absolute coordinates

A series of numerical positions that are calculated from a fixed point of origin.

arc center method

A method for programming circular tool movements that requires an I code and J code to indicate the location of the arc's center along the X- and Y-axes.

canned cycle

A sequence of machine operations initiated by a single G code. Canned cycles act as shortcuts that simplify the program.

circular interpolation

A translation of linear axis positions into curved tool motions. Circular interpolation requires an endpoint, a feed rate, a center, a radius, and a direction of movement.

computer-aided design

The use of computers and software to design a part.

computer-aided manufacturing

The use of computers and software to manufacture a part.

cutter radius compensation

An offset used on the machining center that accounts for variations in tool diameter. CRC is only necessary for tools that continuously cut along a horizontal plane.

end milling

A milling operation that uses a narrow cutter to machine surfaces both parallel and perpendicular to the spindle axis. End milling may cut with both the bottom and sides of the cutting tool.

F code

A program code that determines the feed during a cutting operation.

face milling

A milling operation in which the surface of the workpiece is perpendicular to the spindle axis. Face milling primarily cuts with the bottom of the cutting tool.

feed

The rate that the cutting tool travels along the surface of the workpiece. In milling programs, feed is measured in inches per minute (ipm).

G code

A program code that determines the type of operation performed on the machine.

H code

A program code that indicates the matching tool length offset for a particular cutting tool.

I code

For circular interpolation, the program code that indicates the location of the arc's center along the X-axis. I and J codes are used for the arc center method.

inch per revolution

A unit of measurement for feed that indicates the fraction of an inch that the tool travels in one revolution.

inch per tooth

A unit of measurement for feed that indicates the thickness of material removed by each cutting edge as it enters the workpiece.

inches per minute

A unit of measurement for feed that indicates how many inches the cutting tool has traveled in one minute.

incremental coordinates

A series of numerical positions that use the previous position as the point of origin for the next position.

J code

For circular interpolation, the program code that indicates the location of the arc's center along the Y-axis. I and J codes are used for the arc center method.

linear interpolation

A translation of linear axis positions into straight vertical, horizontal, or diagonal tool movements. Linear interpolation requires an endpoint and a feed rate.

mode

A programmed function that stays in effect until it is either cancelled or substituted with another function.

optional stop

A code that pauses the program if the appropriate switch is selected on the machine. Optional stops allow the operator to inspect the machine between operations.

P code

A program code that indicates the name of the subprogram to execute.

part program

A series of numerical instructions used by a CNC machine to perform the necessary sequence of operations to machine a specific workpiece.

peck drilling

A drilling operation that periodically retracts the tool to clear chips or flood the hole with coolant. Peck drilling is often used for holes that are three or four times deeper than the drill diameter.

pocket

An interior recess that is cut into the surface of a workpiece.

program zero

The position that acts as the origin for the part program of a particular workpiece. This position is unique to each workpiece design, and it is selected by the part programmer.

prove out

To perform a series of steps to manually verify the accuracy of a part program. Operators use dry runs and single blocking to thoroughly check a program.

R code

For circular interpolation, the program code that indicates the length of the arc's radius. In certain canned cycles, an R code indicates the R level for tool return.

R level

The imaginary plane parallel to the X- and Y-axes indicating the safe distance for rapid tool movement from one operation to the next. A typical R level is 0.1 inches away from the part surface.

radius

The distance between a point on a circle and its center. A radius also indicates a point that is the same distance from any point located on an arc.

radius method

A method for programming circular tool movements that requires an R code to indicate the size of the arc's radius. The control calculates the location of the arc's center.

rapid

To move at the machine's maximum rate of travel.

rapid positioning

The movement of machine components at the fastest possible rate of travel. Rapid positioning merely requires an endpoint for the movement.

revolutions per minute

A unit of measurement for speed that indicates how many times the cutting tool has rotated in one minute.

S code

A program code that determines the speed during a cutting operation.

speed

The rate at which a cutting edge of the tool moves past the workpiece surface at the point of contact. Speed is measured in revolutions per minute (rpm).

spot drilling

The use of a shorter, sturdier drill to locate a hole for drilling. The small hole created by the spot drill prevents the regular drill from wandering off center.

subprogram

A program separate from the main program that executes a series of operations that occurs multiple times during the machining cycle. Subprograms shorten and simplify manual programming.

T code

A program code used to indicate the specific tool for a tool change.

tapping

The process of cutting internal threads in a round hole with a multi-point tool.

tool length offset

An offset used on the machining center that accounts for variations in tool length along the Z-axis. Each tool requires its own offset, which is measured from the tip of the tool to the gage line.

toolchanger

A device that arranges multiple cutting tools in order and then positions these cutting tools for replacement in the machining center.

toolpath

The series of coordinate positions that determine the movement of a tool during a machining operation.

turning center

A sophisticated CNC lathe that specializes in turning, boring, drilling, and threading operations, all at the same location.

U code

A program code that determines incremental positions along the X-axis.

V code

A program code that determines incremental positions along the Y-axis.

W code

A program code that determines incremental positions along the Z-axis.

workshift offset

An offset used to adjust the location of every tool loaded in the machine. Workshift offsets change the position of the spindle on a machining center.

X code

A program code that indicates a specific coordinate position along the X-axis.

X-axis

On the mill, the linear axis representing coordinate positions along the longest distance parallel to the worktable.

Y code

A program code that indicates a specific coordinate position along the Y-axis.

Y-axis

On the mill, the linear axis representing coordinate positions along the shortest distance parallel to the worktable.

Z code

A program code that indicates a specific coordinate position along the Z-axis.

Z-axis

On the mill, the linear axis representing coordinate positions perpendicular to the worktable. The Z-axis is always parallel to the spindle.