Product Overview
The Extended Socket Head Cap Screw is a precision-engineered, non-standard length variant of the classic Socket Head Cap Screw. Characterized by its significantly extended shank length, it is specifically designed to accommodate applications requiring deep penetration through thick materials, assemblies with multiple stacked components, or where standard bolt lengths are insufficient. It retains all the performance advantages of the internal hex drive—high torque capacity, compact head profile, and clean aesthetics—while solving unique spacing and fastening depth challenges.
Key Advantages
Solves Length Constraints: Provides a ready-made solution for assemblies where the grip length exceeds the range of standard stocked fasteners, eliminating the need for makeshift spacers or stacked washers.
Optimized Strength-to-Length Ratio: Manufactured from high-strength alloy steel and heat-treated, maintaining consistent mechanical properties along its entire length.
Full Thread Engagement: Available in fully threaded versions to maximize adjustability and load distribution, or with a designed unthreaded shoulder for precise bearing applications.
Streamlined Design: A single, long fastener is often more reliable and easier to install than multiple joined components, improving assembly integrity.
Manufacturing Precision: Produced via cold-heading where possible to preserve superior grain flow and strength, even in extended dimensions.
Material Specifications & Strength Grades
| Material Standard | Grade / Class | Minimum Tensile Strength | Core Hardness (HRC) | Characteristics |
|---|---|---|---|---|
| Alloy Steel | ASTM A574 (12.9) | 1220 MPa | 39-44 | Premium Grade. Highest strength for critical, high-stress applications. |
| Alloy Steel | ASTM A574 (10.9) | 1040 MPa | 33-39 | High Grade. Excellent strength for demanding mechanical uses. |
| Stainless Steel | ASTM F837 (A2-70 / A4-80) | 700 MPa (A2-70) / 800 MPa (A4-80) | – | Corrosion-resistant grades for harsh environments. A4-80 offers superior chloride resistance. |
Product Series & Specifications
Standard: Based on ISO 4762 / ASME B18.3 for head and drive dimensions. The “extended” attribute refers to custom lengths beyond standard catalog offerings.
Drive: Internal Hex Socket, compliant with ISO 10664.
Common Size Range:
Thread Diameters: M3 to M20 (Metric); #6 to 3/4″ (Imperial).
Extended Lengths: Typically available from 50mm up to 500mm+ (2″ to 20″+) depending on diameter. Length-to-Diameter (L/D) ratios are carefully considered for manufacturability and straightness.
Thread Options: Fully threaded (most common for extended screws) or with a specified grip length (unthreaded shoulder).
Available Surface Finishes
| Finish Type | Specification / Process | Key Benefit for Extended Length |
|---|---|---|
| Black Oxide | MIL-DTL-13924 | Uniform coating on long dimensions, mild corrosion resistance, reduces glare. |
| Zinc Plated (Trivalent/Blue) | ASTM B633 | Good overall protection. Plating thickness consistency along the entire length is controlled. |
| Electroless Nickel (ENP) | ASTM B656 | Excellent corrosion and wear resistance with a uniform deposit, ideal for precision components. |
| Geomet® / Zinc-Flake Coating | Proprietary | Premium Choice. Provides exceptional corrosion resistance (>500 hrs salt spray) and a consistent, lubricious surface for accurate torque-tension relationship. |
| Passivation (Stainless Steel) | ASTM A967 | Enhances the natural corrosion resistance of stainless steel fasteners. |
Typical Applications
Heavy Machinery & Presses: Securing thick die plates, fixtures, and structural members.
Mold & Tool Making: Clamping large mold halves and securing ejector plates in deep molds.
Energy Sector: Assembly of wind turbine components, generator housings, and oil & gas drilling equipment.
Marine & Transportation: Fastening in hull structures, chassis components, and large fabricated assemblies.
Semiconductor & Large Equipment: Securing panels and internal assemblies on wafer handling tools and large-scale industrial systems.
Quality Assurance
Dimensional Verification: Critical inspection for straightness (permitted bow is checked over the full length), thread accuracy along the entire threaded section, and head dimensions.
Mechanical Testing: Tensile and hardness testing is performed on sample batches to ensure grade compliance throughout the fastener’s cross-section.
Material Traceability: Full traceability from raw material to finished product is maintained, with Mill Test Certificates (MTCs) available.
Process Standard: Manufacturing adheres to a certified ISO 9001:2015 quality management system, with specific controls for long-part machining and handling.
Manufacturing Expertise
Producing consistent, high-strength extended length screws requires specialized equipment and process knowledge. Hebei Wohe Fastener Manufacturing Co., Ltd. possesses the capability to cold-head longer blanks where feasible and employs precision secondary machining and thread-rolling techniques for the largest dimensions. Our experience ensures that these long fasteners meet strict straightness and strength requirements, providing reliable performance in our clients’ most challenging custom assemblies. We work closely with engineers to determine the optimal manufacturing route for specific L/D ratios and quantities.
Technical & Commercial Support:
Design Consultation: We provide engineering support for optimal length, thread engagement, and grade selection.
Samples: Prototype samples are available for fit and function testing prior to production orders.
Customization: We specialize in non-standard diameters, lengths, threads, and proprietary markings. Ground shanks for precise bearing fits are also available.
MOQ: Minimum order quantities are highly flexible for extended screws, often starting from 100 pieces depending on specification complexity.
Lead Time: Typically 25-35 working days for custom extended lengths, subject to current capacity and order specifics.
Note: For very long screws (high L/D ratio), proper handling and storage to prevent bending are essential. In application, consider the potential for column buckling under compressive loads and ensure adequate support. Always verify that the tapped hole depth or nut engagement is sufficient for the applied load. Specifications subject to change without notice.
