Things You'll Need

Instructions

1

Select a proper cutting bit for the material. Oscillating cutter bits are sold with manufacturer recommendations regarding the hardness of material they should cut. Usually, you will be able to buy one type of bit for plastic, wood and soft metals (such as aluminum) and another type of bit for cutting materials like stone or hard metal. Get a tip of the proper hardness for your material.
2

Draw a 3-inch line on the material's surface using the ruler. If the surface is curved or otherwise irregular, cut a 3-inch piece of string and stretch this over the contours of the surface to trace.
3

Transcribe the line into a circle with a 6-inch diameter. Poke the needle end of the compass into one end of the line. Open the compass, adjusting it so that the tip of the pencil touches at the other end of the line. Rotate the pencil in a circle around the needle tip to draw a circle with a 6-inch diameter.
4

Cut out the circle. Turn on the oscillating tool and set it to a medium speed. Insert the tip of the spinning router bit into the center of the circle you've outlined. Cut a line from this point out to the edge of the circle. Trace the outside of the circle to cut, erring on the inside of the outline (since you can remove material later if the hole's too small).