If you need to drill a hole in the center of a circular material, you’ll have to find it first. You could buy a fancy center-finding tool, or you can use simple measuring tools and these easy methods to mark the point.
Place a carpenter square on the face of the material with the outside corner on the edge of the circle. Trace the outside edge of the square on the circle to draw two perpendicular lines across the circle.
Use the straightedge to draw a third line perpendicular to one of the others. Then, using the square as a straight edge, draw lines from one end of the parallel lines to the opposite end.
TIP: Don’t have a carpenter square? Use a piece of paper, book, or anything with a precise right angle to make your marks.
Carpenter Square and Ruler
Place a carpenter square on the face of the material with the outside corner on the edge of the circle. Lay a ruler across the square where the edges of the square touch the outside edges of the circle. Draw a line along the inside edge of the ruler.
Rotate the squares and repeat Step 1 to draw another line.
Carpenter Square and Speed Square
Place the inside edges of the carpenter square against the edge of the circle. Place the base of a speed square against the carpenter square and align the angled side with the inside corner of the carpenter square. Draw a line along the angle of the speed square.
Rotate the material and repeat Step 1 to draw another line.