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By George Hart for the Museum of Mathematics

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Last week’s Math Monday column looked at a tricky construction of four equilateral triangles. Let’s revisit it, but instead of using paper, we’ll use square sticks. These twelve identical wood parts fit together using 60-degree half-lap joints.

This wood version is made from 3/8 inch square stock, with slots cut as indicated below. It is easy to make these with a table saw or radial arm saw. Assembling them so each triangle links symmetrically with the other three triangles is the tricky part.

Alternatively, you can make the components on a 3D printer. Then the lap joints don’t need to be cut. They are formed as the piece is built up. If you have access to a 3D printer, you can make your own copy using the STL file available here.

More:
See all of George Hart’s Math Monday columns

Gareth Branwyn

Gareth Branwyn is a freelancer writer and the former Editorial Director of Maker Media. He is the author or editor of a dozen books on technology, DIY, and geek culture, including the first book about the web (Mosaic Quick Tour) and the Absolute Beginner’s Guide to Building Robots. He is currently working on a best-of collection of his writing, called Borg Like Me.


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Comments

  1. Jim Watters says:

    I had a few pieces of the ash left over from installing my hardwood floor.

    I failed to read the directions right the first time and placed the two
    slots on the same side. I needed a shape with even number of sides to
    close it off.

    http://photocreations.ca/tri/triangles_3.jpg

    http://photocreations.ca/tri/triangles_4.jpg

    But I did manage to cut them correctly on my second attempt. My stock on
    my second attempt was 1/64 inch smaller to get rid of some tool marks.
    The pieces fit together quite easily.

    http://photocreations.ca/tri/triangles_1.jpg

    http://photocreations.ca/tri/triangles_2.jpg

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