grinding-operations

name	grinding-operations
description	Grinding operations — abrasive types, wheel specification, specific energy, grinding ratio, surface roughness, thermal damage, dressing, CBN wheels, ANSI B74.13.
metadata	{"priority":7,"promptSignals":{"phrases":["grinding operation","grinding wheel","surface grinding","cylindrical grinding","specific grinding energy","grinding burn","CBN wheel"],"minScore":3}}

Grinding Operations — Complete Skill

Wheel Specification (ANSI B74.13)

Standard marking: 39C 60 K 8 V BE

Position	Meaning	Example
Prefix	Manufacturer prefix	39
Abrasive type	A=Al₂O₃, C=SiC, B=CBN, D=diamond	A or C
Grit size	Coarser → finer: 10,16,24,36,46,60,80,100,120,150,180,220	60
Grade	Soft (A) to Hard (Z)	K
Structure	Open (1) to Dense (16)	8
Bond	V=vitrified, R=rubber, B=resinoid, E=shellac	V

Abrasive Selection

Abrasive	Application	Notes
Al₂O₃ (WA, A)	Steel, ferrous metals	Most common; white = friable; brown = tough
SiC (C, GC)	Cast iron, aluminum, ceramics	Harder but more brittle than Al₂O₃
CBN (B)	Hardened steel (HRC > 45); high productivity	Very expensive; long life
Diamond (D)	Ceramics, carbides, glass, CFRP	Cannot grind steel (carbon diffusion)

Cutting Parameters

Wheel peripheral speed: V_s = π D_s N / 1000 [m/s; D in mm, N in rpm] Standard: V_s = 25–35 m/s; high speed: 45–120 m/s; HEDG: > 150 m/s

Workpiece speed: V_w = 0.02–0.10 × V_s (too slow → rubbing; too fast → poor finish)

Infeed (depth of cut per pass): a_p: Rough: 0.025–0.125 mm; Finish: 0.005–0.025 mm; Spark-out: 0–0.002 mm

Grinding ratio (G-ratio): G = Volume removed from workpiece / Volume removed from wheel G typical: Al₂O₃ on steel ≈ 5–50; CBN on hardened steel ≈ 500–5000

Specific Grinding Energy

u = F_c V_s / (v_f a_p b) [J/mm³ = GPa effectively]

Typical u values: Steel (soft): 20–30 J/mm³; Steel (hardened): 30–60 J/mm³; Ti: 15–25 J/mm³; Ceramics: 50–200 J/mm³

Higher u → more heat generated → risk of thermal damage

Thermal Analysis — Grinding Burn

Heat flux to workpiece: q = u × v_f × a_p × b × ε_w / (contact area)

ε_w = fraction of heat to workpiece (0.5–0.75 typical; coolant reduces)

Maximum workpiece temperature (Jaeger): T_max = 1.13 q √(k/V_w a_p) / √(ρ c k) (simplified)

Burn criterion: T_max > A_1 (tempered) → ≥150°C; T_max > A_3 (re-hardened) → ≥727°C for steel

Signs of burn: discoloration (blue/straw), microstructure change (white layer), tensile residual stress, rehardened layer

Prevention:

• Reduce infeed; increase V_w; improve coolant flow (18–30 L/min, high pressure)
• Use sharp wheel (dress frequently)
• Use harder grade wheel if glazing; softer if burning
• Switch to CBN for hardened steel (lower u per contact, higher G)

Surface Roughness

Theoretical: Ra = f² / (8 r_s) (by analogy; r_s = abrasive grain radius ≈ 0.5–5 μm)

Practical factors: Ra decreases with: lower V_w, more spark-out passes, finer grit, dressing lead per rev Ra typical range: 0.1–6.3 μm (Ra); 0.05–3.2 μm with superfinishing

Dressing

Removes dull grains; restores wheel profile and sharpness

Single-point diamond dresser: Dressing infeed: a_d = 0.01–0.05 mm/pass Dressing feed: f_d = 0.05–0.3 mm/rev (coarser → more open, sharper; finer → dense, smoother) After dressing: G-ratio resets; fewer passes before next dress

Rotary diamond roll dresser: continuous dress; consistent surface finish; higher cost

Vitrified CBN wheels: dress sparingly (crush dress or laser); very long life between dresses

Operations

Surface grinding: reciprocating table; typical Ra 0.4–1.6 μm; flatness 5–25 μm Cylindrical grinding (OD): rotating workpiece + wheel; Ra 0.1–0.8 μm; roundness 1–5 μm ID grinding: internal bore; wheel size limited; high L/D → vibration challenge Centerless grinding: no centers; high production; Ra 0.1–0.8 μm; roundness 1–3 μm

Grinding Fluids

Conventional grinding: soluble oil 3–5% concentration at 18–50 L/min CBN grinding: straight oil or soluble oil at high flow; wetting is critical Creep-feed grinding: flood coolant at 20–40 bar; removes large amounts in one pass

Output

Provide: wheel specification (abrasive-grit-grade-structure-bond), V_s [m/s], V_w [m/min], a_p [mm], feed [mm/rev or mm/stroke], G-ratio, specific energy u [J/mm³], T_max [°C] vs. burn threshold, Ra [μm], dressing interval estimate.