Glossary Terms for

CNC Machining

CNC machining is a subtractive manufacturing process that uses computer-controlled cutting tools to remove material from a solid workpiece, producing parts with precise dimensions, tight tolerances, and specific surface finishes.

Ball Nose End Mill
A cylindrical milling cutter with a hemispherical cutting tip, used for machining curved surfaces, 3D contours, fillets, and complex geometries.
Boring
A machining operation that uses a single-point tool to enlarge and precisely finish a pre-drilled or cast hole.
CAM Programming (Computer-Aided Manufacturing)
The process of using software to generate CNC tool paths and machine code from 3D CAD models.
CNC Machining Center
A multi-axis CNC machine tool capable of performing milling, drilling, tapping, boring, and contouring from a single setup, typically equipped with an automatic tool changer for unattended multi-operation production.
CNC Milling
A subtractive machining process in which rotating multi-flute cutting tools remove material from a stationary or moving workpiece.
CNC Turning (Lathe)
A machining process in which a stationary cutting tool removes material from a rotating cylindrical workpiece.
Chip Load
The thickness of material removed by each cutting tooth per revolution.
Coolant
A liquid or mist applied to the cutting zone during machining to dissipate heat, extend tool life, flush chips, and improve surface finish.
Counterbore
A cylindrical recess machined concentric to an existing hole to allow the head of a socket cap screw or bolt to sit flush with or below the part surface.
Countersink
A conical machining operation that creates a beveled recess at the opening of a drilled hole to accept the tapered head of a flathead fastener flush with the part surface.
Datum
A reference feature such as a point, line, axis, or plane from which part dimensions and tolerances are measured.
Depth of Cut
The amount of material removed per machining pass, measured radially for milling or from the outer surface inward for turning.
Drilling
A machining operation using a rotating drill to create cylindrical holes.
End Mill
A multi-flute rotating cutting tool used for profiling, pocketing, slotting, facing, and plunging operations.
Face Milling
A milling operation that uses a large-diameter, insert-style cutter to rapidly remove material from a flat workpiece surface, producing a smooth, flat face.
Feed Rate
The speed at which the cutting tool advances relative to the workpiece, expressed in inches per minute.
Fixturing (Workholding)
The devices and methods used to securely hold and position a workpiece on the machine table.
G-Code
The standardized CNC programming language that controls machine motion, spindle speed, feed rate, coolant, and auxiliary functions.
GD&T (Geometric Dimensioning and Tolerancing)
An engineering drawing standard (ASME Y14.5) that uses symbols to precisely define the allowable variation in part geometry, including size, form, orientation, location, and runout.
M-Code
Machine function codes in CNC programming that control auxiliary operations including spindle on/off, coolant on/off, tool changes, pallet changes, and program stop.
Reaming
A precision finishing operation that uses a multi-flute reamer to enlarge a drilled hole to a specific, tight-tolerance diameter.
Runout
The deviation of a rotating feature (spindle, tool, or machined journal) from true circular motion.
Spindle Speed (RPM)
The rotational speed of the machine spindle and cutting tool, expressed in revolutions per minute.
Surface Finish (Machined)
The texture quality of a machined surface, expressed as an Ra value in microinches or micrometers.
Tapping
A machining operation that cuts internal threads in a pre-drilled hole using a tap.
Tolerance (Machining)
The permissible dimensional variation specified on an engineering drawing.
Tool Path
The programmed trajectory of the cutting tool relative to the workpiece, generated by CAM software.
Work Offset (Fixture Offset)
A CNC controller parameter that defines the position of the workpiece coordinate system relative to the machine coordinate system.

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