Axial Depth of Cut (doc) - 1. The perpendicular distance from an uncut surface to a cut surface. 2. Perpendicular distance measured from the face edge of the insert to the face of the cutter.

Axial Rake - The angle between the axial centerline of the cutter and any plane parallel to the cutting edge of the insert in the axial view. The axial rake has the greatest effect on controlling chip flow.

Axial Runout - The total variation in an axial direction of a cutter element measured parallel from a true plane of rotation.

Brinell Hardness (BHN) - A test to determine the hardness of metallic materials. It involves applying a known load to the material surface to be tested through a hardened steel ball with a known diameter. The diameter of the resulting permanent impression in the metal is measured and then calculated in the Brinell hardness number.

Chatter - Chatter is a condition of vibration involving the milling machine, workpiece and cutter. Once this condition arises, it is often self-sustaining until the problem is corrected. Chatter can be identified when lines or grooves appear at regular intervals in the workpiece. These lines or grooves are caused by the teeth of the cutter as they vibrate in and out if the workpiece and their spacing depends upon the frequency of vibration.

Climb Milling - Rotation of a cutter in the same direction as the feed at the point of contact. Chips are cut to maximum thickness at the initial engagement of the cutter's teeth with the work, and decrease in thickness at the end of engagement.

Conventional Milling - Cutter rotation is opposite that of the feed at the point of contact. Chips are cut starting with minimal thickness at initial engagement of cutter teeth with the work, and increase to a maximum thickness at the end of engagement.

Cycle Time - The time required to complete all machining operations on the workpiece.

Depth of Cut (doc) - The perpendicular distance between the original and final surfaces of the workpiece being milled, reflecting axial depth in face milling and radial depth in end milling.

Double Negative - A cutter with both negative axial and radial rake. Known for a strong cutting edge, double negative cutters are very economical and produce very high cutting forces.

Effective Cutting Diameter - The maximum width of the flat surface which a face mill produces in one pass.

Effective Number of Teeth - The number of effective teeth is normally equal to the total number of teeth. However, in some types of cutters (such as a staggered tooth slotting cutter or a step mill) the effective number of teeth will be less than the total number of teeth.

Feed - The rate of change of position of the milling cutter as a whole, relative to the work while cutting. Usually expressed in inches per minute (ipm).

Gullet - Name typically applied to the space between cutter teeth that accommodates existing chips during cut.

Horsepower - Maximum available horsepower at the machine spindle is a critical factor as it can limit your milling capacity.

To calculate horsepower at the cutter use the formula: HPc = mrr/ K

To calculate horsepower at the motor, use the formula: HPm = HPc /E

ipm (inches per minute) - ipm is also known as the table feed or machine feed. The ipm value refers to how far the workpiece or cutter advances linearly in one minute, defined as:
ipm = ipt x nt x rpm

ipt (inches per tooth) - Sometimes referred to as chip load, ipt is the linear distance traveled by the cutter during the engagement of one tooth. Although the milling cutter is a multi-edge tool, it is the capacity of each individual cutting edge that sets the limit of the tool, defined as:
ipt = ipm/nt x rpm, or as: ipt = ipr/nt

K Factor - The "K" factor is a power constant that represents the number of cubic inches of metal per minute that can be removed by one horsepower input.
mrr - Metal removal rate, defined as:
mrr = doc x woc x ipm = cu. inches / min
nt - Number of effective teeth

Negative Rake - A rake angle that is less than 90« between the insert's rake face and surface.

Radial Rake - The angle between the radial centerline of a cutter and a radial line passing through the center of a cutter and the cutting point (point "P" or point "Z") of the insert.

Radial Width of Cut (woc) - 1. The length of engagement of a face milling cutter, perpendicular to the axis of the cutter. 2. Radial woc is measured from the leading edge of the insert in a direction parallel to the face of the cutter.

Rake Angle - The angle between the face of the cutting tool and the work. If the face of the tool lies perpendicular to the work, it has a zero-degree, or neutral rake. If the angle of the tool faces the cutting edge more acute, then it has a positive rake. If it's more blunt, it has a negative rake.

Ramp Milling - A milling process where the machine tool spindle is feeding simultaneously in an axial and radial direction.

Relief - The clearance angle behind or below the cutting edge which allows the cutting edge to be forced into the work. It is sometimes divided into primary relief (adjacent to the cutting edge) and secondary relief (beyond the primary relief).

RMS (root mean square) - A measurement of the average deviation from the mean surface of the machined workpiece. Mean surface is the perfect surface that would be formed if all of the roughness peaks were cut off and filled into valleys below the surface.

Rockwell Hardness (HRC) - A measure of hardness calculated from the difference in depth of penetration of an indenture between a major and a minor load. The more commonly used Rockwell scales are "C" (Rc), using a diamond sphero-conical penetrator, and a Rockwell "B" (Ro), using aa 1/16 inch diameter steel ball penetrator.
Rpm (revolution per minute) - Defined as:
rpm = 12 x sfm / ( x D
sfm (surface feet per minute) - Defined as:
sfm = ( x D x rpm /12

Wiper - Large corner radius inserts that are designed to "top off" the peaks of feed marks and improve the surface finish.