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    Re: Ruminations on Bygrave and Hohenrechenschieber scale markings
    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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