time, even in the absence of any known earthquakes. Foundations and buildings do settle.

12-21-2006, 12:16 AM
It is very unlikely that a minor earthquake upset your lathe. Concrete foundations are not noted for their flexibility and in any event the wavelength of an earthquake seismic wave is about 8 miles. I suppose it might be possible in a small earthquake if your house is on soil subject to liquifaction but I would expect to see new cracks in the floor or foundation.

Unless you are directly over a fault line the earth moves as a whole when the seismic wave passes by. In the case of a small earthquake the actual motion of the earth is only on the order of millimeters over several miles at most and it isn't enough to exceed the yield strength of solid earth or concrete. It's a long wavelength sound wave with a period of a second or two for the short wavelengths and up to 20 seconds for the long waves. What happens is the ground tilts a very tiny fraction of a degree as the wave goes by. It doesn't stay tilted though. The seismometer I have in my basement is actually a very sensitive tilt meter.