Red Seal Machinist Practice Exam

The cutting speed in machining is primarily determined by the RPM (revolutions per minute) of the spindle. Cutting speed is defined as the speed at which the cutting edge of the tool moves relative to the workpiece, and it is typically measured in surface feet per minute (SFM) or meters per minute (MPM).

The relationship between the cutting speed, spindle RPM, and the diameter of the workpiece can be described by the formula:

Cutting Speed (S) = (π × D × RPM) / 12 (for inches)

or

Cutting Speed (S) = (π × D × RPM) / 1000 (for metric)

where D is the diameter of the workpiece. As such, by adjusting the RPM of the spindle, the machinist can effectively control the cutting speed, optimizing it according to the material being machined and the type of tool used.

While other factors, such as cutting depth and tool material, certainly influence the overall effectiveness and success of the machining process, they do not directly determine the cutting speed. The type of coolant used can help manage heat and chip removal but does not impact the calculation of cutting speed itself. Therefore, understanding how spindle RPM affects cutting speed is crucial for