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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. What is the effect of increasing depth of cut on cutting forces?

    Answer: Cutting forces increase proportionally with depth of cut

    Greater depth of cut increases the volume of material sheared per pass, requiring proportionally higher cutting forces on both the tool and workpiece.

  2. For a CNC milling finishing pass, which parameter combination is most appropriate?

    Answer: Low feed rate, light depth of cut, high spindle speed

    Finishing passes use light cuts and low feed rates to minimize tool deflection and surface roughness, while high spindle speed improves cutting efficiency and finish.

  3. What is the formula for Material Removal Rate (MRR) in CNC milling?

    Answer: MRR = Radial depth of cut × Axial depth of cut × Feed rate

    MRR (in³/min) = RDOC × ADOC × Feed rate (IPM), capturing all three spatial dimensions of the cutting engagement to give volumetric removal rate.

  4. When roughing hardened steel (>45 HRC) on a CNC machining center, the recommended approach is:

    Answer: Lower cutting speeds, smaller depths of cut, and robust carbide tooling

    Hard materials demand conservative parameters — lower SFM and smaller DOC — to manage heat and prevent catastrophic tool failure or workpiece damage.

  5. The optimal chip load for a given end mill is best described as:

    Answer: The manufacturer-recommended range that balances tool life, MRR, and surface quality

    Optimal chip load falls within the tool manufacturer's recommended range for the material, balancing removal efficiency, acceptable tool wear, and target surface finish.

  6. In high-speed machining (HSM), which parameter change most defines the strategy compared to conventional machining?

    Answer: Cutting speed (SFM) is significantly increased, often paired with lighter radial engagement

    HSM is characterized by very high cutting speeds (SFM), often combined with reduced RDOC and appropriate chip load adjustments to maintain manageable cutting forces and tool life.

  7. When programming a CNC lathe for a facing operation using G96 (CSS), which code is used to set the maximum allowable spindle speed?

    Answer: G50

    G50 sets the maximum RPM clamp so the spindle does not over-speed dangerously as the tool approaches the center during constant surface speed (G96) facing.