S-91512A110 4-40 x 1/4" 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 and passivated finish, ideal for harsh environments
- Exceptional mechanical strength with 70,000 psi tensile strength and Rockwell B70 hardness for reliable load-bearing performance
- Precise thread engagement with Class 3A fit and UNC coarse threads ensuring secure, vibration-resistant connections
- Flush mounting capability featuring an 82° countersink angle and standard flat head profile for seamless surface integration
- Left-hand threading provides specialized directional security in rotating assemblies where reverse-thread retention is critical
- Easy installation with 1/16" hex drive enabling efficient torque application in confined spaces
- Full regulatory compliance meeting RoHS 3 and REACH standards for global industrial applications
Professional Applications & Engineering Value
These 4-40 UNC left-hand thread flat head screws deliver critical engineering solutions where standard right-hand threads would loosen under counter-clockwise rotation. The 18-8 stainless steel construction with passivated finish provides exceptional corrosion resistance for demanding environments including marine, chemical processing, and outdoor equipment. The Class 3A thread fit ensures precise tolerances for vibration-prone applications, while the 82° countersink angle creates perfectly flush surfaces in precision machinery, aerospace components, and electronic enclosures. With full threading along the 1/4" length, these screws maintain consistent clamping force across the entire engagement area, preventing joint failure in high-stress assemblies.
Specification Summary & Compliance
This fastener maintains Class 3A thread fit per UNC standards with coarse thread spacing for rapid assembly. Manufacturing complies with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations. The 82° countersink angle matches standard chamfered holes, while the left-hand thread direction and fully threaded design ensure consistent performance across the specified 1/4" length.
