An Engineer's Level

摘要

In issue 9 of MEW, Bill Morris referred to a requirement for a precision level when levelling a lathe, stating that one with a calibration of 60 seconds per division was barely adequate. I must confess that this value was largely meaningless to me. Small divisions of, say, 1 thou or 1 millilitre, or even 1 gram I could visualise, but an angle of 60 seconds I could not. I knew this to be a small angle, but beyond that I was lost. Bill did go on to explain that the need to detect errors of 10 seconds was about 0.04mm error in 1 metre. This led me to consider what I had available in the workshop, though I realised that nothing was in any way close to this. My builders level would give a 2mm movement to the bubble for an 8mm error over 1 metre. The level in my combination set protractor was surprisingly even less accurate, requiring about a 10mm error over 1 metre for a similar movement of the bubble.