S-91259A871 1/2"-13 ASME B18.3, ASTM A574 Shoulder Screws

Key Features & Benefits at a Glance

• Superior Corrosion Resistance: The black oxide finish provides excellent protection against rust and wear, extending the screw's service life in harsh industrial environments.
• Exceptional Strength and Durability: Made from alloy steel and heat-treated to a Rockwell C32 hardness, this screw offers high tensile strength and reliable performance under heavy loads.
• Precision Alignment and Bearing Surface: The generous 4 1/4" shoulder length with a controlled diameter tolerance ensures accurate component positioning and acts as a sturdy pivot or axle.
• High-Reliability Thread Engagement: Featuring a Class 3A thread fit for unified coarse (UNC) threads, ensuring tight, secure fastening with minimal risk of cross-threading or loosening.
• Secure and Easy Installation: The knurled socket head with a 5/16" hex drive provides a positive grip, allowing for high-torque installation without cam-out, even in confined spaces.
• Guaranteed Quality and Compliance: Manufactured to meet ASME B18.3 specifications and compliant with RoHS 3 and REACH regulations, ensuring material safety and international standard adherence.

Professional Applications & Engineering Value

This alloy steel shoulder screw is engineered to solve critical challenges in heavy-duty applications such as machinery assembly, automotive jigs, and precision rotating mechanisms. The 1/2"-13 UNC coarse thread with a 3/4" thread length ensures rapid assembly and a strong grip in tapped holes, while the long, precisely machined shoulder provides a smooth, hardened bearing surface that prevents wear on mating components. The black oxide finish not only enhances corrosion resistance but also reduces galling and friction. Its socket head design with a knurled texture allows for reliable tool engagement, making it ideal for high-vibration environments where fastener integrity is paramount. This combination of material strength, precision tolerances, and protective coating delivers long-term reliability, reducing maintenance downtime and ensuring consistent performance in demanding industrial settings.

Specification Summary & Compliance

This shoulder screw features a 1/2"-13 UNC thread with a Class 3A fit for precise engagement. The shoulder diameter is 5/8" with a tolerance of -0.004" to -0.002", and the shoulder length is 4 1/4" with a tolerance of -0.005" to 0.005". It is manufactured in compliance with the ASME B18.3 standard and is confirmed to be RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) compliant, ensuring it meets stringent environmental and safety regulations for global use.