Mark circles with a center hole
When using a compass to make circles for my chip-carving projects, there are times when I don't want to leave a hole in the center of the circle. What to do? I created a "temporary" hole from a small square of clear acrylic as shown in the drawing. For "feet," I went with self-adhesive cabinet-door bumpers (Woodcraft part no. 02S81, $7.50, 800/225-1153 or woodcraft.com).
To use the device, I first draw diagonals on my workpiece as shown at right. Next, I position the intersection of the acrylic square's scribed lines over the center mark. Finally, with the point of the compass in the center of the scribed lines, I draw the circle. Downward pressure on the compass and feet keeps the acrylic from slipping on the workpiece.
-- Merle Krug, Marion, Iowa
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You can eliminate the parallax distortion problem by scribing the lines on both sides of the clear plastic false center. Scirbe the lines very fine, then look straight down through the plastic center. If your not perfectly above the plastic center, the two sets of scribed marks won't line up until you are.
3/25/2010 08:51:32 PM Report AbuseGood idea, but why not just a clear plastic door bumper by itself (with center marked on the bottom)? Adjust compass point so it won't go through bumper. No matter, watch out for parallax distortion.
3/9/2010 05:03:19 PM Report AbuseGreat tips!
3/5/2010 09:35:23 AM Report Abuse