Just curious because I've never worked in a shop with fluorescent lights,
but is it true that the blade on a saw can appear to be stopped due to the
60 cycle strobing of the lights?
A tidbit that some people might be interested in:
Fluorescent lights will flicker at twice the AC frequency, which would
be 120 Hz for North America. You get two cycles of the light
flickering for each AC cycle because the current flows one way and the
light comes on, then the current goes to zero and the light goes out,
and then flows the other way and the light comes on again. The light
doesn't care which way the curernt is flowing. In theory this happens
with other light sources such as a regular tungsten bulb, but you never
see the flicker in a tungsten bulb because the glowing filament doesn't
cool off quick enough to see any flickering.
A calibrated strobe light is one way to measure the rotational speed of
things. For the case of the table saw, you would gradually adjust the
strobe rate until you got the blade to "freeze". What is really
happening is that the blade moved in integer number of teeth from one
flash to the next. The problem is that you don't know if it moved one
tooth or two teeth, or whatever. You then change the strobe light
frequency until you get the blade to "freeze" again. There is some
procedure and calculations that are used to determine the rotational
speed of the saw based on the strobe frequencies that froze the blade,
but it's been too long since I have done that and I'd have to think too
hard right now to remember how that part works.
So there's today's science lesson.