What's this brass tool?

February 2, 2012 8:26 AM

At a website I write for, a reader sent in a photo of a brass tool, wondering what it was. I'm sure somebody here knows!

Here it is.

I have noted that the graduations on the item are radius vs circumference -- r of 4/3 is a c of about 8, r of 3 is a c of about 18.5, etc. It's to inexact to be a machining tool, and the points at each end are interesting. Any thoughts?

posted by AzraelBrown to technology (5 answers total)

maybe a force gauge?
posted by chasles at 8:32 AM on February 2, 2012

Proportional dividers. You measure an object with one end and transfer the measurement to a smaler or bigger thing that you're creating.
posted by bonobothegreat at 8:52 AM on February 2, 2012 [1 favorite]

...the position of the knob dictates the ratio of enlargement/reduction, a measuring tool used by artists and architects. You can find a bunch on eBay
posted by bonobothegreat at 9:07 AM on February 2, 2012 [1 favorite]

Ah, I knew somebody would know -- thanks much!
posted by AzraelBrown at 9:14 AM on February 2, 2012

...another thing, that I just found out while looking up a link, is that the graduations on the left make it possible to divide a circle into equal sections. Useful if you needed to do something like decorate a vase or a column.
posted by bonobothegreat at 9:21 AM on February 2, 2012 [1 favorite]