ANSI/ASME B18.5 Round Head Square Neck Bolts combining a smooth, rounded head with a square neck to prevent rotation during installation. This unique design ensures secure seating in square-shaped recesses or mating components, eliminating slippage even under extreme torque. Manufactured to ANSI/ASME B18.5 standards, these bolts deliver consistent dimensions and mechanical properties, making them ideal for assemblies requiring both aesthetic smoothness and anti-rotational stability. In automotive engineering, ANSI/ASME B18.5 bolts are commonly used in components exposed to high vibration and torsional stress. Their square neck feature is particularly advantageous in drivetrain systems, axle housings, and heavy-duty suspension linkages, where rotational resistance is critical to maintaining structural integrity. The rounded head design also reduces protrusion risks, making them suitable for automotive applications requiring streamlined profiles, such as underbody panels or transmission mounts. Key Advantages for Your Applications: Positive Anti-Rotation: The square neck design effectively prevents bolt rotation, ensuring joint integrity under high torque and vibration. Aesthetic Smoothness: The rounded head provides a clean and streamlined appearance, suitable for visible automotive components. Consistent Dimensions & Properties: Manufactured to ANSI/ASME B18.5 standards, guaranteeing dimensional accuracy and reliable mechanical performance. Enhanced Structural Integrity: Prevents loosening and maintains the clamping force of critical automotive joints. Reduced Assembly Time: The self-locking feature can simplify the assembly process by eliminating the need for additional anti-rotation hardware. Minimized Damage Risk: The rounded head reduces the potential for snagging or damage to surrounding components. Ideal for: Drivetrain Systems: Securing components where high torsional stress and vibration are present, such as transmission mounts and axle housings. Heavy-Duty Suspension Linkages: Providing reliable, non-rotating connections in critical suspension components. Underbody Panels: Offering a low-profile, secure fastening solution that minimizes protrusion. Transmission Mounts: Ensuring stable and vibration-resistant mounting of the transmission. Seating Assemblies: Providing secure and aesthetically pleasing fastening for seat frames and mechanisms. Body Panels: Securing panels where a smooth exterior finish is desired along with robust fastening. Agricultural and Construction Equipment: Applications requiring resistance to rotation in demanding environments. Product NameStandardMaterial & FinishDiameter (Shank)Length (Shank)Round Head Square Neck BoltASTM A449Grade 5 Carbon Steel, Zinc Plated1/2" (12.7mm)2" (50.8mm)Round Head Square Neck BoltASTM A449Grade 8 Alloy Steel, Hot-Dip Galv5/8" (16mm)3" (76.2mm)Round Head Square Neck BoltASTM A449AISI 304 Stainless Steel, Plain3/4" (19.05mm)4" (101.6mm)Round Head Square Neck BoltDIN 6038.8 Steel, Zinc Flake CoatedM1240mmRound Head Square Neck BoltDIN 60310.9 Steel, Dacromet CoatedM1660mmRound Head Square Neck BoltDIN 603A2-70 Stainless SteelM2080mmRound Head Square Neck BoltISO 7412Class 8.8 Steel, ElectrogalvanizedM24100mmRound Head Square Neck BoltISO 7412Class 10.9 Steel, PhosphatedM30120mmRound Head Square Neck BoltGB/T 122840Cr Steel, Hot-Dip GalvanizedM36150mmRound Head Square Neck BoltASME B18.5ASTM A325 Type 1, Plain1" (25.4mm)6" (152.4mm)Round Head Square Neck BoltASME B18.5ASTM A490, Xylan Coated1-1/4" (31.75mm)8" (203.2mm)Round Head Square Neck BoltJIS B1180SCM435 Alloy Steel, Zinc PlatedM1030mmRound Head Square Neck BoltJIS B1180SUS316 Stainless SteelM1450mmRound Head Square Neck BoltBS 3692Grade 8.8 Steel, Geomet CoatedM1870mmRound Head Square Neck BoltSAE J429Grade 2 Steel, Plain7/16" (11.11mm)1-1/2" (38.1mm)Round Head Square Neck BoltSAE J429Grade 5 Steel, Zinc-Nickel3/4" (19.05mm)5" (127mm)