A

Arbor — A shaft or spindle used to hold and drive a cutting tool such as a milling cutter or saw blade.

Axial Depth of Cut (ap) — The depth of engagement along the tool axis in milling operations. Determines how much material is removed per pass in the Z direction.

B

Back Rake Angle — The angle between the top face of a cutting tool and a line parallel to the tool shank, measured in the direction of cut. Positive rake reduces cutting forces; negative rake increases edge strength.

Boring — An internal machining operation that enlarges an existing hole to achieve precise diameter and surface finish. Uses a single-point boring bar mounted in the spindle.

Built-Up Edge (BUE) — Material from the workpiece that welds to the cutting edge during machining, typically caused by low cutting speed or inadequate lubrication. Degrades surface finish and reduces tool life.

Brazed Tool — A cutting tool where a carbide tip is permanently joined to a steel shank using brazing alloy. Common in turning and facing operations where indexable inserts are not practical.

C

Carbide Insert — A replaceable cutting tip made from tungsten carbide (WC-Co) used in turning, milling, and drilling. Available in various shapes (CNMG, WNMG, DNMG) defined by ISO 1832. Browse carbide inserts

Cermet — A composite cutting tool material combining ceramic particles (typically TiCN) with a metallic binder. Provides excellent surface finish at high cutting speeds, particularly on steel.

Chip Breaker — A groove or geometry pressed or ground into the rake face of a cutting insert that controls chip formation, preventing long continuous chips that can wrap around the workpiece or tool.

Chipload — The thickness of material removed by each cutting edge per revolution, calculated as feed rate divided by number of flutes. Also called feed per tooth (fz).

Clearance Angle — The angle between the flank face of a cutting tool and the workpiece surface. Prevents rubbing and allows the tool to cut freely. Designated by the second letter in ISO insert codes (N=0°, A=3°, etc.).

Climb Milling — Milling method where the cutter rotation direction matches the feed direction. Produces better surface finish and less tool deflection than conventional milling. Preferred for CNC machines with zero backlash.

CNC (Computer Numerical Control) — Automated control of machining tools using programmed G-code commands. Enables precise, repeatable production of complex geometries.

Coating (Tool) — A thin layer applied to cutting tools to increase hardness, reduce friction, and improve heat resistance. Common coatings include TiN (gold), TiAlN (violet-gray), TiCN (blue-gray), and AlCrN. Coating comparison guide

Collet — A spring-loaded clamping device that holds round-shank cutting tools in the spindle with high concentricity and gripping force.

Conventional Milling — Milling where the cutter rotation opposes the feed direction. Creates more heat and deflection than climb milling but is safer on machines with backlash.

Coolant — Fluid applied during machining to reduce heat, lubricate the cutting zone, and flush chips. Types include soluble oils, semi-synthetics, synthetics, and straight cutting oils.

D

Depth of Cut (DOC) — The distance the cutting tool penetrates into the workpiece surface, measured perpendicular to the machined surface.

Dividing Head — A workholding device that rotates the workpiece to precise angular positions for operations like gear cutting, spline milling, or indexing holes. View dividing heads

Dwelltime — A programmed pause at a specific position during CNC machining, used to ensure complete cutting in operations like drilling (to clean the hole bottom) or threading.

E

End Mill — A milling cutter with cutting edges on both the end face and periphery, used for profiling, slotting, plunging, and contouring operations. Available in flat, ball-nose, and corner-radius geometries. Browse milling tools

Edge Preparation — Treatment applied to the cutting edge of a tool (honing, chamfering, or rounding) to improve edge strength and predictability. Critical for hard-material machining.

F

Face Milling — Milling operation where the cutter axis is perpendicular to the workpiece surface, producing a flat face. The primary cutting action occurs at the insert tips on the cutter periphery.

Feed Rate — The speed at which the cutting tool advances through the workpiece, expressed as mm/rev (turning) or mm/min (milling). Higher feed rates increase productivity but may reduce surface finish.

Flank Wear — Progressive wear on the clearance (flank) face of a cutting tool caused by abrasion against the workpiece. Measured as VB in mm. Maximum acceptable VB is typically 0.3mm for finishing.

Flute — A helical groove cut into the body of a drill, end mill, or tap that provides cutting edges and channels for chip evacuation.

G

G-Code — The programming language used to control CNC machines. G-codes define movements (G00=rapid, G01=linear feed, G02/G03=circular interpolation), while M-codes control machine functions (M03=spindle on, M08=coolant on).

Grade (Insert) — A classification of carbide insert composition and coating that determines its suitability for specific materials and conditions. ISO grades: P (steel), M (stainless), K (cast iron), N (non-ferrous), S (superalloys), H (hardened).

H

High-Speed Steel (HSS) — A tool steel containing tungsten, molybdenum, and other alloying elements that maintains hardness at elevated temperatures. Used for drills, taps, and reamers where toughness is critical.

Holder (Tool) — A device that secures the cutting tool or insert in the machine spindle or turret. Types include boring bars, turning tool holders, milling arbors, and collet chucks. Browse tool holders

I

Indexable Insert — A cutting insert with multiple usable cutting edges that can be rotated (indexed) to a fresh edge when one is worn. More cost-effective than regrinding solid tools.

Inscribed Circle (IC) — The largest circle that fits inside the shape of a turning insert. Used to specify insert size (e.g., IC 12.7mm for size code 12). Decode insert sizes

L

Lathe — A machine tool that rotates the workpiece against a stationary cutting tool for operations like turning, facing, threading, and boring. Available as manual engine lathes and CNC turning centers.

Lead Angle — The angle between the cutting edge and the direction of feed in a turning operation. Affects chip thickness, cutting forces, and surface finish.

M

Machinability — A measure of how easily a material can be cut. Influenced by hardness, ductility, abrasiveness, and thermal conductivity. Free-machining steels (12L14) have high machinability; titanium and Inconel have low machinability.

MRO (Maintenance, Repair, Operations) — Consumable tools and supplies used in manufacturing operations, including hand tools, measuring instruments, abrasives, and safety equipment. Browse MRO tools

N

Nose Radius — The radius at the tip of a turning insert where the cutting edges meet. Larger nose radius (1.2-1.6mm) gives better surface finish but requires more rigidity; smaller radius (0.4-0.8mm) reduces cutting forces. Nose radius guide

Notch Wear — Localized wear at the depth-of-cut line on a cutting tool, caused by work-hardened surface layers or abrasive inclusions. Common when machining stainless steel and superalloys.

P

PCD (Polycrystalline Diamond) — An ultra-hard cutting tool material made from diamond particles sintered with a metallic binder. Used for machining non-ferrous metals, composites, and abrasive materials at very high speeds.

Positive Rake — A cutting geometry where the top face of the tool tilts away from the workpiece, reducing cutting forces. Used for machining soft materials and thin-walled parts.

R

Radial Depth of Cut (ae) — The width of engagement perpendicular to the tool axis in milling. Also called stepover or width of cut.

Rake Angle — The angle between the cutting face of the tool and a line perpendicular to the workpiece surface. Positive rake = easier cutting, lower forces. Negative rake = stronger edge, handles hard materials.

Reamer — A precision cutting tool used to finish drilled holes to tight diameter tolerances and smooth surface finish. Available in HSS, carbide, and carbide-tipped versions. Browse reamers

S

SFM (Surface Feet per Minute) — The speed at which the workpiece surface passes the cutting edge, calculated from spindle RPM and workpiece/tool diameter. The primary variable for tool life optimization.

Spindle — The rotating component of a machine tool that holds the workpiece (lathe) or cutting tool (mill) and provides the rotational motion for cutting.

Surface Finish (Ra) — A measure of surface roughness expressed as the arithmetic average of surface deviations in micrometers or microinches. Typical values: rough turning Ra 3.2-6.3 µm; finish turning Ra 0.8-1.6 µm; grinding Ra 0.2-0.8 µm.

Swarf — Metal chips and debris produced during machining operations. Also called chips or turnings.

T

Threading — Machining operation that cuts helical grooves (threads) on external or internal surfaces. Methods include single-point threading, thread milling, tapping, and die cutting. Browse threading tools

Tool Life — The cutting time a tool can operate before requiring replacement, measured in minutes or number of parts. Influenced by cutting speed, feed rate, material, and coating.

Tool Nose Compensation (TNC) — A CNC feature that offsets the tool path to account for the actual nose radius of the insert, ensuring accurate profile machining.

Turning — A machining process where the workpiece rotates while a single-point cutting tool removes material to create cylindrical shapes, faces, tapers, and contours.

W

Wiper Insert — A turning insert with a modified nose geometry featuring a small flat or very large radius that produces superior surface finish at higher feed rates than standard inserts.

Work Hardening — The increase in hardness and strength of a metal caused by plastic deformation during machining. Common in austenitic stainless steels (304, 316) and nickel alloys. Requires sharp tools and adequate feed rates to cut below the hardened layer. Stainless steel machining guide

Workholding — Devices and methods used to secure a workpiece during machining, including chucks, vises, fixtures, magnetic tables, and collets. Browse workholding solutions

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