Machining Processes — Family Index

Tier 3 family index for subtractive manufacturing. Covers conventional mechanical cutting, abrasive finishing, non-conventional (thermal / electrical / chemical / fluid jet) removal, and hybrid hot-soft / vibration-assisted methods. SI primary; US customary in parentheses where the shop floor still defaults to it.

1. At a glance

Conventional mechanical cutting — defined chip geometry, single- or multi-point tool, plastic shear at the rake face:

• Turning (lathe — workpiece rotates, single-point tool feeds).
• Milling (rotating multi-point cutter, work feeds — face / peripheral / end / slot / form).
• Drilling / hole-making (rotating multi-edge axial tool — twist, gun, BTA, indexable, step, spade).
• Sawing (band, cold, abrasive cut-off, hack).
• Broaching (linear progressive multi-tooth tool — internal keyway / spline / polygon; external fir-tree flat / form).
• Gear-cutting — hobbing (continuous-generating), shaping (Fellows reciprocating cutter — internal / cluster gears), gear-skiving (combined rotation 4–7× faster than shaping), generating gear-grinding.

Abrasive (bonded + loose grain) — undefined chip geometry, hard ceramic grit, slow material removal at high precision:

• Grinding: surface (reciprocating + rotary table), cylindrical OD / ID, centerless, creep-feed (deep + slow — turbine fir-tree), jig grinding (hardened tool steel die work).
• Honing — cross-hatched bore finishing (IC engine cylinder).
• Lapping — flat free-abrasive between plates (gauge blocks).
• Superfinishing — fine stone / tape oscillation (bearing race, crankshaft journal).
• Polishing, buffing.
• Abrasive blast (shot, grit, bead), abrasive-flow machining (AFM — extrude-honing for cross-drilled intersections).

Non-conventional — energy domain other than mechanical shear:

• EDM (electrical-discharge — die-sink / wire / small-hole).
• ECM + PECM (electrochemical — anodic dissolution; no thermal / mechanical stress).
• ECG (electrochemical grinding — combined ECM + bonded abrasive).
• Water-jet (pure + abrasive entrained garnet — 4000–6500 bar).
• Laser cutting (CO₂ legacy; fiber/disk for sheet + tube; femto/pico for micromachining).
• Plasma cutting (ionized gas — heavy plate).
• Oxy-fuel cutting (very heavy carbon-steel plate to 300 mm).
• Ultrasonic machining (USM) — abrasive slurry oscillated 20–40 kHz against hard brittle (ceramic, glass, Si).
• Chemical machining / etching (photochemical machining PCM — shim stock, leadframes).

Hybrid — superposition of two energy domains for synergistic improvement:

• Laser-assisted turning (LAT) of nickel-superalloys (Inconel 718).
• Ultrasonic-assisted milling / drilling (UAM / UAD) of CFRP and titanium.
• Cryogenic-assisted machining (LN₂ jet at the rake face).
• High-pressure coolant-thru (70–300 bar — chip breakage in Ti / Ni-superalloys).

2. Turning (lathe)

Workpiece rotates on the spindle; single-point insert feeds axially / radially.

Operations — straight (OD) / facing / taper / parting (cut-off) / threading / grooving / boring (internal turning) / knurling / drilling-on-centerline / form turning.

Machine families:

• Engine lathe (legacy manual — South Bend, Hardinge HLV-H toolroom).
• CNC turning center / chucker — 2-axis flatbed (Mazak QT, Okuma LB, Mori NLX, Doosan Puma, Haas ST). Live tooling (driven mill spindle on the turret) + Y-axis + sub-spindle → 6–9-axis effective.
• Multi-tasking mill-turn — Mazak Integrex i-series, DMG MORI NTX, Okuma MULTUS, Mori NT — turn + 5-axis mill + B-axis tilt + sub-spindle, full done-in-one for complex aerospace shafts.
• Swiss-type (sliding-headstock) — Tornos Swiss GT / DECO, Citizen Cincom L / M, Star SR / SV — bar feed + headstock slides past a guide bushing → 1–32 mm bar stock at very high accuracy and rigidity, ideal for medical bone screws, watch components, micro-electronics pins.
• Vertical turret lathe (VTL) — large diameter parts (rail wheels, mining gear blanks — Toshiba, Schiess, Doosan VT).
• Hard-turning lathe — high-rigidity, low-vibration (Hembrug, Hardinge T-series, JUNG Mikrosa) — CBN-inserted 60–66 HRC bearing rings as substitute for grind.

Insert designation (ISO 1832) — 7-position code:

1. Shape: C (80° diamond), D (55° diamond), R (round), S (square), T (triangle), V (35° diamond), W (trigon).
2. Clearance: B (5°), C (7°), N (0° — negative double-sided), P (11°).
3. Tolerance class (A, C, E, F, G, H, J, K, L, M, U).
4. Hole / chip-breaker code.
5. Inscribed-circle size (mm × 10).
6. Thickness.
7. Corner radius (mm × 10 — e.g. 08 = 0.8 mm nose).

Example: CNMG 120408-PM = 80° diamond, negative, M-tolerance, with-hole + chip-breaker, IC 12.7 mm, 4.76 mm thick, 0.8 mm nose, PM medium chip-breaker.

3. Milling

Rotating multi-point cutter; work feeds linearly past it.

Operation classes — face (large flat shoulders), end (slots + pockets + 3D contour), peripheral (large flat sides), slot, T-slot, dovetail, keyseat, gear / form, slab (heavy stock removal).

Tool styles:

• Solid-carbide endmill — 2/3/4/6/8 flute, square / ball / bull-nose / radius / chamfer. Coatings TiAlN, AlCrN, AlTiSiN for high-temp dry milling. Vendors: Hanita, OSG, Mitsubishi MS / MV, Kennametal HARVI / KOR5, YG-1 X-Power, Garr Tool, Helical (Helical Solutions Tool), Walter Prototyp.
• Insert-tooled face / shoulder / copy mills — Sandvik CoroMill 245 (face), CoroMill 345 (shoulder + face), CoroMill 390 (90° shoulder), CoroMill 590 (90° fine pitch), CoroMill 790 (high-feed); Iscar HELIDO H600 / FLEXFIT; Kennametal Mill 1-14, KSSM, Mill 4-15; Mitsubishi VOX400, ASX445; Walter Xtra·tec M3024; Seco Turbo10.
• High-feed milling (HFM / fast-feed) — small ap (axial depth 0.5–2 mm) + high fz (0.8–3 mm/tooth) + low entry angle (10–17°) → very high MRR. Ingersoll Hi-FeedMini, Iscar FEEDMILL, Sandvik CoroMill 745 / 419.
• Plunge milling — vertical chip evacuation; high-MRR roughing of pockets in tough alloys.
• Trochoidal / dynamic toolpath — small radial engagement (5–10% Dc) + high axial (1.5–3× Dc) → constant chip thickness + high MRR + extended tool life. Strategy in Mastercam (Dynamic), Fusion 360 (Adaptive), hyperMILL MAXX, NX CAM (Adaptive), Esprit ProfitMilling.

CAM packages — Mastercam (long shop-floor lead), Fusion 360 (cloud + integrated), Siemens NX CAM (enterprise + complex 5-axis), hyperMILL (high-end 5-axis mold + aerospace), GibbsCAM, Esprit, PowerMill (Autodesk), Edgecam.

4. Drilling / hole-making

Axial multi-edge rotating cutter; chip flutes evacuate swarf.

Drill types:

• Twist drill — HSS (general), HSS-Co (M35 / M42 — tough alloys), solid-carbide (high-speed dry / coated). 118° (general), 135° split-point (self-centering), 140° (stainless). Lengths: jobber, screw-machine (stub), taper / extra-length.
• Step drill (Unibit) — sheet metal multi-size.
• Gun drill — single-flute carbide tip + steel shank + coolant-thru hole, V-shaped flute. Deep hole (L/D 25:1 to 100:1) with mirror finish + tight straightness. Mfg: Botek, Sterling, Iscar, Star Cutter.
• BTA / STS (Boring-Trepanning Assoc. / Single-Tube System) — for very deep large-diameter holes (oil-and-gas valves, gun barrels, hydraulic cylinders) — coolant pressurizes annulus, chips evacuate through tube center. Mfg: Botek, TBT (Tiefbohrtechnik), UNISIG.
• Spade drill — flat insert in holder, low-cost large diameter (Allied Spade, Walter T2710).
• Indexable insert drill — peripheral + central insert; Sandvik CoroDrill 880 / DS20, ISCAR DR-Twist / SUMOCHAM (replaceable head), Kennametal KSEM / KenTIP FS, Mitsubishi MVS / MVX, Walter Xtra·tec D4140.

Boring — opens / finishes a previously drilled hole to a precise diameter. Boring head: Wohlhaupter MVS / VarioBore, Big Kaiser BIG-NEW BORING (twin-cutter EWN, EWB), Ingersoll, Komet ABS, Iscar BHF. Fine-bore heads to ±0.002 mm.

Reaming — finishing pass to tight tolerance (H7 typical) and improved surface. Straight / spiral flute, HSS / carbide. Allowance: 0.1–0.5 mm. Speed ~⅔ drill, feed 2–3× drill.

Tapping — internal-thread cutting. Rigid tapping (synchronized spindle + Z-feed, modern CNC), floating tap holder (legacy mechanical compensation). Form-tap (cold-form, no chip — ductile materials only, stronger threads) vs cut-tap (general). H-limit (H1–H7) controls thread fit. Vendors: OSG, Emuge, Walter Prototyp, YG-1.

Thread mill — solid-carbide helical cutter generates thread in single revolution; one tool fits multiple diameters + pitches, no broken-tap risk in expensive parts, supports left / right and metric / UN.

5. Sawing

Bulk stock cut-off and slabbing.

• Bandsaw — continuous loop (bi-metal HSS-edged + spring-steel back, or carbide-tipped). Vertical (DoAll, Marvel) for contour and limited-radius profile; horizontal (Cosen, Marvel 2120, DoAll C-916S, HE&M, Behringer) for production cut-off. Pitch: variable-pitch (2/3, 3/4, 4/6 TPI). Cutting fluid: water-soluble flood.
• Cold saw — circular HSS or carbide-tipped blade, slow rpm + heavy coolant + clean square cut. Kalamazoo, KMT, Pedrazzoli. Used for shop-floor structural-tube cut-off.
• Abrasive cut-off — bonded Al₂O₃ wheel 50–100 m/s; rough but fast; widely used in production tube/bar cut-off (Everising).
• Friction saw — high-speed steel blade rubbing through hot rolled stock — mill setting.
• Waterjet / laser / plasma — see §12 / §13 / §14 for sheet and plate.
• Hand hacksaw — bench / portable.

6. Broaching

Linear (or rotary helical) pull / push of a tool with progressively rising teeth. Each tooth removes 0.05–0.15 mm; final teeth do finish + sizing.

• Internal broaching — keyway (square, round-square), spline (involute / parallel), polygon hex / hex-bolt heads, irregular shapes through a pre-drilled pilot. Pull-type vertical broaching machine.
• External broaching — flats, slots, fir-tree turbine-blade roots (the only economic process for the fir-tree silhouette of a turbine-blade root machined into a disk — extremely tight Z2 / Z3 form on Inconel 718).
• Pot broaching — external tool stack (pot) is stationary, work pulls through (gear teeth on truck transmission blanks).

Vendors: Apex Broaching Systems, La Pointe (Hassay-Savage), Forst (Germany — large-format aerospace pot + internal broaches), ELO (Switzerland), Ohio Broach, American Broach & Machine.

7. Gear cutting

Generating + form processes; finishing by grinding / honing / lapping.

• Hobbing — continuous generating: work + hob rotate in synchronized ratio. Produces spur, helical, worm. Liebherr LC / LH, Mitsubishi GE / GR / SE, Gleason 200H / 260H / 280H, Koepfer (now Emag). Module range 0.3–25 mm.
• Shaping (Fellows) — reciprocating gear-cutter rocks past blank in generating motion. Cuts internal gears, cluster gears (where hob clearance is impossible), shouldered shaft pinions. Liebherr LSE / LSF, Lorenz (now Liebherr), Mitsubishi ST.
• Gear-skiving (Power Skiving) — combined-motion cutter angled to work axis; 4–7× faster than shaping, cuts internal + external + cluster + helicals. Gleason Genesis 200PS / 280PS, DMG MORI gearMILL / DMP 35 PS, Mazak NEXUS Power Skiver, EMAG VLC 200 GS. Resurgent technology since ~2010 thanks to CNC synchronization.
• Generating gear-grinding — finishing precision (DIN 3 / AGMA 13) gears post-hardening. Reishauer RZ / 260 / 410 (threaded-wheel grinding — fastest), Gleason 280G / 400G / TWG (profile-grinding option), Höfler RAPID 1250 / 2400, Klingelnberg Höfler Genus / VIPER.
• Profile (form) gear-grinding — single disc profile wheel; slower than generating but flexible for one-offs and very large gears.
• Gear honing — CBN-bonded mating gear runs under load with work-gear at slight skew → finishing post-grinding (Faessler — now ZF, Praewema Synchroform, Gleason 130GH).
• Gear lapping — meshed pair lapped together with abrasive paste (legacy spiral-bevel finishing — Gleason Roto-Test).
• Form-milling (disc cutter or end-mill cutter) — one-off / repair gear cutting on universal mill. Slow and lower-accuracy.

8. Grinding

Bonded abrasive wheel; defined Gw (grit) and bond.

Process families:

• Surface grinding — reciprocating (work table traverses under wheel — Okamoto ACC-DX, Chevalier FSG, Jung A series, ELB Schliff Smart Line, Mägerle MFP) or rotary-table (large flat batch — Blanchard, Mattison, Bourn & Koch).
• Cylindrical OD grinding — work rotates between centers; wheel grinds OD diameter. Studer S31 / S41 / S121, JUNG / Kellenberger 1000U, Toyoda GE / GS, Tsugami / Tsudakoma, Voumard.
• Cylindrical ID grinding — internal bore grinding; long quill + small wheel limits stiffness. Studer S20 / S22, Voumard 1000.
• Centerless grinding — work supported on a work-rest blade between grinding wheel + regulating wheel; no chucking → very high throughput on cylindrical parts (auto + bearing + injector pins). Cincinnati Centerless, Studer Mikrosa Kronos, Glebar, Royal Master TG-12X12.
• Jig grinding — high-precision hardened tool steel die work; small wheel orbits in toolpath driven X-Y-Z. Moore G18 / G48, Hauser Stähli H35.
• Creep-feed grinding — single deep pass (1–30 mm) at very slow feed (50–500 mm/min) with continuous-dressing CD wheel + heavy coolant → forms turbine-blade fir-tree roots, broach replacement for Ni-superalloy. Blohm Profimat MT, Mägerle MFP, MAG creep-feed.
• Double-disc grinding — work passes between two opposed wheels (parallel faces — washers, ring gears, valve plates). Stähli, Diskus.
• Gear grinding — see §7 (Reishauer, Höfler, Klingelnberg, Gleason).
• Thread grinding — single-rib (V-form) or multi-rib wheel; precision threads (ball-screw, lead-screw). TOS Vansdorf, Reishauer NZA, Matrix.

Wheel composition:

• Abrasive grit: aluminum oxide Al₂O₃ (ferrous), silicon carbide SiC (Al, Cu, brass, ceramic), CBN (cubic boron nitride — hardened steel ≥60 HRC, super-life), diamond (carbide, ceramic, glass, composite).
• Bond: vitrified (ceramic — most common, easy dress, porous coolant access), resinoid (resin — cut-off, fettling), metal (diamond / CBN, super-rigid), electroplated single-layer (CBN — form grinding, no dressing).
• Grit size, hardness grade (A–Z soft→hard), structure (1–15 open→dense).

Dressing — restoring wheel form + sharpness:

• Single-point natural-diamond.
• Multi-point cluster diamond / impregnated.
• Rotary diamond dresser / form roll (for continuous-dressing creep-feed and gear-grinding).

9. Honing / lapping / superfinishing

Ultra-fine surface improvement and geometric correction.

• Bore honing — multi-stone expandable head reciprocates + rotates → cross-hatch pattern at controlled angle (45° typical) for oil retention. IC-engine cylinder bore (Nagel ECO 110, Sunnen SV-310 / SV-1010), hydraulic valve bore. Plateau honing (smooth peaks while keeping valleys — for low oil consumption + low friction).
• Flat lapping — work floats on rotating cast-iron or composite plate with free-abrasive slurry (diamond or Al₂O₃ + oil/water carrier). Gauge blocks, optical flats, HDD read-head sliders, semiconductor wafers. Lapmaster, Speedfam, Stähli, Logitech.
• Superfinishing (microfinishing) — fine bonded stone or coated abrasive tape oscillates against rotating work at low pressure → micro-finish (Ra 0.02–0.1 µm) + removes peaks left by grinding. Bearing inner / outer race, crank journal, cam-lobe, rolling-element ball. Supfina (Grieshaber), Thielenhaus Microfinish, 3M.
• Tape (film) finishing — coated film abrasive driven against work by contact shoe; consumable belt, fresh grit each pass. Crankshaft mains and pins in automotive (Supfina, Thielenhaus, Nagel).

10. EDM (Electrical Discharge Machining)

Thermo-electrical erosion: spark between charged electrode and work in dielectric (oil or deionized water); each spark vaporizes a tiny crater (~5 µm) of work material. Requires electrically conductive workpiece; no contact force → ideal for hardened tool steel + tungsten carbide + Inconel.

Variants:

• Die-sink (RAM, sinker) EDM — shaped electrode (graphite, copper, copper-tungsten) plunges into work; produces 3D cavity (injection-mold cavity, forging die, blisk pocket, sharp inside corners impossible by milling). Sodick AP / AG, Makino EDAC1 / EDGE / AS, Mitsubishi EA-S Advance, Agie Charmilles Form 200 / 350 SP, GF AgieCharmilles FORM.
• Wire-EDM (WEDM) — brass / coated wire (0.05–0.3 mm) acts as continuously-renewed electrode; cuts 2D extrusion-style profiles to ±2 µm + Ra 0.1 µm. Punches and dies, gear forms, fixtures, micro-features. Sodick AQ / MM / AL series, Mitsubishi MV / MD / MX, Charmilles ROBOFIL / CUT 200 / 1000 / 3000, Makino UPV / U series, ONA AV.
• Small-hole / hole-popper / hole-drilling EDM — fast (relative to drill) cutting of small deep holes through hardened or conductive-ceramic materials; tube electrode (brass / copper) with internal dielectric flush. Turbine-blade cooling-air holes (0.3–1.0 mm × 30+ mm deep), starter holes for wire-EDM. Sodick K1C / SLP, Belmont, AccuteX, EDM Sales & Supplies.

Process notes — recast layer (5–20 µm) of resolidified material left on surface; finishing pass with lower energy reduces it. Sub-surface heat-affected zone (HAZ) — concern for aerospace fatigue-critical parts (chemical etch + polish to remove).

11. ECM and ECG

Electrochemical machining — anodic dissolution: shaped cathode tool + work as anode, separated by gap (0.1–0.5 mm), flooded by flowing electrolyte (NaNO₃ or NaCl, 5–20 m/s); no contact, no heat damage, no tool wear.

• Pulsed ECM (PECM) — pulsed current + oscillating tool gap → very tight geometric tolerances (±10 µm) + mirror finish (Ra 0.05–0.2 µm). Turbine-blade fir-tree roots (GE, Pratt, RR), compressor blades, blisk integral airfoil finishing. No thermal damage, no recast → directly meets aerospace fatigue spec. Vendors: Indec, PEMTec, Voxeljet, EMAG ECM.
• Electrochemical grinding (ECG) — bonded abrasive wheel + electrolyte + DC current; abrasive depassivates while ECM dissolves bulk → low force on the wheel, ideal for hardened cobalt-chrome surgical-tool sharpening (scalpel, hypodermic needle bevel).
• STEM (Shaped-Tube Electrochemical Machining) — coated tube electrode pushed down through work in acid electrolyte → bores small deep cooling holes in turbine blades (alternative to small-hole EDM, no recast).

12. Water-jet machining

High-pressure water (4000–6500 bar / 60–90 kpsi) accelerated through diamond / sapphire orifice (0.1–0.4 mm) → cuts. Optional garnet 80-mesh (80 grit) entrained in mixing tube → abrasive water-jet (AWJ) — cuts almost anything.

• Abrasive water-jet — steel up to 150 mm, aluminum to 300 mm, titanium to 100 mm, ceramic / glass / stone / composite. No heat-affected zone, no metallurgical damage, ±0.1 mm typical. Vendors: Flow IFB / Mach 4C / Mach 500, OMAX MAXIEM / GlobalMAX / ProtoMAX, KMT Streamline, Bystronic Byjet, WARDJet.
• Pure-water jet — soft materials only — food trim, gasket, foam, paper, textile. No abrasive contamination of work or food product.
• Cold cutting — process is room temperature → suitable for explosives, energetics, magnesium, plastics, prepreg composites where laser / plasma cannot risk thermal ignition or matrix degradation.

13. Laser cutting

Focused beam (10⁶ W/cm² at focus) melts / vaporizes / sublimes work; assist gas (O₂ for steel exothermic, N₂ for stainless / Al inert, air for thin mild steel) blows molten material clear.

Source types:

• CO₂ laser (10.6 µm) — legacy 2–10 kW (Bystronic ByAutonom, Trumpf TruLaser 5030 CO₂, Amada FOL-A); flat-bed sheet for years; declining.
• Fiber laser (1.07 µm) — IPG / nLight engines, 2–30 kW; replaces CO₂ for sheet + tube + plate. Higher absorption in reflective metals (Al, Cu, brass), 3× faster on thin sheet, lower running cost (no gas, no resonator service). Bystronic ByStar Fiber, Trumpf TruLaser 3030 / 5030 fiber, Amada Ventis-3015AJ / Regius, Mitsubishi GX-F Advanced 12 kW, Mazak Optiplex 3015 fiber, LVD Phoenix FL.
• Disk laser (1.03 µm — Yb:YAG thin-disk, Trumpf TruDisk) — similar to fiber, used in welding and remote-laser cutting.
• Femto- / pico-second lasers — ultrashort pulses; ablation regime (non-thermal); micromachining of stents, fuel injectors, MEMS, glass display cover-plates. Trumpf TruMicro 5000 / 7000, Coherent Talon / HyperRapid, Light Conversion Pharos / Carbide, EKSPLA, Amplitude Satsuma.

Tube laser — combined chuck + bed cuts 2D / 3D features in tube and structural section in one fixture (BLM LT8 / LT FIBER, Mazak FT-150, Trumpf TruLaser Tube 7000, Adige).

14. Plasma cutting

Ionized gas (compressed air + plasma) channel between electrode and work → arc + supersonic jet melts + ejects metal. Conductive materials only.

• Air-plasma (handheld + small CNC) — Hypertherm Powermax 30 / 45 / 65 / 105 / 125 — portable shop + thin plate up to 50 mm steel.
• HD plasma (precision plasma) — Hypertherm XPR300 / Sound DigiKey, Kjellberg HiFocus 280i / 360i, Thermal Dynamics — to 100 mm heavy plate at near-laser edge quality. Argon-H₂ + N₂ mixes; ±0.5 mm typical.
• Bevel cutting — multi-axis torch tilts ±45° (V, X, Y, K bevels for weld preparation in heavy fabrication / shipbuilding).

Oxy-fuel cutting — exothermic oxidation of carbon steel only; very heavy plate to 300 mm; cheap consumables; coarse kerf. Acetylene or propane / methane / propylene fuel + pure O₂. Common in shipyards and structural steel fabrication. Cannot cut stainless, Al, Cu (oxide film prevents reaction).

15. Ultrasonic machining (USM and rotary USM / RUM)

Tool oscillates axially at 20–40 kHz (amplitude 10–50 µm); abrasive slurry (boron carbide or SiC) between tool and work hammers grit into work surface → micro-fracture removal. Brittle non-conductive materials primarily: structural ceramic (Al₂O₃, ZrO₂, Si₃N₄), glass, quartz, silicon, sapphire, ferrite, CFRP (rotary version).

• Stationary USM — slurry-fed; shaped horn (sonotrode) plunges in (Sonic Mill).
• Rotary ultrasonic machining (RUM) — diamond-bonded rotating tool with superimposed axial 20–40 kHz oscillation (no slurry — tool is bonded); much higher MRR than stationary USM. DMG MORI Ultrasonic 20 / 50 / 65 linear (3- and 5-axis), Sauer Ultrasonic — drills + mills + grinds optical glass / ceramic / composite cleanly. Cited for stealth-aircraft RAM ceramic and advanced semiconductor parts.

16. Cutting-tool materials

Performance envelope set by red-hot hardness (hot hardness) + toughness trade-off.

• HSS — high-speed steel — M2 (general), M7 (low-V), M35 (5% Co), M42 (8% Co — tough alloys, taps), T15 (12% V — wear in abrasive). Tough, low cost, low temp (~600 °C max). Used for drills, taps, broaches, form tools, hobs.
• Cobalt HSS — M35 / M42 — added 5–8% Co bumps hot hardness, primary for stainless and Ni-superalloy tapping where solid carbide is too brittle.
• Solid carbide (WC-Co) — 6–10% Co binder; submicron (0.5–0.8 µm) grain for hard milling / endmills; fine (1.0 µm) for general; medium (1.5–2.5 µm) for tough roughing. Hot hardness ~900 °C.
• Coated carbide — PVD coatings (lower temp, sharp edges) — TiN (gold, general), TiCN, TiAlN / AlTiN (high temp, hard milling Ti / Ni-superalloy), AlCrN (mold + die), CrN (Al / brass). PVD multi-layer stacks: TiCN-TiAlN-TiN. CVD coatings (higher temp, robust) — TiCN-Al₂O₃-TiN for turning (Sandvik GC4325, Walter Tiger·tec, Kennametal KCM35, Mitsubishi MC6035).
• Cermet (TiCN-Ni-Mo) — titanium-carbide ceramic in nickel binder; light finishing turning + finishing milling of steel (mirror finish, no built-up edge). Mitsubishi NX series, Sandvik GC1525.
• Ceramic — Al₂O₃ (white, finishing cast iron + finishing hardened steel), Al₂O₃-TiC (black, roughing hardened steel — interrupted cut hard turning), Si₃N₄ + SiAlON (cast-iron roughing at >800 m/min and Ni-superalloy roughing). Brittle → no interrupted cut on steel.
• CBN — cubic boron nitride — hardness behind diamond, but reactive with iron at high T (diamond is not viable for steel). Hard-steel turning (62–66 HRC) at 150–250 m/min; replaces grinding for many bearing + gear finishing operations. Sandvik CB7015 / CB7115, Mitsubishi BC8120, Kennametal KB1340.
• PCD — polycrystalline diamond — sintered diamond layer on carbide; non-ferrous only (no Fe + C affinity). Aluminum (high Si — pistons), copper, brass, MMC (Al-SiC), CFRP, GFRP, wood. Tool life 100× carbide on abrasive composites.

17. Coolants and lubricants

• Flood emulsion — semi-synthetic / soluble-oil at 5–10% in water; bulk cooling + chip flush + lubrication; legacy default; problems: bacterial / fungal growth, mist inhalation, disposal cost.
• MQL (Minimum Quantity Lubrication / near-dry) — 5–50 mL/h fatty-ester aerosol delivered through the spindle or external nozzle. Environmental + air quality improvement; works well in Al + many steels; not enough cooling for Ni-superalloy.
• High-pressure coolant-thru-spindle (70–300 bar) — directed jet at the rake face breaks chips in Ti and Ni-superalloy (long stringy chip is otherwise unmanageable); enables higher cutting speed; required for many gun-drill and indexable-drill operations. ChipBlaster, MP Systems, Knoll.
• Dry machining — gray cast iron (graphite is self-lubricating); some Al (with TiAlN-coated carbide); plastics. Pure economic + environmental driver.
• Cryogenic LN₂ (-196 °C / -321 °F) — liquid nitrogen jet at the rake face; intense local cooling, no chemical residue, no mist. Doubled tool life on Ti-6Al-4V and Inconel 718 vs flood. Now offered by MAG Cryomill, Mazak Smart Box LN₂, and 5ME aftermarket retrofit. Capex barrier (LN₂ supply + insulated lines + Dewar) limits to high-value aero applications.

18. Selection heuristics

Workpiece / feature	Best process
Round bar precision part	CNC turning; if mill features + back-side ops → mill-turn
Bar stock < 32 mm, very high precision	Swiss-type (Citizen / Star / Tornos)
Deep hole / oil-port L/D 25–100:1	Gun drill (small), BTA / STS (large)
Injection-mold cavity with deep ribs, hardened tool steel	Die-sink EDM with graphite or copper electrode
Precision punch + die in tool steel ≥60 HRC	Wire-EDM
Turbine-blade fir-tree root in Ni-superalloy	Creep-feed grind (Mägerle / Blohm) or PECM
Jet-engine blisk (integrally bladed disk)	5-axis milling + ECM / PECM airfoil finishing
Bearing race	Centerless OD grind + tape superfinish
Surgical scalpel	Wire-EDM rough + ECG hone
Hard-turning of 62 HRC bearing component	CBN insert at 150–250 m/min, replaces grinding
Sheet-metal prototype to production	Fiber laser (CO₂ legacy)
Glass / Si / ceramic semi-pieces	Wafer diamond-blade dicing or rotary USM
Food product trim	Pure-water jet (no abrasive)
Regrinding worn carbide tooling	Vitrified Al₂O₃ or CBN wheel
Aluminum engine block bore	Single-point bore + plateau honing
Crankshaft journal	Turn-broach + grind + tape superfinish
Internal involute spline	Push broach
Mass-production helical gear (auto transmission)	Hob + carburize + Reishauer threaded-wheel grind
Heavy plate 80 mm steel	HD plasma (Hypertherm XPR300) or oxy-fuel
Magnesium part (fire risk)	Water-jet or dry milling (no oil mist)

19. CNC controls and standards

• ISO 6983 (G-code) / EIA RS-274D — legacy block-based numerical-control language. G00–G99 motion + canned cycles, M-codes for auxiliary, T-codes for tool-change, S for spindle, F for feed.
• STEP-NC ISO 14649 — feature-based machining data (replaces G-code with semantic features: pocket, slot, hole, contour). Slow adoption; in research and select aero MES.
• Mazatrol (Mazak) — proprietary conversational programming on-machine; engineers without G-code expertise can program common cycles.
• Heidenhain ITNC 530 / TNC7 — popular on European 5-axis (DMG MORI, Hermle, Mikron); friendly conversational input + powerful 5-axis kinematics.
• Fanuc Series 30i / 31i / 32i / 35i — dominant global CNC; Series 0i mid-range; classic compatibility, large code base, controls Mazak (most), Mori, Doosan, many Asian builders.
• Siemens Sinumerik 840D sl / 828D / ONE — high-end European builds (open architecture, ShopMill / ShopTurn conversational shells), dominant on European 5-axis + grinding + gear.
• Mitsubishi M7-series / M8-series — Mitsubishi-built EDM + lathe + mill.
• Okuma OSP — proprietary; thermo-friendly (Thermo-Friendly Concept compensates spindle growth) for high-precision turning + grinding.

20. Cross-references

• [[Engineering/machining]] — Tier 2 machining survey (parent).
• [[Engineering/Tier3/welding-processes]] — joining sibling.
• [[Engineering/Tier3/forming-processes]] — bulk + sheet forming (rolling, forging, extrusion, stamping, deep-draw).
• [[Engineering/Tier3/gears-taxonomy]] — gear types, manufacturing detail.
• [[Engineering/Tier3/surface-treatments]] — heat treat, nitride, plate, coating that follows machining.
• [[Engineering/Tier3/bearings-taxonomy]] — application driver for centerless grinding + tape superfinish.
• [[Engineering/Tier3/machining-processes]] — Tier 2 overview of all manufacturing.

21. Citations and standards

• ISO 3685:1993 — Tool-life testing with single-point turning tools.
• ISO 6983-1:2009 — Numerical control of machines — Program format and definitions (G-code base spec).
• ISO 14649 (parts 1, 10, 11, 12, 14, etc.) — STEP-NC feature data model.
• ISO 1832:2017 — Indexable inserts for cutting tools — Designation.
• ISO 513:2012 — Carbide grade group designation (P / M / K / N / S / H — steel / stainless / cast-iron / non-ferrous / superalloy / hard).
• ISO 4287 / 4288 / 21920 — Surface texture (Ra, Rq, Rz, Rt — replacement of ISO 4287 by 21920-2 in 2021).
• CIRP Encyclopedia of Production Engineering, 2nd ed., Springer 2014 (Laperrière, Reinhart, eds.).
• Sandvik Coromant — Modern Metal Cutting: A Practical Handbook (Sandviken 1994 + updates).
• Kennametal Master Catalog; Iscar Master Catalog; Mitsubishi Materials Tooling Catalog; Walter General Catalog; Seco Master Catalog.
• ASM Handbook Vol. 16: Machining (ASM International 1989, reprinted).
• E.J.A. Armarego, R.H. Brown — The Machining of Metals (Prentice-Hall 1969 — classical).
• M.C. Shaw — Metal Cutting Principles, 2nd ed., Oxford 2005.
• Trent + Wright — Metal Cutting, 4th ed., Butterworth-Heinemann 2000.
• DIN 8580 — Manufacturing process classification (German classification framework adopted widely in EU).