The Milling Process – Definitions
Indicates the surface speed at which the cutting edge machines the workpiece.
Effective or true cutting speed, ve
Indicates the surface speed at the effective diameter (DCap). This value is necessary for determining the true cutting data at the actual depth of cut (ap). This is a particularly important value when using round insert cutters, ball nose end mills, and all cutters with larger corner radii, as well as cutters with an entering angle smaller than 90 degrees.
Spindle speed, n
The number of revolutions the milling tool makes per minute on the spindle. This is a machine-oriented value, which is calculated from the recommended cutting speed value for an operation.
Feed per tooth, fz
A value for calculating the table feed. The feed per tooth value is calculated from the recommended maximum chip thickness value.
Feed per revolution, fn
Auxiliary value indicating how far the tool moves during one complete rotation. It is used specifically for feed calculations and often to determine the finishing capability of a cutter.
Feed per minute, vf
Also known as the table feed, machine feed, or feed speed. It is the feed of the tool in relation to the workpiece in distance per time unit related to feed per tooth and number of teeth in the cutter. The number of available cutter teeth in the tool (zn) varies considerably and is used to determine the table feed while the effective number of teeth (zc) is the number of effective teeth in cut. Feed per revolution (fn) in mm/rev (inch/rev) is a value used specifically for feed calculations and often to determine the finishing capability of a cutter.
Maximum chip thickness, hex
This value is a result of the cutter engagement as it is related to (fz), (ae), and (kr). The chip thickness is an important consideration when deciding the feed per tooth to ensure that the most productive table feed is employed.
Average chip thickness, hm
A useful value in determining the specific cutting force, used for net power calculations.
Metal removal rate, Q (cm3/min)
The volume of metal removed in cubic mm per minute (inch3/minute). It is established using the values for cutting depth, width, and feed.
Specific cutting force, kct
A material constant which is a factor used for power calculations, expressed in N/mm2
Machining time, Tc (min)
Machining length (lm) divided by the table feed (vf).
Net power, Pc and efficiency, ηmt
Machine tool oriented values, which assist in calculating the net power to ensure that the machine can handle the cutter and operation.
Milling Techniques – Definitions
A simultaneous straight movement in axial and radial feed directions.
A circular tool path on a constant z-level (circular interpolation).
A circular ramping tool path (helical interpolation).
Milling on a constant z-level.
A shallow radial cut with round insert or ball nose cutters in which the cutting zone is moved away from the tool center.
A configuration with cusps that occurs when producing sculptured surfaces.