approach

A slight distance added to a toolpath at the beginning of a cut for safety reasons.

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 Yaxes. The arc center method is best used for fullarc motions.

arcin motion

A partialarc motion that leads into a larger arc motion. Arc in and arc out motions leave a smooth surface finish.

arcout motion

A partialarc motion that exits from a larger arc motion. Arc in and arc out motions leave a smooth surface finish.

bolthole pattern

A common specification on milled parts that requires a series of equally spaced holes around the circumference of a larger imaginary circle.

boxing routine

A series of increasingly larger rectangular toolpaths used to machine a rectangular pocket.

CAD/CAM

Computeraided design/computeraided manufacturing. CAD/CAM is the use of software to aid in the design and manufacturing of a part.

chamfer

A small, angled surface added to an edge of a workpiece. A chamfer removes the sharp edge and helps eliminate burrs.

clearance

Any useful space that is intentionally maintained between components.

contour feature

A part feature that is nonlinear, or curved.

coordinate system

The numerical system that describes the location of an object by numerically expressing its distance from a fixed position along three linear axes. The coordinate system consists of the X, Y, and Zaxes.

cosine

In a right triangle, the ratio of the length of the side adjacent to the angle divided by the hypotenuse.

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.

deflection

The unintended movement or repositioning of a component due to a mechanical force. Deflection of a cutting tool can cause poor surface finish and inaccurate dimensions.

end mill

A thin, tall mill cutter with a flat bottom and cutting edges that wind up the sides. Both the bottom and side of the end mill provide cutting surfaces during milling operations.

face mill

A flat mill cutter with multiple cutting teeth surrounding the tool. The bottom of the face mill is primarily the cutting surface during milling operations.

face milling

A milling operation in which the surface of the workpiece is perpendicular to the spindle axis. Face milling primarily is used to mill the top surface of the part.

finishing pass

A final cutting pass that produces the necessary surface finish and brings a feature to its proper size.

finishing stock

The small amount of material that is intentionally left for a finishing pass.

hypotenuse

In a right triangle, the side located opposite the right angle.

I code

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

J code

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

lengthtodiameter ratio

A ratio describing the length of a cylindrical tool or workpiece compared to its diameter. Higher lengthtodiameter ratios offer less rigidity.

milling cutter

Any multipoint tool that is used to remove metal from the surface of a workpiece.

part program

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

pocket

An interior recess that is cut into the surface of a workpiece. Pockets may be round or rectangular.

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.

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.

radius method

A method for programming circular tool movements that requires an R code to indicate the size of the arc's radius. The radius method is best used for partialarc motions.

ramping motion

A linear motion of the tool that is required for a control to adjust for a particular tool offset.

sine

In a right triangle, the ratio of the length of the side opposite the angle divided by the hypotenuse.

spot drill

A short, sturdy drill used to start a hole and accurately locate it. Most spot drills have a 90° tip.

stepover

The size of the cutter's diameter that is engaged in a cut. The stepover should be 75% to 80% of the cutter's diameter.

symmetrical part

A part that can be divided by a line into two equal halves, with identical features that are equal distances from the dividing line. Both sides appear as mirror images of each other.

tangent

In a right triangle, the ratio of the length of the side opposite the angle divided by the adjacent side.

toolpath

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

trigonometry

The branch of mathematics that addresses the measurements and relationships of a triangle and its parts.

wear offset

An offset used on a turning center and some machining centers that allows for the slight adjustment of tool tip location. Wear offsets account for part deflection, tool wear, etc.

Xaxis

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

Yaxis

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

Zaxis

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