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Post by Mastercaster on Nov 29, 2011 9:11:24 GMT -8
  Hi All. I found this cool little gizmo in a box of junk in a custodial closet at work. I took a pic of both sides of it through my magnifier light cause the print is tiny. I 'm hoping FMW will know what this thing is since he is a retired engineer. It looks like some sort of circular slide ruler. |
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Post by FMW on Nov 29, 2011 10:07:12 GMT -8
It is indeed a circular slide rule. I have a similar one in a bottom drawer (except mine is all chipped around the edges). Instead of having a fixed ruler, a sliding ruler, and a cursor it has one ruler and two cursors. You put the first cursor on 0 and hold it there while you put the second cursor on the first number you want to work with. You then rotate the first cursor to the second number you want to work with, allowing the second cursor to rotate with the first cursor. You read the result from the second cursor. The big advantage to a circular slide rule is that you never have to switch ends when you "wrap around" your result. I used mine a lot in the pre-calculator age (when dinosaurs roamed the earth). A 6" circular slide rule is the equivalent of an 18" straight ruler on the outer (multiply and divide) scales.
Now wasn't that a lot more information than you really wanted?
FMW
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Post by Mastercaster on Nov 29, 2011 11:10:00 GMT -8
Actually it is pretty fascinating to look at. My smarter and older brother used to use a slide rule in high school math. He's the only one that went to college. Thanks, I figured you would know. If anybody local would like to play with this thing you can have it.
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Post by davewilly on Nov 30, 2011 6:31:03 GMT -8
Hey Greg I would be interested in it if its still unspoken for. I have a couple other old "tools" like that I think there are kind of cool.
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