CNC Cutting Parameters and Speeds/Feeds 2

Question 1

According to Taylor's tool life equation (VTⁿ = C), what happens to tool life as cutting speed increases?

Accepted Answer

Tool life decreases as cutting speed increases

Answer

Taylor's equation shows an inverse relationship: as cutting speed V rises, the tool life T falls because higher speeds generate more heat at the cutting edge.

Question 2

In CNC turning, feed rate is most commonly expressed as:

Accepted Answer

Inches per revolution (IPR)

Answer

In turning, feed rate is expressed as inches per revolution (IPR) because it directly sets chip thickness relative to each full rotation of the workpiece, independent of RPM.

Question 3

If you switch from a 2-flute to a 4-flute end mill at the same RPM and want to maintain the same chip load per tooth, you must:

Accepted Answer

Double the feed rate

Answer

With twice as many flutes cutting per revolution, feed rate must be doubled to maintain the same chip load: Chip load = IPM / (RPM × flutes).

Question 4

What does the G96 code activate on a CNC lathe?

Accepted Answer

Constant surface speed (CSS) mode

Answer

G96 enables constant surface speed mode, automatically adjusting the spindle RPM as the tool moves radially to maintain a consistent SFM at the cutting point.

Question 5

Which cutting parameter has the greatest direct influence on surface finish quality in CNC milling?

Accepted Answer

Feed rate

Answer

Feed rate directly determines the cusp (scallop) height left between tool passes; lower feed rates produce smaller cusps and finer surface finishes.

CNC - Cutting Practice Test

CNC - Cutting Practice Test

CNC Cutting Parameters and Speeds/Feeds 2