CNC Lathe Turning Operations Flashcards

What is the purpose of a G28 command in a CNC lathe program?

Answer: Returns the axes to machine home position

G28 commands the machine to rapid the specified axes through an intermediate point back to the machine reference (home) position.

Which condition causes 'built-up edge' (BUE) on a turning insert?

Answer: Low cutting speed and high workpiece adhesion

BUE forms when workpiece material welds to the tool edge at low speeds due to high friction and adhesion, degrading surface finish and dimensional accuracy.

On a CNC lathe, work coordinate system offset G54 is used to:

Answer: Define the workpiece zero point relative to machine zero

G54 recalls a stored work offset that shifts the coordinate system origin to the workpiece datum, allowing programs to be written from a part-based zero.

The 'lead angle' of a turning tool affects which of the following most directly?

Answer: Radial cutting force and chip thickness

Lead angle (side cutting edge angle) distributes cutting forces and changes chip thickness — a larger lead angle reduces radial force and thins the chip.

Which of the following best describes 'feed per revolution' (FPR) in lathe turning?

Answer: The distance the tool advances along the axis for each complete spindle rotation

FPR (in./rev or mm/rev) is the axial distance the tool travels per single revolution of the spindle, directly controlling surface finish and chip load.

When programming a G71 OD roughing cycle on a Fanuc control, the 'U' value specifies:

Answer: The finishing allowance left on the diameter

In G71, the U address defines the diameter finishing allowance (stock left for the G70 finish pass) on the OD.

Which type of CNC lathe operation is best described as 'parting'?

Answer: Cutting through the workpiece radially to separate it from bar stock

Parting (cutoff) uses a narrow grooving insert plunged radially into the workpiece until the part is fully severed from the bar stock.