NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2013 Feb 11, 08:29 -0800
Hi Robin
These dimensions are from an MHR-1, as this is the explicit marking on the slide rule itself, as a factory issue.
Images with my ruler were not possible with the camera I have. As such, I have simply measured this myself.
All dimensions include the base line width
Smallest Tick Mark
4/100"
Medium Tick Mark (meets middle line)
8/100"
Large Tick Mark without Dot (exceeds middle line)
8/100" + 1/64"
Dot Adds
1/32" (diameter)
Heavy Division that does NOT meet the line above
8/100" + 1/64"
Major Heavy Division that meets line above
11/64" (does not include line above)
Base Line Width (Heavy line)
1/100"
This is also the width of the heavy tick marks
Middle very fine line
1/3*BaseLineWidth??
This is also the width of the minor tick marks
In so far as natural units, it is my view that these scales were produced on a much larger scale and then photo reduced for production. I think this because it would be well nigh impossible to ACCURATELY generate this image by hand in 1:1 scale. If drawn very large, then minor drawing errors become insignificant when photo reduced. Just a theory on my part, but in any event, a monumental drawing task.
The linked imaged are from Tube II, the (co)Tangent scale, where the measurements were taken.
Regards
Brad
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