M2/M4/M5/M6 Grade 12.9 fine tooth black concave end inner hexagon machine rice screw fixed stop bolt top wire for Machinery Fixing & Positioning

Our Grade 12.9 Fine Tooth Black Concave End Hex Socket Set Screws (Grub Screws/Stop Bolts) are high-strength industrial fasteners engineered for precise fixing, positioning, and stopping applications in machinery and equipment. Crafted with Grade 12.9 high-carbon alloy steel, these screws deliver exceptional tensile strength, hardness, and wear resistance—ideal for heavy-duty industrial use where stability and reliability are critical.

 

Featuring a fine tooth (fine thread) design, the screws provide a tight, secure grip that prevents loosening even under vibration, ensuring long-lasting fixation. The black oxide finish enhances corrosion resistance and wear resistance, while the concave end (cup point) allows for precise contact and positioning, making them perfect for securing rotating parts, shafts, and components that require a flush, non-protruding fastener.

 

Designed with an inner hexagon (hex socket) drive, these set screws are easy to install and tighten with standard hex keys, enabling efficient operation for professionals and industrial users. Available in M2, M4, M5, and M6 sizes, they cater to a wide range of industrial, mechanical, and equipment maintenance needs.

 

Suitable for machinery positioning, equipment stop fixation, shaft locking, and industrial assembly, these Grade 12.9 fine tooth hex socket set screws are the go-to choice for high-demand applications. They combine professional-grade durability, precise performance, and easy installation—perfect for wholesale, industrial supply, and mechanical maintenance projects.