What is a small-diameter channel worn into the side of a larger diameter borehole?

• A. Groove
• B. Slot
• C. Notch
• D. Keyseat

Answer: (D)

This item tests recognizing a precise machine-shop term for a channel formed in a bore. A keyseat is a small-diameter channel cut into the side of a larger borehole, specifically made to receive a key. This key locks rotation between components and helps with precise alignment, which is exactly what a recessed pocket of that size and location is used for.

The other terms are more general: a groove is any elongated recess, a slot is a broader opening or gap, and a notch is a shallow cut near an edge. None of those imply the dedicated purpose of transmitting torque and locating parts with a key, which is what defines a keyseat.