CHANGZHOU, China – Changzhou Yongmao Special Fastener Co., Ltd., a cold heading fastener manufacturer operating since 1993, has been granted a Chinese invention patent for a cold forming process and cold extrusion elongation die designed specifically for ultra-deep hole slender parts. The patent, formally issued under certificate number 4604667, was filed in September 2019 and represents a significant technical milestone in the company's long-running effort to push the boundaries of what cold heading can achieve in the difficult territory of deep-hole, extra-long, and high-head-to-shank-ratio fasteners.
The patented technology addresses a manufacturing challenge that has traditionally forced suppliers to choose between two unattractive options: machining, which is slow, material-wasteful, and breaks the grain flow of the metal, or refusing the order entirely. The cold extrusion elongation die covered by this patent allows Yongmao to form ultra-deep holes and slender shafts through multi-station cold heading, preserving continuous grain flow through the shank and head transition. The result is a part with greater fatigue strength and dimensional consistency than a machined equivalent, produced at a fraction of the cycle time and material cost.
Yongmao's specialization in this area is not incidental. The company built its reputation over more than three decades around the categories that standard fastener factories typically decline: extra long bolts, slender screws, deep-hole drilled bolts, hollow bolts, and large head thin shank bolts. The invention patent formalizes a process capability that has already been deployed across its production lines, where multi-station cold heading machines, automatic thread rolling equipment, and CNC machining centers work in sequence to produce parts that would otherwise require multiple machining operations.
The practical applications of this technology span several growing industrial segments. In the bicycle and e-bike sector, Yongmao manufactures hollow thru-axles for road bikes, mountain bikes, and electric bicycles in 7075 and 6066 aluminum as well as 10B21 and 20CrMo alloy steel. These axles rely on the same deep-hole and slender-shaft forming principles covered by the patent, delivering weight reduction without compromising the structural integrity needed for disc-brake loads. The company also produces hollow stem bolts for BMX and trial bicycle stems at grade 10.9, and fully hollow front fork axles and swingarm axles for electric bicycles and scooters.
Beyond two-wheeled applications, the patented process supports Yongmao's work in the new energy vehicle segment, where it manufactures EV battery module bolts, battery pack bolts, busbar bolts, and battery hold-down bolts for pack assemblers and tier-one suppliers. Deep-hole hollow designs are among the custom head shapes the company produces for these applications, where consistency and traceability are non-negotiable. The company's broader cold headed fastener portfolio serves automotive, electric motor, construction machinery, and agricultural equipment industries, with export experience spanning Asia, Europe, the Americas, and the Middle East.
The company holds ISO 9001 quality management system certification, valid through 2027, and was recognized as a National High-Tech Enterprise in 2023. Its in-house laboratory is equipped with universal testing machines, salt spray chambers, Rockwell hardness testers, projectors, magnetic particle flaw detectors, and torque testing equipment, allowing full verification of tensile strength, hardness, corrosion resistance, and dimensional accuracy on every production batch. This combination of patented forming technology and comprehensive in-house testing supports the company's positioning as a factory-direct supplier for OEM and ODM fastener programs, including custom screws made to drawing and low-MOQ trial orders.
The global cold forming and cold heading fastener market continues to expand as manufacturers seek alternatives to machining for high-volume precision parts. Cold heading offers superior material utilization, faster cycle times, and improved grain flow compared to cutting processes, making it particularly attractive for safety-critical components such as axle shafts and battery fasteners. Within this market, the ability to cold form deep holes and slender shafts remains a differentiating capability held by a relatively small number of specialized manufacturers. Yongmao's invention patent adds formal protection to a technical advantage it has been building since its founding in 1993.
For engineers and procurement teams dealing with difficult fastener specifications, the patent also signals a practical benefit: a supplier that has already solved the tooling and process challenges for ultra-deep-hole slender parts, rather than one that will need to experiment on a first order. The company accepts drawings in STEP or PDF format and provides cold-heading feasibility feedback, including an honest assessment of when machining may be the lower-cost route, before quoting tooling and production.
Changzhou Yongmao Special Fastener Co., Ltd. welcomes inquiries for custom cold headed fasteners, bicycle thru axles, hollow stem bolts, e-bike axles, and EV battery fasteners. For more information, visit www.yonmach.com or contact the company directly.
www.yonmach.com
Changzhou Yongmao Special Fastener Co.,Ltd.
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