SERRATED FLANGE

1 — INDUSTRY CONTEXT, FUNCTIONAL MECHANICS & JOINT DESIGN PRINCIPLES

1.1 Industrial Context of Serrated Flange Fasteners

Serrated flange fasteners represent an engineered evolution of conventional bolting systems developed to address joint loosening under vibration, cyclic loading, and dynamic operational environments.

Modern industrial assemblies increasingly operate under:

• High-frequency vibration
• Thermal expansion cycling
• Shock loading
• Rotational forces
• Maintenance-limited installations

Industries such as oil & gas, heavy equipment manufacturing, offshore platforms, structural steel erection, rail systems, and power generation demand fastening solutions that combine:

• High clamp load retention
• Reduced assembly complexity
• Controlled friction behavior
• Reliable anti-loosening performance

Serrated flange configurations integrate washer functionality directly into the fastener, eliminating secondary components while improving joint integrity.

At SM Fasteners, serrated flange products are manufactured under ISO 9001 certified quality systems, supporting EPC contractors, OEM manufacturers, and global procurement organizations requiring audit-ready fastener solutions.

1.2 Technical Definition

A Serrated Flange Fastener (bolt or nut) incorporates:

1. Integral flange face
2. Radial serrations beneath bearing surface
3. Threaded fastening body

Structural Elements

Component	Function
Hex Head Nut / Nut Body	Torque transmission
Integral Flange	Load distribution
Serrations	Mechanical locking
Thread	Preload generation
Bearing Surface	Friction stabilization

Unlike standard hex fasteners requiring washers, serrated flange fasteners perform three functions simultaneously:

• Clamping
• Load spreading
• Anti-rotation locking

1.3 Functional Principle of Serrations

Serrations are precision-machined or forged radial teeth oriented opposite tightening direction.

During Tightening:

1. Fastener torque generates axial tension.
2. Flange distributes contact pressure.
3. Serrations plastically embed into mating surface.
4. Micro-biting action increases resistance to rotation.

Resulting Benefits

• Increased prevailing torque
• Reduced loosening tendency
• Higher vibration resistance
• Lower dependency on thread friction

1.4 Load Mechanics & Force Behavior

Serrated flange fasteners operate fundamentally as preloaded tension members.

1.4.1 Preload Generation

Applied torque produces axial tension:$$F = \frac{T}{K \times D}$$

Where:

• F = Preload force (N)
• T = Applied torque (Nm)
• K = Nut factor (0.12–0.22)
• D = Nominal diameter (m)

1.4.2 Load Transfer Mechanism

External loads should ideally never reach bolt shear capacity.

Correct joint design ensures:

External Load → Joint Compression → Friction Resistance → Bolt remains elastic

Serrated flange geometry enhances:

• Contact friction coefficient
• Slip resistance
• Clamp load stability

1.4.3 Contact Stress Distribution

The flange increases effective bearing diameter.

Fastener Type	Contact Area	Stress Distribution
Standard Hex + Washer	Moderate	Localized
Hex Without Washer	Low	High Stress
Serrated Flange	High	Uniform

Reduced bearing stress prevents:

• Surface galling
• Joint embedding loss
• Relaxation failures

1.5 Torque–Tension Relationship

Torque applied to a fastener is consumed as:

Torque Usage	Percentage
Thread friction	40–50%
Bearing friction	35–45%
Useful preload	10–15%

Serrations stabilize bearing friction variability, improving preload repeatability.

1.6 Friction Mechanics & Nut Factor

Typical Nut Factor Values:

Condition	Nut Factor (K)
Dry Carbon Steel	0.20
Zinc Plated	0.18
Lubricated	0.14
PTFE Coated	0.12

Serrated flanges reduce friction fluctuation during service rather than during tightening.

1.7 Joint Design Principles

Fundamental Engineering Rules

1. Clamp force must exceed service load.
2. Fastener must remain in elastic region.
3. Joint separation must never occur.
4. Friction must resist transverse motion.

Recommended Joint Stack

✔ Structural member
✔ Flat mating surface
✔ Serrated flange fastener
✘ Washer typically unnecessary

When Serrated Flange Fasteners Are Preferred

Condition	Suitability
High vibration	Excellent
Automotive assemblies	Preferred
Thin plate structures	Highly effective
Repetitive maintenance	Suitable
Rotating equipment	Recommended

1.8 Mechanical Behavior Under Service Conditions

1.8.1 Vibration Resistance

Serrations create mechanical interlock preventing self-loosening described by the Junker vibration model.

1.8.2 Fatigue Performance

Maintained preload reduces alternating stress amplitude.

Higher retained preload → Lower fatigue failure probability.

1.8.3 Slip Resistance

Flange increases frictional resistance:$$F_{slip} = \mu \times F_{preload}$$

Where μ increases due to serration bite.

1.9 Failure Mechanisms and Engineering Control

Fatigue Failure

Cause:

• Preload loss
• Cyclic loading

Mitigation:

• Proper torque control
• High-strength grades
• Serrated flange usage

Shear Failure

Occurs when:

• Joint separation occurs
• Load bypasses friction interface

Prevention:

• Correct preload ratio
• Adequate thread engagement

Hydrogen Embrittlement

Risk materials:

• High-strength carbon steels (>1000 MPa)

Controls:

• Baking after plating
• Controlled electroplating processes
• SM Fasteners verified coating systems

Stress Corrosion Cracking (SCC)

Affected Materials:

• Austenitic stainless steels in chlorides
• High-strength steels in H₂S

Solutions:

• Duplex alloys
• Nickel alloys
• NACE-compliant materials

1.10 Thread Engagement Requirements

Minimum engagement:

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

1.11 Design Advantages Over Conventional Fasteners

Parameter	Standard Hex	Serrated Flange
Washer Required	Yes	No
Assembly Time	Higher	Reduced
Vibration Resistance	Moderate	High
Clamp Retention	Variable	Stable
Inventory Complexity	High	Lower

1.12 Engineering Selection Criteria

Mechanical Factors

• Required preload
• Dynamic loading
• Surface hardness
• Reusability requirement

Environmental Factors

• Temperature
• Corrosion exposure
• Chemical presence
• Offshore conditions

Procurement Factors

• Global standards compliance
• Traceability
• Inspection documentation
• Interchangeability

SM Fasteners designs serrated flange products aligned with international EPC specifications, ensuring compatibility with ISO, ASTM, DIN, and BS-based project documentation.

2 .PRODUCT TYPES, GEOMETRY, DIMENSIONAL LOGIC & INTERNATIONAL STANDARDS

2.1 Product Types and Engineering Variants

Serrated flange fastening systems are supplied in multiple engineered configurations depending on load requirement, assembly accessibility, vibration severity, and material compatibility.

At SM Fasteners, serrated flange products are manufactured through controlled forging and precision machining processes aligned with ISO 9001 quality management systems, ensuring dimensional repeatability and global interchangeability.

2.1.1 Serrated Flange Bolt

Description:
Hex head bolt incorporating an integral serrated washer face.

Key Functional Characteristics

• Eliminates loose washer
• Rapid installation
• Controlled bearing pressure
• High vibration resistance

Typical Uses

• Automotive frames
• Structural steel connections
• Machinery housings
• Rail assemblies
• Equipment panels

2.1.2 Serrated Flange Nut

Description:
Hex nut with integral flange and radial locking serrations.

Engineering Benefits

• Maintains preload under cyclic loading
• Reduces installation components
• Improved torque retention

Common Pairing

• With standard hex bolts
• Stud bolt assemblies
• Structural anchor systems

2.1.3 Serrated Flange Screw

Used where threaded holes exist.

Applications include:

• Motor housings
• Gearboxes
• Sheet metal assemblies
• Precision equipment

2.1.4 Metric vs Imperial Configurations

System	Thread Type	Primary Regions
Metric	ISO Metric	Europe, Asia, Middle East
UNC	Unified Coarse	USA, Canada
UNF	Unified Fine	Aerospace & precision
BSW	British Standard Whitworth	Legacy infrastructure
BSF	British Standard Fine	Older mechanical equipment

SM Fasteners supplies fully interchangeable thread systems supporting multinational EPC projects.

2.2 Geometry and Dimensional Logic

The effectiveness of serrated flange fasteners depends heavily on engineered geometry relationships.

2.2.1 Critical Design Dimensions

Symbol	Parameter	Engineering Function
d	Nominal Diameter	Load capacity
P	Thread Pitch	Preload resolution
s	Hex Size	Tool interface
dc	Flange Diameter	Load distribution
k	Head Height	Torque strength
rf	Serration Depth	Locking efficiency

2.2.2 Flange Diameter Engineering

Flange diameter is intentionally larger than hex bearing area.$$D_{flange} \approx 1.6 – 2.2 \times Bolt\ Diameter$$Dflange​≈1.6−2.2×Bolt Diameter

Benefits:

• Reduced surface pressure
• Prevention of joint embedding
• Improved fatigue life

2.2.3 Serration Geometry

Key parameters:

Parameter	Typical Range
Serration angle	25°–40°
Tooth pitch	0.5–1.5 mm
Penetration depth	0.1–0.3 mm
Direction	Opposite tightening

Engineering Purpose:

• Resist reverse rotation
• Maintain clamp load

2.3 Standard Dimensional Specification Table (Metric)

Serrated Flange Bolt Dimensions — ISO Pattern

Size	Pitch (mm)	Hex (mm)	Flange Dia (mm)	Head Height (mm)
M5	0.8	8	11.8	3.5
M6	1.0	10	14.2	4.0
M8	1.25	13	17.9	5.3
M10	1.5	15	21.8	6.4
M12	1.75	18	26.0	7.5
M16	2.0	24	34.9	10.0
M20	2.5	30	42.8	12.5

(Values aligned with ISO flange bolt proportions used in EPC procurement.)

2.4 Serrated Flange Nut Dimensions

Size	Pitch	Width Across Flats	Flange Diameter	Height
M6	1.0	10	14	6
M8	1.25	13	17	8
M10	1.5	15	21	10
M12	1.75	18	25	12
M16	2.0	24	34	16
M20	2.5	30	42	20

2.5 Dimensional Logic for Load Distribution

Bearing Pressure Formula

$$P = \frac{F}{A}$$

Where:

• P = Bearing pressure
• F = Clamp load
• A = Flange contact area

Increasing flange area reduces localized stress, enabling thinner substrates without deformation.

2.6 Applicable International Standards

Serrated flange fasteners are governed by multiple global standards ensuring interchangeability.

2.6.1 ISO Standards

Standard	Scope
ISO 4162	Hex flange bolts
ISO 7044	Prevailing torque nuts
ISO 898-1	Mechanical properties of bolts
ISO 898-2	Mechanical properties of nuts
ISO 965	Thread tolerances
ISO 4032	Hex nuts dimensions
ISO 16047	Torque/clamp testing

2.6.2 DIN Standards

Standard	Description
DIN 6921	Hex flange bolts
DIN 6923	Flange nuts
DIN 267	Mechanical testing
DIN EN ISO 3506	Stainless fasteners

2.6.3 ASTM Standards

Standard	Application
ASTM A307	Carbon steel bolts
ASTM A325	Structural bolting
ASTM A449	High strength
ASTM F594	Stainless nuts
ASTM F593	Stainless bolts
ASTM B633	Zinc plating

2.6.4 British Standards (BS)

Standard	Application
BS 3692	Metric fasteners
BS EN ISO 4017	Hex bolts
BS 4190	Unified threads

2.7 Property Class System (Metric)

Property Class	Yield Strength (MPa)	Tensile Strength (MPa)
8.8	640	800
10.9	940	1040
12.9	1100	1220

2.8 Thread Standards & Tolerance Table

| Thread System | Angle | Tolerance Class | Application |
|—|—|—|
| ISO Metric | 60° | 6g / 6H | Global standard |
| UNC | 60° | 2A / 2B | General engineering |
| UNF | 60° | 2A / 2B | High precision |
| BSW | 55° | Medium | Legacy systems |
| BSF | 55° | Fine | Precision equipment |

SM Fasteners manufactures rolled threads ensuring superior fatigue strength compared to cut threads.

2.9 Interchangeability Considerations

Critical procurement checks:

• Thread compatibility
• Property class equivalency
• Flange diameter clearance
• Surface hardness compatibility

Incorrect substitutions can cause:

• Galling
• Loss of preload
• Joint damage

2.10 Weight Chart — Serrated Flange Bolts

(Aligned with SM Fasteners production data)

Size	Length (mm)	Weight/Piece (kg)	Weight/100 pcs (kg)
M6 × 20	0.007	0.7
M8 × 25	0.015	1.5
M10 × 30	0.030	3.0
M12 × 40	0.065	6.5
M16 × 50	0.145	14.5
M20 × 60	0.285	28.5

Weights used for logistics planning and export documentation.

2.11 Engineering Advantages of Integrated Flange Geometry

Feature	Engineering Result
Integral washer	Reduced parts
Serrated face	Anti-loosening
Wide bearing surface	Lower stress
Controlled friction	Stable preload
Forged construction	Grain flow strength

2.12 Design Selection Guidance

Select Serrated Flange Fasteners When:

✔ Washer loss risk exists
✔ Vibration present
✔ Automated assembly lines used
✔ Assembly speed critical
✔ Maintenance access limited

Avoid Serrations When:

✘ Surface coating must remain undamaged
✘ Soft mating materials (plastic/aluminum without design allowance)
✘ Reusable cosmetic surfaces

3 — MATERIAL ENGINEERING, HEAT TREATMENT, MANUFACTURING WORKFLOW & SURFACE ENGINEERING

3.1 Materials Engineering Philosophy for Serrated Flange Fasteners

Material selection for serrated flange fasteners is not driven solely by strength. Proper engineering requires simultaneous consideration of:

• Mechanical load capacity
• Corrosion resistance
• Temperature exposure
• Hydrogen sulfide compatibility
• Galling resistance
• Lifecycle cost
• Inspection and certification requirements

Because serrated flange fasteners introduce localized surface penetration through serrations, material hardness balance between fastener and joint surface becomes critically important.

SM Fasteners manufactures serrated flange products across a full industrial alloy spectrum under ISO 9001-certified process control, enabling global EPC compliance.

3.2 Industrial Material Range

3.2.1 Carbon Steel

Primary industrial material for structural and machinery applications.

Typical Grades

• ASTM A307
• ASTM A449
• ISO Property Class 8.8 / 10.9

Characteristics

• High strength-to-cost ratio
• Good machinability
• Requires corrosion protection

Applications

• Structural steel
• Equipment frames
• Heavy fabrication

3.2.2 Alloy Steel

Used where high strength and fatigue resistance are required.

Typical Grades

• ASTM A193 B7
• ISO 10.9 / 12.9
• EN 42CrMo4

Advantages

• High preload capability
• Excellent fatigue resistance
• High torque capacity

Typical Industries

• Power plants
• Oil & gas equipment
• Rotating machinery

3.2.3 Stainless Steel

Corrosion-resistant applications.

Grades

• AISI 304 / A2-70
• AISI 316 / A4-80
• ASTM F593/F594

Benefits

• Atmospheric corrosion resistance
• Chemical exposure suitability
• Low maintenance

Limitations:

• Lower yield strength vs alloy steel
• Galling risk without lubrication

3.2.4 Duplex & Super Duplex Stainless Steel

Critical offshore and sour-service materials.

Examples

• UNS S31803
• UNS S32205
• Super Duplex S32750

Advantages

• High strength + corrosion resistance
• Excellent chloride resistance
• Suitable for seawater exposure

3.2.5 Nickel Alloys

High-performance environments.

Alloy	Typical Use
Inconel 625	Offshore, high temperature
Inconel 718	Aerospace & turbines
Hastelloy C276	Chemical plants
Monel 400	Marine service
Incoloy 825	Acid resistance
SMO 254	Extreme chloride exposure

3.2.6 PEEK Fasteners (Advanced Polymer Option)

SM Fasteners also supplies PEEK serrated flange designs where metallic fasteners are unsuitable.

Advantages

• Non-metallic
• Electrical insulation
• Chemical resistance
• Lightweight
• MRI-safe applications

Used in:

• Semiconductor manufacturing
• Chemical dosing systems
• Medical equipment
• Electrical insulation assemblies

3.3 Material Comparison Table

Material	UTS (MPa)	Yield (MPa)	Corrosion Resistance	Temp Limit °C	Relative Cost	Typical Application
Carbon Steel 8.8	800	640	Low	300	Low	Structures
Alloy Steel 10.9	1040	940	Moderate	400	Medium	Heavy machinery
SS 304	700	450	Good	425	Medium	General corrosion
SS 316	800	550	Excellent	450	Medium	Marine
Duplex 2205	950	650	Very High	300	High	Offshore
Super Duplex	1000	750	Extreme	300	Very High	Subsea
Inconel 625	1030	725	Extreme	980	Premium	Turbines
PEEK	100	90	Excellent	250	High	Electrical/chemical

3.4 Corrosion Resistance vs Environment

Environment	Recommended Material
Atmospheric	Zinc plated carbon steel
Marine	SS316 / Duplex
Offshore Splash Zone	Super Duplex
Acidic Chemical	Hastelloy
Sour Service (H₂S)	NACE-compliant alloys
High Temperature	Inconel
Electrical Insulation	PEEK

3.5 NACE MR0175 / ISO 15156 Compliance

Oil & gas sour environments require strict hardness limitations.

Requirements

• Controlled heat treatment
• Hardness typically ≤ 22 HRC
• Verified chemical composition
• Traceable heat numbers

SM Fasteners supports:

• NACE material selection
• Hardness verification
• Project-specific compliance documentation

3.6 Heat Treatment Processes

Heat treatment defines final mechanical performance.

3.6.1 Quenching & Tempering

Applied to:

• Property class 8.8, 10.9, 12.9

Process:

1. Austenitizing
2. Oil quench
3. Tempering

Result:

• High strength
• Controlled toughness
• Fatigue resistance

3.6.2 Solution Annealing (Stainless/Duplex)

Purpose:

• Restore corrosion resistance
• Remove carbide precipitation
• Improve ductility

3.6.3 Age Hardening (Nickel Alloys)

Used for:

• Inconel 718
• High-temperature service

3.6.4 Stress Relieving

Applied after forming to reduce residual stress.

Heat Treatment Property Table

Property Class	Hardness (HRC)	Heat Treatment
8.8	22–32	Q&T
10.9	32–39	Q&T
12.9	39–44	Q&T
Stainless A4-80	25 max	Cold worked
Duplex	28 max	Solution annealed

3.7 End-to-End Manufacturing Workflow

SM Fasteners applies controlled manufacturing stages ensuring dimensional accuracy and metallurgical integrity.

3.7.1 Raw Material Verification

Incoming material undergoes:

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

3.7.2 Forging Operations

Preferred manufacturing route for serrated flange fasteners.

Hot Forging Advantages

• Continuous grain flow
• Superior fatigue strength
• Reduced internal defects

Processes:

• Head forging
• Flange forming
• Serration die formation

3.7.3 Precision Machining

Applied where required:

• Tight tolerance parts
• Exotic alloys
• Custom EPC designs

3.7.4 Thread Manufacturing

Thread Rolling (Preferred)

Benefits:

• Work-hardened surface
• Increased fatigue strength
• Superior surface finish

Thread Cutting

Used for:

• Large diameters
• Hard materials
• Low-volume custom parts

3.7.5 Serration Formation

Critical engineering step.

Methods:

• Forged serrations (preferred)
• Precision broaching
• CNC machining

Quality requirement:
Uniform tooth geometry ensuring consistent locking performance.

3.7.6 Heat Treatment Control

Controlled furnace environments:

• Temperature monitoring
• Time control
• Cooling rate verification

3.7.7 Surface Preparation

Before coating:

• Shot blasting
• Degreasing
• Pickling/passivation

3.8 Surface Finishing & Coating Technologies

Surface engineering protects against corrosion and friction variability.

Surface Finish Comparison Table

Coating	Corrosion Resistance	Temp Limit	Friction Stability	Typical Use
Zinc Plating	Moderate	120°C	Good	General industry
Hot Dip Galvanizing	High	200°C	Moderate	Structural
Mechanical Galvanizing	High	200°C	Stable	Heavy bolts
Dacromet/Geomet	Very High	300°C	Excellent	Automotive
PTFE Coating	Excellent	260°C	Low friction	Chemical plants
Phosphate & Oil	Low	150°C	Controlled	Assembly
Passivation	Stainless protection	400°C	Stable	SS fasteners
Nickel Plating	Decorative/corrosion	300°C	Good	Equipment

3.9 Hydrogen Embrittlement Control

High-strength serrated flange fasteners are susceptible during electroplating.

SM Fasteners applies:

• Controlled plating chemistry
• Post-plating baking (200°C)
• Hardness monitoring
• Batch traceability

3.10 Galling Prevention (Stainless Steel)

Recommended practices:

• Lubricated assembly
• Silver/PTFE coatings
• Different material pairing
• Controlled torque application

3.11 Temperature Capability Summary

Material	Continuous Service Temp
Carbon Steel	300°C
Alloy Steel	400°C
Stainless 316	450°C
Duplex	300°C
Inconel	980°C
PEEK	250°C

3.12 Manufacturing Capability Integration — SM Fasteners

SM Fasteners supports global project supply through:

• ISO 9001 certified production control
• MSME & UKAF registered quality systems
• Custom fastener engineering
• Advanced alloy manufacturing capability
• Batch traceability and inspection readiness
• Precision forged serrated flange geometry
• Export-oriented production planning

Capabilities include:

• Standard catalogue fasteners
• Drawing-based manufacturing
• Special coatings
• High-performance alloys
• PEEK engineered fasteners

4 — INSPECTION, QUALITY CONTROL, APPLICATION ENGINEERING, EXPORT READINESS & COMPLETE ENGINEERING TABLES

4.1 Quality Assurance Philosophy — SM Fasteners

Serrated flange fasteners used in EPC, offshore, structural, and critical equipment assemblies must demonstrate verifiable mechanical integrity, dimensional accuracy, and traceable manufacturing history.

SM Fasteners operates under:

• ISO 9001 Certified Quality Management System
• MSME Registered Manufacturing Facility
• UKAF Accredited Quality Compliance Framework

The objective is to ensure every serrated flange fastener supplied for global projects meets:

• Engineering specification compliance
• Inspection readiness
• Third-party audit acceptance
• Long-term service reliability

4.2 Inspection & Quality Control Workflow

4.2.1 Incoming Material Inspection

Inspection	Method	Purpose
Chemical composition	Spectrometer / PMI	Alloy verification
Mill Test Certificate review	EN 10204	Traceability
Heat number marking	Physical verification	Batch control
Visual inspection	ISO 3269	Surface defects

4.2.2 In-Process Manufacturing Inspection

Critical checkpoints during production:

• Forging dimensional verification
• Serration profile inspection
• Thread gauge verification
• Heat treatment monitoring
• Hardness testing

4.2.3 Final Dimensional Inspection

Measured Parameters:

Parameter	Instrument
Thread pitch	GO / NO-GO gauges
Hex size	Vernier / CMM
Flange diameter	Digital micrometer
Head height	Height gauge
Serration depth	Optical comparator

4.3 Mechanical Testing Requirements

Proof Load Testing

Verifies elastic load capability without permanent deformation.

Tensile Testing

Conducted per ISO 898-1.

Hardness Testing

Methods:

• Rockwell (HRC)
• Vickers (HV)
• Brinell (HB)

Torque–Tension Testing

Performed per ISO 16047 to validate preload characteristics.

4.4 Non-Destructive Testing (NDT)

Applied for critical project fasteners.

NDT Method	Purpose
Magnetic Particle Inspection	Surface cracks
Dye Penetrant Testing	Non-ferrous crack detection
Ultrasonic Testing	Internal defects
Eddy Current Testing	Surface discontinuities

4.5 Positive Material Identification (PMI)

Mandatory for:

• Duplex
• Super Duplex
• Nickel alloys
• Sour service materials

Ensures compliance with:

• NACE MR0175
• ISO 15156
• Project metallurgy specifications

4.6 Certification & Documentation Package

SM Fasteners supplies full export documentation:

Document	Standard
Mill Test Certificate	EN 10204 3.1 / 3.2
Heat Treatment Report	Furnace traceability
Dimensional Inspection Report	ISO compliance
Coating Certificate	ASTM standards
Certificate of Conformity	Project compliance
Packing List	Export logistics
Material Traceability Record	Batch control

4.7 Mechanical Properties Table (Grade-Wise)

Property Class	Proof Load (MPa)	Yield Strength (MPa)	Tensile Strength (MPa)	Hardness Range
8.8	600	640	800	22–32 HRC
10.9	830	940	1040	32–39 HRC
12.9	970	1100	1220	39–44 HRC
A2-70	450	450	700	≤ 95 HRB
A4-80	600	600	800	≤ 100 HRB

4.8 Proof Load & Tensile Capacity by Size

Size	Stress Area (mm²)	Proof Load 8.8 (kN)	Tensile Load 10.9 (kN)
M6	20.1	12	21
M8	36.6	22	38
M10	58.0	35	60
M12	84.3	51	88
M16	157	94	163
M20	245	147	255

4.9 Tightening Torque Chart (Engineering Reference)

Dry Condition Torque Values

Size	Class 8.8 (Nm)	Class 10.9 (Nm)	Class 12.9 (Nm)
M6	10	14	17
M8	25	35	42
M10	49	69	83
M12	85	120	145
M16	210	295	355
M20	410	575	690

Lubricated Condition

Reduce torque ≈ 15–20%

4.10 Preload Calculation — Worked Example

Given:

• Bolt: M12
• Torque: 120 Nm
• Nut Factor: 0.18
• Diameter: 12 mm (0.012 m)

$$F=\frac{T}{K\times D}$$$$F=\frac{120}{0.18\times0.012}$$​ $$F=55,555\ N \approx 55.5\ kN$$

Result:
Expected clamp load ≈ 55 kN

4.11 Thread Standards & Tolerances Table

Thread	Tolerance	Fit Type
ISO Metric	6g / 6H	General engineering
UNC	2A / 2B	Standard
UNF	2A / 2B	Precision
BSW	Medium fit	Legacy
BSF	Close fit	Precision

Rolled threads supplied by SM Fasteners improve fatigue life through compressive residual stress.

4.12 Surface Finish Performance Comparison

Coating	Salt Spray Resistance	Friction Control	Reusability	Industry
Zinc	72–120 hrs	Good	Moderate	General
HDG	500+ hrs	Variable	High	Structural
Geomet	1000+ hrs	Excellent	High	Automotive
PTFE	Excellent	Very Low	Excellent	Chemical
Passivated SS	Natural	Stable	Excellent	Marine

4.13 Corrosion Resistance vs Operating Environment

Environment	Recommended Material / Finish
Indoor industrial	Zinc plated
Coastal atmosphere	SS316
Offshore platform	Duplex
Chemical processing	Hastelloy
LNG facilities	Nickel alloys
High vibration machinery	Alloy steel + Geomet
Electrical systems	PEEK

4.14 Weight Chart — Serrated Flange Fasteners

(Aligned with SM Fasteners logistics standards)

Size	Length	Weight/Piece (kg)	Weight/100 pcs (kg)
M6 × 20	0.007	0.7
M8 × 25	0.015	1.5
M10 × 30	0.030	3.0
M12 × 40	0.065	6.5
M16 × 50	0.145	14.5
M20 × 60	0.285	28.5

Used for:

• Container planning
• Freight estimation
• EPC material take-off calculations

4.15 Industry Applications

Construction & Structural Steel

• Steel frames
• Bridge assemblies
• Tower structures
• Pre-engineered buildings

Serrated flange design reduces installation time and washer inventory.

Oil & Gas (Upstream, Midstream, Downstream)

Applications:

• Skid packages
• Pump bases
• Pipe supports
• Valve actuators
• Compressor housings

NACE-compliant materials available through SM Fasteners.

Power Generation

Used in:

• Turbine auxiliaries
• Boiler equipment
• Generator frames
• Solar mounting structures

Petrochemical & Chemical Processing

Requirements:

• Chemical resistance
• Stable preload
• Anti-loosening reliability

Materials:

• SS316
• Hastelloy
• Incoloy
• PTFE-coated fasteners

LNG & Offshore Installations

Critical considerations:

• Chloride attack
• Vibration
• Thermal cycling

Preferred materials:
Duplex / Super Duplex / Inconel.

Automotive & Heavy Equipment

Serrated flange fasteners are widely used in:

• Engine mounts
• Suspension assemblies
• Transmission housings
• Agricultural machinery

Benefits:

• Fast assembly
• Reliable locking
• Automation compatibility

Railways & Infrastructure

• Bogie assemblies
• Signaling equipment
• Trackside structures
• Bridge hardware

Shipbuilding & Marine Engineering

Applications include:

• Deck equipment
• Structural panels
• Marine engines
• Offshore modules

PEEK Fastener Applications

Where metallic fasteners fail:

• Chemical dosing equipment
• Semiconductor fabrication
• Electrical insulation systems
• Non-magnetic installations

4.16 Packaging & Export Logistics

SM Fasteners provides export-ready industrial packaging.

Packaging Methods

Method	Purpose
VCI Packaging	Corrosion prevention
Thread Protectors	Damage prevention
Batch labeling	Traceability
Heat number marking	Inspection readiness

Export Crating

• ISPM-15 compliant wooden crates
• Palletized bulk packaging
• Moisture barrier protection
• Container optimization

4.17 Global Procurement Readiness

SM Fasteners supports international EPC supply chains through:

• Drawing-based manufacturing
• Custom serrated flange geometries
• Special alloy capability
• Project documentation packages
• Third-party inspection coordination
• Lot traceability systems
• Global shipping capability

4.18 Engineering Summary — Serrated Flange Fasteners

Serrated flange fasteners provide a mechanically integrated locking and load-distribution solution engineered to maintain clamp force under vibration and dynamic service conditions.

When correctly selected and installed, they deliver:

• Stable preload retention
• Reduced assembly components
• Improved fatigue life
• Enhanced operational reliability

Through certified manufacturing, advanced material capability, and inspection-controlled production, SM Fasteners demonstrates readiness to support:

• EPC mega projects
• Oil & Gas installations
• Offshore structures
• Heavy industrial equipment manufacturing
• Global OEM supply programs