Practice Test Geeks(CNC) Computer Numerical Control Machinist Technical Practice Test
← All CNC Flashcard Decks

CNC Mill Setup & Operation 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.

Read the first 7 CNC Mill Setup & Operation flashcards as text

  1. What is the recommended practice when loading a large-diameter face mill into a CNC mill spindle?

    Answer: Support the cutter with a rag or padded cradle to avoid dropping and damaging the spindle taper

    Heavy face mills should be supported during insertion to protect both the operator and the precision spindle taper from impact damage.

  2. When using a center-cutting end mill, which operation can it perform that a non-center-cutting end mill cannot?

    Answer: Plunge cutting directly into solid material

    Center-cutting end mills have cutting edges that extend to the center, allowing them to plunge straight down into material like a drill.

  3. What does the term 'runout' refer to in CNC milling tool setup?

    Answer: Radial deviation of the tool tip from true rotation axis, causing uneven chip loads

    Runout is measured with a DTI on the tool OD while rotating; excessive runout causes one flute to cut more than others, reducing tool life and surface quality.

  4. What is the function of G54–G59 work coordinate systems on a CNC mill?

    Answer: Define multiple workpiece zero origins so different fixtures or parts can be programmed independently

    G54–G59 store separate X, Y, Z offsets for up to six different work origins, allowing multiple parts or fixtures to be machined in one program.

  5. Which M-code is used to stop the program and allow the operator to measure the part before continuing?

    Answer: M00 (Program Stop)

    M00 is an unconditional program stop that halts execution and requires the operator to press cycle start to resume.

  6. What is the primary advantage of using a high-speed steel (HSS) end mill over a solid carbide end mill for a CNC milling application?

    Answer: HSS is tougher and more resistant to chipping under interrupted cuts or vibration

    HSS has higher toughness (impact resistance) than carbide, making it preferable in interrupted cutting or unstable setups where carbide would chip.

  7. In a CNC mill program, what does the R-value in a canned drilling cycle (e.g., G81 Z-1.0 R0.1 F5.0) specify?

    Answer: The retract plane height above the workpiece where rapid motion transitions to feed rate

    The R value sets the rapid-to-feed transition (reference) plane, typically just above the work surface to minimize air-cutting time.