Surface Finish Standards Catalog
Encyclopedic catalog of surface metrology and finish specification: profile parameters (Ra, Rq, Rz, Rt, Rp, Rv, Rsk, Rku, Rsm, Rmr), areal parameters (ISO 25178: Sa, Sq, Sz, Sp, Sv, Sku, Ssk, Sdr, Sk, Spk, Svk), standards (ISO 4287, ISO 4288, ISO 12085, ISO 13565, ISO 25178, ASME B46.1, DIN 4760-4768), process-capability roughness ranges, lay symbols (ISO 1302, ASME Y14.36M), contact + non-contact metrology equipment, Gaussian cutoff filters, coating thickness measurement, blast-cleanliness, peening + Almen control, and surface engineering for adhesion, tribology, fatigue, and compressive residual stress.
1. Surface Texture Fundamentals
A surface’s geometry consists of three superimposed orders:
| Order | Wavelength range | Origin | Captured by |
|---|---|---|---|
| 1st: Form | > 10 mm | Machine geometry, fixturing | Form measurement (CMM, roundness, flatness) |
| 2nd: Waviness | 0.8-10 mm | Machine vibration, chatter | Waviness profile (W) after long-wavelength cutoff |
| 3rd: Roughness | 0.0025-0.8 mm | Tool marks, grit, finishing process | Roughness profile (R) after short + long cutoffs |
| 4th-6th: Sub-roughness | < 0.0025 mm | Microcracks, micro-grains | AFM, scanning probe |
Per DIN 4760 (1982 classification) + ISO 25178 (areal extension).
The primary surface profile P contains all components; band-pass filtering separates R from W from F.
2. Roughness Parameters — Profile (R, 2D)
2.1 Amplitude Parameters
| Parameter | Symbol | Definition | Typical relation |
|---|---|---|---|
| Arithmetic mean deviation | Ra | (1/L) ∫ |z(x)| dx over evaluation length L | most common single-number spec |
| Root-mean-square | Rq (RMS) | √[(1/L) ∫ z²(x) dx] | Rq ≈ 1.11 × Ra for Gaussian surface; Rq more sensitive to peaks |
| Maximum peak height | Rp | max z(x) above mean line in sampling length lr | — |
| Maximum valley depth | Rv | max |z(x)| below mean line | — |
| Maximum height of profile | Rz | Rp + Rv per sampling length, averaged over 5 sampling lengths (current ISO 4287 definition) | Rz ≈ 4-8 × Ra depending on process |
| Maximum height (any sample) | Rt | max Rp + max Rv over evaluation length | Rt ≥ Rz |
| Mean peak-to-valley | Rc | mean of profile element heights | — |
| Total height | Rt | Rp + Rv over entire evaluation length | strictest peak metric |
| Maximum height of profile (old DIN) | Rmax (Rmax = Rt per modern ISO) | — | Legacy designation |
Note on Rz: pre-1997 DIN definition (Rz_DIN) = average of 10 highest peak-to-valley values (5 peaks + 5 valleys averaged). Post-1997 ISO 4287 Rz = average of Rt across 5 sampling lengths (different value). Always specify which definition.
2.2 Statistical Parameters
| Parameter | Symbol | Use |
|---|---|---|
| Skewness | Rsk | < 0 valley-dominated (lapped, polished); > 0 peak-dominated (turned). Influences lubrication retention + bearing area |
| Kurtosis | Rku | < 3 plateau-like; = 3 Gaussian; > 3 sharp peaks |
| Mean spacing of profile elements | RSm | Lateral peak-to-peak spacing |
| Material ratio (bearing-area) | Rmr(c) | % of profile material at depth c below highest peak; basis of bearing-area curve (Abbott-Firestone) |
| Profile section height | Rδc | Height difference between two material ratios |
2.3 Bearing Area / Abbott-Firestone Curve
| Parameter | Symbol | Definition |
|---|---|---|
| Core roughness depth | Rk | Depth of “core” region of bearing curve (most contact-bearing area) |
| Reduced peak height | Rpk | Above-core peaks (initial wear-in) |
| Reduced valley depth | Rvk | Below-core valleys (oil retention) |
| Material portion at peak | Mr1 | % material at top of core region |
| Material portion at valley | Mr2 | % material at bottom of core region |
| Oil retention volume (Vvc/Vvv) | — | Volume parameter from areal data |
Standardized in ISO 13565-2:1996 (Rk family) — defining for plateau-honed cylinder liners, bearing surfaces, lapped gears.
3. Areal Parameters (ISO 25178, 3D / S-set)
ISO 25178 extends profile metrology to 3D / areal — measurement over a defined surface area rather than a single line trace. Required because process directionality and isolated features (single deep scratch, pit, lubrication pocket) aren’t captured by 2D profile.
| Parameter | Symbol | 3D analog of |
|---|---|---|
| Arithmetic mean height | Sa | Ra |
| RMS height | Sq | Rq |
| Max peak height | Sp | Rp |
| Max valley depth | Sv | Rv |
| Max height | Sz | Rz / Rt |
| Skewness | Ssk | Rsk |
| Kurtosis | Sku | Rku |
| Developed interfacial area ratio | Sdr | Fractional increase in actual area vs flat — important for adhesion, coatings, wettability |
| Density of peaks | Spd | Peaks per unit area |
| Arithmetic mean peak curvature | Spc | Peak sharpness |
| Texture aspect ratio | Str | Isotropy index (1 = isotropic, ~0 = highly anisotropic) |
| Texture direction | Std | Dominant lay angle |
| Core roughness | Sk | Areal Rk |
| Reduced peak height | Spk | Areal Rpk |
| Reduced valley depth | Svk | Areal Rvk |
| Void volume | Vv, Vvc, Vvv | Free volume in valleys (lubricant capacity) |
| Material volume | Vm, Vmp, Vmc | Material volume above thresholds |
3.1 Why Areal
- Profile measurement assumes lay direction; if measurement crosses oblique lay, Ra value depends on direction
- Discrete features (single chatter mark, single inclusion) easily missed by line trace
- Functional correlations (tribology, sealing, adhesion, optical) better predicted from areal Sk-family + Sdr than profile Ra alone
4. Standards Summary
| Standard | Topic | Region |
|---|---|---|
| ISO 4287:1997 + A1:2009 | Profile terms + Ra, Rz, Rq, Rt, Rsk, Rku, RSm, Rmr | Global |
| ISO 4288:1996 | Evaluation rules + cutoff selection for Ra range | Global |
| ISO 3274:1996 | Nominal characteristics of contact (stylus) instruments | Global |
| ISO 11562:1996 | Metrological characterization of phase-correct (Gaussian) filters | Global |
| ISO 12085:1996 | Motif-based parameters (R, AR, Rx) — French automotive tradition | Global |
| ISO 13565-1/-2/-3 | Plateau-honed surfaces, Rk family | Global |
| ISO 16610 (multi-part) | Modern filters (Gaussian, robust Gaussian, spline, morphological) — replaces ISO 11562 | Global |
| ISO 25178 (multi-part) | Areal surface texture; ISO 25178-2 defines Sa, Sq, Sz, Sk, Sdr etc.; -6 metrology, -7 software | Global |
| ISO 1302:2002 | Indication of surface texture in technical drawings | Global |
| ISO 21920 (parts 1-3, 2021) | Profile surface texture next-generation (replacing ISO 4287/4288/3274) | Global |
| ASME B46.1-2019 | US: Surface Texture (Surface Roughness, Waviness, and Lay) | US |
| ASME Y14.36M-2018 | Surface texture symbols on US drawings | US |
| ASME B89.6.2 | Temperature + humidity in metrology | US |
| DIN 4760:1982 | Form deviation classification (Orders 1-6) | DE |
| DIN 4762 | Surface texture terminology | DE (legacy) |
| DIN 4768 | Determination of Ra, Rz, Rmax | DE (legacy, superseded by ISO 4287) |
| DIN 4776 | Bearing-area parameters | DE (legacy, superseded by ISO 13565) |
| DIN EN 10049 | Roughness for cold-rolled steel sheet | DE/EN |
| JIS B 0601:2013 | Profile parameters (JP, aligned with ISO 4287) | JP |
| JIS B 0633:2001 | Cutoff specification | JP |
| JIS B 0671 | Rk family | JP |
| JIS B 0681 | Areal (aligned with ISO 25178) | JP |
| GOST 2789 | Surface roughness parameters (RU) | RU |
| AMS 02178 | Aerospace surface roughness | US aero |
| VDA 2007 | German auto industry surface texture spec | DE auto |
| ASTM E1078 | Specimen prep for surface analysis | US |
| ANSI / SAE J911 | Surface texture spec for sheet metal | US auto |
5. Process Capability — Typical Ra Achievable
Per ASME B46.1 Appendix B + ISO 16610 + industry data. Values are typical ranges; specific process parameters shift ranges 2-3x.
| Process | Ra range (μm) | Notes |
|---|---|---|
| Sand casting | 12.5-50 | As-cast surface |
| Permanent-mold casting | 1.6-12.5 | Smoother due to mold finish |
| Investment casting | 1.6-6.3 | Wax + ceramic shell process |
| Die casting (HPDC) | 0.4-3.2 | Steel die polish transferred |
| Hot rolling (plate) | 12.5-25 | Mill scale + rolling marks |
| Cold rolling (sheet) | 0.4-3.2 | Smoother |
| Forging (open + closed die) | 1.6-12.5 | Flash + die finish dependent |
| Flame cutting (oxy-acetylene) | 6.3-25 | Heat-affected oxidized edge |
| Plasma cutting | 3.2-12.5 | Cleaner than flame |
| Laser cutting (thin steel) | 0.8-6.3 | Striations from cutting kerf |
| Waterjet cutting | 3.2-12.5 | Frosted texture |
| Rough turning / milling | 6.3-25 | Coarse feed |
| Semi-finish turning / milling | 1.6-6.3 | Standard machining |
| Finish turning / milling | 0.4-3.2 | Tight nose-radius + fine feed |
| Drilling | 1.6-6.3 | Depending on drill condition |
| Reaming | 0.4-3.2 | Standard finish |
| Tapping | 1.6-3.2 | Cut threads |
| Broaching | 0.4-3.2 | Multi-tooth |
| Rough grinding | 1.6-3.2 | — |
| Finish grinding | 0.2-1.6 | Standard precision |
| Precision grinding (surface, cylindrical) | 0.05-0.4 | Lab + precision parts |
| Centerless grinding | 0.1-1.6 | Cylindrical |
| Internal grinding | 0.2-1.6 | Bore finishing |
| Honing | 0.05-0.4 | Plateau honing for engine cylinders (cross-hatch + plateau) |
| Lapping | 0.012-0.2 | Loose abrasive between part + lap plate |
| Polishing (mechanical) | 0.025-0.4 | Mirror finish achievable |
| Superfinishing (Microfinish, Norton SuperHone) | 0.012-0.1 | Bearing race + cam lobe; near-zero Rsk; spring-back-loaded oscillating stones |
| Burnishing (roller, ball) | 0.05-0.4 | Cold-work-improves Ra + induces compressive stress |
| Diamond turning (SPDT) | 0.005-0.05 | Optics, mirrors |
| Electrical Discharge Machining (sinker EDM) | 0.4-6.3 | Pitted (white-layer); finish with subsequent polish |
| Wire EDM | 0.8-3.2 | Striated kerf |
| Electrochemical Machining (ECM) | 0.4-3.2 | Smooth, no white layer |
| Photochemical Machining (PCM) | 0.8-3.2 | Etched |
| Electroplating | matches substrate | — |
| Anodizing (Type II / III) | matches substrate; Type III rougher | — |
| Chemical etching | varies | — |
| Tumbling / vibratory deburring | 0.4-6.3 | Edge rounding + light polish |
| Mass finishing (centrifugal disc, spindle) | 0.2-1.6 | High-energy finish |
| Sandblasting (silica) | 1.6-12.5 | Matte texture |
| Glass-bead blasting | 0.8-3.2 | Satin |
| Shot blasting (S70-S930 cast steel shot) | 1.6-12.5 | Heavy texture + light residual compression |
| Shot peening | 1.6-6.3 | Compressive residual stress (see §11) |
| Laser shock peening (LSP) | minimal added roughness | Deeper compressive than shot |
| Selective Laser Melting (DMLS as-built top + sides) | 5-25 | AM as-built; downskin worse |
| Electron Beam Melting (EBM as-built) | 20-50 | Worst of common AM |
| Binder Jet (post-sinter) | 5-15 | Coarse; HIP improves |
| FDM / FFF | 5-50 | Layer lines |
| SLA / DLP | 0.4-3.2 | Smoothest AM |
| Mass-finishing of AM | 0.4-3.2 | Vibratory + Hirtisation (Rena) electrochemical for internal channels |
6. Cutoff (λc) Selection — ISO 4288 / ASME B46.1
Cutoff filter (long-wavelength filter λc, also called sampling length lr per ISO 4287) separates roughness from waviness. Wrong cutoff yields meaningless Ra.
| Ra range (μm) | Cutoff λc (mm) | Sampling length lr (mm) | Evaluation length ln (default 5 × lr) |
|---|---|---|---|
| (0.006-0.02) | 0.08 | 0.08 | 0.4 |
| 0.02-0.1 | 0.25 | 0.25 | 1.25 |
| 0.1-2.0 | 0.8 | 0.8 | 4.0 (most common default) |
| 2.0-10 | 2.5 | 2.5 | 12.5 |
| 10-80 | 8.0 | 8.0 | 40 |
If cutoff not specified on drawing, ISO 4288 default applies (0.8 mm for typical machined finish 0.1-2 μm Ra).
Phase-correct (Gaussian) filter per ISO 11562 / 16610-21 introduces no phase shift. Robust Gaussian (ISO 16610-31) suppresses outlier influence; spline (ISO 16610-22) follows surface contour for non-stationary signals. Morphological (ISO 16610-40 series) uses disc/sphere as structuring element — closer to functional bearing surface model.
7. Lay Symbols (ISO 1302 / ASME Y14.36M)
Lay = dominant direction of surface texture pattern from finishing process.
| Symbol | Lay direction | Process |
|---|---|---|
| = | Parallel to line of symbol on drawing | Shaping, planing, turning across the axis |
| ⊥ | Perpendicular to line of symbol | Turning along axis as viewed |
| X | Crossed in two slant directions to line | Honing, lapping cross-hatch |
| M | Multidirectional | EDM, lapping random |
| C | Approximately circular relative to center | Face milling, face grinding |
| R | Approximately radial relative to center | Bevel face grinding |
| P | Particulate, non-directional, protuberant | Cast, plastic, peened, AM |
Drawing symbol shape:
- Equilateral triangle pointing down → basic surface texture symbol
- Open triangle → material removal optional
- Crossed-bar over triangle → material removal required (machined)
- Circle in triangle → material removal prohibited (must be cast / forged / AM)
Around the triangle: Ra in μm (top); production process (right of long stroke); lay symbol (bottom right); machining allowance in mm (left of triangle).
8. Metrology Equipment — Contact (Stylus)
8.1 Bench / Portable Profilometer OEMs
| OEM | Country | Flagship | Resolution | Range |
|---|---|---|---|---|
| Mitutoyo | JP | Surftest SJ-410 / SJ-310 (portable); Surftest SV-3200 (bench); Formtracer SV-C | 0.001 μm | up to 350 μm Z, 100 mm X |
| Mahr | DE | MarSurf XCR 20, M300, PS10 (portable), CD 140 (bench), SD 26/PCV | 0.001 μm | similar |
| Taylor Hobson (AMETEK) | UK | Surtronic (portable), Form Talysurf intra/PGI (bench + form), Talysurf CCI (areal optical) | 0.0008 μm (PGI); 0.1 nm (CCI) | up to 500 mm scan |
| Bruker (Veeco / Wyko heritage) | US | DektakXT, Dektak 8 stylus + optical | 0.05 nm | 1 mm Z, 200 mm X |
| Tokyo Seimitsu (Accretech) | JP | Surfcom 1500SD/2000SD/5000DX | 0.001 μm | — |
| Zeiss | DE | SURFCOM (Tokyo Seimitsu rebranded), CONTURA/PRISMO with rotary table | — | — |
| Jenoptik (Hommel-Etamic) | DE | T8000, T1000 mobile profilometer; nanoscan 855 | 0.001 μm | — |
| Marposs / Movomatic | IT/CH | in-process gauging + Talysurf-style | — | — |
8.2 Stylus Specifications
Per ISO 3274:1996:
- Tip radius: 2 μm (Standard), 5 μm (most common general), 10 μm (rougher surfaces), 25 μm or 50 μm (very rough)
- Tip material: diamond (most), sapphire, tungsten carbide
- Tip cone angle: 60° or 90°
- Tip load: 0.75 mN (typical), 4 mN max — high enough to maintain contact, low enough to avoid plastic deformation
Stylus limits:
- Min feature size = tip radius (smaller features under-sampled)
- Tip flies over deep narrow valleys (gives smoother reading than actual)
- Heavy stylus on soft material (Al, plastic) ploughs and biases reading
8.3 In-Process / Production Gauging
- Marposs Aeroel, Mahr in-process gauging
- Renishaw Equator comparator (machine-shop gauging)
- Roundness measuring: Mahr MMQ, Mitutoyo Roundtest, Taylor Hobson Talyrond
- Form measuring (combined form + roughness + contour): Mahr MarForm MFK, Mitutoyo Roundtest RA-2200, Taylor Hobson PGI Optics + Mountains software
9. Metrology Equipment — Non-Contact (Optical)
9.1 Confocal Microscopy
Principle: pinhole rejects out-of-focus light; Z-stack yields 3D map.
| OEM | Country | Flagship | Z-resolution | XY |
|---|---|---|---|---|
| Keyence | JP | VK-X3000 / VK-X1000 (confocal + interferometric laser) | 0.5 nm | 0.13 μm |
| Olympus / Evident | JP | LEXT OLS5100 (laser confocal) | 6 nm | — |
| Sensofar | ES | S neox (multi-mode: confocal + interferometry + focus variation) | 0.1 nm | — |
| Leica | DE | DCM8 (confocal) | — | — |
| Carl Zeiss | DE | LSM 700 / 800 / 900 | — | — |
| Lasertec | JP | Optelics Hybrid | — | — |
| Alicona (Bruker) | AT | InfiniteFocus (focus-variation) | 10 nm | — |
9.2 White-Light Interferometry (WLI / Coherence Scanning)
Principle: low-coherence light interference fringes localize Z-position.
| OEM | Flagship |
|---|---|
| Bruker | ContourX (NPFLEX, GT-K), Contour Elite |
| Veeco (now part of Bruker) | NT9000, NT3000 |
| Zygo (AMETEK) | NewView 9000, GPI series |
| Polytec | TMS-1200 TopMap |
| Filmetrics (KLA) | optical thin-film + topography |
9.3 Focus Variation
Principle: scan focus through Z; sharp focus marks each Z height.
| OEM | Flagship |
|---|---|
| Alicona (Bruker) | InfiniteFocusSL / G6 / Edge Master / RoughnessLab |
| Hexagon | Optiv (combined optical + tactile) |
9.4 AFM (Atomic Force Microscopy)
Sub-nm Z + lateral resolution; small scan area (typ 100×100 μm max).
| OEM | Flagship |
|---|---|
| Bruker | Dimension Icon, FastScan, MultiMode 8 |
| Park Systems | NX series |
| Hitachi High-Tech | AFM5500M, Park-rebranded |
| Asylum Research (Oxford Instruments) | Cypher, MFP-3D Infinity |
| NT-MDT | NTEGRA |
9.5 Laser Triangulation + Chromatic Confocal
| OEM | Flagship | Use |
|---|---|---|
| Keyence | LJ-X8000 (laser triangulation), LK-G5000 (point laser), LT-9000 (chromatic confocal) | In-line + production |
| Micro-Epsilon | scanCONTROL (line laser), confocalDT (chromatic confocal) | Industrial inline |
| Hexagon (HxGN) | various | — |
| Cognex | DSMax DS series 3D | Inline inspection |
9.6 Areal Acquisition Comparison
| Method | Lateral res | Z res | Speed | Limit |
|---|---|---|---|---|
| Stylus profilometer | 2-25 μm (tip) | 1 nm | slow | Single line; tip-radius bias |
| Confocal | 0.13 μm | 0.5 nm | moderate | Sloped surfaces (>30°) struggle |
| WLI | 0.4-1 μm | 0.1 nm | fast | Steep slopes, transparent films |
| Focus variation | 0.4 μm | 10 nm | moderate | Best for rough + steep surfaces (mfr Alicona) |
| AFM | sub-nm | sub-nm | very slow | Tiny area; soft samples |
| Chromatic confocal | 1 μm | 5 nm | fast (single-pt) | Standoff varies w/ wavelength |
10. Coating Thickness Measurement
| Method | Coating-substrate combo | Range | OEM |
|---|---|---|---|
| Eddy current (ISO 2360, ASTM B244) | Non-conductive coating (paint, anodize, polymer) on non-ferrous (Al, brass, austenitic SS) | 0-5 mm | Fischer DUALSCOPE / FERITSCOPE, ElektroPhysik MiniTest, DeFelsko PosiTector 6000 |
| Magnetic induction (ISO 2178, ASTM B499) | Non-magnetic coating (paint, zinc, anodize, plate) on ferromagnetic (CS, low-alloy) | 0-5 mm | same OEMs |
| Combined eddy + magnetic | Both substrates | — | Fischer DUALSCOPE FMP, DeFelsko 6000 FNDS |
| XRF (X-Ray Fluorescence) | Multiple layers, very thin (0.01-50 μm); composition + thickness simultaneously | 0.01-50 μm | Fischer XDV-SDD, Hitachi FT150, Bruker S1 TITAN handheld |
| Ultrasonic (ASTM B763) | Coatings on plastic, ceramic | 0.005-200 mm | Olympus MagnaMike, Defelsko PosiTector 200 |
| β-backscatter (ISO 3543) | Metal on dissimilar-Z metal | — | Fischer Betascope |
| Cross-section (ASTM B748, destructive) | Reference standard | unlimited | Microscope + photomicrograph |
| Coulometric (ASTM B504, destructive) | Single-metal electroplate on metal substrate | — | — |
| Confocal optical thin-film | Transparent / semi-transparent coatings | nm to mm | Filmetrics, Sensofar |
| Ellipsometry | Very thin transparent films (semiconductor) | sub-nm to μm | J. A. Woollam, Horiba |
11. Surface Cleanliness (Pre-Coating / Pre-Paint)
11.1 ISO 8501 — Visual Assessment of Blast Cleaning
| Grade | Description |
|---|---|
| Sa 1 | Light blast cleaning (loose scale, rust removed) |
| Sa 2 | Thorough blast cleaning (most mill scale removed) |
| Sa 2 1/2 | Very thorough blast cleaning (almost free, slight shadows) — most common spec for marine + heavy-industrial coatings |
| Sa 3 | Blast cleaning to visually clean steel (white metal, fully metallic appearance) |
| St 2, St 3 | Hand / power tool cleaning grades |
| Pma, Be, Bl | Cleaning with hand tools (less common) |
11.2 Profile (Surface Roughness After Blasting)
Per NACE RP0287 / ISO 8503-1 (depth-of-profile gauges, dial gauges, replica tape).
| Profile | Use |
|---|---|
| 25-50 μm (1-2 mil) | Light coating systems |
| 50-100 μm (2-4 mil) | Heavy-duty epoxy, intermediate |
| 100-150 μm (4-6 mil) | Thick-film, ceramic, metallizing, thermal spray |
Replica tape (Testex Press-O-Film X-Coarse + Coarse): impression of profile, measured with micrometer.
11.3 Salt Contamination
Conductivity / chloride test per ISO 8502-6 / 8502-9 (Bresle method) — patch holds water, measure conductivity. Max chloride often 20-50 mg/m² for marine coatings.
12. Peening for Compressive Residual Stress + Fatigue
12.1 Shot Peening — Almen Strip Control (SAE J442 / J443 / J2597)
Standardized control: a thin steel strip (Almen A / N / C) is peened on one side; bending arc-height (deflection) measures peening intensity.
| Almen strip | Thickness | Use range |
|---|---|---|
| N | 0.79 mm | Very light peening |
| A | 1.30 mm | Standard (most automotive, aerospace) |
| C | 2.39 mm | Heavy peening (large springs, gears, landing gear) |
Intensity designation: e.g., “8A” = 0.008 inch arc on Almen A strip; “12A” = 0.012 inch.
| Almen A | Typical service |
|---|---|
| 4-6 A | Light fatigue improvement (small springs, fasteners) |
| 6-12 A | Auto valve springs, suspension springs |
| 12-16 A | Gears, larger springs |
| 16-24 A | Heavy aerospace landing gear |
| 24-40 A | High-stress aerospace, military |
Coverage: 100% baseline (each point hit at least once); 200% (each hit twice on average); aerospace often spec 200-400% for critical fatigue.
12.2 Almen Test System OEMs
Empire Abrasive Equipment (Hodge Clemco), Wheelabrator, Rosler, Pangborn (DISA), Pauli + Griffin, Goff Group, Engineered Abrasives, Pellets LLC (shot media).
12.3 Shot Media Types
| Media | Spec | Use |
|---|---|---|
| Cast steel shot | SAE J827, sizes S70-S930 | Standard, hard 40-50 HRC (S110, S280, S330 most common) |
| Conditioned cut wire (CCW) | SAE J441 | Higher uniformity, longer life; aerospace |
| Ceramic bead | various | Non-ferrous (Al, Ti, Mg) to avoid contamination |
| Glass bead | various | Light intensity; cosmetic finish |
| Stainless shot (CrNi or 18-8) | various | Non-magnetic, non-corrosive (medical, food) |
12.4 Process Variants
| Process | Notes |
|---|---|
| Air-blast peening | Most common; controllable, masking-friendly |
| Wheel peening (centrifugal) | High throughput; cast-steel shot |
| Flapper peening | Hand-held flexible arm; field repair |
| Ultrasonic peening (UNSM) | Hammer-impact with ultrasonic frequency; surface refinement + compressive stress |
| Laser Shock Peening (LSP) | Nd:YAG pulsed laser + opaque/water layer creates plasma shock; deeper compressive than shot (1+ mm); aerospace turbine blade root + critical fillets — Metal Improvement Company (Curtiss-Wright), LSPT |
| Cavitation peening | Cavitation bubble collapse on submerged part; water + venturi; replaces shot on delicate components |
| Roller / ball burnishing | Tool rolls under load; combines finishing + compressive stress; Ecoroll, Yamasa, Sugino |
12.5 Effect on Fatigue
Shot peening typically increases fatigue limit 50-200% (springs, gears, axles, landing gear). Effect comes from:
- Compressive residual stress 200-1000 MPa to depth 0.05-0.5 mm
- Cold-work hardening
- Microstructural refinement
- BUT: increased Ra (typically 1.6-6.3 μm) — for highly polished service, peening + secondary polish needed (e.g., camshaft journals)
13. Surface Function — Why Texture Matters
| Function | Critical parameter | Target |
|---|---|---|
| Static friction (anti-slip) | Ra, Rku, Rsk > 0 | Higher Ra + peak skewness |
| Sliding friction (lubricated) | Rk family — Rk small, Rvk large | Plateau-honed surface (cylinder liner) |
| Boundary lubrication (oil retention) | Rvk, Vvv | Deep narrow valleys (cross-hatched hone) |
| Hydrodynamic seal | Sa < 0.4 μm, Sdr low | Smooth + minimal real-area enlargement |
| Mechanical seal face | Sa < 0.1 μm (lapped) | Flat, plateau-finished, near-zero leakage |
| Adhesive bonding | Sa moderate, Sdr high | Mechanical interlock + chemical area |
| Powder-coat adhesion | Sa 1.6-6.3 μm | Blast profile |
| Galvanic + electroplate adhesion | Sa 0.4-1.6 μm + clean | Activation + nucleation sites |
| Optical reflectance | Sa < λ/10 of light | Diamond-turn or polish to ~0.01 μm |
| Aerodynamic / hydrodynamic drag | Sa minimized + isotropy | Ra < 1.6 μm for smooth boundary layer |
| Wettability (hydrophilicity / -phobicity) | Sa, Sdr, Sku | Lotus-effect microstructure |
| Cell adhesion (medical implant) | Sa 0.5-2.0 μm | Sandblasted-acid-etched (SLA Straumann) |
| Bone in-growth (orthopedic) | Sa 1-10 μm, Sdr high | Porous Ti coating, beadblast |
| Heat transfer (boiling enhancement) | porous, microchannel | TurboB cap, Wieland Gewa |
| Bearing surface (rolling element) | Sa < 0.1 μm + Rsk < 0 | Superfinished |
| Spring fatigue | Sa low + compressive residual | Peened then sometimes polished |
| Stamping die release | Sa moderate + textured | EDM textured + nitrided |
| Stamp release on auto sheet | Rsm, Rmr — Mill Stuckl & Sandberg | Controlled stochastic + deterministic texture (Tata Steel Sigma Pretex, Cosma) |
14. Surface Engineering — Selected Examples
- Engine cylinder liner: plateau honing (rough hone + plateau hone) → Rk small, Rvk large for oil; ISO 13565 / Daimler / VW spec
- Crankshaft journal: superfinished to Sa < 0.2 μm + smooth profile (Rk + Rvk minimal) to minimize friction in hydrodynamic-bearing operation
- Gear flank: ground or honed; pre-2010 industry shifted toward Sa 0.4 μm to reduce micropitting (ISO 6336-22)
- Hydraulic cylinder rod: hard chrome plated (15-50 μm) + polished to Sa < 0.4 μm for seal life
- Mechanical seal face: SiC or carbon, lapped + polished to flatness 0.6 μm + Sa < 0.05 μm
- Bearing race: superfinished raceway + ball lapped to <0.05 μm Ra
- Forming die: EDM-textured + nitrided + DLC-coated; surface profile drives stamping lubrication
- Medical implant (hip ball): Ti6Al4V + cobalt-chrome ball; ball polished to <0.025 μm Sa for low wear of UHMWPE socket
- Dental implant: sandblasted + acid-etched (Straumann SLA, Nobel TiUnite) for Sa 1-2 μm — promotes osseointegration
- AM (LPBF) post-processing: machined or polished critical surfaces; vibratory + electropolish or chemical (Hirtisation by Rena) for internal channels
15. Roundness, Cylindricity, Form — Adjacent Standards
Surface finish lives within form metrology hierarchy (ASME B89, ISO 12180-12181):
| Form parameter | Standard |
|---|---|
| Straightness | ISO 12780-1, ASME Y14.5-2018 |
| Flatness | ISO 12781-1, ASME Y14.5 |
| Roundness | ISO 12181-1 |
| Cylindricity | ISO 12180-1 |
| Profile of line / surface | ISO 1660, ASME Y14.5 |
| Runout (circular, total) | ISO 1101, ASME Y14.5 |
CMM (coordinate measuring machine) measures form to micron level; roundness machines (Mahr MMQ, Mitutoyo Roundtest, Taylor Hobson Talyrond) measure roundness in nm range.
16. Common Pitfalls
- Spec sheet says “Ra 1.6” with no process or cutoff: ambiguous; specify cutoff (e.g., “Ra 1.6 μm, λc 0.8 mm, ISO 4287”) to avoid disputes
- Using Ra alone for plateau-honed cylinder bore: Ra is similar for rough hone vs plateau hone; specify Rk / Rpk / Rvk family per ISO 13565
- Stylus tip too large for fine surface: 5 μm tip on Ra 0.05 surface integrates over peaks → under-reads roughness; specify 2 μm tip
- Measuring across multiple lay directions: anisotropic surface (turned, ground) gives different Ra by direction; specify direction or use areal Sa
- Wrong cutoff: 0.8 mm cutoff on Ra 8 μm surface omits real waviness; use ISO 4288 table or specify
- Confusing Rz_DIN (pre-1997, 5-peak avg) with Rz_ISO (post-1997, max in 5 sample lengths): always state which definition
- Using 2D profile data alone to predict tribology: lay direction + isotropy + Sdr matter; areal is better
- Spec on drawing missing lay symbol when functional: parallel grinding marks under reciprocating seal cause leakage; specify perpendicular lay
- Trying to measure transparent thin film with stylus or WLI without considering refractive index: introduces phase errors; use ellipsometry or chromatic confocal
- Skipping Almen calibration after blast wheel media changes: shot mix degrades over time; verify intensity with new strip each shift
- Coverage measurement by visual only: <100% coverage compromises fatigue benefit; use fluorescent tracer (Magnaflux Met-L-Check 5) or measured indentation density
- Coating thickness measured on sharp edge / corner: edge effect distorts eddy / magnetic measurement; measure 25 mm from edge
- XRF coating thickness without standardization for substrate composition: matrix effects; calibrate with matching substrate
- Blast profile too aggressive for coating system: thick coatings bridge peaks but thin coatings get peak-stress concentration → premature failure
- Specifying “polished” without Ra value: subjective; quote actual Ra or finish grit (e.g., #4 mill, #6 mirror, #8 mirror)
- Mass-finishing time / media not validated: too-long tumbling rounds critical edges; setup process windows
- Superfinished part subsequently honed for assembly: destroys surface (Rk, Rvk re-introduced); plan finishing sequence
- Anodize as “surface finish” — actually grows surface (Type II ~50% in, 50% out; Type III ~50/50); affects fit on tight-tolerance parts
- Surface roughness for explosive (Be/Cu, EOD) parts measured with steel stylus: contamination + spark risk; use diamond
- Forgetting that any blast or peen process introduces surface roughness — must be followed by polish if smooth required (e.g., shot-peened gear flank then honed)
- Areal scan stitched from sub-fields without overlap: artificial steps at field boundaries; specify ≥10% overlap
Adjacent
- machining-processes
- surface-treatments
- tribology
- ndt-methods
- bearings-catalog-deep
- gears-and-power-transmission-catalog
- springs-catalog
- fasteners-catalog
- weldment-standards-and-joints-catalog
- additive-manufacturing-taxonomy
- sensors-catalog
- standards-bodies
- engineering-codes
- fatigue-analysis
- mechanics-of-materials