S-91512A120 4-40 x 1/2" Left-Hand-Thread Stainless Steel Hex-Drive Flat Head Screws
Left-Hand-Thread Stainless Steel Hex-Drive Flat Head Screws
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Basic Information
Head Parameters
Dimensions
Thread Parameters
Tip & Drive Parameters
Material & Strength
Temperature & Environment
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Key Features & Benefits at a Glance
- Superior corrosion resistance with 18-8 stainless steel construction and passivated finish, ideal for harsh environments
- Exceptional thread engagement with Class 3A fit and UNC coarse thread spacing, ensuring vibration-resistant connections
- High mechanical strength with 70,000 psi tensile strength and Rockwell B70 hardness for demanding applications
- Secure, flush installation featuring a standard flat head profile with 82° countersink angle and hex drive design
- Left-hand thread direction provides specialized functionality for reverse-thread applications and safety mechanisms
- Full threading along the 1/2" length maximizes grip and load distribution across the entire fastener
- Regulatory compliance assurance meeting RoHS 3 and REACH standards for global industrial use
Professional Applications & Engineering Value
Engineered for precision and durability, these 4-40 UNC left-hand thread flat head screws address critical needs in industrial assembly where reverse-threading prevents loosening under counter-clockwise motion. The 18-8 stainless steel material, combined with a passivated finish, offers excellent resistance to oxidation and chemical exposure, making them suitable for marine, automotive, and electronics applications. The hex drive and 82° countersink angle ensure a secure, flush fit that minimizes protrusion and maintains aerodynamic or aesthetic surfaces. With Class 3A thread fit and coarse thread spacing, these screws provide reliable performance in high-vibration environments, reducing maintenance frequency and enhancing operational safety.
Specification Summary & Compliance
This fastener maintains Class 3A thread fit per UNC standards with a thread size of 4-40 and left-hand direction. Dimensions include a 1/2" length, 0.255" head diameter, and 1/16" hex drive size. Manufacturing adheres to RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) compliance, ensuring environmental and safety standards are met for industrial distribution.
