| adjacent |
In a triangle, a side that touches an angle. The adjacent sides form the angle. |
| aeronautical |
Having to do with airplanes or other flying craft. Aeronautical applications tend to require extremely precise tolerances. |
| approach distance |
A short distance added to the beginning of a toolpath. Approach distance helps to prevent damage to the machine and the workpiece. |
| arc center method |
A method for programming circular tool movements that indicates the location of the arc's center along the X and Y axes using I and J codes. The arc center method is usually used for full-arc motions. |
| arc-in motion |
A partial-arc motion that leads into a larger-arc motion. Arc-in and arc-out motions leave a smooth surface finish. |
| arc-out motion |
A partial-arc motion that exits from a larger-arc motion. Arc-out and arc-in motions leave a smooth surface finish. |
| axes |
Imaginary lines that pass through the center of a point or object. Axes are used to describe the positions of objects on the Cartesian coordinate system. |
| bolt-hole pattern |
A series of equally spaced holes around the circumference of a larger imaginary circle. Bolt-hole patterns are calculated with trigonometry. |
| boxing routine |
A series of toolpaths used to machine a rectangular pocket. A boxing routine starts in the center of the pocket and moves outward in a rectangular pattern. |
| CAD/CAM |
Computer-aided design/computer-aided manufacturing. The use of computers to aid in the design and manufacturing of a part. CAD/CAM makes it comparatively easy to machine complex surfaces, especially parts with three-dimensional contour features. |
| calculator |
A small, handheld device used to solve mathematical problems. Calculators can be useful for finding the sine, cosine, or tangent of an angle. |
| Cartesian coordinate system |
The system that describes the position of any point or object in three-dimensional space by expressing its distance from a fixed position along linear axes. The Cartesian coordinate system is used to describe measurements in CNC milling and turning. |
| chamfer |
An angled surface added to an edge of a workpiece. Chamfers replace a sharp edge with a 45° angle. |
| chatter |
The development of surface imperfections on the workpiece caused by vibrations of the cutting tool. Chatter can occur if step-over is either too little or too much. |
| circumference |
The distance around a curve or circle. The circumference is the circle's outer perimeter. |
| clearance |
Any useful space that is intentionally maintained between components. Clearance is often necessary to prevent machine damage. |
| computer numerical control mills |
CNC mills. A milling machine that makes precise cuts according to numerical data. Computer numerical control mills are much more precise than their manual counterparts. |
| contour features |
A curved part of a workpiece. Contour features are complex and generally calculated using CAD/CAM software. |
| cosine |
In a right triangle, the ratio of the length of the side adjacent to the angle and the hypotenuse. The cosine of a right triangle can be found by calculating the ratio as a division. |
| cutter radius compensation |
CRC. An offset that accounts for variations in tool diameter. Cutter radius compensation is necessary for tools that continuously cut in the X or Y axis. |
| 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. |
| diameter |
The distance from edge to edge of the widest point of a circle. The diameter of a circle is always twice its radius. |
| end mill |
A long, thin milling cutter with a flat bottom and cutting edges that wind up the sides. End mills have helical flutes and relatively small diameters. |
| face mill |
A flat milling cutter with multiple cutting teeth on its periphery. Face mills rapidly remove metal from the top surface of a workpiece. |
| face milling |
A milling operation in which the surface of the workpiece is perpendicular to the spindle axis. Face milling is primarily used to mill the top surface of the part. |
| finishing pass |
A cutting pass that produces the surface finish and brings a feature to its proper size. The finishing pass is typically the last operation in the part program. |
| G code |
A code that determines the type of operation performed on the machine. G codes select the type of motion, speed or feed mode, etc. |
| geometry |
A branch of mathematics that involves the measurements, properties, and relationships of dimensional objects. Geometry is used in CNC machining. |
| hypotenuse |
In a right triangle, the side located opposite the right angle. The hypotenuse is the longest side of the triangle. |
| I code |
The program code that indicates the location of an arc's center along the X axis. I and J codes are used for the arc center method. |
| isosceles right triangle |
A triangle with one 90° angle and two 45° angles. The two 45° sides of an isosceles right triangle are always equal in length. |
| J code |
The program code that indicates the location of an arc's center along the Y axis. J and I codes are used for the arc center method. |
| length-to-diameter ratio |
A ratio comparing the length of a cylindrical tool to its diameter. Higher length-to-diameter ratios offer less rigidity. |
| machine control |
A computer that directs a CNC machine. The machine control interprets the part program and relays its instructions to the CNC machine. |
| milling cutter |
A multipoint tool that removes metal from the surface of a workpiece. Milling cutters can create parts with complex shapes. |
| offset |
A fixed adjustment that moves the tool to compensate for the tool's length, width, or another factor. Offsets help to ensure that finished parts are to specifications. |
| origin |
The fixed center point of the Cartesian coordinate system. The origin has a numerical value of zero for any axis. |
| part program |
A series of instructions used by a CNC machine to perform the necessary sequence of operations to machine a specific workpiece. Part programs are written in G code. |
| pocket |
An interior recess that is cut into the surface of a workpiece. Pockets can be circular, rectangular, or a combination of the two. |
| program zero |
The position that acts as the origin for the part program of each particular workpiece. Program zero is selected by the part programmer. |
| programming language |
A language used to program or provide directions to a computer or machine. The programming language used by CNC machines is called G code. |
| R code |
The program code that indicates the length of an arc's radius. In certain canned cycles, an R code indicates the R level for tool return. |
| radius |
A straight line extending from the center point to the periphery of a circle. The radius of a circle is always one-half of its diameter. |
| radius method |
A method for programming circular tool movements that indicates the size of the arc's radius using an R code. The radius method is best used for partial-arc motions. |
| right triangles |
A triangle that includes a 90° angle as one of its three angles. Right triangles are often used in drilling calculations. |
| sine |
In a right triangle, the ratio of the length of the side opposite the angle and the hypotenuse. The sine of a right triangle can be found by calculating the ratio as a division. |
| spot drill |
A short, sturdy drill used to start a hole and accurately locate it. Most spot drills have a 90° tip. |
| step-over |
The amount of the cutter's diameter that is engaged in a cut. Step-over is generally 75% or less of the cutter's diameter. |
| symmetrical parts |
A part that can be divided into two equal halves with identical features that are equal distances from the centerline. Symmetrical parts typically have program zero placed in the center. |
| tangent |
In a right triangle, the ratio of the length of the side opposite the angle and the side adjacent to the angle. The tangents of a right triangle can be found by calculating the ratio as a division. |
| three-dimensional |
Having length, width, and depth. Three-dimensional parts can be machined with CNC machines. |
| through holes |
A hole that passes completely through a workpiece. Through holes require that the depth of the hole, the length of the drill tip, and a small amount of additional clearance all be calculated. |
| toolpaths |
The series of coordinate positions that dictate the movement of a tool during a machining operation. Toolpaths are programmed using G code. |
| trigonometry |
A branch of mathematics that addresses the measurements and relationships of triangles and their components. Trigonometry is often used in milling calculations. |
| twist drill |
A common drill characterized by helical flutes along its length and two cutting edges at the drill point. Twist drilling is usually preceded by spot drilling. |
| X axis |
The linear axis representing the longest distance of travel parallel to the worktable, or left to right on a vertical mill. The X axis is perpendicular to the Y and Z axes. |
| Y axis |
The linear axis representing the shortest distance parallel to the worktable, or towards and away on a vertical mill. The Y axis is perpendicular to the X and Z axes. |
| Z axis |
The linear axis that represents motion towards and away from the worktable, or up and down on a vertical mill. The Z axis is perpendicular to the X and Y axes. |