I have a solid wood table approximately 30″ in diameter and I need to find the exact center so that I can route out the center so my wife can inlay tile.
Rob Johnstone: Remember junior high geometry? I don’t either – but the easiest way I know to find the center of a circle is to find the approximate distance to the center, make a trammel or use a compass to draw a series of arcs through the center of the table top (starting the arcs from different points on the circumference of the top). This will get you to a point that is rootin’ tootin’ (geometry terms) close to the exact center of the top.
Michael Dresdner: There are lots of ways — most of which you can find in your old high school geometry book (How to bisect a circle). But here’s a slick “woodworker” type method. Join two straight boards at 90 degrees — a lap joint will do just fine. Glue another straight edged board on top so that one edge of the board goes right through the 90 degree angle at 45 degrees. Now butt the two inside edges of the 90 degree boards against the edge of the table so they both are tangent at some point, and the 45 degree board will be laying on the table. Its inside edge will go right through the center of the table. Draw a line or mark it with masking tape, then move the gizmo you made about a quarter of the way around the table — it doesn’t have to be exact — just approximate. The point where this line crossed your first line is the center of the table. If you don’t trust that, try the gizmo in two or three other spots, and you will notice that all lines will cross at the same point.