In mechanical assemblies, the Hex Head Shoulder Bolt (also known as a shoulder screw or stripper bolt) acts as a structural pivot, alignment guide, and high-tensile connection point. Unlike conventional fasteners, a shoulder bolt is divided into three key anatomical sections: the hex head, an unthreaded shoulder, and the threaded shank. The unthreaded shoulder is machined to ultra-precise tolerances, acting as a dowel or shaft to support rotating components, linkages, pulleys, and gears.
Our ODM (Original Design Manufacturing) service ensures that we produce shoulder bolts with a shoulder diameter tolerance matching g6, h8, or f9 clearances. By optimizing the transition radius between the head, shoulder, and thread runout, our components reduce local stress concentrations. This design prevents mechanical failure under shear loads and high vibration, ensuring reliability in demanding industrial applications.
To assist mechanical designers in selecting appropriate hardware, the table below provides engineering details for Sinsun Hardware's custom ODM Hex Head Shoulder Bolts. We offer customized production covering a wide array of raw material compositions and surface coatings.
| Specification Parameter | Alloy Steel (Class 12.9) | Stainless Steel (304 / 316) | Carbon Steel (Class 8.8 / 10.9) |
|---|---|---|---|
| Tensile Strength | 1,220 MPa minimum | 700 - 850 MPa | 800 - 1,040 MPa |
| Hardness Range | HRC 39 - 44 | HRB 80 - 95 | HRC 22 - 32 |
| Dimensional Tolerance | ±0.02 mm (Precision ground) | ±0.03 mm | ±0.05 mm |
| Surface Roughness (Ra) | ≤ 0.4 μm (Shoulder portion) | ≤ 0.6 μm | ≤ 0.8 μm |
| Corrosion Resistance | Black Oxide / Zinc Flake (240h-720h) | Passivated / Electro-polished (1,000h+) | Hot Dip Galvanized / Zinc Plate (120h-480h) |
| Primary Applications | Heavy Machinery, Tool & Die, Aerospace | Marine, Medical, Food Processing Equipment | Automotive, Construction, Electrical Panels |
At Sinsun Hardware, established in 2006, our competitive edge rests on complete control over the manufacturing lifecycle. We begin by sourcing premium-grade steel rods from industry leader Xing Tai Steel. Our plant processes these rods through in-house spheroidizing annealing and wire drawing, using advanced gas-fired furnaces. This critical step ensures a uniform micro-structure and prevents internal stresses that could compromise the bolt's performance under dynamic loads.
Our manufacturing floor is equipped with German-engineered multi-station cold heading machines and high-precision Taiwanese tooling. This machinery allows us to shape complex fastener profiles, including hex heads and shoulders, in a single run. This process maintains fiber flow continuity in the steel, increasing fatigue limits and thread shear resistance. In 2025, we expanded our thermal treatment facilities by adding four new automated heat treatment lines. This expansion ensures uniform hardness depth (HRC 28-32 for standard fasteners, up to HRC 39-44 for high-tensile alloy steels) and consistent batch production, supporting our global delivery schedules.
Shoulder bolts act as pivoting hinge pins in suspension assemblies and anti-roll bars. Their tight tolerances prevent lateral play, ensuring smooth pivot action and quiet operation.
With the rise of robotic pick-and-place lines, shoulder bolts act as guide shafts for pneumatic pistons and gripper hinges. They deliver durable performance over millions of cycles.
In metal stamping dies, stripper bolts guide heavy-duty springs and return plates. They absorb high-impact shock loads, extending the service life of tooling assemblies.
From our founding in 2006, Sinsun has grown into a leading Chinese fastener manufacturer. Explore our journey of expansion, from establishing exports in 2012 and integrating German technology in 2018, to reaching a 36,000-ton annual output and adding advanced heat treatment lines by 2025.
Sinsun began with a singular focus in 2006: to build a factory dedicated to self-tapping screws. This established our core manufacturing expertise from the ground up.
Established the Export Department, expanding our reach beyond domestic markets to service international industrial clients globally.
Installed four spheroidizing furnaces and in-house wire drawing lines, allowing us to control quality starting from the raw steel material stage.
Introduced German multi-station cold heading machinery, expanding production capabilities to include specialized self-drilling and high-precision fasteners.
Achieved an annual output of 36,000 tons and shipped over 1,100 export containers, establishing ourselves as a reliable high-volume supplier.
Established a dedicated 1,200 m² warehouse for ready stock, supporting rapid shipment times and daily distribution requirements.
Added four automated heat treatment lines, boosting our internal processing capacity and ensuring on-schedule deliveries.
Our development plan focuses on automated quality verification and sustainable manufacturing processes. By integrating multi-camera automated optical inspection (AOI) systems, we target a zero-defect rate for critical tolerances in shoulder bolts. In response to global environmental regulations, we are transitioning our coating lines to chrome-free zinc flake finishes, conforming to RoHS and REACH environmental standards.
Additionally, we are expanding our warehouse space to 12,000 m², which will provide a storage capacity of over 18,000 pallets. Managed by a smart warehouse management system (WMS), this facility will support quick-ship delivery, allowing us to export over 8,500 containers annually to the Middle East, Southeast Asia, South America, and Russia.
Sinsun provides customized packaging options tailored to your logistics needs. Our technical design team offers 3D design previews, customized barcode integration, and logistics support to ensure a smooth, worry-free procurement process.
Sinsun regularly hosts international buyers, technical auditors, and procurement managers for on-site factory tours. We participate in global fastener exhibitions in Europe, South America, and Asia to showcase our products and connect with partners. Our multi-language sales and customer service teams support overseas distributors from initial design validation through container shipment.
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