Speeds, Feeds & Machining Parameters Flashcards
6 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 6 Speeds, Feeds & Machining Parameters flashcards as text
If a CNC lathe is running at 800 RPM and the workpiece diameter is 2.0 inches, what is the approximate surface footage (SFM)?
Answer: About 420 SFM
SFM = (RPM × Diameter × π) / 12 = (800 × 2.0 × 3.14159) / 12 ≈ 419 SFM, which rounds to about 420 SFM.
What does 'radial depth of cut' (RDOC) refer to in a milling operation?
Answer: The stepover distance of the cutter across the workpiece
Radial depth of cut (RDOC) is the lateral engagement of the cutter, measured perpendicular to the spindle axis, often expressed as a percentage of cutter diameter.
Which machining parameter most directly affects tool deflection and dimensional accuracy in CNC milling?
Answer: Tool stick-out length
Excessive tool stick-out increases leverage on the cutter, magnifying deflection forces and causing dimensional error and chatter.
When using a constant surface speed (CSS) mode on a CNC lathe, what happens to RPM as the tool moves toward the center of the workpiece?
Answer: RPM increases to maintain SFM
As diameter decreases toward center, the control raises RPM automatically to keep surface feet per minute constant.
Which of the following best describes 'climb milling' compared to 'conventional milling'?
Answer: The cutter rotates in the same direction as the feed, starting with thick chips
In climb milling the cutter rotates in the feed direction, starting with a thick chip that thins to zero, reducing heat and improving surface finish.
What is the most common reason a programmer specifies a 'finishing pass' at reduced depth of cut and feed?
Answer: To achieve tighter dimensional tolerances and better surface finish
A light finishing pass removes only the stock left from roughing, minimizing tool deflection and producing the specified tolerance and surface finish.