Certified Machinist Certification Exam

Certified Machinist Certification Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• Which material is most commonly used for cutting tools due to its high

hardness and wear resistance?

• Aluminum
• High-Speed Steel (HSS)
• Brass
• Mild Steel

Rationale: High-Speed Steel is widely used for cutting tools because it

maintains hardness at high temperatures and resists wear.

• What is the purpose of a lathe tailstock?
• Hold the cutting tool
• Support the workpiece for machining operations
• Rotate the workpiece 1 / 4

• Cool the cutting tool

Rationale: The tailstock provides support for long or thin workpieces to

prevent deflection during machining.

• Which type of fit is used when parts must slide freely without binding?
• Interference fit
• Transition fit
• Clearance fit
• Force fit

Rationale: Clearance fits provide a gap between parts, allowing free

movement.

• What is the function of a micrometer?
• Drill small holes
• Measure precise dimensions
• Cut threads
• Grind surfaces

Rationale: Micrometers are precision measuring instruments used to

measure external or internal dimensions.

• In milling, what is the primary motion of the workpiece?
• Rotational
• Feed motion
• Cutting motion
• Oscillatory 2 / 4

Rationale: The workpiece moves along the feed direction while the

cutter provides the primary cutting motion.

• Which of the following is a common method for heat treatment of

steel to increase hardness?

• Annealing
• Normalizing
• Quenching
• Tempering

Rationale: Quenching involves rapid cooling of steel to harden it.

• What type of thread is most commonly used for general-purpose

fastening?

• Buttress thread
• Unified National Thread (UNC/UNF)
• Acme thread
• Square thread

Rationale: UNC and UNF threads are standard for general fastening

due to ease of manufacture and interchangeability.

• Which cutting fluid property helps reduce friction and heat

generation?

• Corrosion resistance
• Color
• Odor
• Lubrication 3 / 4

Rationale: Lubrication reduces friction between the tool and

workpiece, prolonging tool life and improving surface finish.

• What is the main advantage of CNC machines over manual machines?
• Lower cost
• Higher precision and repeatability
• Simpler operation
• Less training required

Rationale: CNC machines can produce complex parts with high

precision and repeatability.

• When drilling a hole, which tool is used to center the drill on a

workpiece?

• Reamer
• Tap
• Center punch
• Countersink

Rationale: A center punch marks the exact location to guide the drill

bit and prevent wandering.

• Which instrument is used to measure angles accurately?
• Caliper
• Ruler
• Protractor
• Micrometer
• / 4