At what speed range may aluminum and brass be drilled?

• A. 50-100 ft per minute
• B. 100-150 ft per minute
• C. 200-300 ft per minute
• D. 400-500 ft per minute

Answer: (C)

Choosing the proper cutting speed for drilling aluminum and brass is the main idea. These metals are soft and heat-conductive, so they cut best at higher surface speeds than harder steels. A range of 200–300 ft per minute gives a balance: it’s fast enough to cut efficiently and form good chips without excessive rubbing, which helps keep tool life long and produces a cleaner hole. If you run much slower, the drill tends to rub instead of cut, causing built-up edge, rough surface finish, and slower drilling. If you go much faster, heat rises quickly, which can dull the tool and affect hole quality. Therefore, 200–300 ft per minute is the best choice for aluminum and brass in typical drilling conditions.