Engaging the burr

The drill is running in a clockwise direction.

It is best if you not only have the freedom to use the equatorial side of the burr but also a view of this surface acting on the bone.

When finding a tubular structure start by removing bone that could jerk the burr down into the structure being sought. Then drill along the plane you have created parallel to the structure - not across it. The reason is that if the drill were to become in any way uncontrolled when drilling across the structure there is a chance of the drill damaging that structure.

Drilling along the structure identifies irregularities or deviations from a straight line. This provides a better guide to the depth of the target.