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Another Whatsit Question.

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joe_m

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#1
I'll try it without the pic first, if nobody can answer then I'll break out the camera.

I have part of a tool. No maker's mark anywhere, just the number 19 stamped on the back. Basically it's a big metal circle with an arm that swings around it and a bracket on the back for mounting on something else.
Here's the interesting thing - the circle has a grooved edge like a quarter. And the arm that swings around has two little pins to sit in those grooves and stop the arm at any position.

And the really interesting thing (to me at least but I'm easily impressed) is that the circle is graduated. Not 360 degrees. It's also not 6400 mils, so it's not an artillery related piece. It's divided into 500 parts which is an unusual division for a circle.

So aside from some failed metric circle experiment, I really don't know where to start looking for answers. Does this ring a bell with anyone?

thanks again
Joe
 
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Tom Griffin

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#2
You know what they say: A picture is worth a thousand words.

Tom
 

joe_m

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#3
You know what they say: A picture is worth a thousand words.

Tom
Yea, that was a rather vague description.
Here's a couple pics. The handle is old plastic - like bakelite old. The back says "19" so I guess that's a part #. The circle part is approx 4-7/8" across, or exactly 11 centimeters, which I think is a big clue because if it's metric then it's probably not American made.

whatsit.jpg whatsit2.jpg
 
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Tom Griffin

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Stumped, even with the pic.

The clue has to lie with the number of divisions and the fact that it has a vernier scale for fractional divisions. It doesn't appear to be heavy enough to be machining related.

Tom
 

KBeitz

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#5
My 10 Fingers radial arm saw has a table something like that...
 

hman

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DURN!!! That's a real stumper! At first I thought the circle might have been divided into "grads," a European measure of angle. But I looked it up, and there are 400 grads per circle, not 500:
http://www.compassdude.com/compass-units.php
Anyway, from the size and lightweight nature of the device, my best guess would be some kind of sighting device (for surveying?) I agree it's probably not artillery (ie. radians or milliradians.)

Are you sure that's a vernier on the inner scale? It looks like some kind of a deviation/correction scale that would allow keeping the basic angle (outer scale) intact while making a temporary correction. Mighty fascinating ... thanks for posting! Let's hope somebody on the forum comes up with an answer. I, too, would love to hear what it is!
 

markba633csi

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#7
Very accurate vegetable peeler
 

KBeitz

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#8
I don't know but I just like it.... I would have to make something out of it....
 

GL

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#9
Did a quick search on "500 divisions of a circle ". They had an article on the Greenwich Transit Circle, used in astronomy in the 1800's-early 1900's. So it could be a telescope pointing device. About the right size and age.

I was thinking pizza cutter instead of vegetable peeler. Cool piece. Maybe a steampunk throttle quadrant for a spinning, gear meshed, display.
 

pontiac428

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#10
I've been scratching my head since you posted this, because I have seen this before. It may be in my collection of books on antique scientific instruments. GL is correct, 500 divisions was used for astronomy for a while. The second scale would probably be a correction for magnetic declination. I'm leaning toward it being a navigation instrument part. I'll post if I find it in my books.
 
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