Self tapping screws

1. Industry Context

Self tapping screws occupy a critical position within modern mechanical fastening technology where pre-threaded holes are undesirable, uneconomical, or impractical.

Unlike conventional machine screws, self tapping screws:

• Create mating threads during installation.
• Reduce secondary machining operations.
• Enable faster assembly cycles.
• Maintain high pull-out resistance in thin or soft materials.

Primary Industrial Drivers

Industry Sector	Functional Requirement
Structural Construction	Sheet steel fixing & cladding
Oil & Gas	Equipment housings, panels, instrumentation
Power Plants	Electrical enclosures & HVAC systems
Petrochemical	Corrosion-resistant panel assemblies
Automotive	Thin sheet joining
Railways	Interior modular assemblies
Shipbuilding	Marine panels & deck fittings
OEM Equipment	Rapid assembly production

Within EPC projects, self tapping screws reduce:

• Assembly labor hours
• Thread machining cost
• Alignment complexity
• Field installation time

SM Fasteners manufactures precision self tapping screws under controlled ISO 9001 systems ensuring dimensional repeatability, traceability, and mechanical reliability required by global buyers.

2. Technical Definition

A self tapping screw is a threaded fastener capable of:

1. Penetrating material.
2. Forming or cutting internal mating threads.
3. Generating clamp load without pre-tapped threads.

Functional Characteristics

• Hardened thread profile
• Special tip geometry
• Controlled flank angle
• High surface hardness
• Optimized lead threads

Self tapping screws fall into two fundamental mechanisms:

Mechanism	Function
Thread Forming	Displaces material plastically
Thread Cutting	Removes material chips

3. Functional Role in Mechanical Assemblies

Self tapping screws act simultaneously as:

• Fastener
• Thread generator
• Load transmitting element

They eliminate the need for:

• Tapping operations
• Nut access
• Thread inserts
• Secondary machining

Engineering Advantages

• Reduced component count
• Improved automation compatibility
• Lightweight joint design
• Lower installation torque variability

4. Load Mechanics & Force Behavior

Self tapping screw performance depends on interaction between:

• Applied torque
• Generated preload
• Thread engagement
• Material deformation behavior

4.1 Force Distribution

When installed, the screw generates:

• Axial clamping force
• Radial expansion pressure
• Shear resistance
• Pull-out resistance

Load transfer occurs through:

• Thread flank contact
• Head bearing surface
• Frictional interface

4.2 Torque–Tension Relationship

Fundamental relationship:$$T = K \times F \times d$$

Where:

Symbol	Meaning
T	Installation torque
K	Nut factor (friction coefficient)
F	Preload
d	Nominal diameter

Typical Nut Factor Values:

Condition	K Value
Dry	0.20 – 0.24
Zinc coated	0.16 – 0.20
Lubricated	0.12 – 0.16
PTFE coated	0.08 – 0.12

4.3 Preload Generation

Preload provides:

• Joint rigidity
• Vibration resistance
• Fatigue life improvement

Insufficient preload leads to:

• Loosening
• Fretting wear
• Fatigue cracking

Preload Calculation Example

Given

• Screw: ST5.5 mm
• Tensile stress area: 14.2 mm²
• Property class equivalent: 10.9
• Yield strength: 900 MPa
• Target preload = 70% yield

$$F = 0.7 \times A_s \times \sigma_y$$

$$F = 0.7 \times 14.2 \times 900$$

$$F = 8946 N$$

Required preload ≈ 8.9 kN

5. Joint Design Principles

5.1 Thread Engagement Rule

Recommended engagement:

Material	Engagement Length
Steel	1 × diameter
Aluminum	1.5 × diameter
Plastics	2–2.5 × diameter
Composite panels	2 × diameter

5.2 Pilot Hole Design

Critical engineering parameter.

Screw Size	Typical Pilot Hole
ST3.5	2.7–2.9 mm
ST4.2	3.2–3.4 mm
ST4.8	3.8–4.0 mm
ST5.5	4.5–4.7 mm
ST6.3	5.2–5.4 mm

Incorrect pilot hole causes:

• Over-torque failure
• Thread stripping
• Material cracking

5.3 Failure Mechanisms

Fatigue Failure

Occurs under cyclic loading.

Mitigation:

• Proper preload
• Controlled torque
• Surface coating integrity

Shear Failure

Common in panel joints.

Design rule:$$Shear\ Load < 0.6 \times Tensile\ Capacity$$

Hydrogen Embrittlement

Risk for hardened carbon steel screws.

Controlled by:

• Baking after plating
• Hardness limits
• Process monitoring

SM Fasteners applies strict post-plating baking procedures aligned with ISO requirements.

Stress Corrosion Cracking (SCC)

Occurs in:

• Chloride environments
• Sour gas service
• Marine exposure

Mitigation:

• Duplex stainless steel
• Nickel alloys
• PEEK fasteners

5.4 Friction & Clamp Stability

Joint stability depends on:

• Head bearing friction
• Thread friction
• Surface finish
• Coating type

Approximate torque energy distribution:

Energy Use	Percentage
Thread friction	40%
Under head friction	50%
Actual preload	10%

Engineering implication: small friction variation drastically changes preload.

5.5 Self Tapping Screws in Thin Material Design

Ideal where:

• Thickness < 5 mm
• One-side access only
• Welding undesirable
• Thermal distortion unacceptable

5.6 Design Integration in EPC Projects

Self tapping screws are widely specified for:

• Electrical panels
• HVAC ducting
• Structural decking
• Offshore instrumentation
• Cable trays
• Marine interiors

SM Fasteners supports EPC buyers through:

Global specification compliance

Custom geometry engineering

Material certification traceability

Function:
Cold-form internal threads by plastic deformation of base material.

Engineering Characteristics

• No chip generation
• Improved vibration resistance
• Higher pull-out strength
• Better fatigue life

Suitable Materials

• Low carbon steel sheets
• Aluminum alloys
• Brass
• Plastics
• Thin stainless sheet

Typical Applications

• Automotive assemblies
• Electrical enclosures
• Appliance manufacturing
• Instrument housings

6.2 Thread Cutting Self Tapping Screws

Function:
Cut mating threads through chip removal.

Design Features

• Cutting flute or notch
• Reduced installation torque
• Suitable for harder substrates

Suitable Materials

• Structural steel sections
• Cast iron
• Fiber composites
• Reinforced plastics

6.3 Self Drilling Screws (TEK Type)

Combined drilling and tapping functionality.

Features:

• Drill point tip
• Eliminates pilot hole
• High productivity installation

Applications:

• Steel roofing
• Structural decking
• HVAC duct installation
• Offshore panel work

6.4 Sheet Metal Screws

Widely used industrial configuration.

Characteristics:

• Sharp or blunt tip
• Fully threaded shank
• High flank engagement

6.5 Plastite / Trilobular Screws

Designed for thermoplastics.

Engineering Benefits:

• Reduced stress cracking
• Controlled radial pressure
• Improved reusability

6.6 High Performance Industrial Variants by SM Fasteners

SM Fasteners supplies engineered variants including:

• Stainless steel self tapping screws
• Duplex & Super Duplex marine-grade screws
• Nickel alloy fasteners for corrosive service
• High-temperature alloy screws
• PEEK polymer self tapping screws for insulation and chemical resistance

7. Head Types & Functional Geometry

Head geometry directly affects load distribution and installation torque.

Head Type	Engineering Purpose	Typical Industry Use
Pan Head	Large bearing surface	Electrical panels
Hex Washer Head	High torque transfer	Structural steel
Countersunk (CSK)	Flush finish	Machinery covers
Truss Head	Thin sheet clamping	HVAC
Button Head	Aesthetic + low snag	Rail interiors
Flat Head	Embedded joints	Equipment housings

8. Drive Systems

Drive selection influences torque accuracy and automation compatibility.

Drive Type	Engineering Advantage
Phillips	High-speed installation
Pozidriv	Reduced cam-out
Torx	High torque accuracy
Hex Socket	Precision torque control
External Hex	Structural installation
Square Drive	Automation assembly

Torx and Hex drives are preferred in EPC installations due to consistent torque transmission.

9. Thread Geometry & Dimensional Logic

Self tapping screw performance depends on thread profile engineering.

Thread Elements

• Major diameter
• Minor diameter
• Pitch
• Lead angle
• Flank angle
• Thread depth

Typical Self Tapping Thread Characteristics

Parameter	Typical Range
Flank angle	60°
Thread pitch	Coarse
Thread depth	High engagement
Lead	Single start
Crest radius	Optimized for forming

10. Dimensional Specification Table

(Engineering Reference — SM Fasteners Production Range)

Size	Major Dia (mm)	Pitch (mm)	Head Dia (mm)	Head Height (mm)	Length Range (mm)
ST2.9	2.9	1.1	5.5	2.2	6–25
ST3.5	3.5	1.3	7.0	2.6	6–32
ST4.2	4.2	1.4	8.0	3.0	9–50
ST4.8	4.8	1.6	10.0	3.4	13–75
ST5.5	5.5	1.8	11.0	4.0	19–100
ST6.3	6.3	2.0	12.5	4.6	25–150

Dimensions may be customized by SM Fasteners for OEM and EPC specifications.

11. International Standards & Compliance

Self tapping screws must comply with globally recognized standards ensuring interchangeability.

11.1 ISO Standards

Standard	Description
ISO 1478	Thread dimensions for tapping screws
ISO 7049	Pan head tapping screws
ISO 7050	Countersunk tapping screws
ISO 7051	Raised countersunk
ISO 10666	Drilling screws
ISO 2702	Heat treatment requirements

11.2 DIN Standards

DIN Standard	Application
DIN 7981	Pan head tapping screws
DIN 7982	Countersunk tapping screws
DIN 7983	Raised CSK screws
DIN 7504	Self drilling screws

11.3 ASTM Standards (Material & Performance)

ASTM	Scope
ASTM F568M	Carbon steel mechanical properties
ASTM A193	High temperature alloy fasteners
ASTM A320	Low temperature service
ASTM F1941	Coating systems
ASTM B117	Salt spray corrosion testing

11.4 British Standards (BS)

BS Standard	Description
BS 4174	Self tapping screws
BS 3692	Mechanical properties
BS EN ISO 3506	Stainless steel fasteners

12. Thread Standards & Tolerances

Thread System	Standard	Tolerance Class
Metric	ISO 1478	6g
UNC	ASME B1.1	2A
UNF	ASME B1.1	2A
BSW	BS 84	Medium
BSF	BS 84	Fine

SM Fasteners ensures thread rolling precision within international tolerance bands verified through calibrated gauges.

13. Mechanical Property Classes

Self tapping screws typically follow hardened property classifications.

Property Level	Equivalent Property Class	Typical Hardness
Standard	~8.8	28–34 HRC
High Strength	~10.9	32–39 HRC
Structural	~12.9	39–44 HRC

Heat treatment conformity aligned with ISO 2702.

14. Proof Load & Tensile Strength Table

Size	Tensile Strength (MPa)	Proof Load (kN)
ST3.5	900	3.2
ST4.2	900	4.6
ST4.8	1000	6.5
ST5.5	1000	8.9
ST6.3	1100	11.5

Values depend on material grade and heat treatment condition.

15. Interchangeability & Engineering Considerations

When replacing self tapping screws:

Check:

• Thread forming vs cutting type
• Substrate hardness
• Coating thickness impact
• Head bearing diameter
• Installation torque window

Incorrect substitution may result in:

• Thread stripping
• Loss of preload
• Galvanic corrosion
• Premature fatigue failure

16. Geometry Selection Matrix

Application	Recommended Type
Thin sheet steel	Thread forming
Structural steel	Self drilling
Aluminum panels	Forming screw
Plastics	Trilobular
Offshore equipment	Duplex SS
Chemical plant	Nickel alloy
Electrical panels	Stainless steel
Cryogenic service	Austenitic SS

SM Fasteners supports custom engineering drawings, tolerance optimization, and dimensional validation for global EPC procurement programs.

17. Materials Engineering for Self Tapping Screws

Material selection determines:

• Mechanical strength
• Thread forming capability
• Corrosion resistance
• Temperature performance
• Service life reliability

Self tapping screws require a unique balance between:

• High surface hardness (for thread creation)
• Core ductility (to prevent brittle fracture)

SM Fasteners manufactures self tapping screws across a complete industrial alloy spectrum aligned with ISO 9001 quality systems and global EPC procurement requirements.

18. Industrial Material Grades

18.1 Carbon Steel

Primary material for high-volume industrial fastening.

Characteristics

• Excellent hardenability
• High strength after heat treatment
• Cost-effective
• Suitable for coated systems

Typical Grades:

• C1022
• SAE 1018 / 1022
• ASTM F568M Class 8.8–10.9 equivalent

Applications:

• Structural sheet assemblies
• Roofing systems
• Equipment housings

18.2 Alloy Steel

Used where higher mechanical performance is required.

Grades:

• 4140
• 4340
• 40CrMo

Advantages:

• Higher fatigue resistance
• Improved shear strength
• Elevated temperature performance

18.3 Stainless Steel Fasteners

Essential for corrosion resistance and hygienic environments.

Grade	Features	Typical Service
A2-70 (304)	General corrosion resistance	Construction
A4-80 (316)	Marine & chemical resistance	Offshore
410 SS	Hardenable stainless	Structural tapping
904L	Acid resistance	Chemical plants

18.4 Duplex & Super Duplex Stainless Steel

Designed for aggressive chloride and offshore environments.

Grades:

• UNS S31803
• UNS S32205
• UNS S32750
• UNS S32760

Benefits:

• High strength
• SCC resistance
• Excellent seawater performance

Used extensively in LNG terminals and offshore platforms.

18.5 Nickel & High Performance Alloys

Manufactured by SM Fasteners for extreme operating environments.

Alloy	Key Capability
Inconel 625 / 718	High temperature strength
Incoloy 825	Acid resistance
Monel 400	Seawater corrosion resistance
Hastelloy C276	Chemical processing resistance
SMO 254	Chloride resistance

18.6 PEEK Self Tapping Fasteners

High-performance polymer fasteners supplied by SM Fasteners.

Advantages:

• Electrically non-conductive
• Chemical inertness
• Lightweight
• Non-magnetic
• Radiation resistant
• No galvanic corrosion

Applications:

• Semiconductor equipment
• LNG instrumentation
• Electrical insulation systems
• Chemical dosing equipment

19. Material Selection Comparison Table

Material	UTS (MPa)	Yield (MPa)	Corrosion Resistance	Temperature Limit	Relative Cost	Typical Application
Carbon Steel	800–1000	640	Low	300°C	Low	Construction
Alloy Steel	1000–1200	900	Moderate	450°C	Medium	Heavy equipment
SS 304	700	450	Good	400°C	Medium	Panels
SS 316	800	600	Very Good	500°C	Medium-High	Offshore
Duplex SS	900	650	Excellent	300°C	High	Marine
Inconel 718	1200+	1000	Exceptional	700°C	Very High	Turbines
Hastelloy C276	900	355	Outstanding	600°C	Very High	Chemical plants
PEEK	100	95	Exceptional	260°C	High	Electrical

20. Corrosion Resistance vs Environment

Environment	Carbon Steel	SS304	SS316	Duplex	Nickel Alloy	PEEK
Atmospheric	Fair	Good	Excellent	Excellent	Excellent	Excellent
Seawater	Poor	Moderate	Very Good	Excellent	Excellent	Excellent
Acidic	Poor	Moderate	Good	Very Good	Excellent	Excellent
H₂S / Sour Service	Limited	Moderate	Good	Excellent	Excellent	Excellent
Chlorides	Poor	Moderate	Good	Excellent	Excellent	Excellent
Chemical Processing	Poor	Good	Very Good	Excellent	Excellent	Excellent

Materials for sour service comply with NACE MR0175 / ISO 15156 hardness limits when required.

21. Heat Treatment Processes

Self tapping screws rely heavily on controlled heat treatment.

Objectives

• High thread surface hardness
• Tough core structure
• Controlled brittleness resistance

21.1 Process Flow

1. Austenitizing
2. Quenching
3. Tempering
4. Surface hardening stabilization

Typical Heat Treatment Parameters

Step	Temperature
Austenitizing	850–900°C
Quenching	Oil / Polymer
Tempering	350–450°C

Resulting Properties

Property	Requirement
Surface Hardness	45–55 HRC
Core Hardness	28–38 HRC
Case Depth	Controlled
Toughness	Maintained

ISO 2702 governs tapping screw heat treatment.

Hydrogen Embrittlement Control

SM Fasteners applies:

• Controlled electroplating
• Mandatory baking (190–220°C)
• Time-controlled post plating process
• Hardness verification

Critical for EPC and offshore procurement approval.

22. End-to-End Manufacturing Workflow

SM Fasteners follows a traceable manufacturing process aligned with ISO 9001 and UKAF-certified systems.

22.1 Raw Material Verification

• Mill Test Certificate (MTC)
• Heat number traceability
• PMI verification
• Chemical composition analysis

22.2 Wire Processing

• Wire drawing
• Spheroidizing annealing
• Surface cleaning
• Lubrication coating

22.3 Cold Heading / Forging

Produces:

• Head geometry
• Shank formation
• Grain flow alignment

Advantages:

• Improved fatigue strength
• Material efficiency

22.4 Thread Rolling (Preferred Method)

Thread rolling is superior to thread cutting.

Benefits:

• Work hardening
• Improved fatigue resistance
• Smooth surface finish
• No material removal

22.5 Tip Forming

Specialized tooling creates:

• Sharp points
• Drill tips
• Cutting flutes

22.6 Heat Treatment

Controlled furnace systems ensure:

• Uniform hardness
• Distortion control
• Mechanical consistency

22.7 Surface Finishing

Applied according to application environment.

23. Surface Engineering & Protective Coatings

Surface treatment directly influences corrosion resistance and torque behavior.

Surface Finish Comparison Table

Coating	Corrosion Resistance	Friction Control	Typical Use
Zinc Plating	Moderate	Good	Indoor use
Zinc Flake	High	Excellent	Automotive
Hot Dip Galvanized	Very High	Moderate	Structural
Mechanical Galvanizing	High	Good	Construction
Phosphate	Low	Excellent	Base coating
Dacromet	Very High	Stable	Offshore
PTFE	Excellent	Very Low Friction	Chemical
Black Oxide	Low	Controlled	Machinery
Passivation (SS)	High	Stable	Marine

SM Fasteners validates coatings through ASTM B117 salt spray testing.

Coating Thickness Guidelines

Coating	Thickness
Electro Zinc	5–12 µm
Zinc Flake	8–20 µm
HDG	40–70 µm
PTFE	20–40 µm

24. Torque Behavior vs Surface Condition

Coating significantly alters torque values.

Surface Condition	Torque Reduction
Dry	Baseline
Zinc plated	−10%
Lubricated	−25%
PTFE coated	−40%

Engineering torque recalculation is mandatory after coating selection.

25. Manufacturing Quality Integration at SM Fasteners

Integrated controls include:

• Process qualification
• Heat lot traceability
• Gauge calibration
• SPC monitoring
• Batch inspection
• Certified documentation

Capabilities include:

• Custom self tapping geometries
• Special alloy machining
• PEEK precision molding
• Project-specific coating systems

SM Fasteners delivers self tapping screws engineered for global industrial reliability, material traceability, and audit-ready compliance required by EPC contractors and OEM manufacturers.

26. Inspection & Quality Control Framework

Self tapping screws used in industrial projects must demonstrate mechanical reliability, dimensional precision, and full traceability.

SM Fasteners operates under an ISO 9001 certified quality management system, ensuring every production batch satisfies international inspection protocols demanded by EPC contractors, OEM manufacturers, and third-party inspectors.

Manufacturer Reference:
SM Fasteners

26.1 Incoming Raw Material Inspection

Verification begins prior to manufacturing.

Inspection Activities

• Mill Test Certificate (MTC) verification
• Heat number traceability
• Chemical composition analysis
• Positive Material Identification (PMI)
• Wire rod dimensional inspection
• Surface defect examination

Standards Referenced:

• ASTM A751
• ISO 6892
• EN 10204

26.2 In-Process Manufacturing Inspection

Process Stage	Inspection Method
Cold Heading	Head dimension gauging
Thread Rolling	GO / NO-GO ring gauges
Tip Formation	Optical inspection
Heat Treatment	Hardness verification
Coating	Thickness measurement
Sorting	Automated defect detection

Statistical Process Control (SPC) ensures dimensional stability across production lots.

26.3 Mechanical Testing

Performed according to ISO, ASTM, and BS requirements.

Test	Purpose
Tensile Test	Strength validation
Proof Load Test	Elastic performance
Torsional Test	Installation capability
Hardness Test	Heat treatment verification
Pull-Out Test	Substrate performance
Drive Torque Test	Head integrity

26.4 Non-Destructive Testing (NDT)

Critical for high-integrity applications.

Method	Application
Magnetic Particle Testing	Surface crack detection
Dye Penetrant	Stainless fasteners
Ultrasonic Testing	Alloy fasteners
Eddy Current	Surface discontinuity
Visual Inspection	Final acceptance

26.5 Dimensional Inspection Requirements

Verified parameters include:

• Major diameter
• Pitch accuracy
• Thread angle
• Head height
• Drive recess geometry
• Overall length tolerance

Calibration follows ISO 17025 traceable standards.

26.6 Documentation & Certification

SM Fasteners supplies complete export documentation:

• EN 10204 3.1 Material Test Certificate
• 3.2 certification (third-party witness)
• Heat treatment report
• Coating report
• Inspection & test plan (ITP)
• Certificate of Conformity (CoC)
• PMI reports (when required)

27. Mechanical Properties Table (Grade-wise)

Property Level	Tensile Strength (MPa)	Yield Strength (MPa)	Hardness HRC	Typical Material
Standard	800–900	640	28–34	Carbon Steel
High Strength	900–1040	830	32–39	Alloy Steel
Structural	1100–1220	1000	39–44	Heat Treated Alloy
A2-70	700	450	HRB 95	SS304
A4-80	800	600	HRB 100	SS316
Duplex	900	650	28–36	S32205

28. Tightening Torque Chart

(Engineering Reference — Dry Condition)

Size	8.8 Equivalent (Nm)	10.9 Equivalent (Nm)	Lubricated (Nm)
ST3.5	2.5	3.5	2.0
ST4.2	4.5	6.5	3.5
ST4.8	7.5	10	6
ST5.5	12	16	9
ST6.3	20	26	15

Torque must always be validated through application testing.

29. Preload Engineering — Formula & Example

General Formula

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

Where:

• F = Preload force
• T = Applied torque
• K = Nut factor
• d = Nominal diameter

Worked Example

Given:

• Torque = 16 Nm
• Diameter = 5.5 mm
• Nut factor = 0.18

$$F = \frac{16}{0.18 \times 0.0055}$$

$$F = 16,161 N$$

Approximate preload = 16.1 kN

30. Failure Mechanisms & Preventive Engineering

Failure Mode	Cause	Prevention
Thread Stripping	Small pilot hole	Correct hole sizing
Fatigue Failure	Low preload	Controlled torque
Hydrogen Embrittlement	Electroplating	Baking process
Galling	SS friction	Lubrication/PTFE
Stress Corrosion Cracking	Chlorides	Duplex/Nickel alloy
Head Shear	Over-torque	Torque control tools

31. Industry Application Mapping

31.1 Construction & Structural Steel

Used for:

• Metal decking
• Roofing systems
• Facade fixing
• Steel partitions

Requirements:

• Zinc flake coating
• High pull-out strength

31.2 Oil & Gas Industry

Upstream, midstream, downstream facilities utilize self tapping screws for:

• Instrument panels
• Control cabinets
• Offshore modules
• Cable tray systems

Material Selection:

• SS316
• Duplex
• Nickel alloys
• NACE compliant materials

31.3 Power Generation

Applications include:

• Turbine enclosures
• Electrical panels
• Cooling systems
• Solar mounting assemblies

31.4 Petrochemical & Chemical Processing

Critical factors:

• Chemical resistance
• Non-contamination
• Anti-galling performance

Preferred materials:

• A4-80
• SMO 254
• Hastelloy
• PEEK fasteners

31.5 LNG & Offshore Platforms

Requirements:

• Seawater corrosion resistance
• Vibration endurance
• Salt spray resistance

Preferred grades:

• Duplex
• Super Duplex
• Inconel

31.6 Automotive & Heavy Equipment

Used in:

• Body panels
• Interior assemblies
• HVAC modules
• Engine compartment shields

31.7 Railways & Infrastructure

• Coach interiors
• Signaling equipment
• Control cabinets
• Modular structures

31.8 Shipbuilding & Marine Engineering

• Deck equipment
• Cabin interiors
• Electrical housings
• Marine ventilation systems

31.9 PEEK Fastener Applications

PEEK self tapping screws supplied by SM Fasteners are used where metal fasteners are unsuitable:

• Electrically isolated assemblies
• MRI equipment
• Chemical dosing systems
• Semiconductor manufacturing
• Cryogenic insulation systems

32. Thread Standards & Tolerances Table

Thread Type	Standard	Tolerance
Metric ST	ISO 1478	6g
UNC	ASME B1.1	2A
UNF	ASME B1.1	2A
BSW	BS 84	Medium
BSF	BS 84	Fine

33. Surface Finish Performance Comparison

Finish	Corrosion Protection	Torque Stability	Offshore Suitability
Zinc	Moderate	Good	Limited
Zinc Flake	High	Excellent	Good
Hot Dip Galvanized	Very High	Moderate	Good
Dacromet	Very High	Excellent	Excellent
PTFE	Excellent	Excellent	Excellent
Passivated SS	High	Stable	Excellent

34. Weight Chart — Self Tapping Screws

(Aligned with SM Fasteners Manufacturing Data)

Size	Length (mm)	Weight / Piece (g)	Weight / 100 pcs (kg)
ST3.5	13	0.6	0.06
ST3.5	25	0.9	0.09
ST4.2	25	1.5	0.15
ST4.8	38	2.6	0.26
ST5.5	50	4.5	0.45
ST6.3	75	7.8	0.78

Custom weights available based on material density and coating.

35. Export Packaging & Logistics

SM Fasteners supports global EPC supply chains.

Industrial Packaging

• VCI corrosion protection
• Thread protection caps
• Moisture barrier packing
• Heat number labeling
• Barcode traceability

Export Crating

• ISPM-15 compliant wooden crates
• Vacuum sealed packaging
• Palletized export systems
• Container optimization

Shipment Documentation

• Commercial invoice
• Packing list
• Country of origin certificate
• MTC EN 10204 3.1 / 3.2
• Inspection reports
• Coating compliance certificates

36. Procurement Readiness — EPC Supply Capability

SM Fasteners supports project procurement through:

• Custom engineering drawings
• Special alloy manufacturing
• Project-specific coating systems
• Lot traceability
• Third-party inspection coordination
• Global export compliance

Capabilities include:

• Stainless, Duplex & Super Duplex fasteners
• Nickel alloy and high-temperature fasteners
• Precision PEEK fastening systems
• Custom dimensional manufacturing

37. Engineering Summary

Self tapping screws represent a highly engineered fastening solution combining:

• Controlled material hardness
• Optimized thread geometry
• Accurate torque–tension behavior
• Advanced surface engineering
• Strict inspection protocols

Through ISO 9001 certified manufacturing, UKAF accredited systems, and MSME-recognized industrial capability, SM Fasteners delivers self tapping screws suitable for:

• High-reliability industrial assemblies
• EPC megaproject procurement
• Offshore and chemical environments
• Precision OEM manufacturing