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Thread: Sine bar protractor

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    Supporting Member mklotz's Avatar
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    Sine bar protractor

    Reading a conventional protractor to any decent accuracy always tries my patience. So, I built a sine bar protractor. As can be seen, in addition to the measuring arms, it has two rolls, similar to those on a sine bar.

    An offset half-lap hinge allows both arms to close flat against each other.

    In use the device is set (or read) with calipers reading the separation between the two rolls.

    The mathematics for converting between angle and caliper reading are a bit complicated, so I wrote a program to do the dirty work. It's available in the PROTRAC.ZIP archive on my page.
    45 Best Harbor Freight Tool Modifications

    Last edited by mklotz; 07-07-2017 at 08:28 AM.
    Regards, Marv

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  2. The Following 4 Users Say Thank You to mklotz For This Useful Post:

    C-Bag (09-03-2015), kbalch (09-04-2015), PJs (09-08-2015), Toolmaker51 (11-11-2016)

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    kbalch's Avatar
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    Thanks Marv! I've added your Sine Bar Protractor to our Rulers, Protractors, and Compasses category, as well as to your builder page: mklotz's Homemade Tools. Your receipt:

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