The LD-389 carbon steel hex bolts and cap screws are versatile threaded fasteners manufactured to international dimensional standards for a wide range of mechanical, structural, and general-purpose fastening applications. The product line includes both partially threaded hex cap screws (DIN 931/ISO 4014) and fully threaded hex bolts (DIN 933/ISO 4017), allowing customers to select the appropriate thread configuration for each application. Partially threaded cap screws feature a smooth unthreaded shank section below the head that provides precise alignment, superior shear strength, and reduced fatigue at the threaded-to-shank transition. Fully threaded hex bolts provide maximum thread engagement length, which is advantageous when clamping thick materials or when the bolt length must be adjusted at installation. The hex head design allows for easy installation and removal using standard wrenches, sockets, and power tools.

The bolts are manufactured from carbon steel in multiple strength grades including Grade 4.8, Grade 5.8, Grade 8.8, and Grade 10.9, covering tensile strength requirements from 400 MPa to 1000 MPa. Grade 4.8 and 5.8 bolts are suitable for general-purpose and light-duty applications such as furniture assembly, non-structural connections, and consumer products. Grade 8.8 is the most commonly specified grade for structural and machinery applications, offering a good balance of strength, ductility, and cost. Grade 10.9 bolts provide high tensile strength for demanding structural connections and heavy machinery. All grades are through-hardened and tempered to achieve the specified mechanical properties, and each bolt is marked with the manufacturer identifier and grade marking for traceability and quality assurance.

Surface finishing options include white/blue zinc plating, yellow zinc plating, black oxide, and plain finish. Zinc plating provides sacrificial corrosion protection, with the zinc layer sacrificially corroding to protect the underlying carbon steel substrate. White/blue zinc offers a clean, bright appearance suitable for indoor and consumer applications, while yellow zinc chromate provides enhanced corrosion resistance for outdoor and moderately corrosive environments. Black oxide finish provides a uniform dark appearance with mild corrosion resistance, primarily used for aesthetic purposes and indoor applications. Plain finish bolts are used where plating is not required or where a customer will apply their own surface treatment. The metric coarse thread is the standard thread profile, ensuring universal compatibility with standard nuts, washers, threaded holes, and mating components.

The LD-389 hex bolts and cap screws are available in diameters from M5 to M30 with lengths from 20mm to 300mm, covering an extensive range of fastening requirements from delicate equipment assembly to heavy structural connections. These fasteners are used across virtually every industry and application category, including structural steel assembly and building construction, machinery and industrial equipment manufacturing, automotive and heavy vehicle fastening, construction and infrastructure projects, furniture and fixture assembly, and general industrial maintenance and repair. With CE, ISO 9001, and GB/T 5782 / DIN 933 compliance, the LD-389 series meets international quality and dimensional standards, ensuring interchangeability and reliable performance in professional applications worldwide.