What is a spot drill and why is it used?

• A. A long drill used to drill deep holes.
• B. A short drill used to start a hole accurately and prevent wandering of a subsequent drill.
• C. A drill used to enlarge holes.
• D. A drill used for engraving marks.

Answer: (B)

A spot drill creates a precise starting point for a hole by cutting a small, conical indentation. This guide point keeps the next drill from wandering when you begin cutting, especially on flat or irregular surfaces or with tougher metals. Because the spot drill is short and stiff, it resists deflection, so the hole begins exactly where you intend and along the correct axis. Once the spot is made, you switch to the final drill and bore the hole to the required size, with better concentricity and accuracy. This technique is specifically for guiding the main drill; it isn’t used for enlarging holes, engraving, or lathe center work.