What is a tap used for?

• A. Drilling a hole
• B. Cutting external threads
• C. Measuring thread pitch
• D. Creating internal threads in a hole

Answer: (D)

A tap is a tool used to cut threads inside a hole so you can screw in a bolt or screw. After you drill a hole to the right size, you use the tap to form the internal thread by turning it into the hole with cutting action and lubrication. Different taps are used for different depths and thread forms, but the basic job is the same: create the internal threads that match the external threads on a mating fastener. The other options describe tasks done with other tools—external threads are cut with a die, pitch is measured with a gauge, and drilling is done with a drill—so tapping specifically creates internal threads inside a hole.