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Thread: Sine bar protractor

  1. #1
    Supporting Member mklotz's Avatar
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    Aug 2015
    LA, CA, USA
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    mklotz's Tools

    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.

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    Last edited by mklotz; Jul 7, 2017 at 08:28 AM.
    Regards, Marv

    Home Shop Freeware

  2. The Following 5 Users Say Thank You to mklotz For This Useful Post:

    Altair (Nov 12, 2020), C-Bag (Sep 3, 2015), kbalch (Sep 4, 2015), PJs (Sep 8, 2015), Toolmaker51 (Nov 11, 2016)

  3. #2
    kbalch's Avatar
    Join Date
    Jun 2012
    Clermont, FL
    Thanked 531 Times in 383 Posts
    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:

    2000 Tool Plans

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