Which operation is used to restore the inside diameter of a worn valve guide quickly?

• A. Knurling
• B. Polishing
• C. Grinding
• D. Reaming

Answer: (A)

Restoring the inside diameter quickly means bringing the worn bore back to a precise size with a smooth finish. A reamer is designed for that purpose: it removes a small, controlled amount of material to bring the bore to the exact diameter and produce a refined surface finish, which is ideal for valve guides where the valve stem must fit accurately.

Knurling creates a textured pattern and is typically used on external surfaces to improve grip; doing it inside a bore wouldn’t reliably produce a precise, smooth diameter for a valve guide. Polishing alone smooths but doesn’t fix size, and grinding can size a bore accurately but is slower for a quick restoration.