End Mill Applications and Variables 312

A axis

A rotational axis that describes motion around the X axis. The A axis allows complex workpiece movement on a multi-axis mill.

AE

Radial depth of cut. The amount of an end mill’s diameter that is engaged with the workpiece in a single pass. AE, also known as stepover or radial depth of cut, is generally 75% or less of the tool diameter.

AP

Axial depth of cut. The amount of an end mill’s peripheral cutting edges that are engaged with the workpiece in a single pass. AP, sometimes called axial depth of cut, measures how far beneath the workpiece surface the peripheral cutting edges penetrate.

axial depth of cut

AP. The amount of an end mill’s peripheral cutting edges that are engaged with the workpiece in a single pass. Axial depth of cut, sometimes called AP, measures how far beneath the workpiece surface the peripheral cutting edges penetrate.

axis

An imaginary straight line that runs through the center of an object. An end mill rotates around its axis.

B axis

The rotational axis describing motion around the Y axis. The B axis allows complex workpiece movement on a multi-axis mill.

ball end mill

An end mill with a fully rounded end. Ball end mills, sometimes called ball nose end mills, cut rounded edges and complex three-dimensional shapes into workpieces.

ball nose end mill

An end mill with a fully rounded end. Ball nose end mills, sometimes called ball end mills, cut rounded edges and complex three-dimensional shapes into workpieces.

C axis

The rotational axis describing motion around the Z axis. The C axis describes the rotation of a machine spindle.

Cartesian coordinate system

A numerical system that describes the location of an object by expressing its distance from a fixed position along three perpendicular linear axes. The Cartesian coordinate system is used to program machining positions on a CNC machine.

center cutting

An end mill in which a portion of the cutting edges on the end face extend to the center of the tool. Center cutting end mills can cut straight down into a workpiece.

chip evacuation

The clearance of chips during a metal-cutting process. Chip evacuation can be a challenge in milling operations that create internal features.

chip load

The distance a cutting tool travels along the toolpath while a single cutting tooth cuts into the workpiece. Chip load, which is also known as feed per tooth (fpt), determines how much material a single cutting tooth removes in one tool rotation.

chips

A piece of metal that is removed from a workpiece during a machining operation. Chips are tiny curls, shards, fragments, shavings, or particles of metal.

CNC

Computer numerical control. A combination of software and hardware that directs the operation of a machine tool. CNC machines are much more precise than their manual counterparts.

computer numerical control

CNC. A combination of software and hardware that directs the operation of a machine tool. Computer numerical control machines are much more precise than their manual counterparts.

constant

A variable or number that does not change value. The constant 3.82 (318.3) is used in the formula to convert mill speed from surface feet (meters) per minute to revolutions per minute.

contouring

A milling process that moves the tool in three linear axes simultaneously. Contouring, sometimes called three-dimensional profile milling, can create complex and rounded features in a workpiece.

contours

A curved surface or dimension that is cut into a workpiece. Contours are often created with ball end mills.

coordinates

A series of numerical positions that describe any point of an object in three-dimensional space. Coordinates are usually described on CNC mills using the X, Y, and Z axes of the Cartesian coordinate system.

corner chamfer end mill

An end mill with an angled face between the peripheral cutting edges and the end face. Corner chamfer end mills cut angled edges into workpieces and make the corner of the tool less likely to chip.

corner radius end mill

An end mill with a rounded face between the peripheral cutting edges and the end face. Corner radius end mills cut features with rounded edges into workpieces and make the corner of the tool less likely to chip.

cubic centimeters per minute

cm³/min. A unit of measurement that indicates how much material has been removed from a workpiece in one minute. Cubic centimeters per minute is the metric unit of measurement for material removal rate.

cubic inches per minute

in³/min. A unit of measurement that indicates how much material has been removed from a workpiece in one minute. Cubic inches per minute is the Imperial unit of measurement for material removal rate.

cutter diameter

The maximum width of an end mill’s cutting edges. Cutter diameter determines how wide of a cut an end mill can make in a single pass.

cutting edges

The surface of a cutting tool that is in direct contact with the workpiece. Cutting edges perform the actual metal removal during a cutting operation.

cutting fluid

Any fluid used to cool, lubricate, and clear chips during metal cutting. Cutting fluid, sometimes known as coolant, can be made of oil, water, synthetic fluids, or a combination of these.

cutting speed

The amount of workpiece material a cutting tool contacts in one minute. Cutting speed is measured in surface feet per minute (SFM) or meters per minute (m/min).

cutting variable

Adjustable factors that affect how a cutting tool removes material during a machining operation. Cutting variables include speed, feed, and depth of cut.

depth of cut

DOC. The amount of an end mill’s cutting edges that are engaged with the workpiece in a single pass. Depth of cut can be measured both axially and radially on an end mill.

DOC

Depth of cut. The amount of an end mill’s cutting edges that are engaged with the workpiece in a single pass. DOC can be measured both axially and radially on an end mill.

drill

A multi-point cutting tool used to create a round hole in a workpiece surface. A drill can be used to start a hole in a workpiece before completing certain plunge milling applications with an end mill.

efficiency

The ability to produce an intended result in a way that wastes the the least amount of time, effort, and resources. Material removal rate is an important factor in measuring an operation’s efficiency.

emergency stop

E-stop. Shuts off power to a machine immediately when pressed. The e-stop button is generally large, red, and placed on a yellow background so you can locate it easily.

end face

The bottom of an end mill. The end face is important in a variety of end milling operations, including creating contours.

end mill

A type of milling cutter that cuts with its bottom and side cutting edges. End mills can be used to machine complex features, such as grooves, slots, circular slots, pockets, and contours.

feed

The rate at which the cutting tool travels along the workpiece. Feed, sometimes called feed rate, measures how quickly a tool moves along a toolpath.

feed per revolution

fpr. The distance that a tool advances along a toolpath during one rotation of the workpiece or cutting tool. On the mill, feed per revolution indicates the amount of material all cutting teeth remove during one tool rotation.

feed per tooth

fpt. The distance a cutting tool travels along the toolpath while a single cutting tooth cuts into the workpiece. Feed per tooth, which is also known as chip load, determines how much material a single cutting tooth removes in one tool rotation.

feed rate

The rate at which the cutting tool travels along the workpiece. Feed rate, sometimes called feed, measures how quickly a tool moves along a toolpath.

finishing

A cutting pass that emphasizes tight tolerances and smooth surface finish. Finishing removes only a small amount of material.

flutes

A set of recessed grooves on the periphery of an end mill. Flutes allow chips to evacuate the cutting area.

fpr

Feed per revolution. The distance that a tool advances along a toolpath during one rotation of the workpiece or cutting tool. On the mill, fpr indicates the amount of material all cutting teeth remove during one tool rotation.

fpt

Feed per tooth. The distance a cutting tool travels along the toolpath while a single cutting tooth cuts into the workpiece. Fpt, which is also known as chip load, determines how much material a single cutting tooth removes in one tool rotation.

helix angle

The angle formed by the slant of a flute and the tool’s axis. Helix angles on end mills affect the strength of the cutting edges, the distribution of cutting forces, and chip evacuation.

High Efficiency Milling

HEM. A milling strategy that uses low radial depth of cut and high axial depth of cut and feed. High Efficiency Milling can reduce tool wear and increase material removal rate.

horizontal mill

A mill in which the spindle is oriented horizontally. On a horizontal mill, the Z axis describes left-to-right movement, the X axis describes towards-and-away movement, and the Y axis describes up-and-down movement.

Imperial

A system of measurement used primarily in the United States, the United Kingdom, Myanmar, and Liberia. The Imperial System uses inches and feet to measure length.

inches per minute

ipm. A unit of feed measurement that indicates how far in inches a tool advances along a toolpath in one minute. Inches per minute is the Imperial unit of measurement for feed input into CNC machines.

inches per revolution

ipr. A unit of feed measurement that indicates how far in inches a tool advances along a toolpath in one rotation. Inches per revolution is the Imperial unit of measurement for feed per revolution.

inches per tooth

ipt. A unit of feed measurement that indicates the amount of material each tooth of a cutting tool removes during one tool rotation. Inches per tooth is the Imperial unit of measurement for feed per tooth.

internal features

A channel, recess, or hole in a workpiece or part. Internal features include pockets and slots.

ipm

Inches per minute. A unit of feed measurement that indicates how far in inches a tool advances along a toolpath in one minute. Ipm is the Imperial unit of measurement for feed input into CNC machines.

ipt

Inches per tooth. A unit of feed measurement that indicates the amount of material each tooth of a cutting tool removes during one tool rotation. Ipt is the Imperial unit of measurement for feed per tooth.

length of cut

The maximum amount of the peripheral cutting edges of an end mill that can engage with a workpiece. Length of cut determines how deeply the end mill can cut with its peripheral cutting edges in a single pass.

linear axes

An imaginary straight line that is used to measure the location of an object in three-dimensional space. Axes in the Cartesian coordinate system include the X, Y, and Z axes.

locked out

Isolated from power sources and de-energized of stored energy. Only authorized employees should touch a machine that is locked out.

m/min

Meters per minute. A metric measurement of cutting speed that describes the amount of workpiece material that the cutting tool contacts in one minute. M/min depends on both the cutter diameter and rpm.

machine guards

A shield or cover over hazardous areas on a machine. Machine guards prevent accidental contact with body parts and prevent debris, such as chips, from exiting the machine.

machine tool

A power-driven piece of equipment that cuts or forms metal or other materials. Machine tools, which include CNC and manual mills, can hold a variety of cutting tools or dies.

machining

Manufacturing a part by using a tool to remove material in the form of chips. Milling, drilling, turning, sawing, and grinding are all various forms of machining operations.

material removal rate

MRR. The volume of workpiece material a cutting operation removes in a given amount of time. Material removal rate, sometimes referred to as MRR or Q, helps to measure an operation’s efficiency and is measured in cubic inches or centimeters per minute.

meters per minute

m/min. A metric measurement of cutting speed that describes the amount of workpiece material that the cutting tool contacts in one minute. Meters per minute depends on both the cutter diameter and rpm.

metric

A standard system of measurement based on the gram, liter, and meter. Metric system measurements are widely recognized as standard internationally.

millimeters per minute

mm/min. A unit of feed measurement that indicates how far in millimeters a tool advances along a toolpath in one minute. Millimeters per minute is the metric unit of measurement for feed input into CNC machines.

millimeters per revolution

mm/rev. A unit of feed measurement that indicates how far in millimeters a tool advances along a toolpath in one rotation. Millimeters per revolution is the metric unit of measurement for feed per revolution.

millimeters per tooth

mm/tooth. A unit of feed measurement that indicates the amount of material each tooth of a cutting tool removes during one tool rotation. Millimeters per tooth is the metric unit of measurement for feed per tooth.

milling

A metal cutting operation that uses a rotating multi-point tool to remove metal from the surface of a workpiece. Milling is used to produce a variety of workpiece shapes and features, including contours, slots, and flat surfaces.

mm/min

Millimeters per minute. A unit of feed measurement that indicates how far in millimeters a tool advances along a toolpath in one minute. Mm/min is the metric unit of measurement for feed input into CNC machines.

mm/tooth

Millimeters per tooth. A unit of feed measurement that indicates the amount of material each tooth of a cutting tool removes during one tool rotation. Mm/tooth is the metric unit of measurement for feed per tooth.

MRR

Material removal rate. The volume of workpiece material a cutting operation removes in a given amount of time. MRR, sometimes referred to as material removal rate or Q, helps to measure an operation's efficiency and is measured in cubic inches or centimeters per minute.

Multi-axis CNC mills

A CNC mill that has more than three linear and rotational axes. Multi-axis CNC machines can create particularly complex and highly precise parts.

multi-axis milling

A milling process that cuts in four or more linear and rotational axes simultaneously. Multi-axis milling can create particularly complex three-dimensional shapes.

non-center cutting

An end mill in which the cutting edges on the end face do not extend to the center of the tool. Non-center cutting end mills cannot cut straight down into a workpiece.

peripheral cutting edges

The cutting edges along the side of an end mill. Peripheral cutting edges are important in a variety of end milling operations, including creating slots and pockets.

peripheral milling

A milling operation in which the mill removes material from the outer edges of a workpiece. Peripheral milling primarily cuts with the peripheral cutting edges of the cutting tool.

personal protective equipment

PPE. Any of the safety equipment that workers wear or use to prevent injury in the workplace. Personal protective equipment includes safety glasses, steel-toed boots, and hardhats.

pi

A special constant value that relates the diameter of a circle to its circumference. Pi is roughly 3.14 and is used to find the circumference and area of a circle.

plunging

A strategy for creating internal features that moves an end mill straight down into the workpiece in the Z axis. Plunging operations can quickly remove large amounts of material and must use a center cutting end mill.

pocket

An interior recess that is cut into the surface of a part and is wider than the tool’s diameter. Pockets can be circular, rectangular, or irregular.

pocket milling

A milling process that creates a wide recess in a workpiece. Pocket milling creates a cavity that is wider than the tool’s diameter.

profile milling

The process of milling the overall shape or outline of a part. Profile milling often creates linear, angled, or contoured surfaces.

radial depth of cut

AE. The amount of an end mill’s diameter that is engaged with the workpiece in a single pass. Radial depth of cut, also known as stepover or AE, is generally 75% or less of the tool diameter.

ramp angle

The angle at which the tool engages with the workpiece during a ramping operation. Ramp angles are typically between 1° and 3° for harder workpiece materials and between 3° and 10° for softer workpiece materials.

ramping

A strategy for creating internal features that moves an end mill in the Z axis and one other linear axis simultaneously. Ramping operations reduce tool wear and can create tighter tolerances than plunging.

revolutions per minute

rpm. A measurement of speed that tracks how many times a machine component rotates in one minute. Revolutions per minute measures the spindle speed on a milling machine.

rotational axes

The axes that describe turning or rotation around the linear axes. The rotational axes are the A, B, and C axes.

roughing

An initial machining operation that removes material rapidly without regard to surface finish. Roughing achieves the basic workpiece shape and dimensions.

rpm

Revolutions per minute. A measurement of speed that tracks how many times a machine component rotates in one minute. RPM measures the spindle speed on a milling machine.

safety glasses

A form of protective eyewear, usually made of thick plastic, that shields the eyes from flying debris and other potentially hazardous materials. Safety glasses protect machine operators from chips.

sfm

Surface feet per minute. An Imperial measurement of cutting speed that describes the amount of workpiece material the cutting tool contacts in one minute. Sfm depends on both the tool diameter and rpm.

slot milling

A milling process that creates a narrow channel in a workpiece. Slot milling, sometimes called slotting, creates a recess that is often the same width as the tool’s diameter.

slots

A narrow channel cut into the surface of a workpiece. Slots made by end mills are typically shallow, curved, or angled.

slotting

A milling process that creates a narrow channel in a workpiece. Slotting, sometimes called slot milling, creates a recess that is often the same width as the tool’s diameter.

specifications

A description of the essential physical and technical properties of a finished part. Specifications outline important information, including finished part dimensions and acceptable tolerance ranges.

speed

The rate at which the tool or workpiece rotates during a cutting operation. Speed in an end milling operation refers to how quickly the end mill rotates.

spindle

A rotating component of a machine tool. A mill's spindle holds and rotates cutting tools.

spindle speed

The rate at which the machine spindle rotates. Spindle speed is typically measured in revolutions per minute (rpm).

square end mill

An end mill with a 90° angle between the peripheral cutting edges and the end face. Square end mills cut features with right angles into workpieces.

stepover

The amount of an end mill’s diameter that is engaged with the workpiece. Step-over, also known as radial depth of cut or AE, is generally 75% or less of the tool diameter.

surface feet per minute

sfm. An Imperial measurement of cutting speed that describes the amount of workpiece material the cutting tool contacts in one minute. Surface feet per minute depends on both the tool diameter and rpm.

surface finish

The degree of roughness and variation on the surface of a part after it has been manufactured. Surface finish is typically smoother when you use an end mill with more flutes.

surface speed

The amount of workpiece material a cutting tool contacts in one minute. Surface speed, also called cutting speed, is measured in surface feet per minute (sfm) or meters per minute (m/min).

tagged out

Including a prominent visual warning that indicates the machine should not be turned on. Tagged out machines must not be operated until the tag is removed by an authorized employee.

three-dimensional profile milling

A milling process that moves the tool in three linear axes simultaneously. Three-dimensional profile milling, sometimes called contouring, can create complex and rounded features in a workpiece.

tolerances

The allowable deviation from a given dimension. Tolerances indicate the allowable difference between a physical feature and its intended design.

tool geometry

The collective angles, edges, and shape formed by the dimensions of the cutting tool and the positioning of the tool. Tool geometry is a key factor in tool life, production efficiency, and part quality.

tool wear

The gradual erosion of material from the surface of a cutting tool due to contact and friction. Tool wear can affect part dimensions and part tolerance.

toolpath

The course a cutting tool follows as it shapes a workpiece. Toolpaths are composed of a series of Cartesian coordinate positions.

T-slot

A type of slot where some workpiece material overhangs the recess in the workpiece. T-slots are common features used in machine worktables.

T-slot cutter

A specialized end mill with cutting edges on the periphery of a wide disc. T-slot cutters, sometimes called T-slot end mills, are used to create specialized T-shaped slots, such as the slots in machine worktables that hold workholding devices.

T-slot end mill

A specialized end mill with cutting edges on the periphery of a wide disc. T-slot end mills, sometimes called T-slot cutters, are used to create specialized T-shaped slots, such as the slots in machine worktables that hold workholding devices.

two-dimensional profile milling

A milling process that moves the tool in two linear axes simultaneously. Two-dimensional profile milling can create angled or curved features in a workpiece.

vertical mill

A mill in which the spindle is oriented vertically. On a vertical mill, the Z axis describes up-and-down movement, the X axis describes left-to-right movement, and the Y axis describes towards-and-away movement.

workholding

A device used to support, locate, and hold a workpiece. Workholding is specific to the machine tool and cutting operation.

worktables

A component on a mill that supports the workpiece and any workholding device during machining. Worktables on the mill have T-slots that allow operators to attach a range of workholding devices.

X axis

The linear axis representing coordinate positions along a line parallel to the longest edge of a mill’s worktable. The X axis runs to the left and right on a vertical mill.

Y axis

The linear axis representing coordinate positions along a line parallel to the shortest edge of a mill’s worktable. The Y axis runs from the front to the back of a vertical mill.

Z axis

The linear axis representing coordinate positions along a line parallel to the spindle. The Z axis runs up and down on a vertical mill.