Products

MALAXY, a leading fastener manufacturer headquartered in Shanghai, supplies premium shoulder screws (also known as shoulder bolts or stripper bolts) — specialized fasteners designed with a smooth, precision-ground cylindrical shoulder between the head and threaded portion. Unlike conventional fully threaded screws, shoulder screws feature three distinct sections: the head (typically hex socket), the shoulder (unthreaded cylindrical shaft of precise diameter), and the threaded end.

When installed, the threaded end anchors into the mating component while the shoulder protrudes beyond the surface, providing a smooth, precision bearing surface around which other components can pivot, slide, or rotate. This unique design eliminates the need for separate shafts, dowels, or spacers, making shoulder screws the preferred fastening solution for precision mechanical assemblies where accurate spacing, alignment, and rotational movement are critical.

Key Distinction from Standard Screws: A standard fully-threaded screw provides only clamping force. A shoulder screw provides clamping force PLUS a precision shaft, pivot point, spacer, and bearing surface — replacing up to four separate components in a single fastener.

Key functional roles of the shoulder: The precision-machined cylindrical shoulder serves multiple critical functions in mechanical assemblies — as a pivot pin (allowing controlled rotation of linkages and arms), as a precision spacer (maintaining exact distance between components), as a bearing surface (enabling low-friction rotational movement of pulleys and bushings), as a guide shaft (linear motion guidance in slider assemblies), and as an alignment dowel (ensuring accurate positioning of mating parts).

Standards & Compliance

MALAXY shoulder screws are manufactured in strict compliance with major international standards, ensuring global compatibility and interchangeability:

Metric Standards

Inch Standards

All products undergo rigorous quality control including dimensional verification, shoulder diameter tolerance inspection, concentricity testing, hardness testing, and mechanical performance validation per applicable standards. MALAXY maintains ISO 9001:2015 quality management certification throughout the manufacturing process.

Commercial Grade vs Precision Grade — Critical Distinction

Shoulder screws are classified into two distinct grades based on tolerance levels and intended applications. Understanding this distinction is critical for proper product selection:

Selection Guide: Choose Commercial Grade for general industrial applications where standard tolerances are sufficient. Choose Precision Grade for applications requiring extreme accuracy — aerospace control systems, medical device assemblies, defense equipment, and high-precision instruments where even minimal deviation can affect performance.

Material Grades & Mechanical Properties

Selection Guide:

• Alloy steel 12.9 — Highest strength; for heavy loads, high-stress, and critical safety applications.

• Stainless steel 316 — Maximum corrosion protection for marine, coastal, and harsh chemical environments.

• Stainless steel 304 — Best balance of corrosion resistance and cost for general outdoor use.

• Stainless steel 416 — Excellent machinability for custom high-volume orders.

• Carbon steel 45H — Cost-effective for indoor industrial use with protective coating.

• Titanium — Lightweight, high-strength, biocompatible; for aerospace and medical applications.

Shoulder Hardness Note: For applications where the shoulder functions as a rotating shaft or bearing surface, surface hardness is critical for wear resistance. Alloy steel grade 12.9 shoulder screws provide optimal hardness for high-friction rotating applications. Stainless steel 410 can be heat-treated to achieve enhanced hardness for demanding wear applications.

Head Styles & Drive Types

MALAXY offers multiple head styles and drive types to suit diverse installation requirements:

The hex socket drive is the industry standard for shoulder screws, providing excellent torque transfer while allowing flush or recessed installation. Hex socket shoulder screws are driven using standard Allen keys (hex wrenches) and are ideal for applications where clearance is limited.

Metric Hex Wrench Reference: M3→2.0mm, M4→2.5mm, M5→3.0mm, M6→4.0mm, M8→5.0mm, M10→6.0mm, M12→8.0mm, M16→10.0mm, M20→12.0mm.

Inch Hex Wrench Reference: #10-24→3/16″, 1/4″-20→1/4″, 5/16″-18→5/16″, 3/8″-16→3/8″, 1/2″-13→1/2″, 5/8″-11→5/8″, 3/4″-10→3/4″.

Surface Finishes

Key Applications

Shoulder screws are fundamental precision components across virtually every industrial sector. Because the shoulders have tight tolerances, these fasteners work exceptionally well in industries where precision is essential:

1. Injection Molds & Die Tooling (Stripper Bolts)

The most common application globally. Shoulder screws secure stripper plates in injection molding machines, allowing the plate to move precisely along the shoulder axis while maintaining alignment. Also used in stamping dies, punch press tooling, and fixture assemblies. The name “stripper bolt” originates directly from this application.

2. Automotive Manufacturing & Pivot Assemblies

Suspension system pivot points, transmission linkages, brake caliper guide pins, engine components, steering mechanisms, and door hinge assemblies. Alloy steel grade 12.9 shoulder screws specified for high-stress safety-critical applications. Stainless steel versions for underhood and exterior applications requiring corrosion resistance.

3. Aerospace & Defense Systems

Aircraft control system linkages, actuator assemblies, landing gear components, flap and slat mechanisms, interior cabin structures, and defense equipment. Precision-grade shoulder screws are mandatory for these applications, with tight tolerance requirements and strict material traceability. Common materials include alloy steel 12.9 and titanium Grade 5 for weight-sensitive aerospace applications.

4. Industrial Machinery & Automation

Linear motion guides, cam follower shafts, conveyor system rollers, indexing tables, packaging machinery, printing presses, and general machine building. Shoulder screws function as precision shafts and pivot points in automated production equipment.

5. Robotics & Automation Systems

Robotic arm joints, servo actuator linkages, end-of-arm tooling (EOAT), precision conveyor systems, and pick-and-place mechanisms. Double-shoulder bolts are often specified for complex robotic assemblies requiring multiple bearing surfaces.

6. Pulleys, Gears & Power Transmission

Securing pulleys, gears, sprockets, and timing belt pulleys onto shafts. The shoulder provides a precision bearing surface for bushings and bearings while the threaded end anchors the assembly. This is one of the most common power transmission applications.

7. Medical Devices

Surgical robotics, diagnostic equipment, hospital beds and furniture, laboratory instruments, imaging equipment, and dental chairs. Stainless steel 304 and 316 grades specified for biocompatibility and sterilization resistance. Precision-grade shoulder screws ensure accurate positioning in life-critical medical applications.

8. Electronics & Semiconductor Manufacturing

Semiconductor handling equipment, PCB assembly fixtures, precision alignment stages, and cleanroom-compatible equipment. Stainless steel 304 preferred for corrosion resistance in clean environments.

9. Marine & Offshore Equipment

Deck hardware, navigation equipment, pump assemblies, offshore platform components, and marine engines. Stainless steel 316 shoulder screws provide exceptional resistance to saltwater corrosion for coastal and offshore applications.

10. Consumer Products & Furniture

Bicycle pivot points (suspension forks, brake linkages, derailleur mounts), exercise equipment joints, office chair mechanisms, folding furniture linkages, and appliance assemblies.

Additional applications include: Bearings, bushings, engines, vacuum systems (vented precision shoulder screws allow faster pump-down), motion guiding systems, precision spacing assemblies, and general machinery support.

Key Features

1. Precision-Ground Cylindrical Shoulder – Smooth, unthreaded section between head and threads, ground to tight tolerances for use as bearing surface, pivot point, or precision spacer. Shoulder diameter tolerance ranges from commercial grade ±0.005″ to precision grade +0.000/-0.001″.

2. Three-Section Design – Head (hex socket) + shoulder (smooth bearing surface) + threaded end (anchoring threads). Each section optimized for a specific mechanical function.

3. Hex Socket Drive – Internal hexagonal recess driven with standard Allen keys; provides excellent torque transfer and allows flush installation in confined spaces where external wrench access is limited.

4. Commercial & Precision Grades – Commercial grade (ASME B18.3, shoulder tolerance ±0.005″) for general industrial applications; precision grade (tight tolerance +0.000/-0.001″, thread class 2A) for aerospace, medical, and defense applications requiring extreme accuracy.

5. Multiple Material Options – Alloy steel grade 12.9 (highest strength), carbon steel grade 45H (cost-effective), stainless steel 304/316 (corrosion-resistant), stainless steel 416 (free-machining), stainless steel 410 (heat-treatable hardness), brass (conductivity), and titanium Grade 5 (lightweight high-strength).

6. ISO 7379 & ASME B18.3 Compliance – Manufactured to the world‘s most widely adopted shoulder screw standards, ensuring global compatibility and interchangeability. Metric range: shoulder diameters 4–25mm, thread M3–M20. Inch range: shoulder diameters 1/4″–2″, threads #10 through 3/4″.

7. Multiple Head Variants – Standard hex socket, knurled head (tool-free adjustment), low/ultra low head (space-constrained assemblies), slotted head, Torx, and tamper-resistant drives.

8. Specialty Variants – Double-shoulder bolts (two bearing surfaces for complex assemblies), self-locking (nylon patch for vibration resistance), knurled shoulder (enhanced grip in soft materials), vented shoulder (for vacuum systems).

9. Metric & Inch Sizes – Full range of metric sizes (M3–M20 threads, 4–25mm shoulder diameters) and inch sizes (#10–3/4″ threads, 1/4″–2″ shoulder diameters). Both coarse and fine thread pitches available.

10. Custom Manufacturing – Non-standard shoulder lengths and diameters, special material grades, custom head configurations, proprietary coatings, and OEM packaging available upon request.

Customization & OEM/ODM Services

As a leading fastener manufacturer with decades of industry expertise and a strategic headquarters in Shanghai, MALAXY offers comprehensive customization and OEM/ODM services for shoulder screws:

• Non-standard shoulder lengths beyond ISO 7379 standard ranges

• Custom shoulder diameters and thread combinations

• Special material grades (Inconel, Monel, titanium, custom alloy compositions)

• Proprietary surface treatments and coating systems

• Custom head configurations and drive types

• Double-shoulder bolt designs for complex assemblies

• Self-locking features (nylon patch, nylon pellet, deformed threads)

• Tamper-resistant drive configurations for security applications

• Vented shoulder designs for vacuum system applications

• Logo marking and custom packaging solutions

Our in-house engineering team supports OEM and ODM projects from prototype development to mass production, with strict adherence to ISO 9001:2015 quality management systems. MALAXY maintains full traceability from raw material sourcing to finished product, providing mill test reports (MTRs), dimensional inspection reports, concentricity test reports, hardness test reports, third-party lab testing, and certification upon request. Short lead times and competitive pricing through direct manufacturing with no middlemen.

Why Choose MALAXY?

• Headquarters in Shanghai – Strategic location with efficient global logistics, direct port access, and strong English-speaking export support teams.

• Industry-leading reputation – Recognized as a top-tier fastener supplier across Asia, Europe, North America, the Middle East, and Latin America.

• Comprehensive quality control – Full inspection from raw material to finished product, including dimensional verification, shoulder diameter tolerance inspection, concentricity testing (critical for proper alignment), thread gauge inspection, hardness testing (case and core), and mechanical performance validation per applicable standards.

• Global standard compliance – Full certification to ISO 7379, DIN 7979, ASME B18.3, and ASME B18.3.3; ISO 9001:2015 certified; RoHS/REACH compliance for regulated markets; material certifications and test reports available upon request.

• Competitive pricing – Direct manufacturing with integrated production lines, no middlemen, offering cost-effective solutions for both standard and custom requirements.

• Global export experience – Serving clients across North America, Europe, Southeast Asia, the Middle East, Latin America, and Africa with proven track record in B2B industrial fastener supply.

• Technical support – In-house engineering team available for application consultation, commercial vs precision grade selection guidance, material selection, shoulder length and diameter specification, and custom design development.

• Growing market demand – The global shoulder screw market is experiencing steady growth, driven by increasing demand for precision fasteners across aerospace, automotive, and industrial machinery sectors. As a leading supplier, MALAXY is well-positioned to meet this growing demand.

Contact MALAXY today for quotes, technical specifications, custom manufacturing inquiries, sample requests, or engineering consultation.