All Metal Lock Nut

1. Industrial Context of All Metal Lock Nuts

Threaded fastening systems remain the primary mechanical joining method across heavy engineering industries due to:

• High load-bearing capability
• Maintainability of assemblies
• Predictable preload behavior
• Compatibility with global standards

However, conventional nuts are susceptible to self-loosening under:

• Dynamic vibration
• Thermal cycling
• Rotational loading
• Shock and impact forces
• Differential expansion between materials

Industries such as Oil & Gas, LNG, Power Generation, Rail Infrastructure, Heavy Equipment, Offshore Platforms, and Structural Steel Construction require fastening systems that maintain clamp load without reliance on polymers or secondary locking devices.

The All Metal Lock Nut was developed to address these reliability requirements.

Unlike nylon insert lock nuts, all metal locking designs retain performance under:

• Elevated temperature environments (>300°C)
• Chemical exposure
• Radiation zones
• Fire-safe applications
• Cryogenic service

SM Fasteners manufactures precision all metal lock nuts engineered for critical load retention, supporting global EPC procurement and inspection requirements.

2. Technical Definition

An All Metal Lock Nut is a threaded fastener incorporating a metallic prevailing torque locking feature, eliminating reliance on plastic inserts or external locking mechanisms.

Locking action is achieved through controlled elastic deformation of the nut body.

Core Functional Principle

The locking mechanism produces:

• Prevailing torque resistance during installation
• Continuous frictional resistance after tightening
• Resistance to vibration-induced rotation

Common locking mechanisms include:

• Top-lock deformation
• Elliptical distortion
• Slotted crown deformation
• Beam-style locking sections
• Conical interference threads

3. Functional Role in Bolted Assemblies

An all metal lock nut performs two simultaneous engineering functions:

1. Primary Clamp Load Generation
2. Secondary Anti-Rotation Locking

Mechanical Objectives

Function	Engineering Purpose
Preload generation	Creates clamping force
Friction stabilization	Prevents loosening
Vibration resistance	Maintains joint integrity
Thermal reliability	No polymer degradation
Reusability	Maintains locking torque

4. Load Mechanics & Force Behavior

4.1 Bolt–Nut Load System

When torque is applied:

1. Threads convert torque into axial force.
2. Bolt elongates elastically.
3. Joint members compress.
4. Clamp load develops.

The assembly behaves like two springs:

• Bolt → tension spring
• Joint → compression spring

Stable preload ensures external forces are absorbed without joint separation.

4.2 Preload Fundamentals

Preload is the single most important parameter in fastener performance.$$F_p = \frac{T}{K \times D}$$​

Where:

• $F_p$​ = Preload force (N)
• $T$ = Applied torque (Nm)
• $K$ = Nut factor
• $D$ = Nominal diameter (m)

Typical nut factor values:

Condition	Nut Factor (K)
Dry	0.20–0.25
Zinc coated	0.18–0.22
Lubricated	0.12–0.16
PTFE coated	0.10–0.14

All metal lock nuts introduce prevailing torque, meaning additional torque is required beyond seating torque.

4.3 Prevailing Torque Concept

Prevailing torque = Torque required to rotate the nut without clamp load.

Engineering significance:

• Maintains resistance against loosening
• Independent of clamp force
• Remains effective after load relaxation

4.4 Force Behavior Under Dynamic Loading

Industrial joints experience:

• Transverse vibration
• Axial cyclic loading
• Thermal expansion
• Shock impulses

Self-loosening occurs when transverse displacement reduces friction below rotation resistance.

All metal lock nuts counteract this through:

• Radial thread interference
• Elastic recovery forces
• Continuous contact pressure

5. Joint Design Principles

5.1 Joint Categories

Joint Type	Lock Nut Requirement
Static structural	Optional
Vibratory machinery	Mandatory
Rotating equipment	Mandatory
High temperature	Essential
Offshore assemblies	Recommended
Pressure equipment	Critical

5.2 Recommended Design Rules

Thread Engagement

Minimum engagement:

• Steel → 1 × diameter
• Stainless → 1.5 × diameter
• Aluminum → 2 × diameter

Typical engineering practice:$$70\% – 75\% \text{ of bolt proof load}$$

Clamp Load Target

Ensures:

• Maximum fatigue resistance
• No yielding during service

5.3 Friction Zones in Threaded Assemblies

Torque distribution:

Location	Torque Consumption
Thread friction	40–50%
Bearing surface	40–50%
Bolt stretch	10–15%

This explains why surface finish and lubrication strongly influence performance.

6. Torque–Tension Relationship

Torque alone does not guarantee preload.

Variables affecting accuracy:

• Surface roughness
• Coating thickness
• Lubrication condition
• Material hardness mismatch
• Thread tolerance class

All metal lock nuts must be selected considering combined torque + prevailing torque values.

7. Failure Mechanisms Addressed by All Metal Lock Nuts

7.1 Self-Loosening

Primary failure mode in vibration environments.

Mitigated by:

• Metallic locking deformation
• Continuous interference pressure

7.2 Fatigue Failure

Occurs due to fluctuating stress when preload is lost.

All metal lock nuts maintain preload → reduces fatigue crack initiation.

7.3 Thermal Relaxation

High temperature causes:

• Polymer insert degradation
• Loss of locking ability

All metal designs remain stable above 600°C depending on material.

7.4 Hydrogen Embrittlement

Critical for:

• High-strength alloy steel fasteners
• Electroplated components

SM Fasteners applies controlled finishing and baking procedures compliant with international standards.

7.5 Stress Corrosion Cracking

Relevant environments:

• Chlorides
• H₂S service
• Offshore exposure

Material selection aligned with NACE MR0175 / ISO 15156 mitigates risk.

8. Engineering Advantages Over Other Locking Systems

Locking Method	Temperature Limit	Reusable	Chemical Resistant
nylon insert nut	~120°C	Limited	Poor
Adhesives	Variable	No	Limited
Double nut	Moderate	Yes	Moderate
All Metal Lock Nut	Very High	Yes	Excellent

9. Selection Criteria (Engineering Perspective)

Engineers specify all metal lock nuts when:

• Operating temperature exceeds polymer limits
• Inspection accessibility is limited
• Safety-critical joint exists
• Maintenance cycles are long
• Vibration is continuous

10. SM Fasteners Engineering Capability

SM Fasteners integrates:

• ISO 9001 quality management systems
• UKAF accredited manufacturing processes
• MSME certified industrial production capability

Manufacturing includes:

Advanced materials including PEEK fasteners for lightweight chemical-resistant assemblies

Precision cold forging

CNC machining for specialty alloys

Custom locking torque calibration

11. Product Types and Variants of All Metal Lock Nuts

All metal lock nuts are engineered using controlled metallic deformation to generate prevailing torque.
Selection depends on:

• Load class
• Temperature exposure
• Installation frequency
• Space constraints
• Inspection accessibility
• Applicable international standards

SM Fasteners manufactures multiple geometries aligned with global EPC specifications and OEM engineering requirements.

11.1 Top Lock (Stover Type) All Metal Lock Nut

Construction Principle

The top portion of the nut is elliptically deformed during manufacturing.

• Thread axis slightly offset
• Creates radial interference with mating bolt
• Generates consistent prevailing torque

Engineering Characteristics

Parameter	Description
Locking method	Elliptical deformation
Temperature capability	Very high
Reusability	High
Vibration resistance	Excellent
Typical industries	Structural, heavy equipment

11.2 Center Lock All Metal Nut

Locking achieved at the mid-section of threads rather than the top.

Advantages:

• Reduced installation torque variation
• Improved alignment
• Lower galling risk in stainless assemblies

Used in:

• Precision mechanical assemblies
• Automotive powertrain systems
• Rotating machinery

11.3 Slotted / Crown Lock Nut (All Metal)

Locking achieved by:

• Slot deformation
• Metal beam flexure
• Controlled compression

Typical applications:

• Aerospace hardware
• High-cycle vibration systems
• Maintenance-critical assemblies

11.4 Two-Way Reversible Lock Nut

Designed to function from either installation side.

Benefits:

• Reduced installation errors
• Faster field assembly
• Preferred in maintenance-intensive plants

11.5 Heavy Hex All Metal Lock Nut

Increased width across flats provides:

• Higher bearing surface
• Increased preload capability
• Improved wrench engagement

Common in:

• Oil & Gas flanges
• Pressure vessels
• Structural steel connections

11.6 High Temperature All Metal Lock Nut

Manufactured using:

• Alloy steel
• Inconel
• Hastelloy
• SMO 254
• Duplex & Super Duplex grades

Designed for:

• Turbines
• Refineries
• LNG facilities
• Furnace equipment

11.7 Custom Engineered Lock Nuts — SM Fasteners Capability

SM Fasteners supports project-specific manufacturing:

• Non-standard heights
• Fine pitch threads
• Metric–Imperial hybrid compatibility
• Special prevailing torque calibration
• PEEK-based engineered locking solutions for lightweight corrosion-critical assemblies

12. Dimensional Logic and Geometry

The geometry of an all metal lock nut directly influences:

• Load distribution
• Prevailing torque
• Installation repeatability
• Fatigue performance

12.1 Fundamental Nut Geometry Parameters

Dimension	Symbol	Engineering Role
Nominal diameter	d	Load capacity
Pitch	P	Axial advance
Width across flats	s	Tool engagement
Nut height	m	Thread engagement
Locking zone height	hL	Prevailing torque
Bearing face diameter	dw	Load distribution

12.2 Standard Metric Dimensional Specifications (ISO Pattern)

Size	Pitch (mm)	Width Across Flats (mm)	Height (mm)	Approx Weight (kg/100 pcs)*
M6	1.0	10	6	0.35
M8	1.25	13	8	0.75
M10	1.5	17	10	1.50
M12	1.75	19	12	2.70
M16	2.0	24	16	6.30
M20	2.5	30	20	12.5
M24	3.0	36	24	22.0
M30	3.5	46	30	48.0
M36	4.0	55	36	82.0

*Weights aligned with SM Fasteners manufacturing reference data.

12.3 Dimensional Design Logic

Nut Height vs Strength

General rule:$$m \ge 0.8D$$

Ensures:

• Full proof load development
• Thread shear resistance
• Fatigue durability

Bearing Surface Requirements

Large bearing faces:

• Reduce embedding loss
• Improve preload retention
• Lower surface pressure

12.4 Thread Engagement Engineering

Bolt Material	Minimum Engagement
Carbon Steel	1 × diameter
Stainless Steel	1.5 × diameter
Aluminum Joint	2 × diameter
High temperature alloys	1.25 × diameter

13. Thread Standards & Tolerances

All metal lock nuts must maintain compatibility with internationally interchangeable thread systems.

SM Fasteners manufactures in both metric and imperial standards.

13.1 Thread Standards Comparison

Thread System	Standard	Flank Angle	Application
Metric	ISO 261 / ISO 965	60°	Global industry
UNC	ASME B1.1	60°	Heavy engineering
UNF	ASME B1.1	60°	High strength joints
BSW	BS 84	55°	Legacy equipment
BSF	BS 84	55°	Fine pitch systems

13.2 Tolerance Classes

Class	Fit Type	Application
6H	Standard nut	General industrial
5H	Precision fit	Automotive
4H	Close tolerance	Aerospace
2B	UNC/UNF	Standard US fit

Prevailing torque locking deformation is applied after threading while maintaining tolerance compliance.

14. Applicable International Standards

All metal lock nuts are governed by dimensional, mechanical, and performance standards.

14.1 ISO Standards

Standard	Scope
ISO 7042	All metal prevailing torque nuts
ISO 2320	Prevailing torque testing
ISO 898-2	Mechanical properties
ISO 965	Thread tolerance system
ISO 4032	Hex nut dimensions
ISO 9001	Quality management system

14.2 DIN Standards

Standard	Description
DIN 980	All metal self-locking nuts
DIN 982	Lock nut variants
DIN 934	Hex nuts
DIN 267	Mechanical performance

14.3 ASTM / ASME Standards

Standard	Application
ASTM A194	High pressure nut materials
ASTM A563	Carbon steel nuts
ASTM F594	Stainless steel nuts
ASME B18.2.2	Inch series dimensions

14.4 British Standards

Standard	Scope
BS 3692	Metric fasteners
BS 1083	High temperature fasteners
BS 1768	Mechanical property requirements

15. Property Class Systems

Mechanical capability defined by standardized property classes.

15.1 Metric Property Classes

Property Class	Proof Stress (MPa)	Typical Use
8	600	Structural
10	830	Heavy machinery
12	970	High load dynamic
A2-70	Stainless general
A4-80	Marine / chemical

15.2 Imperial Grade Equivalence

Metric	ASTM Equivalent
Class 8	ASTM A563 Grade A
Class 10	ASTM A563 DH
Class 12	ASTM A194 2H

16. Interchangeability Considerations

Critical procurement factor for EPC buyers.

Engineering Checks

• Thread form compatibility
• Pitch matching
• Property class equivalence
• Coating thickness tolerance
• Prevailing torque compliance

Incorrect interchangeability can cause:

• False torque readings
• Thread seizure
• Reduced preload
• Premature failure

SM Fasteners validates interchangeability through controlled inspection and dimensional verification.

17. Prevailing Torque Performance Requirements (ISO 2320)

Testing ensures locking function consistency.

Size Range	Minimum Prevailing Torque (Example)
M6–M10	0.5–3 Nm
M12–M16	3–10 Nm
M20–M24	10–30 Nm
M30+	Project specific

Tests conducted:

• First installation torque
• Removal torque
• Reusability verification

18. Engineering Advantages of Correct Geometry Selection

Proper geometry delivers:

• Stable preload
• Reduced vibration loosening
• Improved fatigue life
• Repeatable installation torque
• Inspection reliability

19. SM Fasteners — Dimensional Manufacturing Capability

SM Fasteners provides:

• ISO compliant production
• CNC-controlled deformation forming
• Automated thread gauging
• Batch traceability
• Custom engineered dimensions

Supported material platforms include:

• Stainless Steel
• Carbon & Alloy Steel
• Duplex / Super Duplex
• Hastelloy
• Inconel / Incoloy
• Monel
• Nickel alloys
• High-performance PEEK fasteners

All dimensional data aligns with global project documentation and third-party inspection expectations.

20. Material Grades and Engineering Selection Criteria

Material selection for All Metal Lock Nuts directly determines:

• Load capacity
• Temperature capability
• Corrosion resistance
• Galling behavior
• Hydrogen embrittlement susceptibility
• Service life under cyclic loading

SM Fasteners manufactures all metal lock nuts across a complete industrial material spectrum aligned with EPC procurement specifications and international standards.

20.1 Primary Material Categories

Material Group	Typical Grades	Key Characteristics
Carbon Steel	ASTM A563, ISO Class 8	Economical structural applications
Alloy Steel	ASTM A194 2H, Class 10/12	High strength, elevated loads
Stainless Steel	A2-70, A4-80	Corrosion resistance
Duplex Stainless	UNS S31803	High strength + chloride resistance
Super Duplex	UNS S32750	Offshore & seawater service
Nickel Alloys	Monel 400	Marine corrosion resistance
High Temp Alloys	Inconel 625/718	Extreme temperature stability
Chemical Alloys	Hastelloy C276	Acid resistance
Super Austenitic	SMO 254	Chloride & pitting resistance
Polymer Engineering	PEEK	Lightweight chemical systems

20.2 Material Selection Logic

Engineers evaluate:

Load Requirement

Higher property classes → alloy steel selection.

Environment

Corrosion exposure dictates stainless or nickel alloys.

Temperature

Polymer locking solutions fail above ~120°C → all metal preferred.

Maintenance Accessibility

Long maintenance intervals demand metallic locking reliability.

20.3 Material Comparison Table

Material	UTS (MPa)	Yield (MPa)	Corrosion Resistance	Temp Limit	Relative Cost	Typical Industry
Carbon Steel	800	640	Low	300°C	Low	Structural
Alloy Steel	1040	940	Moderate	450°C	Medium	Oil & Gas
A2-70 SS	700	450	Good	400°C	Medium	General industry
A4-80 SS	800	600	Excellent	450°C	Higher	Marine
Duplex	850	620	Excellent	300°C	High	Offshore
Super Duplex	950	750	Extreme	300°C	Very High	Seawater
Inconel 718	1250	1030	Exceptional	700°C+	Premium	Turbines
Hastelloy C276	790	355	Acid resistant	600°C	Premium	Chemical plants
SMO 254	650	300	Extreme chloride	300°C	Premium	Desalination
PEEK	—	—	Chemical resistant	250°C	Specialized	Lightweight assemblies

20.4 Corrosion Resistance vs Environment

Environment	Recommended Material
Atmospheric outdoor	Zinc coated carbon steel
Marine atmosphere	A4-80 / Duplex
Seawater immersion	Super Duplex / Monel
H₂S sour service	NACE compliant alloy steel
Acid processing	Hastelloy
LNG cryogenic	Austenitic stainless
High temperature furnace	Inconel
Chemical lightweight systems	PEEK fasteners

SM Fasteners supports NACE MR0175 / ISO 15156 compliant materials for sour service projects.

21. Mechanical Properties — Grade Wise

Property Class	Proof Load (MPa)	Hardness Range	Application
Class 8	600	22–32 HRC	Structural
Class 10	830	26–36 HRC	Heavy machinery
Class 12	970	32–39 HRC	Dynamic loading
A2-70	450	HRB 95 max	Corrosion resistant
A4-80	600	HRB 95 max	Marine
ASTM A194 2H	850	24–35 HRC	Pressure vessels

Hardness control is critical to prevent:

• Thread stripping
• Galling
• Hydrogen embrittlement

22. Heat Treatment Processes

Heat treatment defines final mechanical performance of all metal lock nuts.

22.1 Heat Treatment Objectives

• Increase strength
• Improve fatigue resistance
• Achieve required hardness
• Stabilize microstructure
• Enable locking deformation without cracking

22.2 Standard Heat Treatment Workflow

1. Austenitizing

Heating steel above transformation temperature.

2. Quenching

Rapid cooling to form martensite.

3. Tempering

Controlled reheating to achieve toughness.

22.3 Typical Heat Treatment Parameters

Grade	Treatment	Result
Class 8	Normalize + temper	Balanced strength
Class 10	Q&T	High tensile
Class 12	Q&T optimized	Maximum strength
A194 2H	Heavy tempering	Pressure service
Duplex	Solution annealed	Corrosion resistance

22.4 Sour Service Hardness Limits

Per NACE MR0175:

• Maximum hardness ≈ 22 HRC
• Prevents sulfide stress cracking

SM Fasteners controls hardness through calibrated furnace cycles.

23. End-to-End Manufacturing Workflow

All metal lock nuts require controlled manufacturing to achieve consistent prevailing torque.

23.1 Raw Material Verification

Incoming inspection includes:

• Mill Test Certificate (MTC)
• Heat number traceability
• Chemical composition verification
• Ultrasonic inspection (when required)

23.2 Forging vs Machining

Method	Advantage	Application
Cold Forging	Grain flow strength	Standard production
Hot Forging	Large sizes	Heavy hex nuts
CNC Machining	Exotic alloys	Low volume precision

SM Fasteners applies forging methods to maximize structural integrity.

23.3 Thread Manufacturing

Thread Rolling (Preferred)

• Improves fatigue strength
• Work hardens surface
• Smooth finish

Thread Cutting

Used for:

• Nickel alloys
• PEEK fasteners
• Custom designs

23.4 Locking Feature Formation

Performed after threading:

• Controlled deformation press
• Elliptical forming tools
• Beam flex design calibration

Critical control parameter:

Prevailing torque must meet ISO 2320 values without thread damage.

23.5 Heat Treatment Integration

Sequence:

1. Forging
2. Threading
3. Heat treatment
4. Locking deformation
5. Inspection
6. Surface finishing

23.6 Process Traceability

SM Fasteners maintains:

• Batch ID control
• Heat number tracking
• Manufacturing routing sheets
• Inspection records aligned with ISO 9001 system requirements

24. Surface Finishing and Coating Engineering

Surface engineering directly affects:

• Corrosion resistance
• Torque coefficient
• Galling tendency
• Hydrogen embrittlement risk

24.1 Common Industrial Surface Finishes

Coating	Thickness	Corrosion Resistance	Notes
Black Oxide	1 µm	Low	Indoor
Zinc Plating	5–12 µm	Moderate	Structural
Hot Dip Galvanizing	50–80 µm	High	Outdoor steel
Mechanical Galvanizing	40 µm	Good	Reduced embrittlement
Phosphate	—	Low	Lubricity
PTFE	20–30 µm	Excellent	Low friction
Dacromet / Geomet	8–12 µm	Very High	Automotive
Nickel Coating	Variable	High	Chemical service
Passivation	—	Stainless protection	Standard for SS

24.2 Surface Finish Performance Comparison

Coating	Salt Spray Resistance	Friction Stability	Temperature Capability
Zinc	Medium	Moderate	120°C
HDG	High	Variable	300°C
PTFE	Excellent	Excellent	260°C
Geomet	Very High	Stable	300°C
Passivated SS	Excellent	Stable	400°C+

24.3 Hydrogen Embrittlement Control

High strength lock nuts require:

• Controlled electroplating
• Post-plate baking
• Process validation

SM Fasteners performs hydrogen relief baking per international requirements.

24.4 Galling Prevention in Stainless Lock Nuts

Mitigation methods:

• Silver plating
• PTFE coating
• Lubricated assembly
• Controlled hardness pairing

24.5 Surface Engineering for PEEK Fasteners

PEEK lock systems offer:

• Non-conductive assemblies
• Chemical resistance
• Weight reduction
• No galvanic corrosion

Used in:

• Semiconductor plants
• Chemical dosing equipment
• Offshore instrumentation

25. Manufacturing Capability — SM Fasteners

SM Fasteners integrates:

• ISO 9001 certified production
• UKAF accredited quality assurance
• MSME recognized manufacturing infrastructure
• Advanced alloy machining capability
• Custom lock torque engineering
• Global export-grade finishing systems

Manufacturing supports:

• Metric & Imperial systems
• Special project drawings
• EPC approved vendor documentation
• Third-party inspection readiness

26. Inspection & Quality Control Philosophy

All Metal Lock Nuts are frequently installed in safety-critical assemblies where joint failure can result in:

• Pressure containment loss
• Structural collapse
• Equipment shutdown
• Safety incidents

Therefore, inspection is not limited to dimensional verification; it must validate mechanical integrity, locking performance, material traceability, and process conformity.

SM Fasteners operates under an ISO 9001 certified Quality Management System, supported by UKAF-accredited procedures and MSME manufacturing compliance.

26.1 Inspection Stages

Stage	Inspection Objective
Raw Material	Verify metallurgy
In-Process	Maintain dimensional control
Post Heat Treatment	Confirm mechanical properties
Post Coating	Validate thickness & torque
Final Inspection	Ensure full specification compliance
Pre-Dispatch	Export readiness verification

26.2 Dimensional Inspection

Performed using calibrated equipment:

• GO / NO-GO thread gauges
• Optical comparators
• Digital micrometers
• Coordinate Measuring Machines (CMM)
• Profile gauges for locking deformation

Critical Dimensions Checked

• Thread pitch diameter
• Across flats
• Nut height
• Locking zone deformation
• Bearing face flatness

26.3 Prevailing Torque Verification (ISO 2320)

Testing ensures locking reliability.

Test Procedure

1. Nut installed on hardened test bolt.
2. Measure first installation torque.
3. Remove nut.
4. Measure removal torque.
5. Repeat installation cycles.

Acceptance ensures:

• Minimum prevailing torque maintained
• No thread damage
• Reusability confirmation

26.4 Mechanical Testing

Test	Standard	Purpose
Proof Load Test	ISO 898-2	Load capacity
Tensile Test	ASTM	Strength validation
Hardness Test	Rockwell / Vickers	Heat treatment control
Wedge Test	ISO	Thread integrity
Impact Test	ASTM E23	Low temperature service

26.5 Chemical & Metallurgical Verification

Performed for critical projects:

• Positive Material Identification (PMI)
• Optical Emission Spectroscopy
• Microstructure examination
• Grain flow verification
• Inclusion analysis

26.6 Non-Destructive Testing (NDT)

Method	Application
Magnetic Particle	Surface cracks
Dye Penetrant	Stainless alloys
Ultrasonic	Forged large nuts
Eddy Current	Surface defects

26.7 Surface Coating Inspection

Verification includes:

• Coating thickness measurement
• Adhesion testing
• Salt spray testing
• Hydrogen embrittlement validation

26.8 Documentation & Traceability

SM Fasteners maintains full batch traceability:

• Heat number stamping
• Production route cards
• Inspection records
• Digital quality archive

27. Engineering Tables — Mechanical Performance

27.1 Proof Load & Tensile Strength Table

Size	Property Class	Proof Load (kN)	Minimum Tensile Strength (MPa)
M8	8	18	800
M10	8	29	800
M12	8	42	800
M16	10	91	1040
M20	10	142	1040
M24	10	205	1040
M30	12	355	1220
M36	12	520	1220

27.2 Mechanical Properties — Grade Comparison

Grade	Yield (MPa)	Tensile (MPa)	Hardness	Service Type
Class 8	640	800	22–32 HRC	Structural
Class 10	940	1040	26–36 HRC	Machinery
Class 12	1100	1220	32–39 HRC	Dynamic load
A2-70	450	700	HRB ≤95	General corrosion
A4-80	600	800	HRB ≤95	Marine
ASTM A194 2H	850	950	24–35 HRC	Pressure vessels

28. Tightening Torque Chart

(Dry condition values — engineering reference)

Size	Class 8 Torque (Nm)	Class 10 Torque (Nm)	Lubricated Torque (Nm)
M8	25	36	20
M10	49	70	40
M12	86	121	70
M16	210	300	170
M20	410	580	330
M24	710	1000	570
M30	1420	2000	1150
M36	2450	3400	1950

Note:
Prevailing torque must be added to seating torque during installation.

29. Preload Calculation — Engineering Example

Formula

$$F = \frac{T}{K \times D}$$F=K×DT​

Where:

• Torque $T$ = 300 Nm
• Nut factor $K$ = 0.18
• Diameter $D$ = 0.016 m (M16)

Calculation

$$F = \frac{300}{0.18 \times 0.016}$$

$$F = 104,166 \text{ N}$$

Result:
Approximate clamp load = 104 kN

This preload ensures vibration resistance and fatigue life stability.

30. Thread Standards & Tolerances Table

Thread Type	Standard	Tolerance
Metric Coarse	ISO 261	6H
Metric Fine	ISO 965	6H / 5H
UNC	ASME B1.1	2B
UNF	ASME B1.1	2B
BSW	BS 84	Medium fit
BSF	BS 84	Fine fit

31. Surface Finish Performance Comparison

Finish	Corrosion Resistance	Torque Stability	Recommended Industry
Black Oxide	Low	Stable	Indoor machinery
Zinc Plated	Medium	Moderate	Construction
HDG	High	Variable	Structural steel
PTFE Coated	Excellent	Excellent	Offshore
Geomet	Very High	Stable	Automotive
Passivated SS	Excellent	Stable	Chemical plants

32. Weight Chart — SM Fasteners Reference

Size	Weight / Piece (kg)	Weight / 100 pcs (kg)
M6	0.0035	0.35
M8	0.0075	0.75
M10	0.015	1.50
M12	0.027	2.70
M16	0.063	6.30
M20	0.125	12.50
M24	0.220	22.00
M30	0.480	48.00
M36	0.820	82.00

Aligned with SM Fasteners production mass references for logistics planning.

33. Industry Applications

33.1 Construction & Structural Steel

Used in:

• High-rise structures
• Bridges
• Steel frameworks
• Seismic joints

Advantages:

• Vibration resistance
• Long-term preload stability

33.2 Oil & Gas Industry

Upstream

• Wellhead equipment
• Drilling rigs
• Offshore platforms

Midstream

• Pipeline supports
• Compressor stations

Downstream

• Refineries
• Pressure vessels
• Flanged joints

All metal lock nuts prevent loosening under continuous vibration and thermal cycles.

33.3 Power Generation

Applications:

• Turbines
• Boilers
• Nuclear auxiliary systems
• Wind tower structures

High temperature capability makes polymer locking unacceptable.

33.4 Petrochemical & Chemical Processing

Materials supplied:

• Hastelloy
• SMO 254
• Duplex
• PEEK fasteners

Used where corrosion resistance dominates design criteria.

33.5 LNG & Offshore Installations

Requirements:

• Cryogenic compatibility
• Saltwater resistance
• Long maintenance intervals

All metal lock nuts maintain preload under extreme temperature variation.

33.6 Automotive & Heavy Equipment

Applied in:

• Engine mounts
• Suspension assemblies
• Mining machinery
• Earthmoving equipment

33.7 Railways & Infrastructure

Applications include:

• Track fastening assemblies
• Signaling structures
• Bridge expansion joints

33.8 Shipbuilding & Marine Engineering

Preferred materials:

• A4-80 stainless
• Duplex
• Monel

Resistant to vibration, salt spray, and cyclic loading.

34. Packaging & Export Engineering

SM Fasteners designs packaging for global EPC shipment conditions.

34.1 Industrial Packaging

• VCI corrosion protection
• Thread protectors
• Batch labeling
• Moisture barrier bags
• Heavy-duty cartons

34.2 Export Crating

• ISPM-15 compliant wooden crates
• Sea-worthy packing
• Palletized loads
• Shock protection systems

34.3 Export Documentation Package

Provided with each shipment:

Document	Purpose
Mill Test Certificate (EN 10204 3.1 / 3.2)	Material traceability
Heat Treatment Report	Mechanical verification
Inspection Report	Dimensional compliance
Coating Certificate	Surface validation
Certificate of Conformity	Order compliance
Packing List	Logistics
Third-Party Inspection	EPC approval

35. SM Fasteners — Global Supply Capability

SM Fasteners positions itself as a precision manufacturer supporting international procurement environments through:

• ISO 9001 certified systems
• UKAF accredited quality assurance
• MSME recognized manufacturing infrastructure
• Advanced alloy manufacturing capability
• Custom engineered lock nut solutions
• Project-specific documentation readiness
• Integration with EPC inspection workflows

Capabilities include:

• Metric & Imperial production
• Exotic alloy machining
• High temperature fasteners
• PEEK engineered fastening solutions
• Custom prevailing torque development
• Large-volume export manufacturing

36. Engineering Summary

The All Metal Lock Nut represents one of the most reliable solutions for maintaining preload in demanding mechanical assemblies.

Key engineering outcomes:

✔ Maintains clamp force under vibration
✔ Operates at extreme temperatures
✔ Eliminates polymer degradation risks
✔ Supports repeat installation cycles
✔ Complies with ISO, ASTM, DIN, and BS standards
✔ Suitable for critical EPC and infrastructure projects

Through controlled manufacturing, certified quality systems, and advanced material capability, SM Fasteners delivers all metal lock nuts engineered for strength, reliability, and global industrial compliance.