DOUBLE END STUD

1 — INDUSTRY CONTEXT, TECHNICAL DEFINITION & LOAD MECHANICS

1.1 Industrial Context of Double End Studs

Double End Studs represent one of the most widely used fastening systems in high-integrity bolted joints across heavy engineering industries. Unlike conventional bolts, the stud-and-nut assembly separates the thread engagement function from the load-bearing clamping function, providing superior reliability in critical assemblies.

Typical operating environments include:

Industry Sector	Functional Requirement
Oil & Gas	Pressure containment joints
Petrochemical	High-temperature flange assemblies
Power Generation	Turbine casings & boilers
Structural Steel	Permanent anchoring systems
Offshore & Marine	Corrosion-resistant fastening
Heavy Equipment	High fatigue resistance joints
LNG Facilities	Cryogenic reliability
Rail & Infrastructure	Long-term vibration resistance

Double end studs are preferred where:

• Frequent dismantling is required
• Alignment precision is critical
• High preload stability is necessary
• Thread wear on parent material must be minimized

SM Fasteners manufactures double end studs aligned with global EPC procurement specifications, ensuring interchangeability with ISO, ASTM, DIN, and BS systems.

1.2 Technical Definition

A Double End Stud is a fully threaded or partially threaded fastener with:

• Threads on both ends
• An unthreaded or reduced shank (optional)
• Equal or unequal thread engagement lengths

It is designed to:

1. Permanently engage one end into tapped material or component.
2. Accept a nut on the exposed end to generate clamping force.

Key Functional Characteristics

• No head → uniform stress distribution
• Improved fatigue life
• Reduced torsional stress during tightening
• Repeatable preload performance

1.3 Functional Role in Mechanical Assemblies

Bolt vs Double End Stud Behavior

Parameter	Bolt	Double End Stud
Installation torque applied to	Bolt head	Nut only
Parent thread wear	Higher	Minimal
Alignment accuracy	Moderate	High
Fatigue resistance	Lower	Superior
Maintenance repeatability	Limited	Excellent

The double end stud converts tightening torque exclusively into axial tensile preload, avoiding thread galling inside equipment housings.

1.4 Load Mechanics & Force Behavior

Primary Forces Acting on Double End Studs

1. Tensile Load
2. Clamping Force
3. Shear Load
4. Bending Stress
5. Thermal Expansion Load
6. Dynamic Fatigue Loading

Fundamental Load Relationship

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

Where:

• F = Preload Force (N)
• T = Applied Torque (Nm)
• K = Nut Factor (0.15–0.25 typical)
• d = Nominal Diameter (m)

Clamping Force Principle

The stud behaves like a spring element.

• Nut tightening stretches the stud elastically.
• Joint members compress simultaneously.
• Stored elastic energy maintains joint integrity.

Elastic Interaction Model

Component	Behavior
Stud	Elastic elongation
Joint	Compression
Result	Stable preload equilibrium

Proper stud selection ensures:

• External load never exceeds preload
• Joint separation does not occur

1.5 Thread Engagement Mechanics

Recommended minimum thread engagement:

Material	Engagement Length
Steel into Steel	1 × Diameter
Steel into Cast Iron	1.5 × Diameter
Steel into Aluminum	2 × Diameter
High Temp Alloy	1.25 × Diameter

Correct engagement prevents:

• Thread stripping
• Pull-out failure
• Fatigue initiation

1.6 Joint Design Principles

High-Integrity Joint Design Criteria

1. Controlled preload
2. Uniform stress distribution
3. Minimal relaxation
4. Resistance to vibration loosening
5. Corrosion compatibility

Double End Stud Advantages in Joint Engineering

• Eliminates repeated installation damage
• Improves gasket sealing reliability
• Enables hydraulic tensioning
• Allows accurate torque calibration

1.7 Torque–Tension Relationship

Only 10–15% of applied torque becomes preload.

Torque Loss Component	Approx. %
Thread friction	40%
Bearing friction	45%
Useful preload	15%

Surface finish and lubrication therefore directly influence joint reliability.

1.8 Preload Calculation — Worked Example

Given:

• Stud Size: M24
• Torque: 600 Nm
• Nut Factor: 0.18

$$F=\frac{600}{0.18 \times 0.024}$$

$$F = 138,888\ N \approx 139\ kN$$

Result:
The stud generates approximately 139 kN clamping force.

SM Fasteners provides torque recommendations validated against ISO preload standards.

1.9 Mechanical Behavior Under Service Conditions

Static Loading

Maintains gasket compression and structural integrity.

Cyclic Loading

Stud elasticity absorbs fluctuating loads.

Thermal Loading

Stud elongation compensates differential expansion.

1.10 Failure Mechanisms

1. Fatigue Failure

Occurs under fluctuating loads.

Mitigation:

• Rolled threads
• Proper preload
• Controlled surface finish

2. Shear Failure

Result of insufficient clamp force.

Design Rule:$$F_{preload} > External\ Shear\ Load$$

3. Hydrogen Embrittlement

Risk for:

• High strength grades
• Improper electroplating

SM Fasteners controls baking cycles post-coating per ISO requirements.

4. Stress Corrosion Cracking (SCC)

Common environments:

• Chlorides
• H₂S sour service
• High temperature caustics

Material selection must comply with NACE MR0175 / ISO 15156 where applicable.

1.11 Friction & Nut Factor Considerations

Surface Condition	Nut Factor (K)
Dry steel	0.22
Zinc plated	0.20
Lubricated	0.18
PTFE coated	0.15

1.12 Role in Modern EPC Projects

Double End Studs are mandatory in:

• ASME B16.5 flange joints
• Pressure vessels
• Turbine casing assemblies
• Pump housings
• Compressor frames

SM Fasteners supports EPC procurement through:

• Traceable heat numbers
• ISO 9001 manufacturing control
• Custom dimensional engineering
• Advanced alloy and PEEK fastener solutions

2 . PRODUCT TYPES, VARIANTS, DIMENSIONAL ENGINEERING & GLOBAL STANDARDS

2.1 Classification of Double End Studs

Double End Studs are engineered in multiple configurations depending on:

• Joint accessibility
• Load distribution requirements
• Installation methodology
• Service environment
• Maintenance frequency

SM Fasteners manufactures double end studs in standardized and fully customized geometries aligned with EPC project drawings and international specifications.

Primary Product Types

Type	Description	Typical Application
Equal Thread Double End Stud	Same thread length both ends	Flange joints
Unequal Thread Stud	Different engagement lengths	Cast housings
Reduced Shank Stud	Smaller center diameter	Fatigue-resistant joints
Fully Threaded Stud	Thread along full length	Structural assemblies
Interference Fit Stud	Tight fit installation end	Permanent mounting
Tap-End Double End Stud	Short engagement side	Machinery housings
Collar Stud	Center locating shoulder	Precision alignment
Continuous Thread Stud	Uniform thread form	General industrial use

2.2 Functional Geometry Differences

Equal Thread Stud

• Balanced loading
• Standard EPC flange requirement
• Interchangeable globally

Unequal Thread Stud

Used where:

• Base material strength differs
• Parent thread depth varies
• Repairable installations are needed

Example:

• Pump casing installation

Reduced Shank Double End Stud

Engineering objective:

Reduce stress concentration at first engaged thread.

Benefits:

• Higher fatigue life
• Uniform stress distribution
• Improved vibration resistance

2.3 Dimensional Logic & Engineering Geometry

Double end stud design follows specific dimensional relationships.

Core Dimensional Elements

Symbol	Description
d	Nominal diameter
P	Thread pitch
L	Overall length
b1	Thread length end 1
b2	Thread length end 2
ls	Unthreaded shank length
ds	Shank diameter

Standard Dimensional Relationship

$$L = b1 + b2 + ls$$

Typical design rules:

• Thread engagement ≥ 1D
• Nut engagement ≥ 1D
• Minimum run-out per ISO thread standards

2.4 Standard Metric Double End Stud Dimensions

(Representative Engineering Reference — SM Fasteners Manufacturing Range)

Size	Pitch (mm)	Standard Length Range (mm)	Thread Length Each End (mm)
M8	1.25	30–150	18
M10	1.5	40–200	22
M12	1.75	50–250	26
M16	2.0	60–300	32
M20	2.5	70–400	40
M24	3.0	80–500	48
M30	3.5	100–600	60
M36	4.0	120–800	72
M42	4.5	150–900	84
M48	5.0	180–1000	96

Custom dimensions supplied by SM Fasteners based on EPC drawings and equipment OEM specifications.

2.5 Unified Thread (UNC/UNF) Dimensions

Size	UNC Pitch	UNF Pitch	Typical Use
1/2″	13 TPI	20 TPI	Structural
5/8″	11 TPI	18 TPI	Heavy equipment
3/4″	10 TPI	16 TPI	Pressure vessels
1″	8 TPI	12 TPI	Flange joints
1-1/4″	7 TPI	12 TPI	Oil & Gas
1-1/2″	6 TPI	12 TPI	Offshore

2.6 Thread Standards & Tolerances

Thread System	Standard	Tolerance Class
Metric Coarse	ISO 261 / ISO 965	6g
Metric Fine	ISO 261	6g
UNC	ASME B1.1	2A
UNF	ASME B1.1	2A
BSW	BS 84	Medium
BSF	BS 84	Fine
NPT (Special)	ASME B1.20	Taper

SM Fasteners verifies thread accuracy using calibrated GO/NO-GO gauges under ISO 9001 controlled inspection systems.

2.7 Thread Engagement Engineering

Recommended Engagement Length

Diameter	Minimum Engagement
≤ M12	1D
M16–M24	1–1.25D
M30–M48	1.25–1.5D
Soft alloys	Up to 2D

2.8 Double End Stud Length Selection Logic

Length selection depends on:

1. Component thickness
2. Washer thickness
3. Nut height
4. Thread protrusion requirement
5. Thermal expansion allowance

Standard Calculation

$$L = Grip\ Length + 2(Nut\ Height) + Allowance$$

Allowance typically:

• 2–3 thread pitches protrusion

2.9 Applicable International Standards

Double end studs manufactured by SM Fasteners conform to major global standards:

ASTM Standards

Standard	Application
ASTM A193	High temperature / pressure studs
ASTM A320	Low temperature service
ASTM A307	General structural
ASTM F1554	Anchor & structural studs
ASTM A453	High strength turbine studs

ISO Standards

Standard	Scope
ISO 898-1	Mechanical properties
ISO 4753	Ends of fasteners
ISO 965	Thread tolerances
ISO 3269	Acceptance inspection

DIN Standards

Standard	Description
DIN 938	Double end studs (short thread)
DIN 939	Double end studs (long thread)
DIN 940	Fully threaded studs
DIN 976	Threaded rods

British Standards

Standard	Application
BS 4439	Stud bolts
BS 1768	General studs
BS 3643	Thread forms

2.10 Property Class & Strength Designation

Metric mechanical classes:

Property Class	Yield Strength (MPa)	Typical Use
4.6	240	Light structures
8.8	640	Structural joints
10.9	900	Heavy equipment
12.9	1080	High-load assemblies

2.11 Dimensional Tolerance Control

Critical tolerances maintained by SM Fasteners:

Feature	Control Method
Major Diameter	Micrometer verification
Pitch Diameter	Thread gauge
Straightness	V-block inspection
Perpendicularity	Optical measurement
Surface Finish	Ra measurement

2.12 Interchangeability Considerations

Global EPC projects require cross-standard compatibility.

Key rules:

• Metric ↔ UNC substitution not permitted without engineering approval
• DIN studs interchangeable with ISO where tolerances align
• ASTM material grades compatible with ISO property classes

SM Fasteners provides engineering cross-reference support during procurement stages.

2.13 Geometry Impact on Mechanical Performance

Geometry Feature	Engineering Impact
Rolled thread root radius	Increased fatigue resistance
Reduced shank	Lower stress concentration
Equal threads	Balanced loading
Precision pitch	Stable preload
Chamfered ends	Improved installation

2.14 Design Considerations for Special Applications

High Temperature Service

• Controlled thread fit
• Creep resistance alloys

Offshore Environments

• Duplex / Super Duplex materials
• Anti-galling coatings

PEEK Double End Studs

Used where:

• Electrical insulation required
• Chemical inertness critical
• Lightweight assemblies necessary

SM Fasteners supplies engineered PEEK stud solutions for chemical processing and electronics equipment.

2.15 SM Fasteners Engineering Capability Integration

SM Fasteners supports global buyers through:

• ISO 9001 certified dimensional control
• CNC precision machining
• Custom stud geometry development
• Drawing-to-manufacture execution
• MSME-recognized manufacturing facility
• UKAF-certified quality assurance

3. MATERIAL GRADES, HEAT TREATMENT, MANUFACTURING & SURFACE FINISHING

3.1 Materials Engineering Philosophy

Material selection for Double End Studs is a critical engineering decision influencing:

• Load capacity
• Corrosion resistance
• Temperature stability
• Fatigue life
• Galling resistance
• Sour service compliance

SM Fasteners manufactures double end studs across a full industrial metallurgy spectrum, supporting EPC specifications, OEM drawings, and international project standards.

Material traceability is maintained through:

• Verified raw material sourcing
• Mill Test Certificates (EN 10204 3.1 / 3.2)
• Heat number traceability
• PMI validation

3.2 Industrial Material Grades for Double End Studs

Carbon Steel Grades

Grade	Standard	UTS (MPa)	Temp Limit	Application
ASTM A307	ASTM	415	300°C	Structural joints
ASTM A36	ASTM	400–550	350°C	Construction
EN 1.0402 (C22)	EN	430	350°C	Machinery

Advantages:

• Economical
• Good machinability
• High availability

Limitations:

• Limited corrosion resistance

Alloy Steel Grades

Grade	Standard	UTS (MPa)	Service Temp
ASTM A193 B7	ASTM	860	450°C
ASTM A193 B16	ASTM	1035	540°C
EN 42CrMo4	EN	1000	500°C

Applications:

• Pressure vessels
• Petrochemical flanges
• Turbine equipment

Stainless Steel Grades

Grade	UNS	Corrosion Resistance	Typical Use
SS304	S30400	General corrosion	Food & chemical
SS316	S31600	Chloride resistant	Marine
SS316L	S31603	Low carbon	Welding environments
SS321	S32100	High temp stability	Exhaust systems

Duplex & Super Duplex Steels

Grade	Yield Strength (MPa)	Environment
Duplex 2205	450	Offshore
Super Duplex 2507	550	Seawater / LNG

Advantages:

• Excellent SCC resistance
• High strength-to-weight ratio
• Long offshore service life

Nickel & High Performance Alloys

SM Fasteners supplies advanced alloys for extreme applications.

Material	Max Temp	Key Property
Inconel 625	980°C	Oxidation resistance
Inconel 718	700°C	High strength
Hastelloy C276	Acid resistant	Chemical plants
Monel 400	Marine resistant	Seawater
Incoloy 825	H₂S resistant	Sour service
SMO 254	High chloride resistance	Desalination

Engineering Polymer — PEEK Double End Studs

Used where metal fasteners are unsuitable.

Properties:

• Continuous temp: 260°C
• Electrically insulating
• Non-magnetic
• Chemical inertness
• Lightweight

Applications:

• Semiconductor equipment
• Chemical dosing systems
• Electrical assemblies

3.3 Material Selection Matrix

Environment	Recommended Material
Indoor structural	Carbon steel
Oil & Gas	A193 B7 / B16
Offshore	Duplex / Super Duplex
Acidic chemical	Hastelloy
Cryogenic LNG	A320 L7
Marine atmosphere	SS316 / Monel
Electrical insulation	PEEK

3.4 Mechanical Properties — Grade Comparison

Grade	Yield (MPa)	UTS (MPa)	Hardness	Fatigue Resistance
8.8	640	800	22–32 HRC	Good
10.9	900	1040	32–39 HRC	Very High
12.9	1080	1220	39–44 HRC	High but HE risk
B7	720	860	24–35 HRC	Excellent
Duplex 2205	450	620	28 HRC	Superior

3.5 NACE MR0175 / ISO 15156 Compliance

Critical for H₂S sour environments.

Requirements:

• Controlled hardness ≤ 22 HRC (typical)
• Verified heat treatment
• Hydrogen embrittlement mitigation
• Material chemistry verification

SM Fasteners supplies NACE-compliant studs with supporting certification.

3.6 Heat Treatment Processes

Heat treatment defines final mechanical properties.

1. Annealing

Purpose:

• Improve machinability
• Reduce internal stress

2. Quenching & Tempering (Q&T)

Primary process for alloy steel studs.

Steps:

1. Austenitizing
2. Rapid quenching
3. Controlled tempering

Result:

• High tensile strength
• Toughness balance

3. Solution Annealing (Stainless Steel)

• Dissolves carbides
• Improves corrosion resistance
• Restores ductility

4. Age Hardening (Nickel Alloys)

Used for:

• Inconel 718
• Precipitation-strengthened alloys

Provides exceptional high-temperature strength.

Heat Treatment Impact Table

Process	Strength	Ductility	Corrosion Resistance
Annealing	Low	High	Moderate
Q&T	High	Balanced	Moderate
Solution Anneal	Medium	High	Excellent
Age Hardening	Very High	Medium	Excellent

3.7 Hardness Control Requirements

Service	Max Hardness
General industrial	35–44 HRC
NACE sour service	≤22 HRC
Stainless steel	HRB scale typical
Offshore	Controlled per spec

SM Fasteners performs hardness verification during batch inspection.

3.8 End-to-End Manufacturing Workflow

SM Fasteners operates under ISO 9001 controlled production systems.

Step 1 — Raw Material Verification

• Chemical composition review
• Heat number identification
• MTC verification
• Ultrasonic bar inspection

Step 2 — Cutting & Preparation

• CNC bar cutting
• Length tolerance control
• End chamfering

Step 3 — Forging / Machining

Method	Application
Hot forging	Large diameter studs
CNC machining	Precision studs
Cold forming	High-volume production

Step 4 — Thread Production

Thread Rolling (Preferred)

Advantages:

• Grain flow continuity
• Higher fatigue resistance
• Smooth surface finish

Thread Cutting

Used for:

• Large diameters
• Exotic alloys
• Small batch customization

Step 5 — Heat Treatment

Controlled furnace cycles with:

• Temperature recording
• Batch traceability
• Hardness validation

Step 6 — Straightening & Stress Relief

Ensures:

• Alignment accuracy
• Proper preload distribution

Step 7 — Surface Finishing

Applied according to environment.

Step 8 — Final Inspection & Marking

• Dimension verification
• Marking with heat number
• Traceability stamping

3.9 Surface Engineering & Coating Systems

Surface finish directly influences:

• Corrosion resistance
• Torque coefficient
• Galling behavior
• Service life

Surface Finish Comparison Table

Coating	Corrosion Resistance	Temp Limit	Typical Use
Black Oxide	Low	300°C	Indoor
Zinc Plating	Moderate	120°C	Structural
Hot Dip Galvanized	High	450°C	Construction
PTFE / Xylan	Excellent	260°C	Offshore
Cadmium	High	Aerospace
Phosphate	Moderate	Machinery
Nickel Plating	High	Chemical
Dacromet / Geomet	Very High	Marine

SM Fasteners selects coating systems aligned with torque-preload consistency requirements.

3.10 Hydrogen Embrittlement Prevention

Critical for high-strength studs (>1000 MPa).

Controls include:

• Limited electroplating exposure
• Post-bake hydrogen relief
• Controlled coating thickness
• Hardness monitoring

3.11 Corrosion Resistance vs Environment

Environment	Recommended Finish
Indoor dry	Black oxide
Coastal atmosphere	HDG / Duplex
Offshore platform	PTFE coated
Chemical plant	Nickel alloy + PTFE
Sour gas	NACE-compliant coating
High humidity	Zinc flake coating

3.12 Surface Roughness & Friction Control

Surface roughness affects torque accuracy.

Finish	Typical Ra Value
Rolled thread	3–6 µm
Machined	6–12 µm
Coated	Variable

Lower roughness → predictable preload.

3.13 Manufacturing Traceability System (SM Fasteners)

Each double end stud maintains:

• Heat number tracking
• Batch identification
• Process history
• Inspection records
• Material origin verification

Aligned with ISO 9001 and UKAF auditing requirements.

3.14 Engineering Customization Capability

SM Fasteners provides:

• Non-standard thread forms
• Special engagement lengths
• Reduced shank designs
• High-temperature alloys
• PEEK custom molded studs
• Project-specific coatings

Supporting global EPC procurement and OEM integration.

4 . INSPECTION, QUALITY ASSURANCE, APPLICATIONS & PROCUREMENT DATA

4.1 Quality Philosophy — SM Fasteners

Double End Studs used in critical industrial systems must comply with strict mechanical, dimensional, and metallurgical verification standards.

SM Fasteners integrates quality control through:

• ISO 9001 certified manufacturing system
• UKAF accredited quality framework
• MSME-recognized production infrastructure
• Fully traceable manufacturing workflow

Quality assurance begins from raw material intake and continues through final dispatch.

4.2 Incoming Material Inspection

Every production batch undergoes verification prior to manufacturing.

Inspection Parameter	Method
Chemical composition	Spectrometer analysis
Mill Test Certificate	EN 10204 3.1 review
Heat number traceability	Physical marking
Surface defects	Visual & magnetic check
Internal defects	Ultrasonic testing

4.3 Dimensional Inspection & Control

Critical tolerances ensure preload reliability and interchangeability.

Feature	Inspection Tool
Major diameter	Micrometer
Pitch diameter	Thread micrometer
Thread pitch	Profile gauge
Length tolerance	Digital caliper
Straightness	V-block & dial gauge
Concentricity	CMM inspection
Thread tolerance	GO / NO-GO gauges

4.4 Mechanical Testing Requirements

Performed according to ISO / ASTM specifications.

Test	Purpose
Tensile test	Verify UTS & yield
Proof load test	Confirm elastic behavior
Hardness test	Heat treatment validation
Impact testing	Low-temperature service
Bend testing	Ductility confirmation
Fatigue testing	Dynamic load reliability

4.5 Non-Destructive Testing (NDT)

Required for critical EPC and oil & gas projects.

Method	Detection Capability
Magnetic Particle (MPI)	Surface cracks
Dye Penetrant (DPT)	Micro defects
Ultrasonic Testing	Internal flaws
Eddy Current	Surface discontinuity
Radiography	Special applications

4.6 Positive Material Identification (PMI)

Mandatory for alloy and corrosion-resistant materials.

PMI verifies:

• Nickel content
• Chromium composition
• Molybdenum percentage
• Alloy grade authenticity

Ensures compliance with:

• ASTM A193
• NACE MR0175
• Project material specifications

4.7 Certification & Documentation Package

SM Fasteners supplies complete export documentation:

Document	Purpose
EN 10204 3.1 / 3.2 MTC	Material traceability
Heat Treatment Report	Mechanical confirmation
Dimensional Inspection Report	QA verification
Coating Certificate	Surface compliance
PMI Report	Alloy validation
NDT Report	Defect verification
Certificate of Conformity	Order compliance
Packing List & Traceability Sheet	Logistics control

4.8 Industrial Applications of Double End Studs

Construction & Structural Steel

• Steel column base plates
• Bridge assemblies
• Heavy structural nodes
• Expansion joints

Engineering Need:

• Long-term preload retention

Oil & Gas Industry

Upstream

• Wellhead equipment
• Christmas trees
• Drilling rigs

Midstream

• Pipeline compressor stations
• Pump skids

Downstream

• Refinery flanges
• Reactor vessels
• Heat exchangers

Material focus:
A193 B7, B16, Duplex, Inconel.

Power Generation

• Steam turbines
• Boiler casings
• Generator frames
• Nuclear auxiliary equipment

Requirement:
High temperature creep resistance.

Petrochemical & Chemical Processing

• Pressure reactors
• Acid handling equipment
• Process piping

Preferred materials:
Hastelloy, SMO 254, Stainless steel.

LNG & Cryogenic Facilities

• Cryogenic valves
• LNG storage tanks
• Gas liquefaction systems

Material:
ASTM A320 L7 or stainless alloys.

Offshore & Marine

• FPSO systems
• Subsea structures
• Shipbuilding assemblies

Requirement:
Chloride stress corrosion resistance.

Automotive & Heavy Equipment

• Engine mounting systems
• Mining machinery
• Hydraulic presses

Railways & Infrastructure

• Track systems
• Signal structures
• Rolling stock assemblies

PEEK Double End Stud Applications

• Semiconductor tooling
• Chemical dosing skids
• Electrical insulation assemblies
• MRI & non-magnetic equipment

4.9 Failure Prevention Engineering

Failure Mode	Preventive Measure
Fatigue	Rolled threads + correct preload
Galling	Lubrication / PTFE coating
Hydrogen embrittlement	Controlled plating & baking
SCC	Proper alloy selection
Thread stripping	Correct engagement length

MANDATORY ENGINEERING TABLES

4.10 Proof Load & Tensile Strength Table

Size	Property Class	Proof Load (kN)	Tensile Strength (kN)
M12	8.8	45	52
M16	8.8	84	98
M20	8.8	131	153
M24	10.9	226	262
M30	10.9	353	409
M36	10.9	520	600

4.11 Material Comparison Table

Material	Yield	UTS	Corrosion Resistance	Cost Level	Typical Industry
Carbon Steel	Medium	Medium	Low	Low	Construction
Alloy Steel B7	High	High	Medium	Medium	Oil & Gas
SS316	Medium	Medium	High	Medium	Marine
Duplex 2205	High	High	Very High	High	Offshore
Inconel 625	Very High	Very High	Excellent	Very High	Aerospace
PEEK	Low	Moderate	Excellent	High	Electronics

4.12 Corrosion Resistance vs Environment

Environment	Carbon Steel	SS316	Duplex	Nickel Alloy	PEEK
Seawater	Poor	Good	Excellent	Excellent	Excellent
Acidic	Poor	Moderate	Good	Excellent	Excellent
H₂S Sour	Poor	Limited	Excellent	Excellent	Excellent
High Temp	Moderate	Good	Good	Excellent	Limited
Cryogenic	Poor	Good	Excellent	Excellent	Excellent

4.13 Mechanical Properties — Grade Wise

Grade	Yield (MPa)	UTS (MPa)	Hardness
4.6	240	400	120 HB
8.8	640	800	22–32 HRC
10.9	900	1040	32–39 HRC
12.9	1080	1220	39–44 HRC
A193 B7	720	860	24–35 HRC

4.14 Tightening Torque Chart (Metric Studs)

(Lubricated condition — Nut Factor ≈ 0.18)

Size	Class 8.8 (Nm)	Class 10.9 (Nm)
M12	80	115
M16	200	300
M20	390	560
M24	680	960
M30	1350	1900
M36	2350	3300

4.15 Preload Calculation Formula

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

Example

• Size: M20
• Torque: 560 Nm
• Nut Factor: 0.18

$$F = \frac{560}{0.18 \times 0.020} = 155,555\ N$$

Approximate Preload = 156 kN

4.16 Thread Standards & Tolerances

Thread	Standard	Class
Metric Coarse	ISO 261	6g
Metric Fine	ISO 965	6g
UNC	ASME B1.1	2A
UNF	ASME B1.1	2A
BSW	BS 84	Medium
BSF	BS 84	Fine

4.17 Surface Finish Performance Comparison

Coating	Corrosion Life	Torque Consistency	Offshore Suitability
Black Oxide	Low	Good	No
Zinc Plated	Medium	Moderate	Limited
HDG	High	Variable	Yes
PTFE/Xylan	Excellent	Excellent	Ideal
Dacromet	Very High	Stable	Excellent
Nickel Plating	High	Good	Chemical

4.18 Weight Chart — Double End Studs

(Approximate — aligned with SM Fasteners manufacturing data)

Size	Weight / Piece (kg)	Weight / 100 pcs (kg)
M12 × 100	0.09	9
M16 × 120	0.19	19
M20 × 150	0.37	37
M24 × 180	0.66	66
M30 × 200	1.15	115
M36 × 220	2.00	200
M42 × 250	3.20	320
M48 × 300	5.10	510

SM Fasteners provides project-specific weight calculations for logistics planning and export packaging optimization.

4.19 Industrial Packaging & Export Logistics

Protective Packaging

• VCI corrosion protection
• Thread protectors
• Oil coating (as required)
• Batch segregation

Export Packaging

• ISPM-15 compliant wooden crates
• Palletized loading
• Moisture barrier wrapping
• Shock protection

4.20 Global Supply & Procurement Readiness

SM Fasteners supports international projects through:

• ISO 9001 certified quality systems
• UKAF accredited inspection compliance
• MSME manufacturing recognition
• Custom fastener engineering capability
• Advanced alloys & PEEK manufacturing
• Full EPC documentation support
• Traceable global export supply chain

Engineering Summary

Double End Studs manufactured by SM Fasteners provide:

✔ Controlled preload performance
✔ Global standards compliance (ISO / ASTM / DIN / BS)
✔ Advanced material capability including Nickel alloys & PEEK
✔ Verified manufacturing and inspection systems
✔ Reliable supply for high-integrity industrial applications