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How do I draw a perfect circle on a square of plywood? Question
I'm working on a string-art project on a 3-ft square of plywood. It will have brass nails in a circle with different colors of string connecting the nails in a pattern.
I'm trying to figure how I can draw large enough circle on the plywood. I've thought about:
- Finding a bowl to trace, but none in my house are large enough.
- Using a compass, but again, mine isn't large enough.
- Freehand drawing the circle, but it comes out too imperfect.
2 answers
There's a few ways to do it:
- Use a compass. I know you said yours is too small, but you can buy a carpenty or woodworking compass that is much larger (foot or more).
- Tie a string to your pencil, keep one end of the string fixed with your finger or something else (toothpick, nail, other pencil) while you rotate the pencil while keeping string taut.
- Fix the center of the plywood (for example, by pinning it down with a nail), hold the pencil in place, and rotate the plywood.
And, one for fun more than practicality: Hang a flashlight above the plywood. It will probably make a circular pattern that you can trace. You can vary the radius by adjusting the height.
When I needed to cut a 4' circle out of the middle of a sheet of plywood, I fabricated a compass by tying a long-enough piece of non-stretchy string to a tack or finishing nail -- I forget which, but it was something small enough that it wouldn't leave a mark on the other side of the plywood.
To the other end of the string I tied a pencil at the desired radius. Working on the side of the plywood that I designated as the back, I found the center point by measuring, drove in the tack, had a friend hold it in place just in case, and walked around the board tracing the line with the pencil. Tip: do this at sawhorse or table height; you want to be able to walk around it and maintain consistent tension while doing so, not crawl around on the floor.
Measure twice, cut once: after I had a line I could see, I measured the diameter in a few places to convince myself that any variability was within the margin of error that cutting it out with a jigsaw would produce. (Maybe there were better ways to cut it, but a jigsaw is what I had.)
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