This video shows some of the techniques for using a compass to layout woodworking projects as described in an article in the October 2013 issue of Popular Woodworking Magazine

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# Mighty Compass Video Bob Lang October 2013 Popular Woodworking Magazine

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8 Replies to “Mighty Compass Video Bob Lang October 2013 Popular Woodworking Magazine”

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Totally awesome

Are you saying the difference between pi and 3 is accounted for by the difference in the circumscribed and the inscribed circles of a hexagon? That could be right. I have a thought on it that probably doesn't contradict your idea. My guess is that the intersections of the circles are in the right places simply because they are circle to circle intersections. I think they'd be off if they were circle to straight line intersections. Somehow circle to circle works out.

If you join up the intersections of the 6 divisions you will get a perfect hexagon. The circumference of the hexagon is slightly smaller than the circumference of the original circle. This is the difference between 3 and 3.14 (π). Another way of thinking about it is making an equilateral triangle with the compass, each angle in the triangle is 60º, so exactly 6 of them fit in a circle (360º). I hope this makes sense but it's difficult for me to explain without physically drawing it

My experience doing this with a compass is that it has always come out short. I'm a pretty careful person so I assumed it had to be because pi is larger than 3.0. I read your reply and decided to try it with computer aided drafting software. It came out perfectly. I have to believe my prior work with an actual compass was off because of cumulative error since the CAD software doesn't have that issue. Please explain how it comes out right since pi is larger than 3.

A compass will make 6 EXACTLY equal divisions of a circle, basic geometry.

Really liked the Mighty Compass Article.

Thanks Bob.

A compass will make 6 ALMOST equal divisions of a circle. If they were equal, pi would equal 3.

Please don't add videos lower than 480p. I'm sure it takes longer to upload but 360p looks blurry no matter what.