Bearings — Complete Guide
A complete engineering reference for bearings: ball, roller, thrust, and needle bearing types, an L10 bearing life calculator, ISO designation decoding, mounting and fits, lubrication, and failure analysis — with live interactive calculators.
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Bearings
Types · Selection · L10 Bearing Life · Mounting · Lubrication · Damage · Linear · Standards
⚙️ Bearing Types
Deep Groove Ball
6xxxMost Common
Radial Load⭐⭐⭐ — Good
Axial Load⭐⭐ — Both directions, limited
Speed⭐⭐⭐⭐⭐ — Very high
UsesElectric motors · pumps · gearboxes
AdvantageSimple · quiet · cheap · available everywhere
Coding6205 = DG · series 2 · ⌀25mm bore
▶ YouTubeAngular Contact Ball
7xxxIn Pairs!
Contact Angles15° · 25° · 40° — ↑angle=↑axial
Radial Load⭐⭐⭐ — Good
Axial Load⭐⭐⭐⭐ — one direction
Speed⭐⭐⭐⭐ — High
ArrangementsDB (Back-to-Back) · DF (Face-to-Face) · DT (Tandem)
UsesSpindles · CNC shafts · gears
NoteAlways in pairs! One alone won't work
▶ YouTubeTapered Roller
3xxxxPreload Mandatory
Radial Load⭐⭐⭐⭐ — Very heavy
Axial Load⭐⭐⭐⭐⭐ — Very heavy
Speed⭐⭐⭐ — Medium
Contact Angle10°-16° (Light) · 25°-29° (Steep)
PreloadMust be calibrated! Otherwise contact is lost
UsesAutomotive axle · milling · bevel gear · pump
StandardISO 355 · ANSI/ABMA 19.1/19.2
▶ YouTubeCylindrical Roller
NU/NJ/NFHigh Radial
Radial Load⭐⭐⭐⭐⭐ — Very high!
NU — Axial Load❌ — None at all
NJ/NF — Axial Load⭐⭐ — one direction only
NNU/NNDouble row — double radial load
Speed⭐⭐⭐⭐ — High
UsesGearboxes · main shafts · large motors
▶ YouTubeSpherical Roller
2xxxxSelf-Aligning
Radial Load⭐⭐⭐⭐⭐ — Very heavy
Axial Load⭐⭐⭐ — Both directions
Self-AlignmentUp to 1°-2.5° — compensates for shaft error
Speed⭐⭐⭐ — Medium-high
UsesMining · paper · cable · heavy equipment
▶ YouTubeSelf-Aligning Ball
1xxx/2xxx
Radial Load⭐⭐ — Low-medium
Axial Load⭐ — Very limited
Self-AlignmentUp to 2°-3° — spherical raceway
UsesAgriculture · Plummer Block · long shafts
NoteCheap and light, but weak. Not for heavy loads
▶ YouTubeThrust Ball
5xxxAxial Only!
Radial Load❌ — Absolutely prohibited!
Axial Load⭐⭐⭐⭐ — one direction (single) / two (double)
Arrangements51xxx = single · 52xxx = double
Speed⭐⭐ — Low-medium
UsesPistons · valves · lifting mechanisms · jacks
▶ YouTubeNeedle Roller
NA/NK/HK/IR
Radial Load⭐⭐⭐⭐⭐ — Very high for its size
Axial Load❌ — Zero
L/D Ratio3-10 (long vs. diameter)
AdvantageVery small OD! Saves space
NA — with Inner RingRegular shaft, easy to disassemble
NK/HK — without RingShaft needs Ra≤0.4μm, HRC58+
UsesCrankshaft · steering column · universal joint
▶ YouTubeCARB / Toroidal
C xxxSKF Patent
Radial Load⭐⭐⭐⭐⭐ — Very high
Self-Alignment⭐⭐⭐⭐⭐ — Full! angle + length
Axial Displacement⭐⭐⭐⭐⭐ — Completely free
UsesPaper machine rolls · mining · large industrial motors
NoteReplaces Spherical Roller when self-alignment is also needed
Manufacturer: SKF (exclusive)
▶ YouTube| Bearing Type | Coding | Radial | Axial | Speed | Self-Aligning | Typical Use |
|---|---|---|---|---|---|---|
| Deep Groove Ball | 6xxx | ⭐⭐⭐ | ⭐⭐ | ⭐⭐⭐⭐⭐ | ❌ | Motors, pumps |
| Angular Contact Ball | 7xxx | ⭐⭐⭐ | ⭐⭐⭐⭐ | ⭐⭐⭐⭐ | ❌ | CNC spindle, gears |
| Tapered Roller | 3xxxx | ⭐⭐⭐⭐ | ⭐⭐⭐⭐⭐ | ⭐⭐⭐ | ❌ | Automotive, milling |
| Cylindrical Roller | NU/NJ | ⭐⭐⭐⭐⭐ | ⭐/❌ | ⭐⭐⭐⭐ | ❌ | Gearboxes, large motors |
| Spherical Roller | 2xxxx | ⭐⭐⭐⭐⭐ | ⭐⭐⭐ | ⭐⭐⭐ | ⭐⭐⭐ | Mining, paper |
| Self-Aligning Ball | 1xxx/2xxx | ⭐⭐ | ⭐ | ⭐⭐⭐⭐ | ⭐⭐⭐⭐ | Agriculture, Plummer Block |
| Thrust Ball | 5xxx | ❌ | ⭐⭐⭐⭐ | ⭐⭐ | ❌ | Lifting, valves |
| Needle Roller | NA/NK/HK | ⭐⭐⭐⭐⭐ | ❌ | ⭐⭐⭐ | ❌ | Crankshaft, steering |
🎯 Bearing Selection Guide
Bearing Selection Steps
6 Steps
1. LoadsFr (radial) · Fa (axial) · direction · dynamics
2. Speedn (RPM) · ndm ≤ 500K grease · 750K oil
3. Service LifeRequired L10h: 20K hours industrial · 50K+ critical
4. Dimensionsbore (d) ← shaft · OD (D) ← housing · B width
5. EnvironmentTemperature · humidity · contamination · vibration
6. Size SelectionC/P ≥ (L10h × 60n / 10⁶)^(1/p)
Equivalent Dynamic Load P
P = X·Fr + Y·Fa
X — Radial Factor1.0 if Fa/Fr ≤ e · 0.56 if Fa/Fr > e
Y — Axial Factor0 if Fa/Fr ≤ e · from catalog if > e
e — Contact Factor0.22-0.44 (depends on bearing and load)
6205 ExampleFr=5kN, Fa=1kN, e=0.30 → P=5×1+0=5kN
Static P0P0 = X0·Fr + Y0·Fa (for static load)
X, Y, e — from the manufacturer's catalog only!
Clearance — Internal Clearance
C2 · CN · C3 · C4 · C5
C2Small clearance — high precision, preload
CN (Normal)Default — most applications
C3Large clearance — high temp., press-fit mounting
C4Very large clearance — very high temp.
Rule of ThumbPress-fit mounting → C3. Temp. >80°C → C3
Too little clearance = overheating = failure. Too much = vibration and noise
Bearing Precision — Precision Class
P0-P2ISO 492
P0 (Normal)Default · general industry
P6↑precision · general machinery, plummer block
P5↑↑precision · CNC shaft, spindle
P4↑↑↑ · precision shaft, metrology
P2 (Ultra)Gyroscopes, watch spindles, space
Relative PriceP0=1× · P6=3× · P5=8× · P4=20×
Bearings for Extreme Temperatures
Above 120°C
Stabilization S1Up to 150°C — coding SN1
Stabilization S2Up to 200°C — coding SN2
Stabilization S3Up to 250°C — coding SN3
Stainless 440CUp to 200°C · anti-corrosion
Ceramic Si3N4Up to 700°C · ↑speed · ↓weight
Full CeramicZrO2/Al2O3 — electrical, corrosion
Manufacturers: SKF · Cerobear (ceramic)
Bearings for Special Conditions
Clean Room · Vacuum · Food
Clean RoomESD/PFPE grease · S/S · ISO Class 3
VacuumPFPE grease · or MoS2 Dry Film · UHV
Food — USDA H1NSF H1 grease · S/S seals · FDA
Marine/HumidityStainless 440C · anti-water grease
MagneticFull ceramic bearing — non-conductive
Manufacturers: SKF Food Line · Igus (plastic)
🔢 ISO Bearing Designation
ISO Designation Structure — 6-2-05-ZZ-C3
ISO 15 / ISO 355
Digit 1 — Type1=Self-Aligning Ball · 2=Spherical Roller · 3=Tapered · 6=DG · 7=AC · N=Roller · 5=Thrust
Digit 2 — Diameter Series0=Extra Light · 1=Extra Light · 2=Light · 3=Medium · 4=Heavy
Digits 3-4 — bore00=10 · 01=12 · 02=15 · 03=17 · 04+=×5mm
SealsZ=metal shield · ZZ=×2 · RS=rubber · 2RS=×2 · RZ=low-friction seal
ClearanceC2/CN/C3/C4/C5
PrecisionP0(unmarked)/P6/P5/P4/P2
MaterialS=stainless · W=Stainless · X=special
Example: 6205-2RS-C3 = DG · series 2 · bore 25mm · rubber×2 · large clearance
Angular Contact — Special Coding
7xxx + Suffixes
B40° contact angle (7205B)
C15° contact angle
AC25° contact angle — most common
DBBack-to-Back pair — ↑rigidity
DFFace-to-Face pair — ↑alignment
DTTandem — ↑axial single direction
Example: 7205BECBJ = AC 40° · Universal · P4
Tapered Roller — ABMA Coding
30xxx / L/M series
Series 3030205 = light angle ~12°
Series 31/32medium angle ~15°
Series 33steep angle ~25°
Timken L/M/LMUnique coding — L44643/L44610 (Cup/Cone)
CupOuter ring
ConeInner ring + rollers
Manufacturer: Timken (world leader)
Bearing Number Decoder
Quick Tool
Enter a bearing number to decode
📊 L10 Bearing Life Calculation
L10 — Basic Rating Life
ISO 28190% Survival
L10 (million revolutions)L10 = (C/P)^p
p — Exponent3 for ball · 10/3 for roller
L10h (hours)L10h = L10 × 10⁶ / (60 × n)
C — Dynamic LoadFrom manufacturer catalog (kN)
P — Equivalent LoadP = XFr + YFa
L10 = 90% of bearings will survive at least L10 hours
aISO Life — Modified Rating
ISO 281:2007More Accurate
Lnm = a1 × aISO × L10— modified life
a1 — Reliability Factor90%=1.0 · 95%=0.64 · 99%=0.21
aISO — Condition FactorLubrication + contamination + load
κ = ν/ν₁ν=actual viscosity · ν₁=required
κ≥2 + CleanlinessaISO up to 50! → L10m up to ×50
SKF/FAG calculation tool: SKF Bearing Calculator
Recommended L10h by Application
Reference Values
Home Appliances1,000-2,000 hours
General Electric Motor20,000-30,000 hours
Industrial 8h/day20,000-30,000 hours
Industrial 24h/day40,000-50,000 hours
Continuous Heavy Duty60,000-100,000 hours
Aerospace — CriticalPer specific TBO (1,500-8,000h)
L10h Calculator
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🔧 Mounting & Fits
Shaft Fits
ISO 286Internal Rotation
j5, js5Light transition — hand movable
k5, m5Light interference — tap required (common)
n5, p5Interference — light shocks
r5, s5Heavy interference — heavy shocks
Rule of ThumbRotating ring = interference · fixed ring = transition
Inner ring rotates ← interference on shaft
Outer ring rotates ← interference on housing
Outer ring rotates ← interference on housing
Housing Fits
H7 — Common
H8, G7Free transition — hand movable
H7 (common)Transition — standard for most applications
J7, JS7Light interference transition
K7, M7Light interference — medium loads
N7, P7Interference — heavy loads/shocks
H7: outer ring easily disassembled
P7: cannot be disassembled without tools
P7: cannot be disassembled without tools
Mounting Methods
Cold · Hot · Press
Tap + PadCold mounting — bore≤50mm · ↑damage risk!
Press Fitbore 50-150mm · up to 200kN · precise
Induction HeatingΔT = Δd / (α × d) → 80-120°C typical
SKF Induction HeaterTMBH1/TIH030 · up to 250°C · safe
Freezing (small bearing)Liquid N2 (-196°C) → shrinks the bore
SKF Mounting ToolsTMFT · TMHN · TMFK — no damage to rollers!
⚠️ Never strike the rolling elements! Force must pass through the ring only
Tool Manufacturer: SKF Mounting Tools
▶ YouTubeTool Manufacturer: SKF Mounting Tools
Surface Finish Requirements
ISO 1101
Ra Shaft (bore ≤80mm)Ra ≤ 0.8μm (N6)
Ra Shaft (bore >80mm)Ra ≤ 1.6μm (N7)
Ra HousingRa ≤ 1.6μm (N7)
Shaft Roundness≤ IT5/2 = ~5μm for ⌀50mm
Housing Roundness≤ IT6/2 = ~8μm for ⌀80mm
Shoulder SupportSquareness ≤ IT4 · r ≤ bearing r_min
Poor finish = ↓bearing life by up to 50%!
Preload
Angular Contact · Tapered
Purpose↑precision · ↓vibration · ↑rigidity · ↓noise
Spring PreloadConstant spring — flexible, less precise
Rigid PreloadSpacer — precise, hard to calibrate
Light / Medium / HeavyA/B/C — SKF coding
⚠️ Too High PreloadOverheating · wear · premature failure!
DB — Back-to-Back↑moment rigidity · DB recommended for most cases
DF — Face-to-Face↑alignment · small space
▶ YouTube💧 Bearing Lubrication
Grease Lubrication
70% of BearingsNLGI 2 — Default
NLGI 1Softer · high speed · low temperature
NLGI 2Standard · default for most bearings
NLGI 3Thicker · vertical orientation · ↓leakage
Fill Quantity30-50% of the free space volume (no more!)
Over-Greasing→ excess heat → failure!
Relubrication Intervaltf = 14,000/n × (dm/2)^{-0.5} hours (SKF)
▶ YouTubeOil Lubrication
High SpeedISO VG
Splash / BathHalf-diameter immersion · ↓rpm · simple
Circulating OilPump + cooling · high speeds
Oil JetOil jet ← ↑↑rpm · aerospace · CNC
Oil-Air (MQL)≤2ml/h · Clean Room · extreme speed
ISO VG 46⌀25-60mm bore · n > 3000 RPM
ISO VG 100⌀60-100mm bore · n 1000-3000 RPM
ISO VG 220Heavy loads · n < 1000 RPM
Manufacturers: Shell Omala · Mobil SHC
▶ YouTubeGrease by Temperature
Important!
Mineral Grease NLGI 2-20°C to +120°C
Lithium Grease-40°C to +150°C
Polyurea Grease-30°C to +180°C · ↑durability
Silicone Grease-60°C to +200°C · food/clean
PFPE (Perfluoro) Grease-60°C to +250°C · vacuum · corrosion
Manufacturers: Krytox PFPE · Klüber Petamo
ndm — Speed Parameter
n × dm ≤ 500,000
dmdm = (bore + OD) / 2 — pitch diameter
ndm ≤ 500,000→ Grease suitable
ndm 500K-750K→ Special grease or oil
ndm > 750,000→ Oil mandatory
Example: 6205dm=(25+52)/2=38.5mm · n=12,000rpm · ndm=462K ← Grease ✅
⚠️ Bearing Failure Analysis
Fatigue Spalling
30% of All Failures
AppearanceFlakes on the raceway · ↑noise
CauseCyclic load → subsurface crack → spalling
Accelerating FactorsOverload · insufficient lubrication · contamination
PreventionC/P ≥ 3 · cleanliness · correct lubrication
Early DetectionVibration monitoring (SKF IMx) · Shock Pulse SPM
▶ YouTubeBrinelling
True / False Brinelling
True BrinellingStatic load exceeding P0 → permanent indentation
False BrinellingVibration during rest → fretting wear
AppearanceEvenly-spaced indentations at rolling element pitch
True PreventionC0/P0 ≥ 4 · upsize the bearing
False PreventionEP grease · SRB/TRB bearing type · avoid contact
▶ YouTubeFluting
Electrical Current!
AppearanceParallel grooves on the raceway · dark discoloration
CauseVFD current passing through the bearing ← EDM discharges
VFD BearingVFD motors → high CMRV level
PreventionInsulated bearing (HV/H) · grounding brush · bonding
SKF HybridSi3N4 balls → electrical insulation!
Manufacturer: SKF Insocoat / Hybrid
▶ YouTubeContamination
20% of All Failures
AppearanceDenting · accelerated wear · spalling
SourcesDust · debris · chips · water
ISO 4406Oil cleanliness: -/16/13 ← minimum
PreventionGood seals · oil filtration · proper storage
SPM Shock PulseContamination detection → dBsv > dBi + 20dB = problem
▶ YouTubeSmearing
High Speed!
AppearanceDirectional scratches · material transfer
CauseSlipping during acceleration/deceleration · Skidding
Susceptible BearingsNU (cylindrical roller) · high-speed bearings
PreventionLight preload · EP grease · ↓acceleration
▶ YouTubeMisalignment
10% of All Failures
AppearanceAsymmetric wear · increased heat
CausesMounting error · housing distortion · bent shaft
DG Ball ThresholdMaximum 0.1° (6') — very sensitive!
PreventionSelf-Aligning · CARB · laser alignment
Laser Alignment≤0.05mm/m Offset · ≤0.05mm/m Angular
Alignment Tools: SKF TKSA · Pruftechnik
▶ YouTube📏 Linear Bearings & Guide Rails
Linear Ball Bearing
LM/LMUUSmooth Shaft
LM6UUbore 6mm · OD 12mm · L 19mm
LM8UUbore 8mm — 3D Printers, light CNC
LM16UUbore 16mm — medium CNC
Dynamic LoadC = 30-200N typical
ShaftSmooth: Ra≤0.4μm · HRC60+ · h6
SealsLMUU=none · LMFUU=flanged · Open=LMO
▶ YouTubeLinear Guide Rail
↑PrecisionHG/EG/MG Series
PrincipleCarriage + Rail · ball/roller
PrecisionNormal/High/Precision/Super P (±3μm)
PreloadZ0/ZA/ZB/ZC — ↑Preload=↑rigidity
HIWIN HG SeriesEqual loads in 4 directions — common in CNC
HIWIN EG SeriesCompact · light loads
Roller Guideway↑rigidity · ↑load · ↑price · HIWIN RG
▶ YouTubeSlide Bushing — Plastic Linear Bushing
No LubricationIgus
MaterialPTFE + polyamide / iglidur J/G/X
LubricationSelf-Lubricated — no oil/grease!
AdvantageQuiet · anti-magnetic · light · chemical resistant
Drawback↓load · ↓speed vs. balls
PV limit0.28 m/s × 0.1 MPa = 0.028 W/m²
Manufacturer: Igus (world leader)
🏆 Leading Standards & Manufacturers
International Standards
ISO · ABMA · JIS
ISO 15Radial Bearings — dimensions
ISO 76Static Load Ratings
ISO 281Dynamic Load Ratings + L10 Life
ISO 355Tapered Roller Bearings
ISO 492Tolerances for Radial Bearings
ABMA 9/11Ball/Roller Bearings (USA)
JIS B 1512Rolling Bearings (Japan)
SKF — Sweden
World Leader #1
HQGothenburg, Sweden · 1907
ProductsAll bearing types · CARB · Explorer
ToolsSKF Bearing Calculator · IMx Monitor
CatalogBearing & Units Catalogue (PDF)
Schaeffler — FAG / INA — Germany
World #2
FAGRolling Bearings · High Precision
INANeedle Rollers · Linear · Engine
ToolsBEARINX · Lifetime Explorer
NSK · NTN · JTEKT — Japan
Japan — World #3-5
NSKPrecision · Automotive · since 1916
NTNAerospace · Industrial · since 1918
JTEKT (Koyo)Toyota Group · Steering
Timken — USA
King of Tapered
HQNorth Canton, Ohio · 1899
SpecialtyTapered Roller · Steel · Alloys
UsesAutomotive · Rail · Aerospace · Mining
Suppliers in Israel
🇮🇱 Israel
AmraiSKF and FAG distributor — nationwide
Dan-RollerBearings, wheels, rails
Techni-RollIndustrial bearings, consulting
RamaBearings + technical hardware
High-precision bearings — SKF/FAG via direct import
🧮 Bearing Calculators
L10h Calculator — Bearing Life
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ndm Calculator — Maximum Speed
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Bearing Number Decoder
Enter a bearing number to decode