How to Measure Curve Cuts With a Compass

There are many occasions during a home renovation when you have to map out a precise curve -- for example, installing trim around porthole windows or cutting tile to fit around a spiral staircase -- and the easiest and most reliable way to draw the needed curve is to use a compass. Hardware and home improvement stores stock larger versions of the kind you remember from high school geometry. But you can easily extend out your compass using a string tied to the free-moving, marking end if you need an even wider curve.

Compass
Marking pencil

Instructions

- 1
  Determine the radius of the curve you need to cut. Remember, the radius of a circle is equal to one-half its diameter, or the circumference of the circle divided by 2 times pi.
- 2
  Install the marking pencil into the grip of the compass. There may be a locking mechanism that keeps it in place, or a screw that must be tightened to secure the pencil.
- 3
  Slide the compass legs open to the radius measurement indicated on the compass. If included, tighten the screw at the top of the compass to keep the compass secure.
- 4
  Place the point of the compass onto the material that must be cut, press the point of the marking pencil down, and slowly rotate the compass, keeping the pointed end from moving as you draw. Use even tension to draw the curve.
- 5
  Cut along the marked line, as desired.

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