Bolts are fundamental components in mechanical engineering and construction, used to fasten objects together. The standard specifications for bolts cover aspects like dimensions, material, thread type, grade, and coating. Here’s a breakdown of the key standard specifications for bolts:
- Dimensions and Sizes
Standards:
- ISO 4014 and ISO 4017: Provide specifications for hex bolts.
- ASME B18.2.1: Covers dimensions for hex bolts and screws.
- DIN 933: Specifies the dimensions for hexagon head bolts with metric threads.
Key Parameters:
- Diameter (D): Measured in millimeters (mm) or inches, standard diameters range from M6 to M64 for metric bolts and 1/4″ to 2″ for imperial bolts.
- Length (L): Length from under the head to the end of the bolt, ranging from 10 mm to 500 mm for metric bolts and 1/4″ to 12″ for imperial bolts.
- Head Size: Varies according to bolt type, such as hex head, flange head, etc.
- Thread Types
Standards:
- ISO 261: Specifies metric thread standards.
- ASME B1.1: Covers Unified Inch Screw Threads, used in the U.S.
Key Parameters:
- Pitch: The distance between threads, measured in millimeters for metric bolts (e.g., M10x1.5 where 1.5 mm is the pitch).
- Thread Length: Typically specified as either full thread or partial thread.
- Material and Grades
Standards:
- ISO 898-1: Defines mechanical properties of steel bolts, screws, and studs with specified tensile strength.
- ASTM A325: Specifies high-strength structural bolts, steel, heat-treated.
- ASTM F593: Covers stainless steel bolts and screws.
Common Materials:
- Carbon Steel: Used for general applications (grades 4.6, 8.8, 10.9, etc.).
- Stainless Steel: Offers corrosion resistance, common grades include A2-70 and A4-80.
- Alloy Steel: For higher strength applications.
- Brass, Bronze, and Titanium: For specialized uses requiring specific properties.
- Coatings and Finishes
Standards:
- ISO 4042: Specifies electroplated coatings for fasteners.
- ASTM B633: Covers zinc coatings applied by electroplating.
Common Coatings:
- Zinc Plating: Provides corrosion resistance, commonly used in outdoor applications.
- Hot-Dip Galvanizing: Offers thicker corrosion-resistant coating than zinc plating.
- Black Oxide: Provides mild corrosion resistance and a black finish.
- Phosphate Coating: Used for better adhesion of paint and other finishes.
- Performance Grades
Standards:
- ISO 898-1: Lists property classes for bolts, such as 4.6, 8.8, 10.9, indicating tensile strength.
- ASTM A325: Grades bolts for structural applications, e.g., ASTM A325 Type 1.
- SAE J429: Covers grades for bolts, such as Grade 2, 5, and 8, based on tensile strength.
Common Grades:
- Grade 8.8: Medium carbon steel quenched and tempered, with high tensile strength (800 MPa).
- Grade 10.9: Alloy steel quenched and tempered, for high-strength applications (1000 MPa).
- Grade A2-70: Austenitic stainless steel, moderate strength with good corrosion resistance.
- Markings
Standards:
- ISO 898-1: Specifies markings for property classes on the bolt head.
- ASTM F606/F606M: Provides test methods for the verification of the mechanical properties of steel bolts.
Marking Guidelines:
- Head Marking: Indicates manufacturer and property class (e.g., “8.8”).
- Thread Length and Grade: Often marked to denote compliance with standards.
- Torque Specifications
Standards:
- ISO 898-1: Defines tightening torque requirements for bolts based on their grade and size.
- ASTM A325: Specifies torque requirements for structural bolts.
Torque Values: Vary depending on bolt diameter, grade, and application; typically measured in Newton-meters (Nm) or pound-feet (lb-ft).
References:
- ISO 4014 – Hexagon head bolts.
- ASME B18.2.1 – Dimensions for bolts and screws.
- ASTM A325 – Structural bolts.
- ISO 898-1 – Mechanical properties of fasteners.
- ISO 261 – Metric thread standard.
This overview provides a foundational understanding of the specifications required for bolts across different applications. Always refer to the specific standards and technical data sheets for detailed information and application-specific requirements.