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Cutting Parameters and Speeds/Feeds Flashcards

7 cards from real CNC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. According to Taylor's tool life equation (VTⁿ = C), what happens to tool life as cutting speed increases?

    Answer: Tool life decreases as cutting speed increases

    Taylor's equation shows an inverse relationship: as cutting speed V rises, the tool life T falls because higher speeds generate more heat at the cutting edge.

  2. In CNC turning, feed rate is most commonly expressed as:

    Answer: Inches per revolution (IPR)

    In turning, feed rate is expressed as inches per revolution (IPR) because it directly sets chip thickness relative to each full rotation of the workpiece, independent of RPM.

  3. If you switch from a 2-flute to a 4-flute end mill at the same RPM and want to maintain the same chip load per tooth, you must:

    Answer: Double the feed rate

    With twice as many flutes cutting per revolution, feed rate must be doubled to maintain the same chip load: Chip load = IPM / (RPM × flutes).

  4. What does the G96 code activate on a CNC lathe?

    Answer: Constant surface speed (CSS) mode

    G96 enables constant surface speed mode, automatically adjusting the spindle RPM as the tool moves radially to maintain a consistent SFM at the cutting point.

  5. Which cutting parameter has the greatest direct influence on surface finish quality in CNC milling?

    Answer: Feed rate

    Feed rate directly determines the cusp (scallop) height left between tool passes; lower feed rates produce smaller cusps and finer surface finishes.

  6. Blue or heavily discolored chips produced while machining steel most likely indicate:

    Answer: Excessive cutting speed generating too much heat at the cutting zone

    Blue discoloration indicates chips exceeded approximately 450°F, a clear sign that cutting speed is too high or coolant delivery is inadequate for the conditions.

  7. Radial depth of cut (RDOC) in CNC milling describes:

    Answer: The percentage of the tool diameter engaged radially in the cut

    RDOC (radial engagement) is the width of cut measured perpendicular to the tool axis, typically expressed as a fraction or percentage of the tool diameter.