Cylindrical Internal Hex Bolts

Cylindrical internal hex bolts are the premier choice for precision, high-strength fastening, featuring a smooth cylindrical head with an internal hex socket. Their defining advantages include concealed internal-hex installation combined with a high-rigidity structure and high-precision fastening. Manufactured in accordance with ISO 4762 for socket head cap screws, the cylindrical head sits flush after installation, presenting a smooth surface with no protruding edges. The internal hex socket is precision-machined to ensure an exact tool fit, providing stable torque transmission and excellent resistance to cam-out. The precision-ground shank maintains straightness within 0.02 mm/m, and the threads are produced to a 6g tolerance. This design delivers overall rigidity approximately 40% higher than that of standard bolts, making cylindrical head internal hex bolts ideal for applications where both precision and strength are critical.

Cylindrical internal hex bolts are widely used in precision molds, aerospace components, electronic precision equipment, high-end medical devices, and automotive engines. In precision mold applications, they secure cavities and plates, with their high-precision characteristics ensuring machining accuracy. In aerospace components, they provide reliable fastening for lightweight, high-strength structures while meeting stringent aviation safety standards. In electronic precision equipment such as semiconductor manufacturing tools, their concealed installation prevents interference with sensitive operations. In high-end medical devices, including surgical instruments, they enable secure fastening with no hygiene dead zones, facilitating effective sterilization. In automotive engines, they withstand high temperatures and pressures, ensuring stable performance. Cylindrical head internal hex bolts are a critical connecting component in the most demanding industries.

These bolts are manufactured from premium alloys such as 40CrNiMoA and 35CrMo, or specialized stainless steel 316Ti. Alloy steel versions are heat-treated to achieve strength grades of 12.9 or even customized 14.9 levels, with grade 12.9 offering a hardness of HRC 39–44 and tensile strength of ≥1200 MPa. Stainless steel 316Ti provides excellent corrosion resistance and high-temperature performance for harsh environments. Available surface treatments include passivation (for stainless steel), black oxide (GB/T 15519), and silver plating (ASTM B700) for precision applications, with stainless steel achieving over 200 hours of salt spray resistance. Certified to ISO 9001 and the stringent AS9100 aerospace standard, cylindrical head internal hex bolts represent the highest level of quality. Customization is available for ultra-small diameters (M1.6–M2.5), extra-long lengths (up to 300 mm), special drive types, and advanced coatings such as PVD titanium. Packaged in sealed packs of 100–200 pieces and supplied with precision inspection reports, these bolts ensure fully controlled quality for your most critical assemblies.