Measure the circumference of the circle, then divide by three. There are two ways to do this.
1) With a piece of non-stretch cord or wire. Attach it at a mark anywhere on the circumference and go all the way around, keeping it taut. Cut it off or mark it where it comes back to the starting point. Lay the wire out straight and measure it with a tape, divide by three and cut a piece of wire of that length, and use it as a measure for each third of the circumference.
2) If you know where the center of the circle is, measure the diameter of the circle and multiply that value by pi, divide by three, and use the result to mark off your measuring tape.
There's probably a way to figure it out with geometry, too. I'll have to look that up tomorrow. It's after midnight here, G'night.
Off Topic » in reply to Question: how do you find 3 points on a plywood circle 120 degrees apart, without a protractor?
Why can't you use a protractor?
The whole thread (37 posts)
- Question: how do you find 3 points on a plywood circle 120 degrees apart, without a protractor? (n/t)
- Without a template, you put your anchor bolts in. Drill out the plate.
- Yet another method
- Here you go, have a protractor:
- If I remember enough geometry...
- Cut a circle out of paper, exactly the same size as your plywood circle
- Yes, there is a way!
- So... tell us what you're building! (n/t)
- Why can't you use a protractor?
- It's impossible