The second hardest material on earth after diamond. Used to grind ferrous metals like hardened steel, cast iron, and superalloys where diamond would react chemically with the workpiece at grinding temperatures.

The hardest known material (10 on Mohs scale). Used to grind non-ferrous materials: carbide, ceramics, glass, composites, PCD, and PCBN. Reacts with ferrous metals at high temperatures — not suitable for grinding steel.

Collective term for diamond and CBN abrasives. Distinguished from conventional abrasives by extreme hardness, long wheel life, superior dimensional accuracy, and ability to grind hardened and exotic materials.

Aluminum oxide (Al₂O₃) or silicon carbide (SiC) used in standard grinding wheels. Much lower hardness and shorter life than superabrasives. Suitable for softer or lower-value materials where CBN or diamond is not cost-justified.

Mesh number describing abrasive grain size. Lower numbers (e.g. 46, 60) = coarse grains for aggressive material removal and roughing. Higher numbers (e.g. 320, 600) = fine grains for smooth surface finish and finishing passes.

The screen-opening count per linear inch used to classify abrasive grain size. A 120-mesh screen has 120 openings per inch; grains passing through are called 120 grit. Mesh and grit are used interchangeably for most abrasives.

Unit of measurement equal to 0.001 mm. Used for very fine grit sizes (e.g. 6 µm, 1 µm) in lapping, polishing, and superfinishing applications. 1 µm = approximately 40 microinches.

Volume percentage of abrasive grain in the bond layer. Standard concentrations: 25, 50, 75, 100. Concentration 100 = 25% abrasive by volume. Higher concentration gives longer wheel life but requires more machine power and force to cut.

The tendency of an abrasive grain to fracture under grinding stress, exposing fresh sharp edges. High friability = self-sharpening wheel. Low friability = longer grain life but risk of dulling, glazing, and workpiece burn.

The individual grain structure of an abrasive. CBN and diamond crystals can be blocky (tough, long-wearing) or irregular/sharp (friable, self-sharpening). Crystal morphology is engineered for specific applications and bond systems.

A single-crystal abrasive grain grown as one intact crystal. Offers high strength, predictable fracture patterns, and long wheel life. Often specified for precision and high-production grinding of carbide and hardened steel.

Abrasive grain composed of many small crystals fused together. Tends to fracture into smaller sharp pieces under load, producing a self-sharpening effect throughout the grain’s life. Common in CBN and synthetic diamond products.

Sintered diamond compacts bonded to a carbide substrate. Used as cutting tool tips and inserts for machining aluminum, composites, and non-ferrous materials. Requires diamond grinding wheels for form grinding and sharpening.

Sintered CBN compacts used in turning inserts for hardened steel and cast iron. Extremely wear-resistant. Ground using diamond or vitrified CBN wheels when sharpening or producing insert forms to tight tolerances.

A glass-ceramic bond fired at high temperature. The most common superabrasive bond system. Rigid and porous, providing excellent coolant flow and chip clearance. Dressable with rotary or stationary tools. Ideal for precision, high-production grinding applications.

Thermosetting polymer bond (typically phenolic or polyimide). More flexible than vitrified, providing a cushioning effect for better surface finish. Not crush-dressable — requires brake-controlled or dressing stick conditioning. Used in tool grinding and finish operations.

Sintered metal matrix (bronze, iron, or cobalt) holding abrasive grains in a rigid structure. Extremely strong with the longest wheel life of any bond. Used where form holding is critical. Requires EDM or crush dressing — difficult to condition conventionally.

Single layer of abrasive grains bonded to a precision steel core by nickel electrodeposition. Cannot be dressed — the wheel is used until the abrasive layer is depleted. Best for complex forms, broaches, hobs, and interrupted cut applications.

A bond combining characteristics of two systems, such as metal-resin or vitrified-polymer. Engineered for applications requiring intermediate properties — more durable than pure resin but more dressable than pure metal bond.

The controlled wearing away of bond material during grinding to expose fresh abrasive grains. Proper bond erosion rate keeps the wheel self-sharpening. Too fast = short wheel life. Too slow = grain dulling, loading, glazing, and workpiece burn.

Rating of how firmly the bond holds grains in place. Soft grades (A–H) release grains easily for self-sharpening. Hard grades (P–Z) retain grains longer for extended wheel life. Softer grade is used on hard workpiece materials to encourage proper self-sharpening action.

Open space within the bond structure allowing coolant penetration and chip clearance. Critical for free cutting and cool grinding in vitrified wheels. Can be naturally occurring or engineered (induced porosity) using filler materials that burn out during firing.

The wheel contacts the outer surface of a rotating cylindrical workpiece. Can be traverse (wheel traverses axially across workpiece) or plunge (wheel feeds radially into one position). Used for shafts, journals, pins, and rollers.

A small grinding wheel rotates at high RPM inside a bore or hole. Used for precision bores, bearing races, hydraulic cylinders, and internal features. Wheel diameter is typically 50–80% of bore diameter to allow coolant flow.

Cylindrical grinding where the workpiece is supported between a grinding wheel, regulating wheel, and work rest blade — no centers or chuck required. Extremely high production rates. Two modes: through-feed and in-feed (plunge).

The workpiece passes axially through the machine between the grinding and regulating wheels. The regulating wheel is angled to advance the part automatically. Used for plain cylinders, pins, and rollers in very high volume production.

The workpiece does not travel axially. The grinding wheel plunges radially to size. Used for parts with shoulders, flanges, tapers, or complex profiles that cannot pass through the machine axially.

Grinding a flat surface on a workpiece. Horizontal-spindle machines use the wheel periphery; vertical-spindle machines use the wheel face (cup or segmented wheel). Used for dies, plates, blocks, and precision flat components.

Single-pass deep cut grinding with very slow table feed. Removes large amounts of stock in one pass rather than many shallow passes. Used for aerospace turbine blades, complex profiles, and slots. Requires very high coolant volume and rigid machines.

Grinding cylindrical surfaces (OD or ID) on a machine with headstock, tailstock, and rotating workpiece. Can be done between centers for maximum accuracy or using a chuck for shouldered or blind-bore parts.

Grinding complex 2D or 3D contours using a formed wheel or CNC axis interpolation. Used for gears, cams, turbine blade roots, thread forms, and punch/die profiles. Requires precise wheel dressing to the required form.

Precision grinding of gear tooth flanks after heat treatment. Two main methods: generating (threaded or worm wheel) and form grinding (profile wheel). Produces tight AGMA or DIN gear accuracy class. CBN wheels dominate production gear grinding.

CNC profile grinding of cam lobes on an automotive camshaft after hardening. Uses CBN wheels with CNC interpolation of wheel feed vs. part rotation angle to reproduce exact cam lobe lift geometry. High-volume automotive application for vitrified CBN.

OD grinding of main journals and eccentric pin journals on engine crankshafts. High-production application for vitrified CBN wheels. Grinding crankpins requires eccentric part rotation (C-axis) synchronized with grinding wheel feed (X-axis).

Two opposing grinding wheels face each other with a controlled gap. Workpieces pass between them on a carrier plate. Simultaneously grinds both faces parallel in a single pass with high throughput. Common for automotive transmission components.

Grinding with the wheel spindle tilted at an angle relative to the workpiece axis. Used for angular faces, chamfers, tapered bores, and combination OD/face grinding in a single setup to reduce part handling and improve position accuracy.

Abrasive finishing of bores using reciprocating abrasive stones to produce a characteristic crosshatch pattern. Improves bore geometry (roundness, cylindricity) and creates a surface texture ideal for oil retention. Not the same as grinding — lower stock removal rates, finishing operation only.

Rubbing two surfaces together with a loose abrasive slurry between them on a flat plate (lap). Produces very flat, fine surfaces. Different from grinding — the abrasive is free (not bonded), and material removal is minimal. Used for valve seats, gauges, and optical flats.

Oscillating abrasive stone applied to a rotating workpiece with very light pressure. Removes the amorphous (disturbed) surface layer left by grinding, producing a plateau finish with excellent bearing ratio. Common on bearing races, crankshaft journals, and camshafts.

Rotational speed of the grinding wheel spindle. Must never exceed the wheel’s maximum operating speed rating. Higher RPM increases surface footage (SFPM/m/s) at the same wheel diameter. Always verify before mounting a wheel.

Linear speed at the wheel’s cutting surface. SFPM = (RPM × Wheel Diameter × π) ÷ 12. Typical superabrasive ranges: 4,000–12,000 SFPM. The single most critical parameter affecting wheel performance, wheel life, and workpiece surface quality.

Meters per second — the metric equivalent of SFPM. 1 m/s = approximately 197 SFPM. Standard production grinding: 30–60 m/s. High-speed grinding (HSG): above 80 m/s. Always confirm the wheel’s speed rating covers the intended operating speed.

Volume of material removed per unit time per unit width of cut (mm³/mm/s or in³/in/min). Q’ = depth of cut × feed rate. The primary metric for comparing grinding process efficiency across different wheel widths or machine setups.

Total volume of material removed per minute across the full width of cut. MRR = width of cut × depth of cut × feed rate. Higher MRR means more productive grinding but also higher wheel wear, heat generation, and potential for workpiece damage.

Volume of workpiece material removed divided by volume of wheel material consumed. G = Vw ÷ Vg. A key measure of grinding efficiency. CBN wheels routinely achieve G-ratios 10–100× higher than conventional abrasive wheels on the same application.

The radial distance the wheel penetrates into the workpiece per pass, in thou (0.001″) or micrometers. Also called infeed. Affects MRR, wheel wear, and surface finish. Roughing: 0.002–0.010″; finishing: 0.0001–0.0005″. Creep feed: up to 0.250″.

Speed at which the workpiece moves relative to the grinding wheel, expressed in ipm (inches per minute) or mm/min. Higher feed rate increases MRR and productivity but produces a coarser surface finish and generates more heat at the contact zone.

Final passes made at zero infeed after reaching target size. Allows elastic deflection (spring) in the machine and workpiece to recover, grinding the remaining material without additional programmed feed. Improves dimensional accuracy, roundness, and size consistency.

The amount the grinding wheel is fed into the workpiece — total programmed stock removal for a plunge cycle or the amount fed per traverse pass. Distinct from depth of cut (per pass) in traverse grinding where multiple passes may be used.

The force exerted by the grinding wheel on the workpiece during grinding. Tangential force (Ft) does the cutting work. Normal force (Fn) deflects the part and machine structure, causing size error. Monitoring force is an indicator of wheel condition and process stability.

Motor power consumed at the grinding spindle, measured in horsepower (hp) or kilowatts (kW). Monitoring power provides an indirect measure of MRR, wheel sharpness, and process health. Rising power with constant infeed indicates wheel glazing or loading — dress required.

Ratio of grinding wheel surface speed to workpiece surface speed (q = vs ÷ vw). Affects chip thickness, surface finish, and thermal load. Typical values: 60–200 for cylindrical grinding. Varying q is one method of controlling surface finish without changing grit size.

The average absolute deviation of the surface profile from the mean line, measured in microinches (µin) or micrometers (µm). The most common surface finish specification worldwide. Lower Ra = smoother surface. Typical ground finish: 4–32 µin Ra.

Average of the maximum peak-to-valley heights over 5 consecutive sampling lengths. More sensitive to isolated peaks and valleys than Ra. Standard in European and DIN specifications. For ground surfaces, Rz ≈ 4–7× Ra.

The single maximum peak-to-valley height over the entire measurement length. Indicates the worst-case surface condition. More relevant than Ra when a single deep scratch or peak could cause sealing failure, stress concentration, or functional problems.

Square root of the mean of the squared deviations from the mean line. Slightly higher than Ra for the same surface — typically Rq ≈ 1.1× Ra. Often used in optical, precision measurement, and semiconductor manufacturing specifications.

US unit of surface roughness: 1 µin = 0.000001 inch = 0.0254 µm. Common in American drawings and specifications. A superabrasive finish pass on bearing steel might achieve 4–8 µin Ra. Conversion: 1 µm = 39.37 µin.

Long-wavelength surface variation below flatness/roundness errors but above roughness. Caused by machine vibration, thermal drift, or wheel imbalance. Measured separately from roughness using a longer evaluation length and cutoff wavelength. Can cause noise in bearing and gear applications.

The direction of the dominant surface texture pattern — parallel, perpendicular, circular, or crosshatch relative to a reference direction. Lay affects tribological performance: oil retention, friction, and sealing ability vary significantly depending on lay direction relative to motion.

Surface texture with sharp peaks removed by superfinishing or plateau honing, leaving wide flat load-bearing plateaus separated by valleys that retain lubricant. Measured by the Rk family of parameters (Rk, Rpk, Rvk). Ideal for cylinder bores, bearing journals, and sliding contact surfaces.

Comprehensive description of a surface condition including roughness, waviness, residual stress state, microstructure, microhardness, and subsurface damage. Goes beyond Ra specification alone. Critical for fatigue life, corrosion resistance, and long-term performance of aerospace, medical, and bearing components.

Metallurgical alteration from excessive grinding heat: re-hardening burn, over-tempering (softening), oxidation, or residual tensile stress. Causes premature component failure. Detected by Barkhausen noise analysis, X-ray diffraction, or acid etch (nital etch) inspection per ASTM or aerospace specifications.

Complete designation describing a superabrasive grinding wheel: abrasive type (B=CBN, D=Diamond), grit size, grade (hardness), concentration, bond type (V=vitrified, R=resin, M=metal, P=electroplated), and wheel dimensions (OD × thickness × bore). Example: B151-N100-V.

Thickness of the superabrasive section on the wheel face, typically 3–6 mm (1/8″–1/4″). Only this layer contains diamond or CBN grains in the bond. The remaining wheel body is an inert steel or aluminum core. Deeper layers give more wheel life between core replacements.

The structural body of a superabrasive wheel, typically precision-machined steel or aluminum. Provides dimensional stability, dynamic balance, and the mounting interface. Accuracy of the core directly affects TIR and the achievable part tolerance of the grinding process.

The center hole of the grinding wheel that mounts onto the machine spindle. Must match spindle diameter precisely with appropriate fit. Flanges or adapters compress the wheel hub to prevent rotation under grinding torque. Hub accuracy directly affects TIR.

The total measured variation in the wheel’s cutting surface position as it rotates one full revolution. Low TIR (under 0.0002″) is essential for precision grinding. Excessive runout causes chatter marks, poor surface finish, and prevents achieving tight size tolerances.

The highest RPM or SFPM the wheel is rated, tested, and approved for. Always marked on the wheel blotter or label per ANSI B7.1 requirements. Never exceed this speed. Exceeding max speed risks catastrophic wheel disintegration — a life-safety issue and legal liability.

Standard designation for wheel geometry defining how the abrasive section contacts the workpiece. Common superabrasive shapes: 1A1 (straight periphery), 1FF1 (face), 11V9 (flaring cup for tool grinding), 12V9 (dish), 14F1 (straight rimmed). Shape selection depends on machine type and grinding operation.

Condition where the wheel’s mass is evenly distributed about its rotational axis. Unbalanced wheels cause vibration, chatter, spindle bearing wear, and poor surface finish. Superabrasive wheels are precision-balanced at the factory and may require field balancing after mounting.

SuperAbrasives’ proprietary manufacturing method using individual precision abrasive segments assembled and bonded onto a reusable steel hub. Allows complex custom forms, faster lead times, and significant cost savings by replacing only worn abrasive segments rather than the entire wheel including the expensive core.

The combined process of truing and conditioning a grinding wheel. Truing restores correct geometry; conditioning opens the bond to expose fresh sharp abrasive grain. Dressing is performed after wheel mounting, after loading or glazing, and periodically to maintain consistent part quality.

Restoring the wheel to its correct geometry — making it perfectly round, flat, or the required form profile. Removes runout, chatter marks, and form error caused by uneven wear. A trued wheel may still need conditioning (opening the bond) to cut freely.

Opening the wheel face to expose sharp abrasive grains by eroding excess bond material. A properly conditioned wheel cuts freely and with minimal heat. Done with a dressing stick for resin bond wheels or by rotary dressing parameters for vitrified bond wheels.

A powered diamond dressing roll that engages the wheel periphery at a precisely controlled speed ratio. The standard method for dressing vitrified CBN and diamond wheels in production grinding. Available as single-point traversing rolls and full-form (crush profile) rolls.

Ratio of dresser roll surface speed to grinding wheel surface speed. Positive ratio (same direction, slower dresser) produces a fine, closed wheel topography. Negative ratio (counter-rotation) creates a coarser, more open topography with higher material removal rate but rougher workpiece finish.

Axial traverse rate of the dressing tool across the wheel face. Slow lead = finer wheel surface topography and smoother workpiece finish. Fast lead = coarser topography, more aggressive cutting action, and higher MRR. Dressing lead is one of the key parameters tuned to balance finish and productivity.

A stationary natural or synthetic diamond tip traversed across the wheel face to true and condition. Simple, low-cost, and effective for straight and angled faces on vitrified wheels. Requires regular 90° indexing to distribute wear and maintain a sharp point geometry.

A rotary dressing tool with a controlled braking mechanism that sets the dresser roll’s surface speed relative to the wheel speed. The standard method for dressing resin bond superabrasive wheels where crush dressing would cause bond fracture. Controls the amount of bond erosion per dress pass.

A rectangular block of conventional abrasive (usually friable aluminum oxide or silicon carbide) applied to a spinning resin bond superabrasive wheel. The stick erodes the bond to expose fresh CBN or diamond grain. The simplest and most common method for conditioning resin bond wheels.

Electrical Discharge Machining used to dress metal bond superabrasive wheels. EDM erodes the metallic bond matrix without applying mechanical grinding forces — the only practical method for accurately conditioning and profiling metal bond wheels to tight form tolerances.

Computer Numerically Controlled grinding machine with programmable axes for wheel feed, traverse, part rotation, and dressing. Enables complex profiles, automatic size compensation, and repeatable production cycles with minimal operator intervention. Standard for superabrasive production grinding.

Versatile machine capable of OD, ID, and limited surface grinding through swiveling wheelhead and table. Common in tool rooms and job shops for prototype and low-volume work. May be manual or CNC. Less rigid than dedicated production grinders.

Machine for grinding cylindrical parts without centers or fixtures. Consists of a grinding wheel, regulating wheel, and work rest blade supporting the part. Excellent for high-volume round parts: pins, shafts, rollers, and needles. Very high throughput with no part-handling time.

Specialized machine for grinding bores and internal features. Uses high-speed internal grinding spindles (10,000–200,000 RPM for small bores) to compensate for the small wheel diameter needed to enter the bore. Achieves precise bore size, roundness, and cylindricity.

Heavy-duty surface grinding machine designed for single-pass deep cuts. Features rigid construction, high-volume flood coolant systems, and low-speed precision servo table drives. Used in aerospace, turbine, and medical component manufacturing for profile and slot grinding.

Dedicated CNC machine for grinding automotive camshafts or crankshafts after hardening. Uses CNC C-X axis interpolation to generate cam lobe profiles or grind eccentric crankpin journals while the part rotates. Primary application for vitrified CBN wheels in the automotive industry.

Precision machine using a high-speed spindle (up to 100,000 RPM) for grinding holes, contours, and surfaces on hardened workpieces to very tight tolerances. Used in tool, die, and mold making. Can interpolate circular paths for bore grinding without a rotary axis.

Vertical-spindle machine where a cup wheel or segmented wheel grinds the face of workpieces held on a rotating magnetic or mechanical chuck. High throughput for parallel flat parts. Segment wheels allow coolant to reach the grinding zone more effectively than cup wheels.

Thermal damage to the workpiece surface or subsurface caused by excessive grinding heat. Visible as discoloration (gold, blue, or white). Causes include dull wheel, insufficient coolant, excessive infeed, or wrong wheel grade. Results in rehardening, soft spots, tensile residual stress, and premature part failure.

Periodic waviness on the ground surface caused by vibration between wheel and workpiece. Appears as regular, evenly spaced marks. Common causes: wheel imbalance, worn spindle bearings, resonance between machine and part, improper wheel grade, or loose fixturing. Diagnosed by FFT vibration analysis.

Metal chips or workpiece material packed into the pores or voids between abrasive grains on the wheel face. A loaded wheel cannot cut — it smears and generates excessive heat. Caused by soft, ductile workpiece material, insufficient coolant, or incorrect bond/porosity for the application. Corrected by dressing.

Condition where abrasive grains become dull and flat-topped without fracturing or releasing from the bond (bond too hard for the application). A glazed wheel rubs rather than cuts, generating extreme heat, poor surface finish, and inconsistent size. Requires dressing with more aggressive parameters or a softer wheel grade.

Workpiece is not truly circular after grinding — diameter varies as the part rotates. Caused by: unbalanced or out-of-true wheel, worn centers, loose tailstock, workpiece deflection under grinding force, or insufficient sparkout passes. Measured by CMM or dedicated roundness gauge (Talyrond).

Diameter varies progressively along the workpiece length — part is larger at one end than the other. Caused by misaligned centers, worn table ways, incorrect wheel-to-table alignment, or thermal growth during grinding. Corrected by adjusting the table swivel angle by a precise amount.

Individual deep marks on the finished surface from oversize abrasive grains, metallic contamination in coolant, or embedded chips from a previous operation. Distinguished from chatter by being random and non-periodic. Address by filtering coolant, examining the dressing tool, and inspecting wheel condition.

Breakout of workpiece material at edges during grinding. Common when grinding brittle materials (carbide, ceramics, glass). Controlled by reducing depth of cut, using a softer bond wheel, optimizing coolant flow at the entry edge, and chamfering sharp edges before grinding.

Steel heat-treated above approximately 55 HRC. The primary application for CBN grinding wheels. Common examples include M2 high speed steel, D2 tool steel, 52100 bearing steel, 4340 alloy steel, and case-hardened gears, camshafts, and crankshafts. CBN is 5–100× more productive than aluminum oxide on hardened steel.

Tungsten carbide in a cobalt binder (WC-Co) — the hardest metal-matrix composite in common industrial use. Requires diamond grinding wheels. Used in cutting tool inserts, wear parts, dies, and punches. Extremely abrasion-resistant; sensitive to thermal shock — requires high coolant volume.

Advanced engineering ceramics including alumina (Al₂O₃), silicon nitride (Si₃N₄), silicon carbide (SiC), and zirconia (ZrO₂). Ground exclusively with diamond wheels. Brittle — prone to chipping and subsurface cracking. Requires light passes, sharp wheels, and high coolant flow to minimize grinding-induced damage.

High-temperature nickel, cobalt, and iron-based alloys including Inconel 718, Hastelloy, Waspaloy, and Rene 88. Very low thermal conductivity — heat concentrates in the grinding zone. Used in aerospace turbine components. Requires CBN or specialist abrasives, high coolant pressure, and careful parameter selection.

Iron alloy with 2–4% carbon content. Graphite inclusions act as a natural lubricant during grinding. Commonly ground with CBN or conventional aluminum oxide wheels. Gray cast iron (most common), white cast iron (very hard, abrasive), and ductile (nodular) iron differ significantly in grinding behavior.

Low density, high strength, with very low thermal conductivity. Titanium chips tend to weld (cold-weld) to abrasive grains at grinding temperatures. Requires sharp free-cutting wheels, high coolant pressure and flow, moderate wheel speeds, and frequent dressing. Ground with CBN in aerospace applications.

Highly alloyed tool steel (M2, M42, T15, Rex 76) retaining hardness at elevated temperatures. Used for drills, end mills, taps, hobs, and broaches. Ground with CBN wheels for resharpening cutting edges and form grinding flutes and profiles — far more productive than conventional aluminum oxide on HSS.

Nickel-chromium superalloy (most commonly Inconel 718) used extensively in jet engine components. Extremely difficult to grind due to rapid work hardening, very low thermal conductivity, and tendency to weld to abrasive grains. Requires CBN wheels, high coolant pressure, conservative infeed rates, and frequent dressing.

The standard hardness measurement for hardened steel. CBN wheels are specified when workpiece hardness exceeds approximately 45–50 HRC. Most bearing steels, tool steels, and gear steels are ground in the range of 58–65 HRC. Harder workpiece = softer wheel grade recommended to maintain self-sharpening action.