Standard CNC Machining Process

CNC machining is a process suitable for producing high accuracy, high tolerance parts in prototype, one-off, and small to medium production runs. While parts are typically produced with tolerances ranging between +/- 0.001 in. to +/- 0.005 in., some machining machines can achieve tolerances of up to and greater than +/- 0.0005 in. The versatility of the machining process allows it to be used in a wide range of industries and for a variety of part features and designs, including slots, chamfers, threads, and pockets. The most common CNC machining operations include:

•      Face machining

•      Plain machining

•      Angular machining

•      Form machining

Face Machining

Face machining refers to machining operations in which the cutting tool’s axis of rotation is perpendicular to the surface of the workpiece. The process employs face machining cutters which have teeth both on the periphery and tool face, with the peripheral teeth primarily being used for cutting and the face teeth being used for finishing applications. Generally, face machining is used to create flat surfaces and contours on the finished piece and is capable of producing higher quality finishes than other machining processes. Both vertical and horizontal machining machines support this process.

Types of face machining include end machining and side machining, which use end machining cutters and side machining cutters, respectively.

Plain Machining

Plain machining, also known as surface or slab machining, refers to machining operations in which the cutting tool’s axis of rotation is parallel to the surface of the workpiece. The process employs plain machining cutters which have teeth on the periphery that perform the cutting operation. Depending on the specifications of the machining application, such as the depth of the cut and the size of the workpiece, both narrow and wide cutters are used. Narrow cutters allow for deeper cuts, while wider cutters are used for cutting larger surface areas. If a plain machining application requires the removal of a large amount of material from the workpiece, the operator first employs a coarse-toothed cutter, slow cutting speeds, and fast feed rates to produce the custom-designed part’s approximate geometry. Then, the operator introduces a finer toothed cutter, faster cutting speeds, and slower feed rates to produce the details of the finished part.

Angular Machining

Angular machining, also known as angle machining, refers to machining operations in which the cutting tool’s axis of rotation is at an angle relative to the surface of the workpiece. The process employs single-angle machining cutters—angled based on the particular design being machined—to produce angular features, such as chamfers, serrations, and grooves. One common application of angular machining is the production of dovetails, which employs 45°, 50°, 55°, or 60° dovetail cutters based on the design of the dovetail.

Form Machining

Form machining refers to machining operations involving irregular surfaces, contours, and outlines, such as parts with curved and flat surfaces, or completely curved surfaces. The process employs formed machining cutters or fly cutters specialized for the particular application, such as convex, concave, and corner rounding cutters. Some of the common applications of form machining include producing hemispherical and semi-circular cavities, beads, and contours, as well as intricate designs and complex parts with a single machine setup.