Spring washers are manufactured in multiple geometrical configurations, each developed to deliver a specific mechanical response within bolted joints.

Selection must consider:

• Joint stiffness
• Load spectrum
• Surface hardness
• Environmental exposure
• Required locking reliability

12.Product Types & Engineering Variants

12.1 Split (Helical) Spring Washers — DIN 127 / DIN 7980

Most widely used industrial spring washer design.

Mechanical Characteristics

Feature	Engineering Function
Split helix geometry	Generates axial spring force
Sharp ends	Increase frictional resistance
Elastic compression	Maintains preload
Radial expansion	Improves locking action

Variants

Type	Description	Application
DIN 127 Type A	Square edge	General engineering
DIN 127 Type B	Chamfered edge	Improved seating
DIN 7980	Heavy duty	High-strength bolts

Typical industries:

• Structural steel
• Machinery manufacturing
• Power equipment
• EPC construction assemblies

12.2 Curved Spring Washers — DIN 137

Designed for controlled low-load elastic compensation.

Parameter	Function
Single curvature	Provides flexible deflection
Low spring rate	Suitable for thin materials
Large elastic range	Prevents joint relaxation

Applications:

• Electrical panels
• Aluminum assemblies
• Sheet metal fastening
• Precision equipment

12.3 Wave Spring Washers — DIN 137B / Wave Type

Wave-shaped geometry increases deflection capability with reduced space requirement.

Advantages:

• High deflection-to-thickness ratio
• Even load distribution
• Reduced installation height

Used in:

• Automotive components
• Bearings
• Electronic housings
• Rotating equipment

12.4 Toothed / Serrated Spring Washers — DIN 6797

Provide locking through surface penetration.

Type	Description
External tooth	Maximum locking torque
Internal tooth	Aesthetic finish protection
Combination tooth	High vibration resistance

Common in:

• Electrical grounding
• Control panels
• Lightweight assemblies

12.5 Heavy Duty Spring Washers

Engineered for:

• High-strength bolts (10.9 / 12.9)
• Structural applications
• Offshore equipment
• Heavy machinery

Manufactured with increased thickness and higher hardness limits.

12.6 Special Engineered Variants — SM Fasteners Capability

SM Fasteners manufactures custom spring washers including:

• Duplex & Super Duplex spring washers
• Nickel alloy high-temperature washers
• Cryogenic LNG service washers
• PEEK spring washers for electrically insulated assemblies
• Custom spring rates based on project load calculations

13. Dimensional Logic & Geometry Engineering

Spring washer performance depends primarily on geometry.

Critical Dimensional Parameters

Parameter	Symbol	Engineering Importance
Nominal size	d	Bolt compatibility
Inner diameter	d₁	Clearance fit
Outer diameter	d₂	Load distribution
Thickness	s	Spring stiffness
Free height	h₀	Available deflection
Gap width	g	Locking effectiveness

13.1 Geometry Influence on Spring Behavior

Geometry Change	Mechanical Effect
Increased thickness	Higher stiffness
Larger OD	Improved load distribution
Larger gap	Increased flexibility
Higher free height	Greater energy storage

14. Dimensional Specification Table

(Aligned with DIN 127 Type B — Typical Industrial Sizes)

Nominal Size	ID d₁ (mm)	OD d₂ (mm)	Thickness s (mm)	Free Height h₀ (mm)	Approx Weight /100 pcs (kg)
M3	3.2	6.2	0.5	1.1	0.03
M4	4.1	7.6	0.7	1.5	0.05
M5	5.1	9.2	1.0	2.0	0.08
M6	6.1	11.8	1.6	2.6	0.15
M8	8.2	14.8	2.0	3.2	0.28
M10	10.2	18.1	2.5	4.0	0.45
M12	12.2	21.1	3.0	4.8	0.70
M16	16.2	27.4	4.0	6.5	1.60
M20	20.2	33.6	5.0	8.0	2.70
M24	24.5	39.6	6.0	9.5	4.40

(SM Fasteners weight data maintained for procurement estimation and logistics planning.)

15. International Standards & Compliance

Spring washers are governed by globally recognized dimensional and performance standards.

15.1 ISO Standards

Standard	Scope
ISO 7089	Plain washers reference
ISO 7090	Chamfered washers
ISO 10683	Coating performance
ISO 4042	Electroplating requirements
ISO 4759	Fastener tolerances

15.2 DIN Standards

DIN Standard	Description
DIN 127	Split spring washers
DIN 7980	Heavy duty spring washers
DIN 137	Curved & wave washers
DIN 6797	Toothed lock washers

DIN standards remain dominant in EPC procurement documentation.

15.3 ASTM Standards

ASTM Standard	Application
ASTM F436	Hardened washers reference
ASTM A684	High carbon steel
ASTM A313	Stainless spring wire
ASTM B633	Zinc coating

15.4 British Standards (BS)

BS Standard	Description
BS 4464	Spring washer dimensions
BS 4320	Metric washers
BS EN ISO adoption	Harmonized European system

16. Thread Compatibility & Tolerance Table

Spring washers must align with bolt thread systems used in global projects.

Thread System	Standard	Typical Tolerance
Metric Coarse	ISO 261	6g / 6H
Metric Fine	ISO 965	6g
UNC	ASME B1.1	2A / 2B
UNF	ASME B1.1	2A / 2B
BSW	BS 84	Medium fit
BSF	BS 84	Fine fit

Spring washer ID tolerances ensure free rotation without interference.

17. Mechanical Property Classification Compatibility

Spring washer hardness must exceed mating surface hardness.

Bolt Property Class	Washer Hardness Requirement
4.6	≥ 200 HV
8.8	300–420 HV
10.9	420–520 HV
12.9	Special hardened washer required

Improper hardness pairing leads to:

• Embedment loss
• Preload relaxation
• Joint failure

18. Interchangeability Considerations

EPC and global OEM projects frequently require interchangeability between standards.

Engineering considerations:

• DIN ↔ ISO dimensional equivalence
• Metric ↔ UNC conversion
• Washer OD seating compatibility
• Load distribution equivalence

SM Fasteners maintains dimensional traceability ensuring compatibility across multinational project specifications.

19. Engineering Selection Matrix

Application Condition	Recommended Spring Washer
General machinery	DIN 127
High strength bolts	DIN 7980
Light assemblies	DIN 137 curved
Space limitation	Wave washer
Electrical bonding	Toothed washer
Offshore corrosion	Duplex / SMO 254
Chemical plants	Nickel alloys
Electrical insulation	PEEK washers

20. Functional Summary — Geometry vs Performance

Washer Type	Spring Effect	Locking Strength	Deflection	Typical Industry
Split	Medium	Medium	Medium	Structural
Curved	Low	Low	High	Electrical
Wave	Medium	Medium	Very High	Automotive
Toothed	Low	Very High	Low	Electrical
Heavy Duty	High	High	Medium	Oil & Gas

21. Material Engineering & Metallurgical Selection

Material selection governs the mechanical reliability, corrosion resistance, temperature capability, and service life of spring washers.

Spring washers function as elastic components; therefore, materials must possess:

• High yield strength
• Controlled hardness
• Elastic recovery capability
• Fatigue resistance
• Environmental compatibility

SM Fasteners manufactures spring washers using globally approved industrial alloys, fully traceable through EN 10204 certification systems under ISO 9001 quality control.

22. Industrial Material Grades Used for Spring Washers

22.1 Carbon Steel Spring Washers

Most common engineering solution for general industrial applications.

Typical Grades:

• C60 / C67 spring steel
• EN 10132 spring steel
• ASTM A684
• SAE 1070 / 1095

Characteristics:

• High elastic modulus
• Excellent spring memory
• Economical large-scale production

Applications:

• Structural assemblies
• Heavy equipment
• Machinery foundations

22.2 Alloy Steel Spring Washers

Used where higher strength or fatigue resistance is required.

Common Materials:

• 51CrV4
• 6150 alloy steel
• EN 10089 spring steels

Advantages:

• Superior fatigue resistance
• Higher allowable stress
• Improved shock load tolerance

Typical Use:

• Mining equipment
• Power turbines
• Railway systems

22.3 Stainless Steel Spring Washers

Used in corrosive environments and hygienic applications.

Grade	Standard	Characteristics
SS 304	ASTM A240	General corrosion resistance
SS 316	ASTM A240	Chloride resistance
SS 316L	Low carbon	Weld compatibility
SS 321	Stabilized	High temperature service
SS 410	Martensitic	High hardness capability

Industries:

• Petrochemical plants
• Offshore structures
• Food processing
• Marine installations

22.4 Duplex & Super Duplex Stainless Steel

Advanced materials supplied by SM Fasteners for aggressive environments.

Material	Key Advantage
Duplex 2205	High strength + corrosion resistance
Super Duplex 2507	Extreme seawater resistance
UNS S32760	Offshore compliance

Suitable for:

• Subsea equipment
• Desalination plants
• Offshore platforms
• LNG terminals

22.5 Nickel & High-Performance Alloys

Designed for severe operating environments.

Alloy	Service Capability
Inconel 625	High temperature + corrosion
Inconel 718	High fatigue strength
Monel 400	Seawater resistance
Hastelloy C276	Acid environments
Incoloy 825	Chemical processing
SMO 254	Chloride & pitting resistance

22.6 PEEK Spring Washers (High-Performance Polymer)

SM Fasteners supplies PEEK spring washers where metal washers are unsuitable.

Advantages:

• Electrical insulation
• Lightweight assemblies
• Non-magnetic properties
• Chemical resistance
• Cryogenic stability
• Temperature range: −196°C to +260°C

Applications:

• Semiconductor equipment
• Aerospace electronics
• Medical devices
• LNG instrumentation

23. Material Comparison Table

Material	UTS (MPa)	Yield (MPa)	Corrosion Resistance	Temp Limit	Relative Cost	Typical Industry
Carbon Steel	800–1000	600	Low	250°C	Low	Construction
Alloy Steel	1000–1400	900	Medium	350°C	Medium	Heavy equipment
SS 304	520–750	210	Good	400°C	Medium	General industry
SS 316	520–750	220	Very Good	450°C	Medium	Marine
Duplex 2205	800	550	Excellent	300°C	High	Offshore
Super Duplex	950	650	Outstanding	300°C	Very High	Subsea
Inconel 718	1200	1000	Exceptional	700°C	Premium	Aerospace
SMO 254	650	300	Extreme	400°C	Premium	Chemical
PEEK	—	—	Excellent	260°C	High	Electronics

24. Corrosion Resistance vs Service Environment

Environment	Carbon Steel	SS304	SS316	Duplex	Nickel Alloy	PEEK
Atmospheric	✓	✓	✓	✓	✓	✓
Marine Seawater	✗	△	✓	✓✓	✓✓	✓
Acidic Media	✗	△	✓	✓	✓✓	✓✓
H₂S Sour Service	✗	△	✓	✓✓	✓✓	✓
Chlorides	✗	△	✓	✓✓	✓✓	✓
Cryogenic LNG	△	✓	✓	✓	✓	✓✓

✓✓ = Recommended
△ = Limited use

25. Heat Treatment Processes

Heat treatment is critical because spring washers rely on elastic recovery.

SM Fasteners performs controlled heat treatment aligned with ISO 898 and metallurgical process validation.

25.1 Austenitizing

Steel heated to 800–900°C.

Purpose:

• Dissolve carbides
• Prepare structure for hardening

25.2 Quenching

Rapid cooling using:

• Oil
• Polymer
• Controlled atmosphere

Result:

• High hardness martensitic structure

25.3 Tempering

Reheating at 350–500°C.

Benefits:

• Removes brittleness
• Improves toughness
• Stabilizes spring properties

25.4 Solution Annealing (Stainless Steels)

Applied to austenitic and duplex grades.

Purpose:

• Restore corrosion resistance
• Remove internal stresses

25.5 Hardness Control Requirements

Washer Type	Hardness Range
Standard spring washer	42–52 HRC
Heavy duty washer	45–55 HRC
Stainless washer	30–45 HRC
NACE sour service	Controlled ≤ 34 HRC

Compliance maintained with NACE MR0175 / ISO 15156 for oil & gas service.

26. End-to-End Manufacturing Workflow — SM Fasteners

Step 1 — Raw Material Verification

• Approved mills only
• Mill Test Certificate (MTC)
• Chemical analysis verification
• Positive Material Identification (PMI)

Step 2 — Wire / Strip Preparation

• Precision slit strip
• Surface cleaning
• Thickness verification

Step 3 — Cold Forming / Stamping

Process:

• High-speed stamping
• Controlled geometry forming
• Gap shaping

Advantages:

• Grain flow continuity
• Improved fatigue strength

Step 4 — Heat Treatment

• Continuous furnace systems
• Atmosphere control
• Hardness validation

Step 5 — Shot Blasting / Surface Conditioning

Removes scale and improves coating adhesion.

Step 6 — Surface Coating

Applied per customer specification.

Step 7 — Final Inspection & Traceability

• Batch marking
• Dimensional audit
• Mechanical validation
• Lot traceability maintained

27. Thread Rolling vs Machining (Related Fastener Compatibility)

Although washers are not threaded, compatibility with rolled threads is essential.

Parameter	Thread Rolled Fasteners	Cut Threads
Surface finish	Superior	Moderate
Fatigue strength	Higher	Lower
Washer seating	Stable	Variable

SM Fasteners recommends pairing spring washers with rolled-thread fasteners for maximum joint reliability.

28. Surface Engineering & Coatings

Surface treatments protect washers from corrosion while maintaining friction characteristics.

28.1 Zinc Plating (Electroplated)

• Economical
• Indoor applications
• Thickness: 5–12 µm

Risk:

• Hydrogen embrittlement (controlled baking required)

28.2 Hot Dip Galvanizing (HDG)

• Thick zinc layer (45–85 µm)
• Structural steel projects
• Outdoor exposure

28.3 Mechanical Galvanizing

• No hydrogen embrittlement risk
• Uniform coating

28.4 Phosphate Coating

• Improves lubrication
• Used with oil coating

28.5 Dacromet / Geomet Coatings

• Non-electrolytic
• Excellent corrosion resistance
• Offshore and automotive use

28.6 Stainless Passivation

Removes free iron contamination.

Standards:

• ASTM A967
• ASTM A380

28.7 PTFE / Xylan Coatings

Provide:

• Low friction coefficient
• Chemical resistance
• Anti-galling performance

---

29. Surface Finish Performance Comparison

30. Manufacturing Quality Advantages — SM Fasteners

• ISO 9001 controlled production
• UKAF-certified systems
• MSME manufacturing infrastructure
• Automated forming lines
• Advanced alloy capability
• Custom spring-rate engineering
• Full traceability from raw material to shipment

SM FASTENERS — Precision Fasteners Engineered for Strength & Reliability

31. Inspection & Quality Control Philosophy

Spring washers are classified as functional elastic components, not merely spacing elements.
Therefore, inspection must validate:

• Geometry accuracy
• Mechanical performance
• Metallurgical integrity
• Surface condition
• Traceability

SM Fasteners integrates inspection within an ISO 9001 certified quality management system, supported by UKAF accreditation requirements and MSME manufacturing compliance.

32. Incoming Raw Material Inspection

Verification Controls

Inspection Stage	Method	Objective
Mill Certificate Review	EN 10204 3.1	Chemical compliance
Spectrometer Analysis	PMI	Alloy confirmation
Wire Diameter Check	Micrometer	Forming accuracy
Surface Examination	Visual	Crack prevention
Hardness Baseline	HV test	Process control

Raw materials remain batch-linked throughout manufacturing for full traceability.

33. In-Process Manufacturing Inspection

Process	Inspection Activity
Stamping/Forming	OD, ID, thickness control
Heat Treatment	Furnace chart validation
Hardening	Rockwell hardness testing
Gap Geometry	Optical measurement
Surface Prep	Scale removal inspection

Statistical Process Control (SPC) ensures dimensional consistency across production lots.

34. Final Inspection & Testing

34.1 Dimensional Inspection

Measured parameters:

• Inner diameter
• Outer diameter
• Thickness
• Free height
• Split gap angle

Standards:

• DIN 127
• DIN 7980
• ISO tolerance systems

34.2 Mechanical Testing

Test	Standard	Purpose
Hardness Test	ISO 6508	Elastic capability
Compression Test	Internal spec	Spring performance
Load Deflection Test	Engineering validation	Preload retention
Metallography	ASTM E3	Grain structure

34.3 Non-Destructive Testing (NDT)

Applied when required by EPC or oil & gas projects.

Method	Application
Magnetic Particle (MPI)	Surface cracks
Dye Penetrant (DPT)	Stainless alloys
Ultrasonic	Critical batches
PMI	Alloy verification

34.4 Certification & Documentation

SM Fasteners supplies:

• EN 10204 3.1 / 3.2 Material Test Certificate
• Heat Treatment Records
• Coating Thickness Report
• Dimensional Inspection Report
• Hardness Report
• Certificate of Conformity (CoC)

All documents aligned with international EPC procurement requirements.

35. Mechanical Properties — Grade Wise Table

Material	Hardness (HRC)	Yield Strength (MPa)	Elastic Recovery	Fatigue Resistance
Carbon Spring Steel	42–52	600–900	High	High
Alloy Steel	45–55	900–1100	Very High	Excellent
SS304	30–40	210	Medium	Good
SS316	30–42	220	Medium	Very Good
Duplex 2205	28–36	550	High	Excellent
Inconel 718	35–45	1000	Exceptional	Outstanding
PEEK	—	—	Controlled	High (non-metallic)

36. Proof Load & Strength Compatibility Table

Spring washer hardness must exceed bolt bearing hardness.

Bolt Grade	Proof Load (MPa)	Recommended Washer Type
4.6	225	Standard spring washer
8.8	580	Hardened washer
10.9	830	Heavy duty washer
12.9	970	Special alloy washer

37. Tightening Torque Chart

(Typical Engineering Reference Values)

Bolt Size	Grade 8.8 Dry (Nm)	Grade 8.8 Lubricated (Nm)	Grade 10.9 Dry (Nm)
M6	10	7	14
M8	25	18	36
M10	49	35	70
M12	85	60	120
M16	210	150	295
M20	410	290	580
M24	710	500	1000

(Values represent engineering guidelines; project specifications prevail.)

38. Torque–Tension Relationship

$$T = K \times F \times D$$

Where:

• T = Torque
• K = Nut factor (0.18–0.25)
• F = Desired preload
• D = Nominal diameter

Spring washers stabilize preload after torque application.

39. Preload Calculation — Engineering Example

Assembly: M12 Bolt Class 8.8

Stress Area = 84.3 mm²
Proof Strength = 580 MPa

Target Preload = 70%$$F = 0.7 \times 580 \times 84.3$$

$$F = 34,200\,N$$

Torque (K = 0.20):$$T = 0.20 \times 34,200 \times 0.012$$

$$T = 82\,Nm$$

Spring washer compensates relaxation caused by:

• Surface embedment
• Thermal cycling
• Vibrational energy

40. Thread Standards & Compatibility Table

Thread Type	Standard	Typical Usage
Metric Coarse	ISO 261	Global EPC
Metric Fine	ISO 965	Automotive
UNC	ASME B1.1	North America
UNF	ASME B1.1	High strength joints
BSW	BS 84	Legacy equipment
BSF	BS 84	Fine pitch systems

Spring washers manufactured by SM Fasteners maintain compatibility across all systems.

41. Weight Chart — Spring Washers

(Aligned with SM Fasteners Logistics Data)

Size	Weight / Piece (kg)	Weight /100 pcs (kg)
M4	0.0005	0.05
M5	0.0008	0.08
M6	0.0015	0.15
M8	0.0028	0.28
M10	0.0045	0.45
M12	0.0070	0.70
M16	0.016	1.60
M20	0.027	2.70
M24	0.044	4.40

Used for:

• Project quantity estimation
• Freight planning
• EPC bid costing

42. Failure Modes & Engineering Prevention

Failure Mode	Cause	Engineering Prevention
Flattening	Over-torque	Torque control
Fatigue cracking	Cyclic loading	Alloy selection
Hydrogen embrittlement	Electroplating	Baking treatment
Stress corrosion	Chlorides	Duplex/Nickel alloys
Embedment loss	Soft surfaces	Hardened washer

43. Industry Applications Mapping

Construction & Structural Steel

• Steel frames
• Towers
• Bridges
• Pre-engineered buildings

Oil & Gas (Upstream / Midstream / Downstream)

• Pumps
• Valves
• Compressors
• Pipe supports
• Skid packages

NACE-compliant materials available.

Power Generation

• Turbines
• Boilers
• Switchyards
• Renewable energy systems

Petrochemical & Chemical Processing

• Reactor systems
• Heat exchangers
• Corrosive service assemblies

LNG & Offshore Platforms

• Cryogenic equipment
• Marine structures
• Subsea systems

Automotive & Heavy Equipment

• Engines
• Suspension assemblies
• Earthmoving machinery

Railways & Infrastructure

• Track systems
• Signaling equipment
• Structural fastening

Shipbuilding & Marine Engineering

• Deck machinery
• Propulsion systems
• Corrosion-resistant assemblies

PEEK Fastener Applications

Used where metallic locking is unsuitable:

• Electrical insulation assemblies
• Medical equipment
• Aerospace electronics
• Semiconductor manufacturing

44. Export Capability & Global Supply Readiness

SM Fasteners supports international EPC projects through structured export systems.

Industrial Packaging

• VCI anti-corrosion packing
• Batch identification labeling
• Thread protection systems
• Moisture-controlled packaging

Export Crating

• ISPM-15 certified wooden crates
• Palletized shipment
• Container load optimization
• Long-distance marine protection

Documentation Package

Supplied with every export shipment:

• Material Test Certificate (EN 10204 3.1 / 3.2)
• Heat Treatment Records
• Inspection Reports
• Dimensional Reports
• Coating Certification
• Packing List
• Certificate of Conformity

45. Quality System Integration — SM Fasteners

Manufacturing operates under:

• ISO 9001 Quality Management
• UKAF certified systems
• MSME registered manufacturing
• Full traceability
• Inspection-controlled production
• Custom engineering capability

Capabilities include:

• Special alloy spring washers
• Custom spring-rate design
• Project-specific standards compliance
• Prototype to bulk EPC supply

46. Engineering Selection Workflow (Procurement Guide)

1. Define bolt size & grade
2. Determine service environment
3. Evaluate vibration severity
4. Select washer geometry
5. Choose material grade
6. Verify hardness compatibility
7. Confirm coating requirement
8. Review inspection documentation
9. Validate logistics weight data
10. Issue purchase specification

47. Final Engineering Summary

Spring washers remain essential elastic locking elements in engineered bolted joints when properly selected and installed.

Correct performance depends on:

• Geometry precision
• Material metallurgy
• Controlled heat treatment
• Surface engineering
• Verified inspection practices
• Standards compliance

Through integrated manufacturing, advanced materials capability—including stainless, duplex, nickel alloys, and PEEK—and ISO 9001 controlled processes, SM Fasteners delivers spring washers engineered for global industrial reliability and EPC procurement readiness.