Overview
ISO 7046-2:2011 is an international standard specifying the characteristics of recessed countersunk flat head screws with type H or type Z cross recess. It addresses screws with thread sizes ranging from M2 to M10, focusing on product grade A screws made from steel of property class 8.8, stainless steel (A2-70), and non-ferrous metals (CU2 and CU3). This part 2 of ISO 7046 provides precise definitions on dimensions, mechanical properties, and tolerances, ensuring interchangeability and reliability in industrial applications.
This standard is essential for manufacturers, engineers, and quality controllers who require consistent quality and performance in fasteners, particularly in the automotive, aerospace, construction, and machinery sectors.
Key Topics
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Screw Types Covered:
- Steel screws (property class 8.8)
- Stainless steel screws (A2-70)
- Non-ferrous metal screws (CU2, CU3)
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Thread Sizes:
M2 up to and including M10
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Cross Recess Types:
- Type H cross recess
- Type Z cross recess
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Penetration Depth Series:
- Series 1: Deep cross recess with underhead shoulder for higher wrench ability and head strength
- Series 2: Shallow cross recess without underhead shoulder for enhanced head strength in high-tensile screws
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Mechanical Property Classes:
- Steel: 8.8 (high tensile strength)
- Stainless steel: A2-70
- Non-ferrous metal: CU2 and CU3
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Dimensional Specifications:
Includes head diameter, cross recess dimensions, shank diameter, thread pitch, and countersunk head geometry per ISO 225 and ISO 7721-2.
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Tolerances and Surface Quality:
Defined according to related standards such as ISO 4759-1 for tolerances and ISO 6157-1 and ISO 6157-3 for surface discontinuities.
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Coating and Corrosion Resistance:
Electroplating (ISO 4042), zinc flake coatings (ISO 10683), and stainless steel passivation (ISO 16048) standards are referenced to ensure durability and resistance.
Applications
ISO 7046-2 countersunk flat head screws are widely used where a flush surface finish is required, and the fastener must provide strong mechanical fastening with reliable torque transmission. Typical applications include:
- Automotive Industry: Securing components requiring high strength and corrosion resistance.
- Aerospace: Lightweight assemblies using stainless steel or non-ferrous screws with strict tolerance and mechanical properties.
- Machinery and Equipment Manufacturing: Fastening parts where countersunk heads promote safety and assembly efficiency.
- Construction: Durable and corrosion-resistant screws for metal frameworks and fixtures.
- Electronics and Electrical Devices: Using smaller thread sizes with precise dimensional controls.
The ability to select screws with different penetration depths of the cross recess allows designers and manufacturers to balance wrenchability and head strength for specific operational requirements, ensuring optimal performance.
Related Standards
ISO 7046-2 references and complements several international standards critical for comprehensive fastener specification:
- ISO 225: Symbols and descriptions of fastener dimensions
- ISO 261 and ISO 965-2: General metric screw threads and tolerances
- ISO 898-1: Mechanical properties of steel fasteners
- ISO 3506-1: Properties of corrosion-resistant stainless steel fasteners
- ISO 4757: Dimensions for cross recesses
- ISO 4759-1: Tolerances for fasteners – product grades
- ISO 6157-1 and ISO 6157-3: Surface discontinuity acceptance criteria
- ISO 7721-2: Penetration depth of cross recess for countersunk head screws
- ISO 4042 and ISO 16048: Coating and passivation requirements for corrosion protection
- ISO 10683: Zinc flake coatings for fasteners
These related standards ensure that ISO 7046-2 screws meet global quality, mechanical, and chemical performance criteria, facilitating international trade and manufacturing consistency.
Keywords: ISO 7046-2, countersunk flat head screws, cross recess type H, cross recess type Z, property class 8.8 screws, stainless steel screws A2-70, non-ferrous metal screws CU2 CU3, metric screws, product grade A, fastener standards, mechanical properties, screw dimensions, thread sizes M2 to M10, industrial screws, corrosion-resistant fasteners.