Enlarging a Hole

If you have an existing hole that is too small and you need to enlarge it for a larger instrument; this tip is a simple solution to this problem. To properly locate the hole and stop wobbles, simply use two hole saws. Use one the same size as the existing hole and a larger one for the new hole.

Mount both hole saws on a deep hole saw mandrel with the smaller inside the larger. The smaller keeps the hole saw centered while the larger on does the cutting. (See illustration)

Hole Saw Smooth Edges

To ensure smooth chip-less edges they recommend this method.

1. Stop drilling once the mandrel goes through.
2. Reverse the drill direction and cut the surface with the hole saw; a groove will appear.
3. Change the drill’s direction and cut through.

To assure the underside is chip-less; stop when the mandrel goes through and repeat steps 1 thru 3 from the other side.