Ultimate CNC Machining Glossary: 100+ Terms Every Buyer Should Know (2026)
CNC machining comes with a dense vocabulary of technical terms, acronyms, and industry jargon. This glossary organizes 100+ essential terms into clear categories — a reference you can bookmark and share with your team when reviewing quotes, drawings, and supplier communications.
Processes & Equipment
Term
Definition
3-Axis Milling
Tool moves in X, Y, Z. Most common. Best for parts with features on ≤3 faces.
5-Axis Milling
Adds 2 rotary axes (A, B or B, C). Single-setup machining of complex parts.
CNC Turning
Workpiece rotates, stationary tool removes material. For cylindrical parts.
Swiss Turning
Uses guide bushing for small, long parts. ±0.002mm precision.
Mill-Turn
Lathe with live milling tools. Turns and mills in one setup.
EDM (Electrical Discharge Machining)
Uses electrical sparks to erode material. For hard metals, sharp corners.
Wire EDM
Uses a thin wire electrode. For precise 2D profiles in hard materials.
Surface Grinding
Abrasive wheel for flat surfaces. Achieves Ra 0.1–0.4μm finish.
Materials & Specifications
Term
Definition
6061-T6
Most common aluminum alloy. 310 MPa strength. Excellent machinability and anodizing.
7075-T6
High-strength aluminum. 572 MPa. Used in aerospace. Harder to anodize.
304 Stainless
General-purpose stainless. 515 MPa. Food-grade. Most welded stainless.
316 Stainless
Marine/medical grade. Added molybdenum for chloride resistance.
Ti-6Al-4V
Titanium workhorse alloy. 950 MPa. Aerospace and medical standard.
PEEK
High-performance thermoplastic. 260°C max service temp. $80-120/kg.
Delrin (POM)
Acetal plastic. Best machinability among plastics. Low friction, self-lubricating.
Annealing
Heat treatment that softens metal, relieves internal stress, improves machinability.
Tolerances & GD&T
Term
Definition
IT Grade
International Tolerance grade (IT5–IT14). IT7 = ±0.01mm at 30mm.
GD&T
Geometric Dimensioning and Tolerancing. Symbol-based engineering language.
True Position
GD&T symbol ⌖. Controls location of a feature relative to datums.
Flatness
GD&T symbol ⏤. All points on a surface must lie between two parallel planes.
Runout
GD&T symbol ○/✕. Controls wobble when part rotates. Critical for shafts.
Ra (Roughness Average)
Surface finish measurement in μm. As-machined: Ra 0.8–3.2. Mirror: Ra 0.05.
Quality & Inspection
Term
Definition
CMM
Coordinate Measuring Machine. Uses touch probe to measure 3D geometry to ±0.001mm.
FAI
First Article Inspection. Full dimensional check of first production part(s).
SPC
Statistical Process Control. Uses data to monitor and control manufacturing quality.
Cpk
Process Capability Index. Cpk ≥1.33 indicates a capable process. ≥1.67 is excellent.
NDA
Non-Disclosure Agreement. Protects your design IP when sharing with suppliers.
Business & Logistics
Term
Definition
RFQ
Request for Quote. Send CAD + quantities + material + tolerances to get pricing.
MOQ
Minimum Order Quantity. Many CNC shops accept MOQ = 1 piece.
FOB
Free On Board. Seller pays until goods are on the ship. Buyer pays freight + insurance.
CIF
Cost, Insurance, Freight. Seller pays freight to destination port. Buyer pays duties.
DDP
Delivered Duty Paid. Seller handles everything door-to-door including import duties.
DFM
Design for Manufacturability. Feedback on how to make your part easier/cheaper to produce.
Lead Time
Calendar days from order to delivery. Prototypes: 3–10 days. Production: 15–30 days.