Fish Bolt

1. Industry Context

Fish Bolts are specialized structural fastening elements primarily engineered for railway joint assemblies, heavy structural alignment systems, and vibration-intensive mechanical connections. Unlike conventional bolts designed purely for clamping, fish bolts function within dynamic load environments where joint continuity, shear transfer, and cyclic stress resistance are critical.

They are extensively deployed across:

• Railway track systems
• Crane rails
• Mining rail infrastructure
• Metro and transit systems
• Steel bridge expansion joints
• Heavy equipment guideways
• Industrial rail-mounted machinery

Within modern infrastructure projects, fish bolts form a safety-critical connection between rail ends through fish plates (joint bars). Their design ensures:

• Controlled joint flexibility
• Load transfer continuity
• Alignment retention under dynamic traffic loads
• Resistance to vibration-induced loosening

EPC contractors and railway authorities classify fish bolts as structural integrity fasteners, requiring traceability, certified metallurgy, and strict dimensional control.

SM Fasteners manufactures fish bolts under certified systems aligned with:

• ISO 9001 Quality Management
• UKAF-accredited procedures
• MSME-certified industrial manufacturing

ensuring global project compliance.

2. Technical Definition

A Fish Bolt is defined as:

A partially threaded structural bolt designed specifically to secure fish plates or joint bars joining rail sections while sustaining combined shear, tensile, and fatigue loading.

Primary Functional Elements

• Oval or square neck preventing rotation
• Precision shank diameter matching plate hole tolerances
• Controlled thread length for load distribution
• High-strength material grades suitable for cyclic loading

Unlike standard hex bolts, fish bolts are engineered to:

• Transfer shear forces through the shank
• Maintain joint preload stability
• Resist vibration loosening from passing loads

3. Typical Fish Bolt Assembly

A standard railway joint includes:

• Rail ends
• Fish plates (joint bars)
• Fish bolts
• heavy hex nut
• Spring or lock washers

The bolt does not merely clamp — it integrates rails into a continuous structural beam.

4. Functional Role in Assemblies

4.1 Structural Functions

Function	Engineering Purpose
Rail Alignment	Maintains track geometry
Load Transfer	Transfers wheel loads across joint
Shear Resistance	Prevents rail displacement
Fatigue Resistance	Withstands cyclic train loading
Vibration Control	Maintains preload stability

5. Load Mechanics & Force Behavior

Fish bolts operate under combined loading conditions.

Applied Forces

1. Axial tensile load
2. Double shear load
3. Bending stress
4. Impact loading
5. Thermal expansion forces
6. Cyclic fatigue loading

5.1 Load Path in Rail Joint

Train wheel load → Rail → Fish Plate → Fish Bolt Shank → Adjacent Rail

Correct bolt selection ensures stress transfers through the unthreaded shank, not threads.

6. Preload and Clamping Force Principle

Preload is essential to prevent joint slip.

Fundamental Relationship

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

Where:

• F = Preload force (N)
• T = Applied torque (Nm)
• K = Nut factor (0.18–0.25 typical)
• D = Nominal diameter (m)

Worked Example

M24 Fish Bolt
Torque = 600 Nm
Nut Factor = 0.20$$F = \frac{600}{0.20 \times 0.024}$$

$$F = 125,000\ N$$

Preload ≈ 125 kN

This preload ensures rail contact integrity.

7. Torque–Tension Relationship

Approximately:

• 10% torque → bolt stretch
• 40% → thread friction
• 50% → bearing friction

Hence lubrication condition critically affects preload accuracy.

8. Joint Design Principles

8.1 Engineering Requirements

• Shear carried by shank
• Threads positioned outside shear plane
• Minimum engagement = 1 × diameter
• Controlled elasticity prevents brittle failure

8.2 Joint Stiffness Concept

Rail joint stiffness depends on:

• Bolt modulus
• Plate thickness
• Clamping force
• Friction coefficient

Higher stiffness → reduced impact loading.

9. Thread Engagement Principles

Recommended engagement:

Material	Minimum Engagement
Carbon Steel	1.0 × Diameter
Stainless Steel	1.25 × Diameter
Alloy Steel	1.0 × Diameter
Nickel Alloy	1.5 × Diameter

10. Mechanical Behavior Under Service

Fish bolts experience:

Elastic Stretch

Allows load redistribution.

Micro-Slip

Occurs under cyclic load if preload insufficient.

Fatigue Cycling

Millions of stress reversals during railway operation.

11. Friction and Nut Factor Influence

Nut factor varies with surface condition:

Condition	Nut Factor (K)
Dry	0.22–0.25
Oiled	0.18
Zinc Coated	0.20
PTFE Coated	0.14

Improper assumptions lead to preload errors >30%.

12. Failure Mechanisms

12.1 Fatigue Failure

Primary cause in rail systems.

Initiated at:

• Thread root
• Corrosion pits
• Surface defects

12.2 Shear Failure

Occurs when:

• Shank undersized
• Joint loosened
• Excessive impact load

12.3 Hydrogen Embrittlement

Risk increases with:

• High hardness (>34 HRC)
• Electroplated coatings

SM Fasteners applies controlled baking procedures compliant with international standards.

12.4 Stress Corrosion Cracking

Critical environments:

• Coastal railways
• Chemical terminals
• H₂S exposure

Material selection per NACE MR0175 / ISO 15156 required.

13. Fatigue Design Considerations

Key engineering practices:

• Rolled threads preferred
• Smooth fillet radius
• Shot peening (where required)
• Correct torque application
• Corrosion-resistant coatings

14. Dynamic Load Behavior

Railway joints undergo:

• Vertical wheel load
• Longitudinal traction force
• Braking force
• Thermal expansion stress

Fish bolts must maintain preload despite vibration amplitudes exceeding conventional structural connections.

15. Selection Criteria for Engineers & EPC Buyers

Parameter	Engineering Consideration
Rail Section	Determines bolt size
Load Frequency	Fatigue grade selection
Environment	Coating/material choice
Temperature	Alloy selection
Maintenance Interval	Preload retention capability
Inspection Requirements	Certification level

16. Interchangeability Philosophy

Global railway systems adopt compatible geometry allowing interchange across:

• ISO
• BS
• AREMA
• DIN railway specifications

SM Fasteners supplies fish bolts engineered for international interchangeability while maintaining certified traceability.

17. Product Types and Variants of Fish Bolts

Fish bolts are engineered based on rail profile, joint design philosophy, loading intensity, and maintenance methodology. Variations primarily arise from head geometry, shank configuration, and thread system compatibility.

Unlike conventional structural bolts, fish bolt variants are dictated by railway engineering standards rather than general fastener standards.

17.1 Standard Fish Bolt Types

Type	Description	Typical Application
Standard Oval Neck Fish Bolt	Prevents rotation inside fish plate	Conventional railway tracks
Square Neck Fish Bolt	High anti-rotation capability	Heavy haul railways
Hex Head Fish Bolt	Easy field installation	Industrial rail systems
Countersunk Fish Bolt	Flush surface requirement	Bridges & crossings
High Strength Fish Bolt	Heat-treated alloy steel	High-speed rail
Insulated Fish Bolt Assembly	Electrical isolation	Signaling zones
Shouldered Fish Bolt	Controlled shear transfer	Crane rails
Custom Engineered Fish Bolt	Project-specific geometry	EPC infrastructure

SM Fasteners manufactures all configurations including custom rail authority drawings.

18. Functional Geometry Logic

Fish bolt geometry is fundamentally different from general-purpose bolts.

Key Design Principles

1. Shear Plane Located in Shank
2. Threads Outside Load Zone
3. Anti-Rotation Neck Feature
4. Controlled Grip Length
5. High Bearing Surface Contact

18.1 Major Geometric Features

Feature	Engineering Function
Head	Torque transmission
Neck	Prevent rotation
Shank	Shear load transfer
Thread	Clamping force generation
Fillet Radius	Fatigue resistance
Grip Length	Joint alignment stability

19. Dimensional Logic for Rail Compatibility

Fish bolt dimensions are governed by:

• Rail section size
• Fish plate thickness
• Hole clearance tolerance
• Required preload capacity

Typical rail standards:

• UIC Rails
• BS Railway Sections
• IRS (Indian Railway Standard)
• AREMA Rail Profiles

20. Standard Dimensional Specification Table

Fish Bolt Dimensional Chart (Typical Engineering Range)

Nominal Size	Thread Pitch	Length Range (mm)	Head Width (mm)	Head Height (mm)	Neck Size	Thread Length
M16	2.0	80–140	27	10	Oval/Square	40
M20	2.5	100–180	32	13	Oval/Square	50
M22	2.5	110–190	36	14	Oval/Square	55
M24	3.0	120–220	41	15	Oval/Square	60
M27	3.0	140–240	46	17	Square	65
M30	3.5	160–260	50	19	Square	70

(Dimensions aligned with SM Fasteners manufacturing capability and railway standards.)

21. Thread Forms Used in Fish Bolts

Railway systems worldwide utilize multiple thread systems for interchangeability.

Thread Standard Compatibility Table

Thread System	Standard	Typical Region
Metric Coarse	ISO 261 / ISO 965	Global
Metric Fine	ISO	High preload applications
UNC	ASME B1.1	North America
UNF	ASME B1.1	High vibration zones
BSW	BS 84	Legacy railways
BSF	BS 84	British rail systems
IRS Threads	Indian Railway Standards	India

SM Fasteners supports multi-standard thread rolling ensuring EPC project compatibility.

22. Thread Tolerances and Classes

Metric Thread Tolerance Classes

Component	Class
External Thread	6g
Internal Thread	6H
Precision Assembly	4g6g
Heavy Structural	8g

Unified Thread Classes

Class	Application
2A/2B	General structural
3A/3B	Precision rail assemblies

23. Applicable International Standards

Fish bolts comply with a combination of fastener standards and railway authority specifications.

23.1 ISO Standards

Standard	Scope
ISO 898-1	Mechanical properties
ISO 4014	Hex bolts reference
ISO 965	Thread tolerances
ISO 3269	Acceptance inspection
ISO 4759	Dimensional tolerances

23.3 DIN Standards

DIN Standard	Scope
DIN 6914	High-strength structural bolts
DIN 933	Thread geometry reference
DIN 267	Fastener properties

23.4 British Standards (BS)

Standard	Application
BS 64	Railway fish bolts
BS 916	Rail joint fasteners
BS EN 14399	Structural bolting assemblies

23.5 Indian Railway Standards (IRS)

Widely adopted across Asia and Africa projects:

• IRS T-23 Fish Bolt Specification
• IRS Mechanical Property Requirements
• IRS Rail Joint Assembly Requirements

SM Fasteners supports IRS-compliant manufacturing with traceable documentation.

24. Property Class Systems

Mechanical property classes determine load capacity.

Metric Property Classes

Class	Yield Strength (MPa)	Tensile Strength (MPa)
4.6	240	400
5.6	300	500
8.8	640	800
10.9	900	1040
12.9	1080	1220

Railway applications commonly specify:

• 8.8 — Standard rail joints
• 10.9 — Heavy haul systems
• 12.9 — High dynamic loading

25. Interchangeability Considerations

Global rail infrastructure requires cross-standard compatibility.

Critical parameters:

• Shank diameter tolerance
• Thread pitch matching
• Head seating geometry
• Nut compatibility
• Washer interface

SM Fasteners performs dimensional validation ensuring interchangeability between:

• ISO ↔ BS
• DIN ↔ IRS
• ASTM ↔ UIC systems

26. Dimensional Tolerance Philosophy

Fish bolts operate in safety-critical environments requiring strict control.

Typical tolerances:

Parameter	Tolerance
Shank Diameter	h9
Length	±1 mm
Thread Pitch	ISO 965 compliant
Head Width	±0.3 mm
Straightness	≤0.2% length

27. Grip Length Engineering

Grip length must equal total clamped thickness.

Incorrect grip causes:

• Thread shear loading
• Fatigue crack initiation
• Joint loosening

Recommended:$$Grip\ Length = Plate\ Thickness + Washer\ Stack$$

28. Hole Clearance Design

Bolt Size	Hole Clearance
M20	+1.5 mm
M24	+2.0 mm
M27	+2.5 mm
M30	+3.0 mm

Provides assembly tolerance while maintaining shear resistance.

29. Head Geometry Engineering

Fish bolt heads are optimized for field installation.

Design objectives:

• Torque application under confined conditions
• Minimal protrusion
• Resistance to tool slip
• High bearing contact

30. Weight Chart — SM Fasteners Reference Data

(Approximate values aligned with SM Fasteners production standards)

Size	Length	Weight per Piece (kg)	Weight per 100 pcs (kg)
M20 × 120	0.36	36
M22 × 130	0.45	45
M24 × 150	0.58	58
M27 × 160	0.75	75
M30 × 180	1.05	105

Weight data supports logistics planning and EPC procurement estimation.

31. Engineering Selection Flow

1. Identify rail standard
2. Determine bolt diameter
3. Select property class
4. Confirm thread system
5. Evaluate environment
6. Select coating/material
7. Validate preload requirement
8. Specify inspection level

32. Integration with SM Fasteners Manufacturing Capability

SM Fasteners provides:

• Multi-standard tooling
• Precision hot forging
• Rolled thread technology
• Certified inspection systems
• Custom drawing execution
• Global EPC project supply

All fish bolts are produced within ISO 9001 controlled processes ensuring traceability from raw material to shipment.

33. Material Engineering for Fish Bolts

Material selection is the most critical engineering decision influencing strength, fatigue resistance, corrosion performance, and service life of fish bolts.

Rail joints operate under:

• Continuous cyclic loading
• Environmental exposure
• Temperature fluctuations
• Vibration and impact stresses

Therefore, material selection must balance:

• Mechanical strength
• Toughness
• Corrosion resistance
• Manufacturability
• Cost efficiency

SM Fasteners manufactures fish bolts using a full industrial material portfolio compliant with global specifications.

34. Industrial Material Grades Used

34.1 Carbon Steel Grades

Standard	Typical Grade	Application
ASTM A36	Mild Carbon Steel	Light rail systems
ASTM A307	General structural	Low load joints
EN 10025	S355	Structural rail fastening
IS 2062	E350	Indian railway systems

Advantages

• Economical
• Good machinability
• Suitable for coating systems

Limitations

• Requires corrosion protection
• Moderate fatigue resistance

34.2 Alloy Steel Grades

Standard	Grade	Typical Property Class
ASTM A193	B7	High strength
EN 10083	42CrMo4	10.9 / 12.9
AISI 4140	Alloy Steel	Heavy haul rail
AISI 4340	Ultra high strength	Extreme fatigue

Used for:

• High-speed rail
• Mining rail systems
• Heavy axle load infrastructure

34.3 Stainless Steel Grades

Grade	Characteristics	Application
SS304	General corrosion resistance	Urban rail
SS316	Chloride resistance	Coastal railways
SS316L	Low carbon	Chemical zones
SS410	High strength martensitic	Wear environments

34.4 Duplex & Super Duplex Stainless Steel

Grade	Standard	Benefits
Duplex 2205	UNS S32205	High strength + corrosion resistance
Super Duplex 2507	UNS S32750	Offshore performance

Used in:

• Offshore terminals
• LNG facilities
• Aggressive chemical exposure

34.5 Nickel Alloy Materials

SM Fasteners supplies advanced metallurgy for severe service:

Alloy	Key Property	Environment
Inconel 625	High temperature strength	Power & LNG
Incoloy 825	Acid resistance	Chemical plants
Monel 400	Seawater resistance	Marine rail
Hastelloy C276	Extreme corrosion resistance	Acid plants
SMO 254	Chloride resistance	Coastal infrastructure

34.6 PEEK Fasteners (Special Applications)

PEEK fish bolt assemblies are used where:

• Electrical insulation required
• Non-magnetic behavior needed
• Chemical exposure extreme
• Weight reduction required

Applications include:

• Signaling systems
• Electrified rail tracks
• Chemical processing plants

35. Material Comparison Table

Material	UTS (MPa)	Yield (MPa)	Corrosion Resistance	Temp Limit	Cost Level	Typical Use
Carbon Steel	400–800	250–640	Low	300°C	Low	Standard rail
Alloy Steel	900–1200	800–1000	Moderate	450°C	Medium	Heavy rail
SS304	515	205	Good	870°C	Medium	Urban rail
SS316	515	205	Excellent	870°C	Medium	Coastal
Duplex 2205	800	550	Very High	300°C	High	Offshore
Inconel 625	930	517	Extreme	980°C	Very High	LNG
PEEK	—	—	Chemical resistant	260°C	High	Electrical isolation

36. Mechanical Properties by Property Class

Property Class	Tensile Strength (MPa)	Yield Strength (MPa)	Hardness (HRC)
4.6	400	240	12–22
5.6	500	300	15–25
8.8	800	640	22–32
10.9	1040	900	32–39
12.9	1220	1080	39–44

Railway fish bolts typically limited to ≤34 HRC for sour-service safety.

37. NACE MR0175 / ISO 15156 Compliance

For H₂S environments:

• Hardness ≤ 34 HRC
• Controlled heat treatment
• Sulfide stress cracking resistance
• Material traceability mandatory

SM Fasteners supplies NACE-compliant materials upon project requirement.

38. Heat Treatment Processes

Heat treatment determines mechanical performance.

38.1 Process Flow

1. Austenitizing
2. Quenching
3. Tempering
4. Stress relieving

38.2 Heat Treatment Types

Process	Purpose
Normalizing	Grain refinement
Quenching	Strength increase
Tempering	Toughness restoration
Annealing	Machinability improvement
Solution Annealing	Stainless steels
Aging	Nickel alloys

38.3 Mechanical Impact of Heat Treatment

Treatment	Strength	Toughness	Fatigue Resistance
Untreated	Low	High	Low
Quenched	High	Low	Medium
Q&T	High	High	Excellent

Q&T is standard for high-strength fish bolts.

39. Hardness Control Requirements

Application	Max Hardness
General Rail	34 HRC
Sour Service	22 HRC max
Stainless Steel	HRB 95 typical
Nickel Alloy	Controlled by spec

40. End-to-End Manufacturing Workflow

(SM Fasteners ISO 9001 Certified System)

40.1 Raw Material Procurement

• Approved mills only
• EN 10204 3.1 MTC verification
• Chemical composition validation
• Heat number traceability

40.2 Incoming Inspection

• Spectrochemical testing
• Visual inspection
• Dimensional verification
• PMI (Positive Material Identification)

40.3 Forging Operations

Hot Forging Preferred

Benefits:

• Grain flow continuity
• Improved fatigue resistance
• Higher strength integrity

Steps:

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

40.4 Machining Operations

Applied when required:

• Special head geometry
• Custom rail standards
• Tight tolerances

40.5 Thread Manufacturing

Thread Rolling (Preferred)

Advantages:

• Compressive residual stress
• Improved fatigue life
• Smooth surface finish

Thread Cutting

Used for:

• Large diameters
• Exotic alloys

40.6 Heat Treatment Execution

• Computer-controlled furnaces
• Batch traceability
• Temperature uniformity validation
• Hardness verification

40.7 Straightening & Calibration

Post-treatment correction ensures:

• Straightness tolerance compliance
• Accurate shank geometry
• Assembly reliability

41. Surface Finishing & Coating Engineering

Surface engineering determines corrosion life and friction behavior.

41.1 Surface Finish Comparison Table

Coating	Corrosion Protection	Friction Control	Temperature Limit	Typical Use
Black Oxide	Low	Stable	300°C	Indoor rail
Zinc Plating	Moderate	Good	120°C	General use
HDG	High	Higher friction	450°C	Outdoor rail
Zinc Flake	Very High	Controlled	300°C	Railways
Phosphate	Assembly aid	Excellent	250°C	Preload control
PTFE	Excellent	Low friction	260°C	Chemical zones
Xylan	Superior	Stable	260°C	Offshore
Cadmium (restricted)	Marine	Excellent	Aerospace

41.2 Hydrogen Embrittlement Prevention

SM Fasteners applies:

• Controlled electroplating parameters
• Post-bake treatment
• Hardness monitoring
• Process validation records

42. Corrosion Resistance vs Environment Table

Environment	Recommended Material/Coating
Dry Inland	Carbon steel + Zinc
Coastal	SS316 / Duplex
Marine Splash	Super Duplex
Acid Plant	Hastelloy
LNG	Inconel
H₂S Service	NACE Alloy Steel
Chemical Exposure	PEEK / PTFE coated

43. Friction Coefficient Control

Surface finish affects preload accuracy.

Surface	Friction Coefficient
Dry Steel	0.20–0.25
Oiled	0.16–0.18
Zinc Flake	0.12–0.16
PTFE	0.08–0.12

Controlled friction ensures predictable torque–tension relationship.

44. Identification & Traceability

Each SM Fasteners fish bolt batch includes:

• Heat number marking
• Grade identification
• Manufacturer traceability
• Inspection linkage

Ensuring audit-ready supply for EPC and railway authorities.

45. Engineering Advantages of SM Fasteners Manufacturing System

• Certified ISO 9001 quality control
• Advanced alloy processing capability
• Precision hot forging technology
• Thread rolling expertise
• Capability for exotic materials including PEEK
• Global export manufacturing readiness

46. Inspection & Quality Control Philosophy

Fish bolts are categorized as safety-critical fastening components because failure directly affects structural continuity and operational safety.

SM Fasteners integrates inspection within an ISO 9001 certified quality management system, ensuring full traceability from raw material to shipment.

Quality assurance objectives:

• Mechanical reliability
• Dimensional conformity
• Metallurgical integrity
• Traceable documentation
• Compliance with EPC inspection protocols

47. Incoming Material Quality Control

Every production batch begins with controlled raw material validation.

Verification Steps

Inspection Stage	Method
Mill Test Certificate Review	EN 10204 3.1
Chemical Analysis	Optical Emission Spectroscopy
Positive Material Identification	PMI Testing
Surface Inspection	Visual & Magnetic
Heat Number Traceability	Barcode/Batch Control

Materials failing verification are rejected prior to manufacturing.

48. In-Process Manufacturing Inspection

Quality checks are embedded throughout production.

Stage	Inspection
Forging	Grain flow & head integrity
Machining	Dimensional verification
Thread Rolling	Pitch gauge validation
Heat Treatment	Hardness testing
Straightening	Runout measurement
Surface Coating	Thickness testing

49. Final Inspection & Mechanical Testing

Mechanical Testing Program

Test	Standard	Purpose
Tensile Test	ISO 898-1	Strength validation
Proof Load Test	ASTM / ISO	Elastic performance
Hardness Test	Rockwell/Brinell	Heat treatment verification
Impact Test	Charpy V-Notch	Toughness evaluation
Shear Test	Project requirement	Joint performance
Elongation Test	ISO	Ductility

50. Non-Destructive Testing (NDT)

NDT ensures absence of critical defects.

Method	Application
Magnetic Particle Inspection	Surface cracks
Ultrasonic Testing	Internal discontinuities
Dye Penetrant	Surface flaws
Eddy Current	Thread defects

51. Dimensional Inspection Requirements

Critical measurements include:

• Shank diameter
• Head geometry
• Thread pitch
• Grip length
• Straightness
• Oval neck dimensions

Inspection tools:

• Coordinate Measuring Machine (CMM)
• Thread ring gauges
• Digital micrometers
• Go/No-Go gauges

52. Certification & Documentation

SM Fasteners provides complete EPC documentation packages.

Standard Documentation

Document	Description
EN 10204 3.1 MTC	Chemical & mechanical certification
Heat Treatment Report	Furnace cycle records
Inspection Report	Dimensional verification
Coating Certificate	Thickness & process
NDT Report	Defect validation
Certificate of Conformance	Compliance declaration

Optional Documentation

• EN 10204 3.2 Third-Party Certification
• TPI inspection approval
• IBR / Railway Authority documentation

53. Mechanical Properties Table — Fish Bolts

Property Class	Proof Load (MPa)	Yield Strength (MPa)	Tensile Strength (MPa)
4.6	225	240	400
5.6	280	300	500
8.8	580	640	800
10.9	830	900	1040
12.9	970	1080	1220

54. Proof Load & Tensile Capacity by Size

Size	Stress Area (mm²)	Proof Load 8.8 (kN)	Ultimate Load 8.8 (kN)
M20	245	142	196
M22	303	176	242
M24	353	205	282
M27	459	266	367
M30	561	325	449

55. Tightening Torque Chart

(Approximate values)

Size	Grade	Dry Torque (Nm)	Lubricated Torque (Nm)
M20	8.8	410	300
M22	8.8	550	400
M24	8.8	710	520
M27	10.9	1050	780
M30	10.9	1450	1100

Torque values must be validated against project specifications.

56. Preload Calculation — Engineering Method

Formula

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

Where:

• F = Preload Force
• T = Torque
• K = Nut Factor
• D = Bolt Diameter

Worked EPC Example

M27 Fish Bolt
Torque = 1050 Nm
Nut Factor = 0.18$$F = \frac{1050}{0.18 \times 0.027}$$

$$F ≈ 216,000\ N$$

Preload ≈ 216 kN

57. Failure Mechanisms & Prevention

Failure Mode	Cause	Prevention
Fatigue	Insufficient preload	Correct torque
Shear	Thread in shear plane	Proper grip length
Hydrogen Embrittlement	Improper plating	Controlled baking
Stress Corrosion	Wrong material	Alloy selection
Galling	Stainless threads	Lubrication

58. Surface Finish Performance Comparison

Finish	Salt Spray Resistance	Friction Stability	Maintenance Need
Black Oxide	Low	Stable	High
Zinc Plated	Medium	Moderate	Medium
Hot Dip Galvanized	High	Variable	Low
Zinc Flake	Very High	Excellent	Very Low
PTFE	Chemical Resistant	Excellent	Very Low

59. Corrosion Resistance vs Environment

Environment	Recommended Solution
Inland Rail	Zinc plated carbon steel
Coastal Railway	SS316 / Duplex
Offshore Terminal	Super Duplex
Chemical Zone	Hastelloy
LNG Facility	Inconel
Electrified Track	PEEK insulated system

60. Industry Applications

60.1 Railways & Metro Infrastructure

Primary application area:

• Rail joint fastening
• Expansion joints
• High-speed rail
• Freight corridors

60.2 Construction & Structural Steel

• Crane rail alignment
• Bridge joints
• Steel guideways
• Expansion assemblies

60.3 Oil & Gas Sector

Used in:

• Rail-mounted loading systems
• Refinery transfer rails
• Maintenance rail infrastructure

Compliance often requires NACE MR0175 materials.

60.4 Power Generation

• Coal handling plant rail systems
• Turbine maintenance rails
• Nuclear auxiliary rail assemblies

60.5 Petrochemical & Chemical Processing

Requirements:

• Corrosion-resistant alloys
• PTFE or Xylan coatings
• Stainless or nickel materials

60.6 LNG & Offshore Installations

Key challenges:

• Saltwater exposure
• Cryogenic temperature variation
• High corrosion risk

SM Fasteners supplies duplex and nickel alloy fish bolts suitable for offshore EPC projects.

60.7 Automotive & Heavy Equipment

• Mining rail vehicles
• Material handling equipment
• Port crane rails

60.8 Shipbuilding & Marine Infrastructure

• Dock rail systems
• Shipyard crane tracks
• Marine loading facilities

61. PEEK Fastener Applications

PEEK fish bolts provide:

• Electrical insulation
• Non-sparking properties
• Chemical resistance
• Lightweight assemblies

Used in:

• Electrified railway signaling
• Hazardous chemical zones
• Non-magnetic installations

62. Thread Standards & Tolerances Table

Thread Type	Standard	Tolerance
Metric	ISO 261	6g/6H
UNC	ASME B1.1	2A/2B
UNF	ASME B1.1	3A/3B
BSW	BS 84	Medium Fit
BSF	BS 84	Fine Fit

63. Weight Chart — SM Fasteners Reference

Size	Length	Weight/Piece (kg)	Weight/100 pcs (kg)
M20×120	0.36	36
M22×130	0.45	45
M24×150	0.58	58
M27×160	0.75	75
M30×180	1.05	105

Used for logistics estimation and freight calculation.

64. Export Packaging System

SM Fasteners packaging complies with international shipping standards.

Industrial Packaging

• VCI corrosion protection
• Thread protectors
• Heat-number labeling
• Moisture barrier packing

Export Crating

• ISPM-15 compliant wooden crates
• Palletized loads
• Shock-resistant packaging
• Container optimization

65. Global Export Documentation

Provided with every shipment:

• Commercial Invoice
• Packing List
• Certificate of Origin
• EN 10204 3.1 MTC
• Inspection Reports
• Heat Treatment Certificates
• Coating Reports
• Certificate of Conformance

66. Traceability & Digital Quality Records

SM Fasteners maintains:

• Batch traceability
• Heat number tracking
• Manufacturing records
• Inspection data retention
• Audit-ready documentation

Supporting EPC, railway authority, and third-party audits.

67. SM FASTENERS — Engineering Capability Integration

SM Fasteners operates as a precision fastener manufacturer delivering:

• ISO 9001 certified production systems
• UKAF-accredited quality framework
• MSME recognized manufacturing capability
• Advanced alloy and PEEK fastener expertise
• Custom engineering & drawing-based manufacturing
• Multi-standard global compliance

Fish bolts supplied are engineered for:

• High reliability infrastructure
• Global railway systems
• EPC mega-project execution
• Long-term operational safety