Copper Pan head SEMS Screws, Copper SEMS Screws, Silicon Bronze SEMS Screws, Hex Head SEMS Screws Bolts
SEMS Screws – Premium Pre-Assembled Washers and Screws
Price: US$ 12.90/kilogram
We are one of the leading manufacturers and exporters of Cold forged and cold headed Copper SEMS Screws and Silicon Bronze SEMS Screws from India. We have been supplying SEMS Screws to the world market for many decades. Our manufacturing facility combines cutting-edge technology with traditional craftsmanship to deliver superior SEMS screws that meet international standards. SEMS (a term derived from “Screw and wasHER asSEMblieS”) provide exceptional efficiency in assembly operations by eliminating the need for separate handling of washers. The pre-assembled washer cannot fall off during installation, yet can rotate freely on the screw, enabling optimal seating during application. Our SEMS screws are engineered to provide consistent performance across diverse industrial applications, from automotive assembly to electronics manufacturing.
Overview
Copper SEMS screws and Silicon Bronze SEMS screws feature permanently pre-assembled fasteners with washers that cannot be removed without destroying the assembly. The washer is captured on the screw between the head and a series of splines or knurls formed on the screw shank. This ingenious design eliminates separate washer handling, prevents washer loss, reduces assembly time by up to 30%, and ensures consistent load distribution. Our precision manufacturing ensures smooth washer rotation while maintaining secure placement on the fastener. Our SEMS Screws in Copper and Silicon Bronze as well as Brass SEMS Screws and fasteners are exported worldwide.
The SEMS screw concept represents a significant advancement in fastener technology, offering substantial time and cost savings for assembly operations while enhancing the reliability of fastened joints. We offer an extensive range of SEMS screws in various materials, head styles, and dimensions to meet diverse application requirements across multiple industries.
Material Selection Guide
| Material | Corrosion Resistance | Strength | Electrical Conductivity | Typical Applications |
|---|---|---|---|---|
| Copper | Excellent | Moderate | Excellent | Electrical connections, marine environments |
| Silicon Bronze | Outstanding | High | Good | Marine hardware, historical restoration |
| Carbon Steel | Low-Moderate | High | Low | General purpose, indoor applications |
| Stainless Steel | Excellent | High | Low | Food processing, outdoor exposure |
| Brass | Good | Moderate | Good | Decorative hardware, non-sparking applications |
| Aluminum | Good | Low-Moderate | Good | Lightweight applications, electronics |
Copper SEMS Screws
Copper SEMS Screws represent the pinnacle of electrical connectivity and corrosion resistance in fastener technology. Manufactured from high-purity Copper alloys (C11000, C12200), these screws offer exceptional electrical conductivity while providing adequate strength for most assembly applications. The naturally forming oxide layer provides additional protection in humid environments, making these fasteners ideal for long-term installations in challenging conditions.
Our Copper SEMS feature precision-machined threads that maintain their integrity even after multiple removal and reinstallation cycles. The permanently attached washers are typically made of compatible materials such as phosphor Bronze or beryllium Copper to prevent galvanic corrosion. These screws excel in applications requiring excellent electrical conductivity combined with good corrosion resistance, including electrical panels, grounding systems, and marine electrical connections.
Material Standards:
- ASTM B152/B152M (USA)
- EN 13601 (Europe)
- IS 191 (India)
- GB/T 5231 (China)
- JIS H3250 (Japan)
Copper SEMS provide exceptional performance in high-moisture environments and are particularly valued in applications where electrical conductivity is paramount. The natural antimicrobial properties of Copper also make these fasteners suitable for medical equipment assembly where hygiene is critical.
Silicon Bronze SEMS Screws
Silicon Bronze SEMS Screws represent our premium offering for applications demanding extraordinary corrosion resistance combined with significant mechanical strength. Composed primarily of Copper with silicon additions (typically C65500 or C66100 alloys), these fasteners deliver exceptional performance in marine environments, chemical processing equipment, and historical restoration projects.
The Silicon Bronze material provides a unique combination of attributes: excellent resistance to saltwater corrosion, high tensile strength (comparable to many steel alloys), and appealing golden-bronze aesthetics. The silicon content enhances the alloy’s strength while maintaining good electrical conductivity and non-magnetic properties. Our manufacturing process ensures precise thread formations and consistent mechanical properties throughout each production batch.
Material Standards:
- ASTM B98/B98M (USA)
- EN 12163 (Europe)
- IS 7965 (India)
- GB/T 5231 (China)
- JIS H3250 (Japan)
Silicon Bronze SEMS Screws are frequently specified for marine hardware, historical building restoration, and outdoor architectural applications where both aesthetic appeal and long-term performance are required. The pre-assembled washer design eliminates the need for separate washer handling in challenging installation environments such as shipyards and offshore platforms, substantially reducing assembly time and the risk of component loss.
Pan Head SEMS Screws (Copper and Silicon Bronze)
Pan Head SEMS Screws feature a distinctive head design with a flat top surface and rounded edges, providing an optimal balance between aesthetic appeal and functional performance. The pan head’s large bearing surface distributes clamping force effectively across the assembled components, reducing the risk of damage to soft or thin materials. This head style accommodates a variety of drive types including Phillips, slotted, combination, and Torx, enabling compatibility with numerous installation tools.
Our Pan Head SEMS are manufactured in various materials including Stainless Steel, Carbon Steel, Brass, Copper, Silicon Bronze, and Aluminum to suit specific application requirements. The pan head’s versatile design makes these fasteners ideal for applications where a low-profile appearance is desired without sacrificing clamping effectiveness. Common applications include electronics assembly, appliance manufacturing, automotive interior components, and general machinery construction.
Dimensional Specifications:
| Nominal Size | Head Diameter (mm) | Head Height (mm) | Washer OD (mm) | Washer Thickness (mm) |
|---|---|---|---|---|
| M3 | 5.6 | 1.8 | 7.0 | 0.5 |
| M4 | 7.0 | 2.2 | 9.0 | 0.8 |
| M5 | 8.5 | 2.8 | 10.0 | 1.0 |
| M6 | 10.0 | 3.3 | 12.0 | 1.6 |
| M8 | 13.0 | 4.0 | 16.0 | 1.6 |
| M10 | 16.0 | 5.0 | 20.0 | 2.0 |
| 1/4″ | 11.1 | 3.5 | 12.7 | 1.6 |
| 5/16″ | 13.5 | 4.0 | 15.9 | 1.6 |
| 3/8″ | 16.7 | 4.7 | 19.1 | 2.0 |
Pan Head SEMS provide excellent vibration resistance when properly torqued, making them ideal for applications subject to movement and vibration. The pre-assembled washer ensures consistent load distribution while simplifying the installation process in production environments.
Copper Hex Head SEMS Screws and Silicon Bronze Hex Head SEMS Screws
Hex Head SEMS Screws combine the convenience of pre-assembled washers with the substantial torque capabilities of hexagonal heads. The hex head design allows for installation using standard wrenches, sockets, and power tools, making these fasteners ideal for applications requiring higher installation torque values. The six-sided head provides positive engagement with installation tools, reducing the risk of cam-out and head damage during assembly operations.
Our Hex Head SEMS are manufactured to exacting tolerances across head dimensions, thread pitch, and washer specifications. Available in a wide range of materials including Carbon Steel (grade 5 and 8.8), Stainless Steel (304/316), Copper alloys, and Silicon Bronze, these versatile fasteners accommodate diverse application requirements from heavy machinery assembly to outdoor structural connections.
Dimensional Specifications:
| Nominal Size | Head Width Across Flats (mm) | Head Height (mm) | Washer OD (mm) | Washer Thickness (mm) |
|---|---|---|---|---|
| M5 | 8.0 | 3.5 | 10.0 | 1.0 |
| M6 | 10.0 | 4.0 | 12.0 | 1.6 |
| M8 | 13.0 | 5.3 | 16.0 | 1.6 |
| M10 | 17.0 | 6.4 | 20.0 | 2.0 |
| M12 | 19.0 | 7.5 | 24.0 | 2.5 |
| 1/4″ | 11.1 | 4.0 | 12.7 | 1.6 |
| 5/16″ | 12.7 | 5.0 | 15.9 | 1.6 |
| 3/8″ | 14.3 | 5.7 | 19.1 | 2.0 |
| 1/2″ | 19.1 | 7.9 | 25.4 | 2.5 |
Hex Head SEMS excel in applications requiring significant clamping force, including automotive chassis assembly, industrial equipment manufacturing, and construction framing. The integrated washer design ensures proper load distribution while eliminating the risk of washer loss during transportation and installation.
Manufacturing Process for Copper SEMS Screws and Silicon Bronze SEMS Screws
Our SEMS screws undergo a sophisticated multi-stage manufacturing process that ensures consistent quality and performance:
- Material Selection: Premium raw materials are sourced from certified suppliers and undergo rigorous testing for chemical composition and mechanical properties.
- Cold Heading: The screw blanks are formed using high-precision cold heading machines that shape the head and part of the screw body without heating, preserving the material’s strength characteristics.
- Thread Rolling: Threads are formed through a rolling process rather than cutting, which compresses the material to create stronger threads with better fatigue resistance and smoother finish.
- Washer Assembly: Specialized equipment positions the washer on the screw shank before creating splines or knurls that permanently capture the washer while allowing free rotation.
- Heat Treatment: When applicable, screws undergo precision heat treatment to achieve specified hardness and strength properties.
- Surface Finishing: Depending on material and application requirements, screws receive appropriate surface treatments such as plating, passivation, or coating.
- Quality Control: Automated optical inspection systems verify dimensional accuracy, thread quality, and washer assembly integrity, while statistical process control monitors manufacturing consistency.
Key Manufacturing Equipment:
- National Machinery Cold Headers (Multi-station)
- Hartford Thread Rolling Machines
- Nakashimada Engineering SEMS Formers
- Sacma Combined Forming Machines
- Mitsubishi Materials Machining Centers
Finishes and Coatings
| Finish Type | Corrosion Resistance | Appearance | Suitable Materials | Applications |
|---|---|---|---|---|
| Plain (Mill Finish) | Material Dependent | Natural | All | Non-critical aesthetic applications |
| Zinc Plating | 96-240 hours (salt spray) | Silver/Blue | Carbon Steel | Indoor/moderate environment |
| Yellow Zinc | 96-240 hours (salt spray) | Gold | Carbon Steel | Decorative, moderate corrosion |
| Black Oxide | Minimal | Black | Carbon Steel, Stainless | Appearance, light oil retention |
| Hot-Dip Galvanizing | 1000+ hours (salt spray) | Dull Gray | Carbon Steel | Outdoor, severe environments |
| Nickel Plating | 400-600 hours (salt spray) | Silver/White | Carbon Steel, Brass | Decorative, good corrosion resistance |
| Chrome Plating | 500-1000 hours (salt spray) | Bright Silver | Carbon Steel, Stainless | High wear, decorative |
| Passivation | Enhances natural resistance | Unchanged | Stainless Steel | Optimizes corrosion resistance |
| Anodizing | 650-1000 hours (salt spray) | Various colors | Aluminum | Decorative, excellent corrosion resistance |
Industries and Applications for Copper SEMS Screws and Silicon Bronze SEMS Screws
Our SEMS screws serve diverse industries with specific material and head style combinations:
Automotive Manufacturing:
- Engine component assembly
- Interior trim installation
- Chassis and frame construction
- Electrical system mounting
Electronics Assembly:
- PCB standoff mounting
- Chassis construction
- Terminal connections
- Copper SEMS for grounding applications
Marine Equipment:
- Silicon Bronze SEMS for deck hardware
- Propulsion system assembly
- Electrical junction boxes
- Navigation equipment mounting
Construction and Infrastructure:
- HVAC equipment assembly
- Electrical panel installation
- Sign and fixture mounting
- Solar panel frame assembly
Industrial Equipment:
- Control panel assembly
- Motor and pump mounting
- Conveyor system construction
- Machine guards and covers
Medical Equipment:
- Non-magnetic applications (MRI equipment)
- Diagnostic equipment assembly
- Laboratory instrument construction
- Equipment housing assembly
Dimensional Tolerances
Our manufacturing processes maintain tight tolerances across all critical dimensions:
| Dimension | Tolerance Range |
|---|---|
| Thread Major Diameter | ±0.13mm (±0.005″) |
| Thread Pitch | ±0.025mm (±0.001″) |
| Head Dimensions | ±0.13mm (±0.005″) |
| Washer Thickness | ±0.08mm (±0.003″) |
| Washer Outside Diameter | ±0.15mm (±0.006″) |
| Overall Length | ±0.40mm (±0.015″) for lengths up to 50mm |
| ±0.80mm (±0.030″) for lengths over 50mm | |
| Straightness | 0.4mm (0.015″) maximum deviation per 25mm (1″) of length |
Performance Metrics
| Performance Attribute | Testing Standard | Typical Values |
|---|---|---|
| Tensile Strength | ISO 898-1, ASTM F606 | Material dependent: 380-1200 MPa |
| Torque-Tension Relationship | ISO 16047 | Varies by size, material and finish |
| Hydrogen Embrittlement | ASTM F606, ISO 15330 | No failure after 200 hours (plated screws) |
| Corrosion Resistance | ASTM B117, ISO 9227 | Material and finish dependent |
| Fatigue Strength | ISO 3800 | Material dependent: typically 50-60% of tensile strength |
| Vibration Resistance | DIN 65151, NASM 1312-7 | No loosening through 30,000 cycles |
Why Choose Our SEMS Screws?
Superior Manufacturing Expertise: With three decades of global experience, our production processes have been refined to ensure consistent quality and performance across all product lines. Our ISO 9001:2015 certified facility employs state-of-the-art equipment and rigorous quality control measures.
Material Excellence: We use only premium-grade raw materials that meet or exceed international standards. Our material sourcing includes thorough documentation and traceability to ensure consistent performance batch after batch.
Customization Capabilities: Unlike many competitors, we offer extensive customization options including non-standard dimensions, specialized coatings, custom packaging, and unique head markings. Our engineering team works directly with customers to develop fastener solutions for specific applications.
Comprehensive Testing: Each production batch undergoes extensive testing for dimensional accuracy, material properties, and performance characteristics. We maintain detailed records of all test results for complete traceability.
Global Supply Chain Experience: Our established logistics network ensures timely delivery to customers worldwide, with extensive experience navigating international shipping requirements and documentation.
Technical Support: Our team of fastener engineers provides expert application assistance, material selection guidance, and installation recommendations to optimize performance in your specific application.
Customer Communication: We pride ourselves on responsive communication, with dedicated account managers providing regular updates on production status, shipping information, and order fulfillment.
Turnaround Time and Ordering
Standard catalog items are typically shipped within 2-3 weeks of order confirmation. Custom or large-volume orders generally require 4-6 weeks lead time, depending on specifications and current production schedules. Rush services are available for time-critical applications at a premium charge.
Our minimum order quantities vary by product type:
- Standard sizes and materials: 5,000 pieces
- Custom configurations: 10,000 pieces
- Special materials or finishes: 15,000 pieces
Volume discounts are available for orders exceeding 50,000 pieces, with additional price breaks at higher quantities.
Packaging and Shipping
Our SEMS screws are packaged in various configurations to suit different handling requirements:
Standard Packaging:
- Bulk cartons with polyethylene inner bags (25kg maximum)
- Small parts bags with specified quantities
- Plastic tubes for precision components
- Vacuum-sealed moisture barrier bags for corrosion-sensitive materials
Custom Packaging Options:
- Customer-branded labels and packaging
- Bar-coded identification for inventory management
- Custom bin quantities for production line integration
- Specialized containers for automated feed systems
Shipping Methods:
- International air freight for urgent shipments
- Sea freight for economical bulk shipping
- Courier services for sample and small quantity orders
- Consolidated shipping options for multi-item orders
All packaging includes appropriate protective measures to prevent damage during transit, including moisture barriers, impact protection, and secure sealing.
SEMS Screws Thread Specifications and Standard Lengths
We are one of the leading manufacturers and exporters of SEMS Screws from India. We have been supplying SEMS Screws to the world market for many decades. Our extensive manufacturing capabilities allow us to produce a wide range of thread sizes and configurations to meet diverse application requirements across multiple industries. Whether you need metric or imperial threads, fine or coarse pitches, or custom thread lengths, our state-of-the-art production facility can deliver precision-manufactured SEMS screws to your exact specifications.
Understanding Thread Designations
Before examining the detailed thread tables, it’s helpful to understand the nomenclature used for different thread systems:
Metric Thread Designation: M[diameter]x[pitch]
- Example: M6x1.0 indicates a 6mm nominal diameter with 1.0mm pitch between threads
UNC (Unified National Coarse) Designation: [diameter]-[threads per inch] UNC
- Example: 1/4-20 UNC indicates a 1/4 inch diameter with 20 threads per inch
UNF (Unified National Fine) Designation: [diameter]-[threads per inch] UNF
- Example: 1/4-28 UNF indicates a 1/4 inch diameter with 28 threads per inch
Comprehensive Thread Size Chart
Our SEMS screw manufacturing capabilities encompass an extensive range of thread sizes in both metric and imperial standards. The following tables outline our standard offerings, though custom threading options are available upon request.
Metric Thread Specifications
| Thread Size | Pitch (mm) | Standard | Head Types Available | Common Applications |
|---|---|---|---|---|
| M2 | 0.4 | ISO 724 | Pan, Round, Fillister | Electronics, Precision Instruments |
| M2.5 | 0.45 | ISO 724 | Pan, Round, Fillister | Electronics, Small Appliances |
| M3 | 0.5 | ISO 724 | Pan, Round, Fillister, Hex | Electronics, Automotive, General Assembly |
| M3.5 | 0.6 | ISO 724 | Pan, Round, Fillister | Light Machinery, Consumer Products |
| M4 | 0.7 | ISO 724 | Pan, Round, Fillister, Hex | General Machinery, Automotive, Electronics |
| M5 | 0.8 | ISO 724 | Pan, Round, Fillister, Hex | Automotive, Equipment Assembly |
| M6 | 1.0 | ISO 724 | Pan, Round, Fillister, Hex | Automotive, Industrial Equipment |
| M8 | 1.25 | ISO 724 | Hex, Pan, Socket | Heavy Machinery, Structural Assembly |
| M10 | 1.5 | ISO 724 | Hex, Socket | Heavy Machinery, Construction Equipment |
| M12 | 1.75 | ISO 724 | Hex, Socket | Heavy Machinery, Structural Steel |
| M14 | 2.0 | ISO 724 | Hex | Industrial Equipment, Heavy Machinery |
| M16 | 2.0 | ISO 724 | Hex | Heavy Equipment, Structural Assembly |
Fine Metric Thread Specifications
| Thread Size | Pitch (mm) | Standard | Head Types Available | Common Applications |
|---|---|---|---|---|
| M3 | 0.35 | ISO 724 | Pan, Round, Fillister | Precision Equipment, Instruments |
| M4 | 0.5 | ISO 724 | Pan, Round, Fillister, Hex | Precision Machinery, Aviation |
| M5 | 0.5 | ISO 724 | Pan, Round, Fillister, Hex | Automotive, Precision Equipment |
| M6 | 0.75 | ISO 724 | Pan, Round, Fillister, Hex | Automotive, Hydraulic Systems |
| M8 | 1.0 | ISO 724 | Hex, Pan, Socket | Automotive, High-Stress Applications |
| M10 | 1.25 | ISO 724 | Hex, Socket | Automotive, Precision Machinery |
| M12 | 1.5 | ISO 724 | Hex, Socket | High-Stress Joints, Automotive |
| M14 | 1.5 | ISO 724 | Hex | Automotive, Hydraulic Components |
| M16 | 1.5 | ISO 724 | Hex | High-Stress Applications |
UNC Thread Specifications
| Thread Size | TPI | Standard | Head Types Available | Common Applications |
|---|---|---|---|---|
| #4 | 40 | ASME B1.1 | Pan, Round, Fillister | Electronics, Small Assemblies |
| #6 | 32 | ASME B1.1 | Pan, Round, Fillister | Electronics, Appliances |
| #8 | 32 | ASME B1.1 | Pan, Round, Fillister | General Assembly, Consumer Products |
| #10 | 24 | ASME B1.1 | Pan, Round, Fillister, Hex | General Purpose, Light Machinery |
| 1/4″ | 20 | ASME B1.1 | Hex, Pan, Round, Fillister | Automotive, General Machinery |
| 5/16″ | 18 | ASME B1.1 | Hex, Pan | Machinery, Equipment Assembly |
| 3/8″ | 16 | ASME B1.1 | Hex, Socket | Heavy Machinery, Structural Assembly |
| 7/16″ | 14 | ASME B1.1 | Hex | Heavy Equipment, Structural Assembly |
| 1/2″ | 13 | ASME B1.1 | Hex | Industrial Equipment, Heavy Machinery |
| 5/8″ | 11 | ASME B1.1 | Hex | Heavy Equipment, Structural Steel |
| 3/4″ | 10 | ASME B1.1 | Hex | Heavy Machinery, Structural Applications |
UNF Thread Specifications
| Thread Size | TPI | Standard | Head Types Available | Common Applications |
|---|---|---|---|---|
| #4 | 48 | ASME B1.1 | Pan, Round, Fillister | Precision Instruments, Electronics |
| #6 | 40 | ASME B1.1 | Pan, Round, Fillister | Electronics, Instruments |
| #8 | 36 | ASME B1.1 | Pan, Round, Fillister | Electronics, Precision Equipment |
| #10 | 32 | ASME B1.1 | Pan, Round, Fillister | Precision Equipment, Automotive |
| 1/4″ | 28 | ASME B1.1 | Hex, Pan, Round, Fillister | Automotive, Aviation |
| 5/16″ | 24 | ASME B1.1 | Hex, Pan | Automotive, High-Stress Applications |
| 3/8″ | 24 | ASME B1.1 | Hex, Socket | Automotive, High-Vibration Equipment |
| 7/16″ | 20 | ASME B1.1 | Hex | Automotive, Precision Machinery |
| 1/2″ | 20 | ASME B1.1 | Hex | Aviation, High-Performance Equipment |
| 5/8″ | 18 | ASME B1.1 | Hex | Aerospace, High-Stress Applications |
| 3/4″ | 16 | ASME B1.1 | Hex | Aerospace, Critical Assemblies |
Standard Length Ranges for SEMS Screws
Our SEMS screws are available in a wide range of standard lengths to accommodate various application requirements. Custom lengths can be manufactured upon request with appropriate minimum order quantities.
Metric SEMS Length Ranges
| Thread Size | Standard Length Range (mm) | Typical Length Increments (mm) |
|---|---|---|
| M2 | 3 – 20 | 1mm from 3-10mm; 2mm from 10-20mm |
| M2.5 | 4 – 25 | 1mm from 4-10mm; 2mm from 10-25mm |
| M3 | 5 – 30 | 1mm from 5-10mm; 2mm from 10-30mm |
| M3.5 | 6 – 35 | 1mm from 6-10mm; 2mm from 10-35mm |
| M4 | 6 – 40 | 1mm from 6-10mm; 2mm from 10-20mm; 5mm from 20-40mm |
| M5 | 8 – 50 | 1mm from 8-10mm; 2mm from 10-20mm; 5mm from 20-50mm |
| M6 | 10 – 60 | 2mm from 10-20mm; 5mm from 20-60mm |
| M8 | 12 – 80 | 2mm from 12-20mm; 5mm from 20-60mm; 10mm from 60-80mm |
| M10 | 16 – 100 | 2mm from 16-20mm; 5mm from 20-60mm; 10mm from 60-100mm |
| M12 | 20 – 120 | 5mm from 20-60mm; 10mm from 60-120mm |
| M14 | 25 – 140 | 5mm from 25-60mm; 10mm from 60-140mm |
| M16 | 30 – 160 | 5mm from 30-60mm; 10mm from 60-160mm |
Imperial SEMS Length Ranges
| Thread Size | Standard Length Range (inches) | Typical Length Increments (inches) |
|---|---|---|
| #4 | 1/8 – 3/4 | 1/16″ from 1/8-1/2″; 1/8″ from 1/2-3/4″ |
| #6 | 1/8 – 1 | 1/16″ from 1/8-1/2″; 1/8″ from 1/2-1″ |
| #8 | 3/16 – 1-1/4 | 1/16″ from 3/16-1/2″; 1/8″ from 1/2-1″; 1/4″ from 1-1-1/4″ |
| #10 | 1/4 – 1-1/2 | 1/16″ from 1/4-1/2″; 1/8″ from 1/2-1″; 1/4″ from 1-1-1/2″ |
| 1/4″ | 3/8 – 2 | 1/16″ from 3/8-1/2″; 1/8″ from 1/2-1″; 1/4″ from 1-2″ |
| 5/16″ | 1/2 – 2-1/2 | 1/8″ from 1/2-1″; 1/4″ from 1-2-1/2″ |
| 3/8″ | 1/2 – 3 | 1/8″ from 1/2-1″; 1/4″ from 1-3″ |
| 7/16″ | 3/4 – 3-1/2 | 1/4″ throughout range |
| 1/2″ | 3/4 – 4 | 1/4″ throughout range |
| 5/8″ | 1 – 5 | 1/4″ from 1-2″; 1/2″ from 2-5″ |
| 3/4″ | 1-1/4 – 6 | 1/4″ from 1-1/4-2″; 1/2″ from 2-6″ |
Frequently Asked Questions
Q: What is the advantage of SEMS screws over standard screws with separate washers?
A: SEMS screws eliminate separate washer handling, prevent washer loss, ensure consistent washer placement, and reduce assembly time by approximately 30%. The permanently attached washer remains free to rotate, ensuring optimal seating during installation.
Q: Are your Copper and Silicon Bronze SEMS screws suitable for marine environments?
A: Yes, both Copper and Silicon Bronze SEMS excel in marine applications. Silicon Bronze offers superior strength while maintaining excellent corrosion resistance, making it ideal for structural marine applications. Copper SEMS are preferred for marine electrical connections where conductivity is paramount.
Q: Can you provide custom thread lengths or non-standard head configurations?
A: Absolutely. Our manufacturing capabilities include custom thread lengths, specialized head designs, and non-standard dimensional requirements. Custom orders typically require minimum quantities of 10,000 pieces and additional lead time.
Q: What quality control measures do you implement during production?
A: Our comprehensive quality control program includes incoming material certification, in-process dimensional verification, automated optical inspection, statistical process control, mechanical property testing, and final inspection sampling based on AQL standards.
Q: How do I determine the appropriate torque specifications for installation?
A: Recommended torque values depend on material, thread size, finish, and application requirements. Our engineering team provides detailed torque specifications for each product based on these factors. We can also perform application-specific testing to determine optimal torque values for critical applications.
Q: Do you offer traceability documentation with your fasteners?
A: Yes, we provide comprehensive documentation including material certifications, dimensional inspection reports, plating/coating certificates, and mechanical testing results upon request. Full lot traceability is maintained for all products.
Q: What is the difference between internal and external tooth lock washers on SEMS?
A: External tooth lock washers have teeth on their outer edge, providing greater contact area with the fastened component. Internal tooth lock washers have teeth pointing toward the screw head, creating a more compact assembly. The choice depends on application requirements and space constraints.
Q: Can your SEMS screws withstand high-vibration environments?
A: Yes, the pre-assembled washer design provides excellent vibration resistance by maintaining consistent tension and preventing backing out. For extreme vibration applications, we recommend SEMS with serrated lock washers or consideration of thread-locking compounds.
Q: Are your fasteners compliant with RoHS and REACH regulations?
A: Yes, all our standard products are fully compliant with current RoHS and REACH requirements. Compliance documentation is available upon request for specific orders or material types.
Q: What payment terms do you offer for international orders?
A: We typically work with Letter of Credit, T/T advance payment, or established credit terms for regular customers. Specific payment arrangements can be discussed based on order volume and customer relationship.
Material Properties
Copper Alloys
| Alloy | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) | Electrical Conductivity (% IACS) |
|---|---|---|---|---|
| C11000 | 220-270 | 70-140 | 45-55 | 100 |
| C12200 | 250-310 | 140-190 | 40-50 | 85-90 |
| C14500 | 310-380 | 240-310 | 25-35 | 80-85 |
| C18200 | 380-450 | 280-350 | 15-25 | 75-80 |
Silicon Bronze Alloys
| Alloy | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) | Corrosion Resistance |
|---|---|---|---|---|
| C65100 | 380-450 | 170-240 | 45-65 | Excellent |
| C65500 | 450-550 | 170-310 | 25-45 | Excellent |
| C66100 | 510-620 | 240-380 | 20-35 | Excellent |
Stainless Steel Alloys
| Alloy | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) | Corrosion Resistance |
|---|---|---|---|---|
| 304 (A2) | 510-620 | 205-310 | 30-40 | Very Good |
| 316 (A4) | 510-620 | 205-310 | 30-40 | Excellent |
| 410 | 450-620 | 275-410 | 15-25 | Good |
| 17-4PH | 860-1000 | 790-950 | 10-15 | Very Good |
Customer Testimonial
Robert Harrington, Purchasing Manager, USA
“We’ve been exclusively using the cold headed Silicon Bronze SEMS screws from this supplier for our custom yacht hardware for over five years now. The consistency and quality are simply outstanding. Even in the harsh saltwater environment of the Gulf Coast, these cold headed SEMS Screws and fasteners show minimal corrosion after years of service. Their ability to customize thread lengths for our specific applications has saved countless hours in our production process. The communication throughout the ordering process is always clear and professional, and despite shipping from India to the USA, deliveries are remarkably consistent. I wouldn’t consider any other source for our marine fastener needs.”
Our USPs
- Customization Flexibility: Unlike many competitors, we offer extensive customization options with reasonable minimum order quantities.
- Material Expertise: Our metallurgical knowledge enables us to recommend optimal material selections for challenging applications.
- Production Adaptability: Our manufacturing processes can be adjusted to accommodate urgent timelines when required.
- Comprehensive Testing: In-house testing capabilities exceed industry standards for quality verification.
- Global Logistics Experience: Established shipping protocols ensure smooth customs clearance and timely delivery worldwide.
- Custom Packaging Solutions: Product packaging can be tailored to your specific requirements, including branded labeling, custom quantities, and specialized containers for automated assembly systems.
- Technical Consultation: Our engineering team provides application-specific recommendations to optimize fastener performance.
- Sample Development: We offer rapid prototype and sample development for new applications and custom requirements.
Glossary of Terms
Cold Heading: A metal forming process performed at room temperature where wire is cut to length and progressively formed into a fastener through a series of dies.
Thread Rolling: A thread forming process that creates threads by displacing material rather than cutting it, resulting in stronger threads with better fatigue resistance.
Pitch: The distance between adjacent threads, measured from crest to crest.
Major Diameter: The largest diameter of a screw thread, measured across the crests.
Minor Diameter: The smallest diameter of a screw thread, measured across the roots.
Torque: The rotational force applied to a fastener during installation.
Preload: The tension created in a fastener when tightened, which provides the clamping force holding components together.
Passivation: A chemical process that enhances the natural corrosion resistance of Stainless Steel by removing free iron from the surface.
Galvanic Corrosion: Accelerated corrosion that occurs when dissimilar metals are in electrical contact in the presence of an electrolyte.
RoHS: Restriction of Hazardous Substances directive that restricts the use of specific hazardous materials in electrical and electronic products.
REACH: European Union regulation concerning the Registration, Evaluation, Authorization, and Restriction of Chemicals.
Hydrogen Embrittlement: A process by which metals, particularly high-strength steels, become brittle and fracture due to exposure to hydrogen.
Thread Class/Fit: Designation that defines the dimensional tolerances for threads, affecting the tightness of fit between mating parts.
Related Terms
- Pre-assembled screw and washer
- Captive washer screws
- Self-locking fasteners
- Conical spring washer screws
- Machine screws with integral washers
- Anti-vibration fasteners
- Combination screws
- External tooth lock washer screws
- Internal tooth lock washer screws
- Assembled washers and screws
- Vibration-resistant fasteners
- Silicon Bronze marine fasteners
- Copper electrical fasteners
- Conductive fastening systems
- Specialty bronze hardware
- Pre-assembled fastening systems
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