Serrated Flange Bolt

1. Industry Context

Serrated flange bolts are engineered fastening elements developed to improve joint reliability under vibration, cyclic loading, and dynamic service environments. They integrate a washer-like flange with radial serrations beneath the head, eliminating the need for separate locking washers while increasing resistance to loosening.

Across modern heavy industries, bolted joints must satisfy increasingly stringent requirements:

• High vibration resistance
• Reduced assembly time
• Controlled preload retention
• Repeatable torque performance
• Reduced component count
• Reliable field maintenance

Industries adopting serrated flange bolts include:

Industry	Functional Requirement
Structural Steel	Slip-resistant structural joints
Oil & Gas	Vibration & pressure cycling resistance
Power Plants	Thermal expansion stability
Automotive & Heavy Equipment	High-cycle fatigue resistance
Railways	Anti-loosening safety assemblies
Petrochemical Plants	Maintenance-friendly bolting
Shipbuilding	Corrosion + vibration tolerance

SM Fasteners manufactures serrated flange bolts engineered for EPC, OEM, and infrastructure projects requiring certified, traceable fastening systems compliant with international standards.

2. Technical Definition

A Serrated Flange Bolt is defined as:

A hex head bolt incorporating an integral circular flange with radial serrations on the bearing surface designed to increase frictional locking and prevent rotational loosening under dynamic loads.

Key Structural Elements

Component	Function
Hex Head	Torque transmission
Integral Flange	Load distribution
Serrations	Mechanical locking action
Threaded Shank	Tensile load transfer
Bearing Face	Friction interface

Unlike standard hex bolts requiring washers or lock washers, the serrated flange performs three simultaneous functions:

1. Clamp load distribution
2. Anti-rotation locking
3. Surface embedding resistance

3. Functional Role in Bolted Assemblies

Serrated flange bolts are selected when:

• Vibration loosening risk exists
• Assembly speed must be optimized
• Washer loss is unacceptable
• Joint slip must be minimized
• Torque repeatability is required

Typical joint configuration:

4. Load Mechanics & Force Behavior

Bolted joints function as preloaded spring systems.

Fundamental Principle

A bolt behaves elastically when tightened.

Applied torque → Bolt elongation → Clamp force → Joint integrity.

4.1 Forces Acting on Serrated Flange Bolts

Force Type	Description
Tensile Load	Axial separation forces
Shear Load	Lateral movement forces
Clamp Load	Compression between members
Frictional Resistance	Generated by serrations
Dynamic Load	Vibration/impact forces

The flange increases the bearing area, reducing localized compressive stresses.

4.2 Torque–Tension Relationship

Preload equation:$$F = \frac{T}{K \times D}$$

Where:

• F = Preload force (N)
• T = Applied torque (Nm)
• K = Nut factor (0.10–0.25)
• D = Nominal diameter (m)

Typical nut factors:

Condition	Nut Factor (K)
Dry	0.20–0.25
Zinc plated	0.18
Lubricated	0.12–0.16
PTFE coated	0.10–0.12

Serrations increase friction variability; therefore torque calibration is essential for critical assemblies.

4.3 Clamp Force Development

Preload must exceed external separating loads.

Recommended Engineering Rule

$$F_{preload} = 70\% – 80\% \text{ of proof load}$$

Benefits:

• Prevents joint separation
• Minimizes fatigue failure
• Maintains friction grip

5. Joint Design Principles

5.1 Bearing Pressure Distribution

Flange bolts reduce:

• Surface indentation
• Washer misalignment
• Local yielding

Flange diameter typically equals 1.6–2.0 × bolt diameter.

5.2 Anti-Loosening Mechanism

Serrations create:

• Micro mechanical interlock
• Increased rotational resistance
• Enhanced vibration stability

Important engineering note:

⚠ Serrated flange bolts should not be used on:

• Soft materials (aluminum, composites)
• Painted precision surfaces
• Hardened mating faces where serrations cannot embed

5.3 Friction Grip Joint Behavior

Joint strength is primarily governed by friction:

$$F_{shear} = \mu \times F_{clamp}$$

Where:

• μ = friction coefficient.

Serrations increase effective friction coefficient at the interface.

5.4 Thread Engagement Requirements

Minimum engagement:

Material	Engagement Length
Steel	1 × diameter
Aluminum	1.5 × diameter
Cast Iron	1.25 × diameter

5.5 Failure Mechanisms

1. Fatigue Failure

Occurs from preload loss or fluctuating stress.

Mitigation:

• Proper torque control
• Correct property class selection

2. Shear Failure

Occurs when joint slip happens.

Prevention:

• Adequate preload
• Correct flange diameter

3. Hydrogen Embrittlement

Risk for high-strength plated bolts (>1000 MPa).

SM Fasteners implements:

• Controlled plating processes
• Baking cycles
• ISO 9001 process control

4. Stress Corrosion Cracking

Occurs in chloride or H₂S environments.

Mitigation:

• Duplex / Super Duplex
• Nickel alloys
• NACE compliant materials

5.6 Dynamic Load Performance

Serrated flange bolts outperform standard hex bolts because:

• No washer rotation
• Increased interface friction
• Reduced micro-slip
• Higher preload retention

6. Application Relevance in Assemblies

Assembly	Functional Benefit
Gearboxes	Anti-vibration locking
Pumps	Seal integrity
Structural frames	Slip resistance
Engines	Reduced loosening
Offshore modules	Maintenance reduction

7. Selection Criteria — Engineering Approach

Engineers select serrated flange bolts based on:

1. Load type
2. Environment
3. Required preload
4. Corrosion exposure
5. Assembly method
6. Inspection requirements

8. Engineering Advantages

• Washer elimination
• Faster installation
• Reduced inventory complexity
• Consistent clamp load
• Improved vibration resistance

9. Product Types and Variants of Serrated Flange Bolts

Serrated flange bolts are manufactured in multiple configurations to satisfy structural, mechanical, automotive, petrochemical, and heavy engineering applications. Selection depends on joint design philosophy, load requirements, and installation conditions.

SM Fasteners manufactures precision-controlled serrated flange bolts under ISO 9001 certified production systems, ensuring dimensional accuracy, interchangeability, and global EPC acceptance.

9.1 Primary Configuration Types

Type	Description	Typical Application
Fully Threaded Serrated Flange Bolt	Threads along entire length	Thin assemblies, machinery
Partially Threaded Flange Bolt	Defined grip length	Structural joints
Heavy Hex Serrated Flange bolt	Increased head width	High-load structural assemblies
Metric Serrated Flange Bolt	ISO metric thread	Global EPC projects
UNC / UNF Flange Bolt	Unified threads	Oil & Gas / North America
Fine Pitch Serrated Flange Bolt	Smaller pitch	High vibration environments
Reduced Shank Type	Weight reduction	Automotive
High Strength Structural Type	High property class	Steel structures

9.2 Serration Designs

Serration geometry directly affects locking performance.

Serration Type	Mechanical Behavior
Radial Serrations	Standard anti-loosening
Diamond Serrations	Enhanced friction
Spiral Serrations	Progressive locking
Fine Micro Serrations	Controlled surface damage

Engineering Note:
Serrations must be harder than the mating surface to achieve proper embedding.

9.3 Head Style Variants

Head Style	Standard Reference	Usage
Hex Flange Head	DIN 6921 / ISO 4162	General industrial
Heavy Hex Flange	ASTM structural systems	Steel construction
12-Point Flange Head	Aerospace/compact zones	Limited clearance
Low Profile Flange	Automotive assemblies	Space constrained

9.4 Drive Configurations

Drive Type	Advantage
External Hex	High torque capacity
12-Point	Increased tool engagement
Torx Flange	Automated assembly
Internal Hex Flange	Precision equipment

10. Dimensional Logic and Geometry

Serrated flange bolt geometry follows strict proportional relationships to maintain mechanical performance.

10.1 Geometry Parameters

Symbol	Description
d	Nominal diameter
P	Thread pitch
k	Head height
s	Across flats
dc	Flange diameter
r	Underhead radius
L	Length under head

10.2 Design Engineering Logic

Flange Diameter (dc)
Provides bearing stress reduction:

$$dc \approx 1.8 \times d$$

Head Height (k)
Ensures torque transmission without head shear.

Underhead Radius (r)
Reduces stress concentration.

11. Standard Dimensional Specification Table

(Typical Metric Serrated Flange Bolt — DIN 6921 / ISO 4162)

Size	Pitch (mm)	Head Height k (mm)	Across Flats s (mm)	Flange Dia dc (mm)	Standard Length Range (mm)
M5	0.8	5.0	8	11.8	10–40
M6	1.0	6.0	10	14.2	10–60
M8	1.25	8.0	13	17.9	12–80
M10	1.5	10.0	15	21.8	16–120
M12	1.75	12.0	18	26.0	20–160
M16	2.0	16.0	24	34.5	25–200
M20	2.5	20.0	30	43.0	30–240
M24	3.0	24.0	36	51.0	40–300

(All dimensions aligned with SM Fasteners manufacturing capability.)

12. Thread Standards & Global Interchangeability

Serrated flange bolts must satisfy international thread compatibility requirements for global EPC projects.

12.1 Thread System Comparison

Thread System	Standard	Region
Metric Coarse	ISO 261 / ISO 965	Global
Metric Fine	ISO 261	Precision assemblies
UNC	ASME B1.1	USA
UNF	ASME B1.1	Oil & Gas
BSW	BS 84	Legacy UK systems
BSF	BS 84	High precision British

12.2 Thread Tolerance Classes

Thread	External Tolerance	Internal Tolerance
Metric Standard	6g	6H
Precision Fit	4g6g	5H
Structural Bolt	6g	6H
UNC	2A	2B
UNF	2A	2B

SM Fasteners maintains calibrated thread rolling dies verified through ISO 9001 inspection procedures.

13. Applicable International Standards

13.1 ISO Standards

Standard	Description
ISO 4162	Hexagon flange bolts
ISO 898-1	Mechanical properties carbon/alloy steel
ISO 965	Thread tolerances
ISO 4017	Fully threaded hex bolts
ISO 3269	Acceptance inspection

13.2 DIN Standards

Standard	Description
DIN 6921	Serrated flange bolt
DIN EN ISO 3506	Stainless fasteners
DIN 267	Fastener requirements

13.3 ASTM Standards

Standard	Application
ASTM A307	General purpose
ASTM A325	Structural bolting
ASTM A490	High-strength structural
ASTM F568M	Metric mechanical properties
ASTM A193	High temperature pressure service
ASTM A320	Low temperature service

13.4 British Standards

Standard	Description
BS 3692	Metric precision fasteners
BS 4190	Hexagon bolts
BS EN 14399	Structural assemblies

14. Property Class System (Metric)

Property Class	Yield Strength (MPa)	Tensile Strength (MPa)	Typical Application
8.8	640	800	General engineering
10.9	900	1040	Heavy machinery
12.9	1080	1220	High fatigue assemblies

15. Unified Inch Grade System

Grade	Equivalent	Application
SAE Grade 5	~8.8	Automotive
SAE Grade 8	~10.9	Heavy equipment
ASTM A490	Structural high strength	Bridges & structures

16. Interchangeability Considerations

Engineering compatibility must verify:

• Thread form
• Pitch equivalence
• Property class
• Head geometry
• Flange diameter
• Serration pattern

Improper interchange may cause:

• Torque mismatch
• Preload variation
• Joint failure

SM Fasteners supports EPC buyers with cross-standard conversion and engineering verification services.

17. Dimensional Tolerance Philosophy

Critical tolerances influencing performance:

Feature	Functional Impact
Thread pitch diameter	Preload accuracy
Head flatness	Torque transfer
Flange runout	Clamp distribution
Serration depth	Locking performance

Inspection performed using:

• GO/NO-GO gauges
• Optical profile measurement
• CMM dimensional verification

18. Weight Chart — Serrated Flange Bolts

(Aligned with SM Fasteners production data — Carbon Steel)

Size	Length (mm)	Weight / Piece (kg)	Weight / 100 pcs (kg)
M6 × 20	0.007	0.70
M8 × 25	0.015	1.50
M10 × 30	0.028	2.80
M12 × 40	0.052	5.20
M16 × 50	0.115	11.5
M20 × 60	0.220	22.0
M24 × 80	0.420	42.0

Weights vary based on material density and coating thickness.

19. Engineering Selection Logic — Geometry vs Application

Requirement	Recommended Geometry
High vibration	Fine pitch serrated flange
Structural steel	Heavy hex flange
Automated assembly	Torx flange
High corrosion	Stainless or Duplex
Space limitation	Low profile flange

20. Integration with SM Fasteners Manufacturing Capability

SM Fasteners provides:

• Metric & Inch standards production
• Custom flange diameter design
• Special serration geometry
• Tight tolerance thread rolling
• Project-specific dimensional control
• Advanced alloys including PEEK fasteners for non-metallic assemblies

Manufacturing adheres to ISO 9001 quality systems ensuring global project compatibility.

21. Material Grades and Engineering Selection Criteria

Material selection for serrated flange bolts is a critical engineering decision directly influencing:

• Mechanical strength
• Corrosion resistance
• Temperature capability
• Hydrogen sulfide resistance
• Fatigue life
• Inspection compliance

SM Fasteners manufactures serrated flange bolts across a full industrial material spectrum aligned with global EPC specifications and ISO 9001 certified quality management systems.

21.1 Carbon Steel Fasteners

Carbon steels remain the most widely used material for general industrial bolting.

Grade	Standard	UTS (MPa)	Yield (MPa)	Temp Limit	Typical Use
ASTM A307	ASTM	415	250	300°C	General fabrication
Class 8.8	ISO 898-1	800	640	300°C	Machinery
Class 10.9	ISO 898-1	1040	940	350°C	Heavy equipment
Class 12.9	ISO 898-1	1220	1080	400°C	Dynamic loading

Advantages:

• High strength-to-cost ratio
• Good machinability
• Heat treatable

Limitation:

• Requires coating for corrosion resistance.

21.2 Alloy Steel Grades

Used where high strength and fatigue resistance are mandatory.

Material	ASTM	Application
AISI 4140	ASTM A193 B7	Oil & Gas
AISI 4340	Special	High fatigue
ASTM A193 B16	High temperature	Power plants

Characteristics:

• Superior fatigue resistance
• Higher hardenability
• Stable mechanical performance

21.3 Stainless Steel Fasteners

Manufactured per ISO 3506 / ASTM standards.

Grade	Structure	Corrosion Resistance	Typical Industry
A2-70 (304)	Austenitic	Atmospheric	Construction
A4-70 (316)	Austenitic	Marine	Offshore
A4-80	Austenitic	Chemical exposure	Petrochemical
316L	Low carbon	Welded assemblies	Process plants

Benefits:

• No coating required
• Excellent corrosion resistance
• Good temperature stability

21.4 Duplex & Super Duplex Stainless Steel

Essential for offshore and sour service.

Grade	Standard	PREN	Application
Duplex 2205	ASTM A182 F51	~35	Offshore
Super Duplex 2507	ASTM F53	>40	Seawater systems

Advantages:

• High strength + corrosion resistance
• Chloride stress corrosion resistance
• NACE compatibility

21.5 Nickel Alloy Fasteners

SM Fasteners supplies advanced alloys for extreme environments.

Alloy	Service Condition
Inconel 625	High temperature + corrosion
Inconel 718	Aerospace strength
Hastelloy C276	Strong acids
Monel 400	Seawater
Incoloy 825	Chemical processing
SMO 254	Chloride environments

21.6 Engineering Polymer — PEEK Fasteners

For electrically isolated or lightweight assemblies.

Property	Value
Continuous Temp	260°C
Corrosion	Excellent
Electrical Isolation	Yes
Weight	Very low

Applications:

• Semiconductor equipment
• Chemical plants
• LNG instrumentation
• Electrical panels

22. Material Comparison Table

Material	UTS	Yield	Corrosion Resistance	Relative Cost	Typical Sector
Carbon Steel	High	High	Low	Low	Structural
Alloy Steel	Very High	Very High	Medium	Medium	Oil & Gas
Stainless 316	Medium	Medium	High	Medium	Marine
Duplex 2205	High	High	Very High	High	Offshore
Super Duplex	Very High	High	Extreme	Very High	Subsea
Inconel	Extreme	Extreme	Extreme	Premium	LNG
PEEK	Low	Low	Chemical resistant	High	Electronics

23. Corrosion Resistance vs Environment

Environment	Recommended Material
Marine Atmosphere	A4-70 / Duplex
Seawater Immersion	Super Duplex / Monel
Sour Gas (H₂S)	NACE compliant alloys
Acidic Chemical	Hastelloy
High Temperature	Inconel
Cryogenic LNG	A320 Grades
Chemical Plants	SMO 254

SM Fasteners supports NACE MR0175 / ISO 15156 compliant manufacturing upon project requirement.

24. Mechanical Properties — Property Class Comparison

Property Class	Hardness (HRC)	Proof Load (MPa)	Tensile Strength (MPa)
8.8	22–32	600	800
10.9	32–39	830	1040
12.9	39–44	970	1220

Hardness limits are controlled to prevent hydrogen embrittlement.

25. Heat Treatment Processes

Heat treatment establishes mechanical performance.

25.1 Heat Treatment Workflow

1. Austenitizing
2. Quenching
3. Tempering
4. Stress Relieving
5. Hardness Verification

25.2 Heat Treatment Effects

Process	Effect
Quenching	Strength increase
Tempering	Toughness improvement
Normalizing	Grain refinement
Stress Relief	Reduced residual stress

25.3 Sour Service Requirements

For H₂S environments:

• Hardness ≤ 34 HRC
• Controlled tempering
• NACE MR0175 compliance

26. End-to-End Manufacturing Workflow

SM Fasteners integrates controlled manufacturing aligned with ISO 9001 systems.

26.1 Raw Material Verification

Incoming material undergoes:

• Mill Test Certificate verification (EN 10204 3.1)
• Chemical composition analysis
• Positive Material Identification (PMI)
• Heat number traceability

26.2 Forging Operations

Hot forging produces optimal grain flow.

Advantages over machining:

• Higher fatigue resistance
• Reduced material waste
• Improved strength

Steps:

1. Billet cutting
2. Induction heating
3. Closed-die forging
4. Trimming
5. Controlled cooling

26.3 Flange Serration Formation

Serrations are produced via:

• Precision forging dies
• Secondary knurling operations
• CNC-controlled forming

Critical requirement:
Uniform serration depth ensuring predictable locking performance.

26.4 Thread Production

Preferred method: Thread Rolling

Method	Advantage
Thread Rolling	Increased fatigue strength
Thread Cutting	Used for special alloys

Rolling compresses grain structure, improving tensile performance.

26.5 Machining & Secondary Operations

• Head facing
• Underhead radius control
• Special flange diameter machining
• Custom tolerances

SM Fasteners provides custom-engineered flange bolts for EPC project drawings.

26.6 Heat Treatment Execution

Performed in controlled atmosphere furnaces:

• Continuous furnaces
• Batch furnaces
• Oil quench systems
• Temper verification

All batches linked to heat numbers.

26.7 Straightening & Deburring

Prevents stress risers and ensures installation safety.

27. Surface Engineering & Coatings

Surface treatment significantly affects corrosion resistance and torque behavior.

27.1 Surface Finish Comparison

Coating	Corrosion Resistance	Friction Control	Temperature Limit
Plain Oil	Low	Stable	High
Black Oxide	Low	Good	300°C
Zinc Plating	Medium	Good	120°C
Hot Dip Galvanized	High	Variable	200°C
Mechanical Galvanized	High	Controlled	200°C
Dacromet / Geomet	Very High	Excellent	300°C
PTFE / Xylan	Excellent	Low friction	260°C
Nickel Plating	High	Stable	400°C

27.2 Hydrogen Embrittlement Control

SM Fasteners implements:

• Low hydrogen plating processes
• Post-plating baking
• Hardness monitoring
• ISO 9001 process validation

27.3 Coating Selection Logic

Requirement	Recommended Finish
Outdoor structural	HDG
Automotive	Geomet
Offshore	PTFE
High temperature	Nickel
Chemical exposure	Fluoropolymer coatings

27.4 Surface Roughness & Friction Impact

Torque coefficient strongly depends on coating.

Typical coefficient of friction:

Condition	μ
Dry steel	0.20
Zinc plated	0.18
Lubricated	0.14
PTFE coated	0.10

Proper torque specification must always consider coating condition.

27.5 Identification & Marking

Each SM Fasteners serrated flange bolt may include:

• Manufacturer identification
• Property class marking
• Heat traceability code

Supports full inspection audit trails.

28. Inspection & Quality Control Philosophy

In critical industrial fastening systems, reliability depends not only on design but on verified manufacturing consistency and traceability. Serrated flange bolts used in EPC, oil & gas, power, and infrastructure projects must comply with rigorous inspection protocols.

SM Fasteners operates under ISO 9001 certified quality management systems, integrating material verification, process monitoring, and final inspection validation aligned with global project specifications.

28.1 Quality Assurance Framework

Stage	Control Activity
Incoming Material	MTC verification, PMI testing
Forging	Die inspection & dimensional checks
Threading	Gauge inspection
Heat Treatment	Hardness & metallurgical verification
Coating	Thickness & adhesion testing
Final Inspection	Mechanical & dimensional validation
Dispatch	Documentation review & traceability

29. Dimensional Inspection

Dimensional accuracy directly influences preload development and joint integrity.

Inspection Methods

• GO / NO-GO thread gauges
• Digital calipers & micrometers
• Optical profile projectors
• Coordinate Measuring Machine (CMM)
• Flange runout measurement
• Serration geometry inspection

Critical features inspected:

Feature	Inspection Purpose
Pitch diameter	Proper thread engagement
Head height	Torque transmission
Flange diameter	Load distribution
Serration depth	Anti-loosening function
Length tolerance	Assembly compatibility

30. Mechanical Testing

Performed according to ISO 898-1, ASTM F606, and DIN EN standards.

Test	Objective
Tensile Test	Verify ultimate strength
Proof Load Test	Confirm elastic behavior
Hardness Test	Heat treatment validation
Wedge Load Test	Head integrity
Impact Testing	Low temperature toughness
Elongation Test	Ductility confirmation

31. Non-Destructive Testing (NDT)

Applied for critical service bolts.

Method	Detection Capability
Magnetic Particle Inspection (MPI)	Surface cracks
Ultrasonic Testing (UT)	Internal defects
Dye Penetrant Testing (DPT)	Surface discontinuities
Eddy Current Testing	Surface anomalies

32. Positive Material Identification (PMI)

Essential for alloy and nickel material verification.

Techniques used:

• XRF Analysis
• Optical Emission Spectroscopy

PMI ensures compliance with:

• NACE MR0175
• Project metallurgy specifications
• Offshore material traceability requirements

33. Documentation & Certification

SM Fasteners supplies complete project documentation packages.

Document	Standard
Mill Test Certificate	EN 10204 3.1 / 3.2
Chemical Analysis	ASTM / ISO
Mechanical Test Report	ISO 898 / ASTM F606
Heat Treatment Record	Furnace traceability
Coating Report	Thickness certification
Inspection Report	Dimensional verification
Certificate of Conformance	Manufacturer declaration

34. Failure Prevention & Reliability Engineering

34.1 Common Failure Modes

Failure Mode	Cause	Engineering Control
Fatigue fracture	Preload loss	Controlled torque
Thread stripping	Poor engagement	Proper thread length
Hydrogen embrittlement	Improper plating	Baking process
Galling	Stainless friction	Lubrication
Stress corrosion cracking	Chlorides/H₂S	Material upgrade

34.2 Reliability Best Practices

• Maintain 70–75% proof load preload
• Avoid mixed property classes
• Use calibrated torque tools
• Verify lubrication condition
• Ensure surface cleanliness

35. Industry Applications

35.1 Construction & Structural Steel

Applications:

• Steel frames
• Modular buildings
• Bridges
• Equipment platforms

Benefits:

• Washer elimination
• Faster installation
• Slip-resistant joints

35.2 Oil & Gas Industry

Upstream

• Wellhead equipment
• Drilling modules

Midstream

• Compressor skids
• Pipeline supports

Downstream

• Refineries
• Process piping supports

Materials frequently supplied:

• ASTM A193 B7
• Duplex stainless
• Super Duplex
• NACE compliant grades

35.3 Power Generation

Used in:

• Steam turbines
• Gas turbines
• Boilers
• Cooling systems

Requirements:

• High temperature stability
• Controlled preload retention

35.4 Petrochemical & Chemical Processing

Typical conditions:

• Chlorides
• Acids
• Chemical exposure

Recommended materials:

• A4-80 stainless
• Hastelloy
• SMO 254

35.5 LNG & Offshore Installations

Requirements include:

• Cryogenic toughness
• Seawater corrosion resistance
• Vibration resistance

Preferred materials:

• Super Duplex
• Inconel
• Monel

35.6 Automotive & Heavy Equipment

Common uses:

• Engine mounts
• Transmission assemblies
• Suspension systems

Advantages:

• Assembly automation compatibility
• Reduced part count

35.7 Railways & Infrastructure

Applications:

• Track equipment
• Signaling structures
• Bridge components

Key requirement:

• Resistance to cyclic loading.

35.8 Shipbuilding & Marine

Exposure:

• Salt spray
• Constant vibration

Preferred materials:

• Duplex
• A4 stainless
• Nickel alloys

35.9 PEEK Fastener Applications

SM Fasteners also manufactures PEEK serrated flange fasteners for specialized environments:

• Electrical insulation systems
• Semiconductor plants
• Chemical reactors
• Medical equipment

Benefits:

• Non-magnetic
• Chemical inertness
• Lightweight

36. Export Capability & Global Supply Readiness

SM Fasteners supports international EPC and OEM procurement programs.

36.1 Industrial Packaging

Method	Purpose
VCI Packaging	Corrosion protection
Thread Caps	Thread protection
Oil wrapping	Transit protection
Moisture barrier bags	Export shipping

36.2 Export Crating

• ISPM-15 compliant wooden crates
• Palletized packaging
• Batch segregation
• Barcode traceability

36.3 Logistics Support

• Bulk project supply
• Container consolidation
• Heat number tracking
• Global documentation compliance

37. ENGINEERING TABLES

37.1 Mechanical Properties (Grade-Wise)

Property Class	Yield (MPa)	Tensile (MPa)	Proof Load (MPa)	Hardness
8.8	640	800	600	22–32 HRC
10.9	940	1040	830	32–39 HRC
12.9	1080	1220	970	39–44 HRC

37.2 Proof Load & Tensile Capacity (Typical)

Size	Stress Area (mm²)	Proof Load 8.8 (kN)	Proof Load 10.9 (kN)	Ultimate Tensile (kN)
M8	36.6	22	30	36
M10	58	35	48	58
M12	84.3	50	70	84
M16	157	94	130	157
M20	245	147	203	245
M24	353	212	293	353

37.3 Tightening Torque Chart

(Lubricated Condition — Approximate)

Size	8.8 Torque (Nm)	10.9 Torque (Nm)	12.9 Torque (Nm)
M6	10	14	17
M8	25	35	42
M10	49	69	83
M12	85	120	145
M16	210	295	355
M20	410	580	700
M24	710	1000	1200

Torque must always be validated against coating friction coefficients.

37.4 Preload Calculation — Worked Example

Given

• Bolt: M16 Class 10.9
• Torque: 295 Nm
• Nut Factor: 0.16
• Diameter: 0.016 m

$$F = \frac{T}{K \times D}$$

$$F = \frac{295}{0.16 \times 0.016}$$

$$F = 115,234 \text{ N} \approx 115 kN$$

Result: Clamp force ≈ 115 kN

37.5 Thread Standards & Tolerances

System	External	Internal
Metric ISO	6g	6H
Precision Metric	4g6g	5H
UNC	2A	2B
UNF	2A	2B
BSW	Medium Fit	Medium Fit
BSF	Close Fit	Close Fit

37.6 Surface Finish Performance Comparison

Coating	Salt Spray Resistance	Friction Stability	Typical Industry
Zinc	72–120 hr	Good	General
HDG	500+ hr	Variable	Structural
Dacromet	1000 hr	Excellent	Automotive
PTFE	1000+ hr	Very Stable	Offshore
Nickel	High Temp	Stable	Power

37.7 Weight Chart — Serrated Flange Bolts (SM Fasteners Reference)

Size	Length	Weight / Piece (kg)	Weight / 100 pcs (kg)
M8 × 25	0.015	1.50
M10 × 30	0.028	2.80
M12 × 40	0.052	5.20
M16 × 50	0.115	11.5
M20 × 60	0.220	22.0
M24 × 80	0.420	42.0

38. SM FASTENERS — ENGINEERING & SUPPLY CAPABILITY

SM Fasteners integrates:

• ISO 9001 certified manufacturing systems
• MSME recognized industrial production
• UKAF accredited quality framework
• Advanced metallurgy capability
• Custom engineered fastener development
• Global EPC project supply readiness

Manufacturing scope includes:

• Bolts, Nuts, Screws, Washers
• Threaded Rods & Rings
• Serrated Flange Bolts
• Special Coated Fasteners
• Exotic Alloy Fasteners
• PEEK Engineering Fasteners

All products are supplied with full traceability, inspection documentation, and export-ready packaging aligned with international procurement expectations.

ENGINEERING CONCLUSION

Serrated flange bolts represent a highly efficient fastening solution combining:

• Load distribution
• Mechanical locking
• Reduced assembly complexity
• Improved vibration resistance
• Consistent preload performance

Through controlled metallurgy, precision forging, validated heat treatment, and certified inspection systems, SM Fasteners delivers serrated flange bolts engineered for reliability across global industrial projects.