When filing the surface of a rough casting, use which file?

• A. Mill file
• B. Round file
• C. Flat file
• D. Taper file

Answer: (A)

When you’re leveling a rough casting, you want to remove the high spots and scale on broad flat areas as quickly and efficiently as possible. A mill file is the best choice because it’s designed for heavy material removal on flat to near-flat surfaces. Its teeth are arranged to cut aggressively, making it well suited for flattening and smoothing a rough, cast surface without spending extra time with lighter files.

A flat file can handle flat areas, but it isn’t as aggressive as a mill file for removing a lot of material. A round file is meant for curved surfaces and holes, and a taper file is intended for narrowing slots and tapered holes, not for quickly surfacing broad flat castings. So for smoothing the surface of a rough casting, the mill file provides the right balance of efficiency and effectiveness.