CNC Basics
Which G‑code starts linear interpolation?
G01
What button should you press before reaching inside the machine enclosure?
Emergency Stop (E‑Stop).
What does Ø symbol represent?
Diameter
What tool is most commonly used to check parallelism on a machined surface?
Dial indicator / test indicator on a surface plate
What does SFM stand for?
Surface Feet per Minute.
In absolute programming (G90), all coordinates reference what location?
The program’s work zero / work offset origin.
Why should you never leave an Allen key in a tool holder or chuck?
It can become a dangerous projectile.
A tolerance of ±.0005" is an example of what type of tolerance?
Bilateral tolerance
What do the letters “HSS” stand for in cutting tool materials?
High Speed Steel
Chip load primarily depends on what two factors?
Cutter diameter and material.
What is the G- code for a rapid movement?
G00 = rapid positioning
Why must you never run the machine with the door open?
Guard interlocks prevent injury from chips, coolant, or tools.
On a print, what does the letter “R” before a number indicate?
Radius
What is the main advantage of carbide tools over HSS tools?
Higher heat resistance and the ability to run at much higher cutting speeds
A tool with more flutes is typically used on what type of material?
Harder materials / high‑rigidity setups.
What is the most common work offset used on Haas mills?
G54
Before pressing Cycle Start, the operator must verify three things. Name at least two.
Correct tool, correct offset, correct program loaded, clear work area, etc.
If a tolerance reads “.250 ± .010,” what is the total tolerance range?
.020
What does the term “flute” refer to on a milling cutter?
The helical grooves that provide chip evacuation as well as cut material
What formula is used to calculate feedrate for milling?
Feed = RPM × chip load × number of flutes.
What is the minimum required PPE when operating a CNC machine?
Safety glasses
When setting a tool manually on a CNC mill, what mistake can lead to tool breakage or a spindle crash?
Jogging in the wrong direction (Z‑) or leaving the machine in the wrong mode
In print reading, what does the note “TYP” next to a dimension mean?
The dimension is typical — applies to repeated features
On a lathe, what tool is required to support long, thin workpieces to prevent deflection?
A steady rest or a follow rest.
Why do large diameter endmills require lower RPM?
Larger diameter increases surface speed per revolution.