Machine Shop Glossary
242+ essential terms covering CNC machining, aerospace manufacturing, certifications, and precision engineering.
3-Axis Machining
CNC machining using three linear axes (X, Y, Z). Most common and cost-effective for simple geometries and 2.5D features.
4-Axis Machining
CNC machining adding one rotary axis (typically A-axis) to standard 3-axis motion. Allows machining on multiple sides without refixturing.
5-Axis Machining
CNC machining using five axes of motion simultaneously, allowing complex geometries to be cut from multiple angles in a single setup. Reduces setup time and improves accuracy for aerospace and medical parts.
6061-T6
Most common general-purpose aluminum alloy with good machinability, weldability, and corrosion resistance. T6 temper indicates solution heat-treated and artificially aged.
7075-T6
High-strength aerospace aluminum alloy with zinc as primary alloying element. Excellent strength-to-weight ratio but lower corrosion resistance than 6061.
Abrasive Machining
Material removal using bonded or loose abrasive particles. Includes grinding, honing, lapping, and polishing operations.
Accuracy
The degree to which a machined dimension conforms to its intended value. Expressed as deviation from nominal (e.g., ±0.001").
Adaptive Machining
CNC machining that automatically adjusts cutting parameters based on real-time feedback from sensors measuring forces, vibration, or tool wear.
Alloy
A metal made by combining two or more metallic elements to achieve specific properties like strength, hardness, or corrosion resistance.
Aluminum
Lightweight, corrosion-resistant metal commonly used in aerospace and automotive applications. Common alloys include 6061 and 7075.
Annealing
Heat treatment process of heating metal to a specific temperature then slowly cooling to relieve internal stresses and increase ductility.
Anodizing
An electrochemical process that creates a protective oxide layer on aluminum parts, improving corrosion resistance and allowing for coloring.
ASME Y14.5
American Society of Mechanical Engineers standard defining the GD&T (Geometric Dimensioning and Tolerancing) symbology and rules.
AS9100
Quality management system standard specifically for aerospace industry suppliers. Builds on ISO 9001 with additional aerospace requirements.
Axis
A direction of motion in CNC machining. Standard mills have 3 axes (X, Y, Z); advanced machines add rotary axes (A, B, C).
Backlash
The clearance or play between mating parts, particularly in gears and lead screws. Can cause positioning errors in CNC machines.
Ball End Mill
A cutting tool with a hemispherical end used for 3D contouring, profiling, and creating curved surfaces.
Ball Screw
Precision linear actuator using recirculating ball bearings between screw and nut. Provides high efficiency and minimal backlash in CNC machines.
Bead Blasting
Surface finishing process using fine glass beads propelled by air to create a uniform matte finish. Removes machine marks without dimensional change.
Bevel
An angled surface cut at other than 90 degrees to an adjacent surface. Similar to chamfer but may be at any angle.
Blank
Raw material cut to approximate size before machining. Also called a slug or workpiece.
Blind Hole
A hole that does not go completely through the workpiece. Requires special consideration for tapping and chip evacuation.
Boring
A machining operation that enlarges an existing hole to precise dimensions using a single-point cutting tool.
Brass
A copper-zinc alloy known for excellent machinability, corrosion resistance, and electrical conductivity.
Broaching
A machining process using a toothed tool to remove material in a single pass, commonly used for keyways and splines.
Bronze
Copper-tin alloy with excellent wear resistance and low friction. Used for bushings, bearings, and marine applications.
BTA Drilling
Boring and Trepanning Association drilling method for deep holes using external chip removal. More rigid than gun drilling.
Burr
A raised edge or small piece of material remaining attached to a workpiece after machining. Requires deburring for quality finish.
CAD
Computer-Aided Design. Software used to create 2D drawings and 3D models of parts before manufacturing.
CAM
Computer-Aided Manufacturing. Software that converts CAD models into toolpaths and G-code for CNC machines.
CAGE Code
Commercial and Government Entity code. A 5-character identifier assigned to companies doing business with the federal government.
Canned Cycle
Pre-programmed CNC routines for common operations like drilling, tapping, and boring. Simplifies programming and reduces errors.
Carbide
Tungsten carbide tooling material offering high hardness and wear resistance. Used for high-speed machining of tough materials.
Castings
Parts formed by pouring molten metal into a mold. Often require machining to achieve final dimensions.
CBN
Cubic Boron Nitride. Second hardest known material after diamond. Used for machining hardened steels and superalloys.
Centerless Grinding
Grinding process where the workpiece is supported by a blade and regulating wheel rather than centers. Excellent for high-volume cylindrical parts.
Chamfer
A beveled edge created by cutting away a 90-degree corner, typically at 45 degrees. Used for deburring and assembly.
Chatter
Vibration during cutting that causes poor surface finish and tool wear. Caused by improper speeds, feeds, or setup.
Chip Load
The thickness of material removed by each cutting edge per revolution. Critical parameter for tool life and finish.
Chuck
A workholding device on a lathe that grips cylindrical workpieces. Types include 3-jaw, 4-jaw, and collet chucks.
Circular Interpolation
CNC capability to cut arcs and circles by coordinating simultaneous axis movements. Uses G02 (clockwise) and G03 (counter-clockwise) commands.
Climb Milling
Milling where the cutter rotates in the same direction as feed motion. Produces better finish but requires rigid setup.
CMM
Coordinate Measuring Machine. Precision inspection equipment that measures part geometry using a touch probe.
CNC
Computer Numerical Control. Automated control of machining tools via programmed commands.
Coating
Thin layers applied to cutting tools (TiN, TiAlN, DLC) or parts (anodizing, plating) to improve performance or corrosion resistance.
Collet
A type of chuck using a sleeve to grip round or hex stock with high precision and concentricity.
Concentricity
The condition where two or more cylindrical features share a common axis. Critical for rotating parts.
Conventional Milling
Milling where cutter rotation opposes feed direction. Causes work hardening but is more forgiving of loose setups.
Coolant
Fluid used during machining to cool the cutting zone, lubricate the tool, and flush chips. Types include water-soluble and oil-based.
Copper
Highly conductive metal with excellent thermal and electrical properties. Commonly machined for electrical and heat transfer applications.
Counterbore
A cylindrical flat-bottomed hole that allows a bolt head to sit flush with or below the surface.
Countersink
A conical hole allowing a flat-head screw to sit flush with the surface. Common angles are 82° and 90°.
Cp/Cpk
Process capability indices measuring how well a manufacturing process meets specifications. Cpk of 1.33 or higher typically required for aerospace.
Cutting Speed
The speed at which the cutting edge moves relative to the workpiece, measured in surface feet per minute (SFM).
Cylindrical Grinding
Grinding operation for producing precise cylindrical surfaces on shafts and pins. Can be performed between centers or centerless.
Datum
A theoretical exact plane, axis, or point from which dimensions are measured. Used in GD&T for part inspection.
DDTC
Directorate of Defense Trade Controls. U.S. State Department agency administering ITAR export controls.
Deburring
The process of removing burrs and sharp edges from machined parts using hand tools, tumbling, or automated methods.
Deep Hole Drilling
Drilling holes with depth-to-diameter ratios greater than 10:1. Requires specialized tooling and techniques.
Depth of Cut
The distance a cutting tool penetrates into the workpiece material. Affects material removal rate and tool life.
DFM
Design for Manufacturability. Engineering practice of designing parts that are easier and more cost-effective to manufacture.
Dial Indicator
Precision measuring instrument used to check runout, flatness, parallelism, and small dimensional variations.
Die
A tool used to cut external threads on a rod or bolt. Also refers to forming tools in stamping operations.
Dressing
Conditioning a grinding wheel to expose fresh abrasive grains and restore cutting ability. Essential for consistent grinding.
Drilling
Creating holes using a rotating drill bit. Different from boring, which enlarges existing holes.
DRO
Digital Read Out. Electronic display showing real-time position of machine axes relative to a set zero point.
Dry Machining
Machining without coolant. Used for certain materials and operations, requires appropriate tooling and parameters.
Ductility
A material's ability to be stretched into wire without breaking. Opposite of brittleness.
DUNS Number
Data Universal Numbering System. Nine-digit identifier for business entities, required for government contracting.
Dwell
A programmed pause in CNC operation, typically at the bottom of a hole for chip breaking or at tool entry/exit points.
EAR
Export Administration Regulations. U.S. Commerce Department export controls for dual-use commercial items.
ECCN
Export Control Classification Number. Five-character code identifying export-controlled items under EAR.
Edge Break
Removal of sharp edges, typically 0.005" to 0.015" radius or chamfer, to prevent injury and improve part handling.
EDM
Electrical Discharge Machining. Non-contact process using electrical sparks to remove material. Used for hard materials and complex shapes.
Electrode
In EDM, the shaped tool (usually graphite or copper) that creates the desired cavity shape through spark erosion.
Electroplating
Surface treatment depositing thin metal layer (chrome, nickel, zinc) using electrical current for corrosion protection or wear resistance.
End Mill
A rotary cutting tool used in milling machines for plunging, slotting, profiling, and facing operations.
Engraving
Cutting text, logos, or patterns into part surfaces for identification, traceability, or decoration.
Extrusion
Manufacturing process forcing material through a die to create continuous profiles. Common for aluminum shapes.
Face Milling
Milling operation that produces a flat surface perpendicular to the spindle axis.
Facing
Lathe operation that machines the end of a workpiece to create a flat surface perpendicular to the axis.
FAI
First Article Inspection. Comprehensive inspection of the first production part to verify compliance with specifications.
Feed Rate
The speed at which the cutting tool advances into the workpiece, measured in inches per minute (IPM) or per revolution (IPR).
Fillet
A rounded interior corner or edge, specified by radius. Reduces stress concentration in parts.
Finish Cut
Final machining pass with light depth of cut and optimized parameters to achieve required surface finish and dimensions.
Fixture
Custom workholding device designed to locate and secure a specific workpiece during machining.
Flatness
GD&T characteristic specifying how close a surface is to a true plane. Measured as total deviation.
Flood Coolant
Traditional machining coolant delivery flooding the cutting zone with high-volume fluid stream.
Flute
The helical groove in a drill, end mill, or tap that provides cutting edges and chip evacuation.
Fly Cutter
Single-point facing tool for milling machines. Produces excellent surface finish on large flat areas.
Forging
Metal forming process using compressive forces. Produces parts with superior grain structure and strength.
Form Tool
Cutting tool ground to a specific profile to produce complex shapes in a single pass.
G-code
Programming language used to control CNC machines. Commands specify movements, speeds, and operations.
Gage
A tool for measuring or checking dimensions. Types include go/no-go, plug, ring, and thread gages.
GD&T
Geometric Dimensioning and Tolerancing. System for defining and communicating engineering tolerances using symbols.
Grinder
Machine tool using an abrasive wheel to achieve fine finishes and tight tolerances on hardened materials.
Grit
The size of abrasive particles in grinding wheels and sandpaper. Higher numbers indicate finer particles.
Gun Drilling
Deep hole drilling technique using a single-flute drill with internal coolant delivery. Achieves depth-to-diameter ratios up to 100:1.
Hand Tap
Tap designed for manual operation, typically in a set of three (taper, plug, bottoming) for progressively cutting threads.
Hardening
Heat treatment process that increases metal hardness, typically by heating above critical temperature and quenching.
Hardness
A material's resistance to indentation and scratching. Measured on scales like Rockwell (HRC), Brinell, and Vickers.
Hastelloy
Nickel-based superalloy family with exceptional corrosion resistance. Used in chemical processing and marine applications.
Heat Treatment
Controlled heating and cooling of metals to modify properties like hardness, strength, and ductility.
Helix Angle
The angle of flutes on an end mill or drill relative to the axis. Affects cutting action and chip evacuation.
High Speed Machining
Machining at significantly higher speeds and feeds with lighter cuts, reducing cycle time while maintaining precision.
High Speed Steel (HSS)
Tool steel alloy maintaining hardness at high temperatures. Used for cutting tools, less expensive than carbide.
Holding Tolerance
The tightest tolerance a machine or process can consistently achieve. Important for capability planning.
Honing
Abrasive finishing process for achieving tight tolerances and surface finish on cylindrical bores.
Horizontal Machining Center
CNC mill with horizontal spindle orientation. Excellent chip evacuation and multi-side access with tombstones.
ID
Inside Diameter. The internal diameter of a hole, bore, or tube.
Inconel
Nickel-based superalloy family resistant to extreme temperatures and corrosion. Used in aerospace and chemical processing.
Indexable Tooling
Cutting tools with multiple cutting edges that can be rotated to present fresh edges when worn.
Insert
Replaceable cutting tip (carbide, ceramic, or CBN) clamped into a tool holder. More economical than solid tools.
Interpolation
CNC capability to coordinate multiple axis movements simultaneously to create lines, arcs, and complex paths.
ISO 9001
International quality management system standard applicable to any industry. Foundation for AS9100 and ISO 13485.
ISO 13485
Quality management system standard specifically for medical device manufacturers.
ITAR
International Traffic in Arms Regulations. U.S. export control regulations for defense-related articles and services.
Jig
Workholding device that both locates the workpiece and guides cutting tools during machining.
Jig Boring
Precision boring operation for accurately locating and sizing holes relative to each other.
Jog
Manual incremental movement of CNC machine axes using the control pendant or handwheel.
Kerf
The width of material removed by a cutting tool. Important in sheet metal cutting and sawing.
Keyway
A slot in a shaft or hub that receives a key for locking rotating components together.
Knurling
Process of creating a pattern of straight, angled, or diamond shapes on a surface for grip.
Lapping
Ultra-fine abrasive finishing process achieving flatness to millionths of an inch and mirror finishes.
Laser Cutting
Non-contact cutting using focused laser beam. Excellent for sheet metal with minimal heat-affected zone.
Laser Engraving
Permanent marking using laser to vaporize surface material. Used for part identification and traceability.
Lathe
Machine tool that rotates a workpiece while a cutting tool moves linearly to create cylindrical parts.
Lead
The axial distance a screw thread advances in one revolution. Also the distance between gear teeth.
Lead Screw
Threaded rod used to convert rotary motion to linear motion in machine tools. Less precise than ball screws.
Lead Time
Time from order placement to delivery. Includes procurement, manufacturing, inspection, and shipping.
Live Tooling
Powered cutting tools on a CNC lathe allowing milling, drilling, and tapping without transferring parts.
Lot
A group of parts manufactured together under the same conditions. Important for traceability and quality.
M-code
Machine code. Auxiliary CNC commands controlling non-motion functions like coolant, spindle, and tool changes.
Machinability
A material's ease of machining, considering tool life, surface finish, and power requirements.
Machining Center
CNC milling machine with automatic tool changer, allowing multiple operations in one setup.
Magnesium
Lightweight metal alloy used where weight savings are critical. Requires special fire safety precautions.
Material Certificate
Documentation (mill cert) verifying material composition, properties, and origin. Required for aerospace.
Metrology
Science of measurement. In manufacturing, refers to inspection equipment and methods for quality verification.
Micron
Unit of measurement equal to one-millionth of a meter (0.000039"). Used for fine tolerances and surface finish.
Mill-Turn
CNC machine combining lathe and milling capabilities for complete part machining in one setup.
Milling
Machining process using rotating multi-tooth cutters to remove material from a workpiece.
Monel
Nickel-copper alloy with excellent corrosion resistance in marine and chemical environments.
MQL
Minimum Quantity Lubrication. Cutting technique using minimal oil mist instead of flood coolant.
Multi-Tasking
CNC machines capable of milling, turning, and other operations in a single setup to reduce handling.
NADCAP
National Aerospace and Defense Contractors Accreditation Program. Special process accreditation for aerospace suppliers.
NAS (National Aerospace Standard)
Standards for aerospace hardware, fasteners, and components. NAS parts require certified sources.
Near Net Shape
Manufacturing processes producing parts close to final dimensions, minimizing machining requirements.
Nesting
Optimizing part arrangement on sheet stock to minimize material waste. Critical for laser and waterjet cutting.
Nickel Alloy
Metal alloys with nickel as primary element, offering high-temperature strength and corrosion resistance.
Nitriding
Surface hardening treatment diffusing nitrogen into steel. Creates hard, wear-resistant surface without quenching.
Non-Destructive Testing (NDT)
Inspection methods that don't damage parts: X-ray, ultrasonic, dye penetrant, magnetic particle, eddy current.
Numerical Control
Automated control of machining tools by programmed commands. Predecessor to CNC.
OD
Outside Diameter. The external diameter of a cylindrical feature.
Offset
In CNC, adjustment values compensating for tool length, diameter, or wear.
Operator
The person running a machine tool. May set up, program, and inspect parts depending on shop structure.
OEM
Original Equipment Manufacturer. The company that produces the final product incorporating machined components.
Pallet
Workholding fixture that can be loaded outside the machine and quickly exchanged for continuous production.
Parallelism
GD&T characteristic specifying how parallel a surface or axis is to a datum.
Parting
Cutting a finished part from bar stock on a lathe using a thin blade.
Passivation
Chemical treatment of stainless steel to remove free iron and enhance corrosion resistance.
Perpendicularity
GD&T characteristic specifying how perpendicular a feature is to a datum plane or axis.
Pitch
The distance between adjacent thread crests or gear teeth. Measured in threads per inch (TPI) or module.
Plunge Milling
Milling technique using axial cuts rather than radial engagement. Useful for deep pockets in hard materials.
Post-Processor
Software that converts CAM toolpaths into machine-specific G-code.
PPAP
Production Part Approval Process. Automotive industry procedure for approving new or modified parts.
Precision
The degree of repeatability in machining. High precision means consistent results across multiple parts.
Probing
Using touch probes on CNC machines to automatically locate workpieces, measure features, or verify dimensions.
Prototype
Initial sample part made to test design, fit, and function before production tooling.
Quality Control
Processes and procedures ensuring manufactured parts meet specified requirements.
Quench
Rapid cooling of heated metal (usually in oil or water) to achieve specific hardness.
Quote
A manufacturer's price estimate for producing specified parts, including lead time and terms.
Ra
Average surface roughness. The arithmetic mean of surface profile deviations from the mean line, in microinches or microns.
Reaming
Finishing operation enlarging and finishing drilled holes to precise diameter and smooth finish.
Repeatability
A machine's ability to return to the same position consistently.
RFQ
Request for Quote. Document sent to suppliers requesting pricing and lead time for specified parts.
Rigid Tapping
Synchronized tapping where spindle rotation and Z-axis feed are precisely coordinated for accurate threads.
Rockwell
Hardness measurement scale. Common scales are HRC (hard materials) and HRB (softer materials).
Roughing
Heavy material removal at high feed rates to quickly approach final dimensions before finishing.
RPM
Revolutions Per Minute. Spindle rotation speed, calculated from cutting speed and tool/workpiece diameter.
Runout
The total variation in a rotating surface's position. Indicates how true a part runs when spinning.
SAM
System for Award Management. Federal database for government contractor registration.
Sand Casting
Casting process using sand molds. Cost-effective for large parts and low volumes but with rougher surface finish.
SFM
Surface Feet per Minute. Cutting speed expressed as the linear speed at the cutting edge.
Setup
The process of preparing a machine, fixtures, and tools to produce a specific part.
Shoulder
A step or ledge formed when a larger diameter meets a smaller diameter on a turned part.
Sinker EDM
EDM process using shaped electrodes to create cavities. Used for molds and dies.
Slot Milling
Milling operation cutting a groove or slot into a workpiece using an end mill or slotting cutter.
SPC
Statistical Process Control. Using statistical methods to monitor and control manufacturing processes.
Spindle
The rotating component of a machine tool that holds the cutting tool (mill) or workpiece (lathe).
Spline
Series of ridges or teeth on a shaft that engage with slots in a mating part for torque transmission.
Spotface
A shallow counterbore providing a flat bearing surface for fastener heads.
Stainless Steel
Steel alloy containing chromium for corrosion resistance. Common grades include 303, 304, 316, and 17-4 PH.
Steel
Iron-carbon alloy in various grades (1018, 4140, A2, D2) offering different combinations of strength, hardness, and machinability.
Step
An abrupt change in diameter on a shaft or bore.
Stock
Raw material from which parts are machined. Available as bar, plate, sheet, or forgings.
Superalloy
High-performance alloys maintaining strength at extreme temperatures. Includes Inconel, Hastelloy, Waspaloy.
Surface Finish
The texture of a machined surface, specified as Ra, Rz, or by standard symbols.
Surface Grinding
Grinding operation producing flat surfaces using a horizontal wheel. Achieves tight flatness and fine finish.
Swiss Machining
Precision turning technique using a sliding headstock and guide bushing for small, long parts.
Tap
Cutting tool for creating internal threads. Types include taper, plug, and bottoming taps.
Taper
A gradual decrease in diameter along the length of a part. Specified by ratio or degrees.
Tapping
The operation of cutting internal threads using a tap. Can be done by hand or CNC.
Temper
A heat treatment that reduces hardness and increases toughness after hardening.
Thread
A helical ridge on a fastener (external) or hole (internal) for mechanical assembly.
Thread Milling
Creating threads using a CNC mill and thread mill cutter. Allows large threads and thread repair.
Through Hole
A hole that passes completely through a workpiece. Easier to tap and machine than blind holes.
Tier 1 Supplier
Direct supplier to an OEM. Tier 2 supplies to Tier 1, and so on down the supply chain.
TiN (Titanium Nitride)
Gold-colored coating applied to cutting tools to increase hardness and reduce friction.
Titanium
High strength-to-weight ratio metal used in aerospace and medical applications. Difficult to machine.
TIR
Total Indicator Reading. The full movement of a dial indicator measuring runout or variation.
Tolerance
The allowable variation in a dimension. Expressed as ± deviation from nominal or limit dimensions.
Tombstone
Multi-sided workholding fixture used on horizontal machining centers to maximize parts per setup.
Tool Holder
Device that secures a cutting tool to the machine spindle. Various styles for different tools.
Tool Life
The cutting time or number of parts a tool can produce before replacement. Affected by material and parameters.
Tool Steel
High-carbon steel grades (A2, D2, O1, S7) used for tooling and dies. Often heat-treated to high hardness.
Toolpath
The calculated path a cutting tool follows during CNC machining, generated by CAM software.
Traceability
The ability to track materials and parts from raw stock through final delivery.
True Position
GD&T tolerance specifying how close a feature's actual location is to its theoretical location.
Truing
Making a grinding wheel concentric with its axis. Performed after dressing for precision grinding.
Tumbling
Mass finishing process using rotating barrel with abrasive media to deburr and polish parts.
Turning
Lathe operation removing material from rotating workpiece with a single-point cutting tool.
UKAS
United Kingdom Accreditation Service. UK body that certifies ISO/AS quality management systems.
Undercut
A recess or groove cut into a surface, often to provide clearance or thread relief.
UNC/UNF
Unified National Coarse/Fine. Standard thread series in inch dimensions.
Unit Cost
The total cost to manufacture one part, including materials, labor, overhead, and profit.
Vacuum Fixtures
Workholding using vacuum suction to hold thin or delicate parts. No clamping marks on finished surfaces.
Vertical Machining Center
CNC mill with vertical spindle orientation. Most common configuration for general milling work.
Vibration
Unwanted oscillation during machining causing chatter marks, poor finish, and reduced tool life.
Vise
Common workholding device using two jaws to clamp workpiece on a milling machine.
Volumetric Accuracy
A machine's positioning accuracy across its entire work envelope, accounting for all axes.
Waterjet Cutting
Cutting with high-pressure water stream, often with abrasive. No heat-affected zone, cuts any material.
Wear
Gradual degradation of cutting tools through use. Affects surface finish, accuracy, and power.
Welding
Joining metals by melting and fusing. Often combined with machining for complex assemblies.
Wire EDM
EDM process using a thin wire to cut complex 2D profiles through conductive materials.
Work Envelope
The maximum travel range of a CNC machine in X, Y, and Z axes. Defines the largest part that can be machined.
Work Offset
CNC parameter defining the relationship between machine zero and workpiece zero.
Workholding
Methods and devices for securing workpieces during machining. Includes vises, fixtures, and chucks.
Workpiece
The raw material or partially finished part being machined. Also called the part or blank.
X-Axis
The horizontal axis perpendicular to the spindle on vertical mills; cross-feed on lathes.
Y-Axis
The horizontal axis parallel to the spindle on vertical mills; table movement on lathes with live tooling.
Z-Axis
The vertical axis (spindle direction) on vertical mills; longitudinal axis on lathes.
Zero Return
Moving CNC machine axes to their reference positions, establishing machine coordinates.
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