The Fundamentals of China Screw Type: Characteristics, Standards, and Performance

Types of Screws: A Comprehensive Guide

Choosing the right screw type is essential in manufacturing, construction, and DIY projects. Screws vary in design, material, and application, and selecting the appropriate one ensures durability, strength, and proper fit. Understanding the distinct characteristics of each screw type helps optimize performance and safety in both industrial and household applications.

Wood Screws

Engineered specifically for joining wooden components, wood screws feature a sharp, tapered tip and deep, coarse threads that grip soft and hardwoods securely without splitting the material.

Advantages

• Strong grip in wood materials
• Minimal splitting with proper pilot holes
• High tensile strength for structural integrity
• Versatile for indoor and outdoor woodworking

Limitations

• Not suitable for metal or masonry
• May corrode if not coated in damp environments
• Requires pre-drilling in hardwoods

Best for: Furniture assembly, cabinetry, decking, and general woodworking projects

Machine Screws

Designed for precision mechanical applications, machine screws have uniform threading and are used with pre-tapped holes or paired with nuts to fasten metal components securely.

Advantages

• Precise fit in tapped holes
• Consistent thread pitch for reliability
• Available in various head types (flat, pan, round)
• Ideal for repeated assembly/disassembly

Limitations

• Requires a nut or threaded hole
• Not self-tapping; needs pre-prepared threads
• Limited grip in soft materials

Best for: Machinery, electronics, automotive components, and industrial equipment

Self-Tapping Screws

These screws create their own threads when driven into materials like plastic, soft metals, or composite panels, eliminating the need for pre-tapping in many cases.

Advantages

• No need for pre-threaded holes
• Fast and efficient installation
• Excellent for lightweight materials
• Versatile across plastics and thin metals

Limitations

• Less durable in high-stress applications
• May strip in soft materials if over-tightened
• Limited reusability in the same hole

Best for: Plastic enclosures, HVAC ducts, signage, and light-duty metal fabrication

Sheet Metal Screws

Specially designed to fasten thin metal sheets, these screws have sharp, aggressive threads and a pointed tip that cuts through metal, forming a tight, secure joint.

Advantages

• Self-cutting threads for metal penetration
• Corrosion-resistant coatings (e.g., zinc, stainless)
• Strong hold in thin-gauge metals
• Suitable for indoor and outdoor use

Limitations

• Can weaken thin metal if over-torqued
• Not ideal for wood or masonry
• May require pilot holes in thicker metals

Best for: HVAC systems, automotive panels, electronic housings, and industrial enclosures

Expert Tip: Always match the screw material (e.g., stainless steel, zinc-plated) to the environment—use corrosion-resistant screws for outdoor or high-moisture applications to prevent rust and failure.

Industry Applications of China Screw Type Fasteners

Screw-type fasteners are foundational elements in modern industrial and construction processes, offering unmatched versatility, strength, and reliability. Originating from advanced manufacturing hubs in China, these screws are engineered to meet international quality standards while supporting cost-effective production across global supply chains. Their precision design and material durability make them indispensable in assembling, securing, and maintaining critical components across a wide range of industries.

Construction and Building Industry

Structural Framing & Drywall Installation

Screws are extensively used in framing wooden and metal structures, offering superior holding power compared to nails. Their threaded design provides increased resistance to withdrawal forces, minimizing the risk of wood splitting and structural loosening over time. This makes them ideal for securing wall studs, floor joists, and roof trusses.

Drywall screws—specifically self-tapping and coarse-threaded variants—are essential for attaching gypsum boards to both steel and wooden frames. Their bugle head design ensures flush mounting without damaging the drywall surface, while corrosion-resistant coatings extend lifespan in humid environments.

Outdoor Decking & Weather Resistance

Deck screws are specially designed for exterior applications, featuring weather-resistant coatings such as zinc plating, ceramic coating, or stainless steel composition. These prevent rust and degradation caused by moisture, UV exposure, and temperature fluctuations.

With high torque tolerance and deep thread engagement, deck screws ensure a secure, long-lasting fit in composite or natural wood decking materials. Many modern variants include anti-strip drive systems (e.g., square or star drives) for efficient installation and reduced head damage during assembly.

Automotive Industry

Engine and Powertrain Assembly

In automotive manufacturing, precision-engineered screws are critical for assembling engine blocks, transmissions, and suspension systems. Engine screws must withstand extreme mechanical stress, thermal cycling, and constant vibration, requiring high-tensile strength materials like alloy steel with heat-treated finishes.

These fasteners ensure tight torque specifications are maintained over time, preventing loosening that could lead to catastrophic component failure. Torque-to-yield (TTY) screws are often used in cylinder head applications where precise clamping force is essential.

Interior and Exterior Component Fastening

Machine screws are widely used throughout vehicles for attaching interior panels, seats, door mechanisms, and electronic modules. They offer repeatable assembly and disassembly without thread wear, which is crucial during maintenance and repair cycles.

Many automotive screws feature specialized coatings—such as black oxide or phosphate—to resist corrosion and reduce friction. Their standardized dimensions ensure compatibility across global production lines, making Chinese-manufactured screws a reliable choice for OEMs and aftermarket suppliers alike.

Electronics and Appliances

Consumer Electronics Assembly

China-produced computer screws—often miniature Phillips, Torx, or Pentalobe types—are integral to assembling smartphones, laptops, tablets, and other compact devices. These small yet precise fasteners secure circuit boards, batteries, screens, and internal brackets without damaging sensitive components.

Their non-magnetic and insulated variants are used in high-precision electronics to avoid interference with circuitry. Additionally, tamper-resistant designs (e.g., security Torx) are employed in public devices to deter unauthorized access.

Home and Commercial Appliances

In household appliances like refrigerators, washing machines, and air conditioners, screws are used to mount motors, compressors, control panels, and structural housings. They allow for modular design, enabling easier servicing and part replacement.

Appliance screws are typically made from stainless steel or nickel-plated brass to resist moisture and chemical exposure. Their consistent thread quality ensures reliable performance in automated assembly lines, reducing defect rates and improving manufacturing efficiency.

Furniture Manufacturing

Modular Furniture Assembly

Screws are the primary fastening solution in modern furniture production, used to join tabletops, chair legs, cabinet frames, and sofa backs. Unlike nails or adhesives, screws provide strong, durable connections that can be disassembled and reassembled multiple times without compromising integrity.

This feature is especially valuable for flat-pack furniture, where ease of transport and DIY assembly are key selling points. Self-drilling and thread-forming wood screws reduce the need for pre-drilling, speeding up production and reducing labor costs.

Durability and Adjustability

Furniture screws are designed for smooth engagement and resistance to stripping, ensuring clean installation even in hardwoods or engineered wood panels. Many feature pan heads or countersunk designs for flush mounting and aesthetic appeal.

One of the major advantages of using screws in furniture is the ability to periodically tighten loose joints, extending the product’s lifespan. This adjustability reduces waste and supports sustainable design practices by promoting repair over replacement.

Important Note: The performance of screw fasteners depends not only on their type and material but also on proper installation techniques. Always use the correct driver bit, torque setting, and pilot hole size to avoid stripping, cracking, or weakening the joint. When sourcing screws—especially from China—ensure compliance with ISO, DIN, or ANSI standards to guarantee reliability and interchangeability in your applications.

Product Specifications and Features of China Screw Types

China is a leading global manufacturer and exporter of high-quality screws, offering a diverse range of fasteners tailored for industrial, commercial, and residential applications. Chinese screw types are engineered to meet international standards while balancing cost-efficiency, durability, and performance. This guide explores the key specifications, installation best practices, and maintenance strategies to ensure optimal use of China-made screws across various environments.

Material Composition

Chinese-manufactured screws are produced using a variety of high-grade materials, each selected based on mechanical requirements, environmental exposure, and application needs.

• Carbon Steel: Offers high tensile strength and is ideal for general construction and structural applications. Often coated with zinc (galvanized) for added corrosion resistance.
• Stainless Steel (A2/A4): Preferred for outdoor, marine, and food-processing environments due to excellent rust resistance and durability. A4 (marine-grade) provides superior performance in saltwater conditions.
• Brass: Used in decorative fixtures, plumbing, and electrical applications where aesthetics, non-magnetic properties, and moderate corrosion resistance are required.
• Titanium: High-performance option for aerospace, automotive, and marine sectors where extreme strength-to-weight ratio and resistance to harsh environments are critical.

Key Insight: Always verify material grade and certification (e.g., ISO, ASTM) when sourcing screws for safety-critical applications.

Thread Design Variants

The thread geometry of Chinese screws is precisely engineered to match specific materials and load requirements, ensuring reliable fastening performance.

• Coarse Threads: Designed for quick assembly in soft materials like wood, plastic, or light metals. Provide greater resistance to stripping during installation.
• Fine Threads: Offer enhanced clamping force and precision in hard materials such as steel or aluminum. Ideal for vibration-prone environments due to better thread engagement.
• Self-Tapping Screws: Feature cutting edges that create their own threads in pre-drilled holes, eliminating the need for tapping. Commonly used in sheet metal and composite materials.
• Self-Drilling (Tek) Screws: Combine drill bit tips with threading, allowing direct installation into metal without pilot holes—ideal for roofing and metal framing.

Pro Tip: Match thread pitch and diameter to the base material to prevent cross-threading and ensure long-term joint integrity.

Head Types and Drive Systems

The head design of a screw determines tool compatibility, torque capacity, and surface finish. Chinese manufacturers produce a wide array of head styles to meet global demand.

• Flat Head (Countersunk): Sits flush with the surface, ideal for woodwork and cabinetry where a smooth finish is desired.
• Pan Head: Features a low-profile rounded top with a flat bearing surface; widely used in electronics and general assembly.
• Round Head: Provides a decorative dome-shaped appearance, often used in visible applications.
• Hex Head: Allows high-torque tightening with wrenches or sockets, commonly used in structural and mechanical applications.
• Drive Types: Includes Phillips, Slotted, Pozidriv, Torx, and Square (Robertson), with Torx offering superior resistance to cam-out and tool wear.

Design Note: Torx and square drives are increasingly preferred in professional settings due to reduced slippage and longer tool life.

Coatings and Surface Treatments

To enhance durability and appearance, many Chinese screws undergo specialized surface treatments that improve performance in challenging environments.

• Zinc Plating: Provides basic corrosion resistance with a shiny finish; suitable for indoor or dry environments.
• Dacromet (Zinc Flake Coating): Offers superior rust protection and heat resistance, often used in automotive and heavy machinery.
• Black Oxide: Adds mild corrosion resistance and a sleek black finish, commonly used in aesthetic or low-moisture applications.
• Hot-Dip Galvanizing: Thick zinc layer for outdoor and marine use, providing long-term protection against rust.

Quality Check: Reputable suppliers provide salt spray test reports (e.g., 48–1000+ hours) to validate coating effectiveness.

Installation Best Practices

1. Preparation

Proper preparation ensures clean installation and prevents material damage.

• Drill a pilot hole slightly smaller than the screw’s major diameter to prevent splitting in wood or cracking in brittle materials.
• For metal applications, use a center punch to guide the drill bit and maintain alignment.
• Ensure hole depth is at least equal to the screw length to allow full engagement.
• Select the correct drill bit size based on screw type—undersized for soft materials, near-equal for hard substrates.

Expert Advice: Use brad-point bits for wood and cobalt bits for metal to achieve clean, accurate holes.

2. Driving the Screw

Correct driving technique ensures secure fastening without damaging the screw or material.

• Align the screwdriver or drill bit perfectly with the screw head to avoid cam-out and head stripping.
• Use variable-speed drivers and start at low speed to engage the screw, then increase as needed.
• Avoid over-tightening, which can strip threads or crack surrounding material.
• For torque-sensitive applications, use a torque-limiting screwdriver or clutch-equipped drill.

Safety Note: Wear eye protection when driving screws at high speed, especially in metal or masonry.

3. Securing the Fit

Final checks ensure the fastener performs as intended under load and environmental stress.

• Verify that the screw head is flush or slightly countersunk, unless a raised finish is desired.
• Check for wobbling or looseness, which may indicate poor thread engagement or incorrect sizing.
• In high-vibration environments, consider using thread-locking compounds or lock washers.
• For structural joints, perform periodic torque verification during initial settling periods.

Installation Tip: Pre-lubricate large or fine-threaded screws with a small amount of wax or anti-seize compound to ease installation and prevent galling.

Maintenance and Repair Guidelines

Regular Inspection

Proactive inspection helps detect early signs of failure and extends the lifespan of assemblies.

• Inspect screws monthly in high-moisture or corrosive environments (e.g., coastal areas, chemical plants).
• Look for rust, pitting, thread wear, or head deformation that compromises structural integrity.
• Check for loosening due to thermal expansion, vibration, or dynamic loads.
• Use visual markers or torque checks to monitor fastener stability over time.

Preventive Strategy: Implement a scheduled inspection program for critical infrastructure and rotating equipment.

Cleaning and Corrosion Prevention

Regular cleaning maintains performance and appearance, especially in harsh operating conditions.

• Clean accumulated dirt and debris with a soft brush or compressed air.
• For corroded screws, use a wire brush and rust dissolver, followed by rinsing and drying.
• Apply anti-corrosive sprays or greases (e.g., lithium-based or silicone) to protect exposed threads.
• In marine environments, use marine-grade grease or wax coatings for long-term protection.

Eco-Friendly Option: Biodegradable anti-seize compounds are available for environmentally sensitive applications.

Replacement and Repair Solutions

Timely replacement prevents cascading failures and maintains system reliability.

• Replace stripped, bent, or severely corroded screws immediately to avoid further damage.
• Use extraction tools (screw extractors or left-handed drill bits) for broken or seized screws.
• For stripped holes, install helical inserts (Helicoils) or use epoxy-based thread repair kits.
• Upgrade to higher-grade materials (e.g., stainless steel instead of carbon steel) during replacement for improved longevity.

Repair Tip: When replacing multiple screws, do so in stages to maintain structural stability during the process.

Professional Recommendation: When sourcing screws from China, prioritize suppliers with ISO 9001 certification and third-party testing documentation. Request sample batches for fit, finish, and performance evaluation before large-scale procurement. For critical applications, opt for screws with traceable lot numbers and material test reports (MTRs) to ensure compliance and accountability.

Additional Considerations

• Standards Compliance: Ensure screws meet international standards such as ISO, DIN, ANSI, or JIS depending on your region and application.
• Supply Chain Reliability: Partner with suppliers offering consistent quality, on-time delivery, and responsive customer support.
• Environmental Resistance: Select coatings and materials based on UV exposure, humidity, salt spray, and temperature extremes.
• Tool Compatibility: Confirm drive type availability and match with commonly used tools in your workshop or field operations.
• Cost vs. Performance: Balance upfront cost with lifecycle value—higher-quality screws often reduce maintenance and replacement costs over time.

Quality and Safety Considerations of China Screw Type Fasteners

When selecting and using screw fasteners—particularly those sourced from China—ensuring high quality and safety standards is paramount. These factors directly influence the performance, longevity, and structural integrity of assemblies across industries such as construction, automotive, aerospace, and consumer electronics. Poor-quality screws can lead to mechanical failure, safety hazards, and costly repairs. This guide outlines essential quality and safety considerations to help you make informed decisions when sourcing and using screw-type fasteners.

Safety Warning: Always verify compliance with international standards before using fasteners in load-bearing or safety-critical applications. Never compromise on material quality or installation procedures, as faulty screws can result in structural collapse, equipment damage, or personal injury.

Quality Assurance: Sourcing Reliable Fasteners

The foundation of reliable performance begins with sourcing screws from reputable manufacturers and certified suppliers. Trusted producers adhere to internationally recognized quality management systems, ensuring consistency and traceability in manufacturing processes.

• Verify Certifications: Request documentation such as ISO 9001 (Quality Management), ISO 14001 (Environmental Management), and product-specific standards like ISO 898 (mechanical properties of fasteners).
• Traceability: Ensure batch traceability and material test reports (MTRs) are available, especially for critical applications.
• Third-Party Inspections: Consider independent quality audits or inspection services (e.g., SGS, Bureau Veritas) for large-volume orders to validate compliance.
• Supplier Vetting: Evaluate supplier history, customer reviews, and factory certifications before placing bulk orders.

Expert Tip: When importing Chinese-manufactured screws, request samples for testing before committing to full production runs. Conduct dimensional checks, torque tests, and salt spray testing for corrosion resistance to confirm specifications.

Material Selection: Matching Performance to Environment

The choice of material significantly affects a screw’s strength, durability, and resistance to environmental degradation. Selecting the appropriate alloy ensures long-term reliability under operational stress and exposure conditions.

• Stainless Steel (A2/A4): Ideal for outdoor, marine, or humid environments due to excellent corrosion resistance. A4 (316 stainless) offers superior protection against chlorides and saltwater.
• Carbon Steel: Offers high tensile strength and is often used in structural applications. Typically coated (e.g., zinc plating, hot-dip galvanizing) to prevent rust.
• Alloy Steels: Used in high-stress applications; heat-treated for enhanced hardness and fatigue resistance (e.g., Grade 8.8, 10.9, 12.9).
• Non-Ferrous Options: Brass or aluminum screws are suitable for electrical conductivity needs or lightweight applications but have lower strength.

Always match the screw material to the operating environment—consider temperature extremes, chemical exposure, moisture levels, and galvanic compatibility with mating materials.

Proper Installation: Preventing Mechanical Failure

Even the highest-quality screws can fail if improperly installed. Correct installation techniques are essential for maintaining clamping force and avoiding damage to threads or base materials.

• Use Appropriate Tools: Employ torque-controlled drivers or wrenches to apply the manufacturer-recommended tightening torque. Over-tightening can strip threads or cause brittle fracture, especially in hardened steels.
• Avoid Cross-Threading: Start screws by hand or with low torque to ensure proper alignment before full tightening.
• Lubrication (When Needed): Use anti-seize compounds for stainless steel fasteners to prevent galling during assembly.
• Worker Training: Ensure technicians are trained in fastener handling, torque procedures, and hazard recognition to minimize human error.

Application Suitability: Choosing the Right Screw Type

Using the wrong type of screw for a given application compromises structural integrity and safety. Each screw type is engineered for specific materials and load conditions.

• Wood Screws: Feature sharp threads and tapered shanks for gripping wood fibers. Not suitable for metal or masonry.
• Metal Screws (Machine Screws): Designed for pre-tapped holes in metal; require nuts or threaded inserts.
• Self-Tapping Screws: Can cut their own threads into metal, plastic, or composite materials. Common in sheet metal applications.
• Drywall or Deck Screws: Optimized for specific substrates—using them outside their intended use increases failure risk.

Always consult engineering guidelines or industry standards (e.g., ASTM, DIN, ANSI) when selecting fasteners. When in doubt, seek advice from a mechanical engineer or fastener specialist.

Safety Standards and Regulatory Compliance

Compliance with occupational health and safety regulations is crucial to protect workers and ensure product reliability. Faulty fasteners contribute to equipment malfunctions, workplace accidents, and regulatory penalties.

• OSHA & ANSI Guidelines: Follow best practices for handling, installation, and inspection of mechanical fasteners in industrial settings.
• Load Requirements: Ensure screws meet required shear, tensile, and fatigue strength for the application. Use safety factors as defined by engineering codes.
• Corrosion Protection Standards: Adhere to ASTM B117 (salt spray testing) or ISO 9227 for environments prone to rust.
• Regional Regulations: Confirm compliance with local building codes, CE marking (EU), RoHS (hazardous substances), and REACH (chemical safety) where applicable.

Maintenance Tip: Implement a periodic fastener inspection program in critical systems. Look for signs of loosening, corrosion, or deformation. Re-torque as needed and replace any compromised screws immediately to maintain system integrity.

Final Recommendations

• Always prioritize quality over cost savings when selecting screws for safety-critical applications.
• Maintain detailed records of fastener specifications, sources, and certifications.
• Invest in employee training on proper fastener selection and installation techniques.
• Stay updated on evolving international standards and regulatory requirements.
• Partner with suppliers who offer technical support and product warranties.

By adhering to rigorous quality and safety practices, you can ensure that screw-type fasteners perform reliably throughout their service life. Whether sourcing from China or elsewhere, due diligence in selection, verification, and installation is essential for protecting people, property, and performance.

Frequently Asked Questions About Screw Selection and Applications

Selecting the right screw for your application involves evaluating several key factors to ensure durability, performance, and compatibility. The most important considerations include:

• Material and Corrosion Resistance: Choose a screw material—such as stainless steel, brass, copper, or coated steel—based on the environment. For outdoor or humid conditions (e.g., coastal areas), corrosion-resistant materials like stainless steel or copper are ideal.
• Length and Diameter: The screw must be long enough to securely anchor into the base material without protruding through the other side. The diameter (gauge) should match the load requirements and pilot hole size to prevent splitting or stripping.
• Head and Drive Type: Common head types include flat, pan, round, and oval, each suited for different flush or raised mounting needs. Drive types—such as Phillips, slotted, Torx, or square—affect torque capacity and ease of installation, with Torx offering better grip and reduced cam-out.
• Purpose and Application: Screws used in woodworking, metalworking, masonry, or electronics require different thread designs and materials. For example, wood screws have tapered threads, while self-tapping metal screws have sharper threads and hardened tips.

By carefully assessing these factors, you can select a screw that ensures a secure, long-lasting, and efficient fastening solution.

Wood screws are specifically engineered for joining wooden materials and offer several advantages over general-purpose metal fasteners:

• Tapered Thread Design: Unlike uniform threads on metal screws, wood screws feature a tapered thread that starts narrow at the tip and widens toward the head. This allows for deeper penetration and a stronger grip in fibrous wood materials.
• Shaft Design: The lower portion of a wood screw is typically unthreaded, allowing the upper threaded section to pull the two pieces of wood tightly together as the screw is driven in. This creates a snug, gap-free joint essential for structural integrity.
• Reduced Splitting Risk: When used with a properly sized pilot hole, wood screws minimize the risk of splitting the wood, especially near edges or in hardwoods.
• Superior Holding Power: The combination of deep thread engagement and clamping action provides greater holding strength compared to nails or generic fasteners, especially under shear and tensile stress.
• Versatility: Available in various materials (e.g., zinc-coated, stainless steel, brass), finishes, and head styles, wood screws can be selected for both functional and aesthetic purposes in furniture, cabinetry, and framing.

These features make wood screws the preferred choice for woodworking projects where strength, precision, and joint quality are critical.

Copper screws are specialized fasteners that offer a unique combination of functional and visual properties, making them suitable for niche applications:

• Corrosion Resistance: Copper naturally forms a protective oxide layer, making it highly resistant to rust and ideal for humid, marine, or outdoor environments such as boat building, roofing, and coastal construction.
• Electrical Conductivity: With excellent electrical conductivity, copper screws are often used in grounding systems, electrical enclosures, and lightning protection installations where reliable current transfer is essential.
• Thermal Conductivity: Their ability to efficiently transfer heat makes them useful in thermal management applications, such as attaching heat sinks or components in specialized electronic assemblies.
• Aesthetic Appeal: Copper develops a distinctive patina over time, transitioning from a bright metallic finish to a greenish-blue hue. This aging process is prized in architectural and decorative applications, including historic restorations, art installations, and premium outdoor fixtures.
• Non-Magnetic and Low Reactivity: Copper is non-magnetic and chemically stable, making it suitable for sensitive environments like laboratories or marine hardware where magnetic interference or galvanic corrosion must be minimized.

While more expensive than steel or aluminum fasteners, copper screws are valued for their longevity, performance, and visual character in specialized contexts.

The thread form of a screw refers to the geometric shape and structure of its helical ridges. Understanding the components of the thread is essential for proper function, fit, and interchangeability. The main elements include:

Precise thread geometry ensures proper engagement, load distribution, and resistance to stripping or vibration loosening. Standards like ISO, Unified National (UN), and others define these parameters for global compatibility.

Plastic screws, typically made from materials like nylon, polypropylene, or acetal (Delrin), are designed for specific lightweight and non-metallic applications. While they offer certain advantages, their durability is context-dependent:

• Moderate Durability: Plastic screws are stable and resistant to moisture, UV radiation (if stabilized), and many chemicals, making them suitable for indoor and outdoor use in non-structural roles.
• Lightweight and Insulating: They are electrically non-conductive and thermally insulating, ideal for use in electronics, enclosures, and environments where metal could cause short circuits.
• Varying Strength Levels: High-performance plastics like nylon 6/6 or PEEK offer good tensile strength and impact resistance, but still fall short of metal fasteners in load-bearing capacity.
• Temperature Sensitivity: Most plastic screws soften or deform at elevated temperatures (typically above 80–120°C), limiting their use in high-heat environments.
• Not for Heavy Loads: Due to lower shear and tensile strength, plastic screws are not recommended for structural or high-stress applications. They are best suited for securing lightweight panels, covers, or components where vibration damping and corrosion resistance are priorities.

In summary, plastic screws are durable within their intended scope but should not be used as substitutes for metal fasteners in demanding mechanical or load-bearing situations.