CNC Machining Glossary
A plain-English guide to the certifications, processes and acronyms you'll see across listings on this directory - useful whether you're sourcing a supplier for the first time or double-checking what a drawing or quote actually means.
General terms
| Term | What it means |
|---|---|
| CNC (Computer Numerical Control) | Machining where a computer program controls the movement of the cutting tool and the workpiece, so parts are made repeatably to the programmed dimensions. |
| Subcontract machining | Machining parts for other companies to their drawings or specifications, rather than making the company's own branded products. |
| OEM (Original Equipment Manufacturer) | A company that designs and sells its own branded products, as distinct from a subcontract machinist that makes parts for other companies. |
| CAD (Computer-Aided Design) | Software used to draw a part in 2D or 3D. |
| CAM (Computer-Aided Manufacturing) | Software that turns a CAD model into the toolpaths and instructions a CNC machine runs. See Design & Engineering (CAD/CAM) suppliers. |
| DFM (Design for Manufacture) | Review of a part design to find and fix features that would make it difficult, unreliable or expensive to machine, before production starts. |
| Prototype / one-off | A single part or a very small number made to prove a design before committing to production. See Prototyping & Rapid Machining suppliers. |
| Batch / volume production | Repeat runs of the same part, from small batches up to high-volume production. |
| Fast turn | Parts made on a short lead time, usually at a premium, for urgent or breakdown work. |
| Free issue | The customer supplies the material (or parts) for the machinist to work on, instead of the machinist buying it. |
| Tolerance | The permitted variation from a stated dimension, for example ±0.01 mm. Tighter tolerances need more capable machines, controlled conditions and inspection. |
| Surface finish (Ra) | A measure of surface roughness. A lower Ra figure means a smoother surface. |
| Jig / fixture | A purpose-made device that holds a part in position while it is machined or inspected. |
| Deburring | Removing the small sharp edges (burrs) left on a part by machining. |
Machining processes
| Process | What it means |
|---|---|
| CNC milling | A rotating cutting tool removes material from a fixed workpiece. Used for flat faces, pockets, slots and complex shapes. See CNC Milling suppliers. |
| CNC turning | The workpiece rotates while a cutting tool shapes it. Used for round or cylindrical parts such as shafts, pins and bushes. See CNC Turning suppliers. |
| 3-axis machining | The tool moves along three linear directions (X, Y and Z). Suitable for many parts machined from one direction at a time. |
| 4-axis machining | Adds rotation of the workpiece around one axis, so more of a part can be machined without resetting it. |
| 5-axis machining | Adds two rotational axes, so the tool can reach complex shapes from several angles in one setup. See 5-Axis & Multi-Axis Machining suppliers. |
| Mill-turn | A machine that combines turning and milling, so a part can be finished in one setup. |
| Live tooling | Powered rotating tools fitted to a lathe, so it can also drill and mill features on a turned part. |
| Multi-spindle | A machine with several spindles working at once, typically for faster production of small turned parts. |
| Swiss-type (sliding head) lathe | A lathe that feeds the bar through a guide bush close to the cutting tool, giving good accuracy on long, slender or small-diameter parts. |
| Wire EDM (wire erosion) | Electrical discharge machining that cuts conductive material with a thin electrically charged wire, with no cutting force on the part. See Wire & Sinker EDM suppliers. |
| Sinker EDM (spark erosion) | Electrical discharge machining that burns a shaped electrode into the material, used for cavities and detailed shapes that are hard to cut conventionally. |
| Sheet metal fabrication | Cutting, forming and joining flat sheet metal into parts. See Sheet Metal Fabrication suppliers. |
| Laser cutting / waterjet cutting | Cutting sheet and plate with a focused laser beam or a high-pressure jet of water. See Laser & Waterjet Cutting suppliers. |
| 3D printing (additive manufacturing) | Building a part layer by layer from a digital model, rather than cutting it from solid material. See 3D Printing / Additive Manufacturing suppliers. |
| Reverse engineering | Measuring or scanning an existing part to recreate a drawing or model of it. |
Inspection & testing
| Term | What it means |
|---|---|
| CMM (Coordinate Measuring Machine) | A machine that measures a part's dimensions with a probe and compares them with the drawing. |
| First Article Inspection (FAIR) | A documented inspection of the first part from a production run, confirming it meets every requirement on the drawing before the run continues. |
| Dimensional report | A record of the measured dimensions of a part against the drawing. |
| Material certification | Paperwork from the material supplier showing the grade and properties of the material used. |
| NDT (Non-Destructive Testing) | Methods such as dye penetrant, magnetic particle, ultrasonic or X-ray inspection that check a part for defects without damaging it. |
Materials
| Material | What it means |
|---|---|
| Aluminium | A light, easily machined metal, widely used across industries. |
| Mild / carbon steel | Common, low-cost steels with good machinability and strength. |
| Stainless steel | Steel with added chromium for corrosion resistance. |
| Tool steel | Hard, wear-resistant steel used for tooling, dies and demanding wear parts. |
| Titanium | A strong, light, corrosion-resistant metal, harder to machine than aluminium or steel. |
| Inconel / superalloys | Nickel-based alloys that keep their strength at high temperature, and are demanding to machine. |
| Brass / copper | Easily machined, conductive metals used for fittings, electrical and decorative parts. |
| Engineering plastics (Delrin, PEEK, Nylon, PTFE) | Machinable plastics with good strength, wear or chemical resistance. |
| Composites | Materials made of fibres in a resin, such as carbon fibre. |
Finishing
| Finish | What it means |
|---|---|
| Anodising | An electrochemical process that builds a hard, corrosion-resistant oxide layer on aluminium, and can add colour. |
| Plating | Coating a part with a thin layer of another metal, for example zinc or nickel, for protection or appearance. |
| Passivation | A chemical treatment that improves the corrosion resistance of stainless steel. |
| Powder coating | A dry powder sprayed onto a part and cured with heat, giving a durable painted finish. |
| Painting | Applying a liquid paint finish for protection or appearance. |
| Bead blasting | Blasting a surface with fine beads to give a uniform matt finish. |
| Polishing | Smoothing a surface to a bright or low-roughness finish. |
| Heat treatment | Heating and cooling a metal part in a controlled way to change its hardness or strength. |
| Laser marking / engraving | Marking a part permanently with a laser, for example with a serial number, logo or barcode. |
Certifications & accreditations
| Certification | What it means |
|---|---|
| ISO 9001 | The international standard for quality management systems - the most common baseline manufacturing certification. |
| AS9100 | The quality management standard for the aerospace industry, built on ISO 9001. |
| ISO 13485 | The quality management standard specific to medical device manufacturing. |
| ISO 14001 | The international standard for environmental management systems. |
| ISO 45001 | The international standard for occupational health and safety management. |
| ISO 27001 | The international standard for information security management. |
| IATF 16949 | The automotive industry quality management standard. |
| Nadcap | An industry accreditation programme for special processes, such as heat treatment, chemical processing and non-destructive testing, used mainly in aerospace and defence. |
| ITAR | The US International Traffic in Arms Regulations, which control defence-related items and data. Listings show it where the company states it. |
A certification shown on a listing is what the company states in its own public information. Always confirm a certificate directly with the company before relying on it. See what "Verified" means.