A Complete Guide to Brass Rods Production Machines: Specifications, Types, and Applications

Types of Brass Rod Production Machines

A brass rod production line consists of specialized machinery designed to transform raw brass into precision-engineered rods for industrial, mechanical, and architectural applications. Each machine plays a critical role in shaping, refining, and finishing the rods to meet exact dimensional, structural, and aesthetic standards. Understanding the function and benefits of each machine helps manufacturers optimize quality, efficiency, and output.

Brass Rod Extrusion Machine

This machine shapes brass billets into long rods by forcing heated material through a precision die under high pressure. The process is typically hydraulic, mechanical, or screw-driven, and determines the rod’s initial cross-sectional profile—round, square, hexagonal, or custom shapes.

Advantages

• High production speed for long continuous rods
• Capable of complex cross-sectional profiles
• Excellent material utilization with minimal waste
• Suitable for large-scale industrial production

Limitations

• Requires pre-heating of billets (energy-intensive)
• High initial equipment cost
• Die wear requires regular maintenance

Best for: Initial shaping of raw brass, high-volume rod manufacturing

Brass Rod Drawing Machine

Used to refine extruded rods by pulling them through a series of progressively smaller dies. This cold-working process reduces diameter, improves dimensional accuracy, and enhances mechanical properties by aligning the grain structure of the brass.

Advantages

• Superior dimensional precision and surface finish
• Increases tensile strength and hardness
• Allows fine-tuning of rod diameter
• Versatile for various alloys and sizes

Limitations

• Slower than extrusion for bulk shaping
• Requires multiple passes for significant size reduction
• Tooling wear affects consistency over time

Best for: Precision finishing, cold-working applications, tight tolerance requirements

Brass Rod Cutting Machine

Automated or manual systems that cut drawn rods into specified lengths using circular saws, shear blades, or abrasive cutters. Precision cutting ensures clean, burr-free ends suitable for further machining or assembly.

Advantages

• High-speed, accurate length control
• Minimizes material waste
• Compatible with automated production lines
• Produces clean, square cuts

Limitations

• Blade wear affects cut quality over time
• Heat generation may require cooling systems
• Limited flexibility for irregular cuts without reprogramming

Best for: Final length preparation, batch processing, integration with CNC systems

Brass Rod Threading Machine

Specialized equipment that cuts or rolls screw threads onto the rod surface. Whether for straight (parallel) or tapered (NPT) threads, these machines use rotating dies or CNC-controlled cutters to achieve precise thread profiles for plumbing, fastening, or mechanical components.

Advantages

• High thread accuracy and consistency
• Fast processing with minimal operator input
• Supports both cutting and roll threading methods
• Integrates well with automated workflows

Limitations

• Tooling must match thread standard (e.g., ISO, NPT)
• Rolled threads require ductile brass alloys
• Improper setup can cause thread damage

Best for: Rods used in plumbing, fasteners, and threaded fittings

Brass Rod Polishing Machine

Used to improve the surface finish and aesthetic appeal of brass rods through abrasive belts, brushes, or buffing wheels. The rods are rotated while contact with polishing media creates a smooth, reflective surface ideal for decorative or visible applications.

Advantages

• Produces high-gloss, mirror-like finishes
• Removes surface imperfections and oxidation
• Enhances corrosion resistance when combined with coatings
• Improves product value for architectural or design uses

Limitations

• Adds time and cost to production
• Generates brass dust requiring ventilation
• Over-polishing can reduce dimensional accuracy

Best for: Decorative rods, architectural hardware, consumer-facing products

Brass Rod Packaging Machine

Automated systems that bundle, wrap, label, and prepare finished rods for shipping. These machines ensure safe handling, prevent surface damage, and streamline logistics by organizing rods into standardized units.

Advantages

• Reduces labor and packaging time
• Protects rods from scratches and moisture
• Enables barcode labeling and inventory tracking
• Improves shipping efficiency and customer presentation

Limitations

• Higher cost for full automation
• Requires space and integration with production line
• May need adjustments for different rod lengths

Best for: Final stage of production, export-ready packaging, bulk distribution

Expert Tip: For optimal production flow, integrate drawing and polishing machines with automated feeding systems to reduce manual handling and maintain consistent surface quality across batches.

Industrial Applications of Brass Rod Production Machines

Brass rod production machines play a pivotal role in modern manufacturing due to the exceptional versatility and performance characteristics of brass. Known for its excellent machinability, high corrosion resistance, and good electrical conductivity, brass is a preferred material across numerous industries. These production machines—equipped with advanced technologies such as metal cutting band saw machines and hydraulic forming systems—enable precise shaping, cutting, and molding of brass rods into components that meet strict industrial standards.

Construction Industry

In the construction sector, brass rods are essential for manufacturing durable hardware components such as bolts, screws, rivets, and fasteners. These parts are critical for joining structural elements in environments exposed to moisture and weather fluctuations. Due to brass’s inherent resistance to rust and galvanic corrosion, it outperforms many ferrous metals in outdoor, coastal, and marine construction projects.

Brass production machines ensure consistent dimensional accuracy and surface finish, which enhances the reliability and longevity of fasteners used in bridges, architectural fixtures, and marine infrastructure. Additionally, the aesthetic appeal of polished brass makes it suitable for decorative hardware in high-end building designs.

Automotive Industry

The automotive industry relies heavily on brass rods for producing precision-engineered components like gears, bushings, bearings, and electrical connectors. These parts must perform reliably under high thermal and mechanical stress, particularly in engine compartments and transmission systems.

Brass production machinery—including CNC lathes, hydraulic presses, and automated cutting systems—enables the mass production of complex automotive parts with tight tolerances. The integration of hydraulic machines allows for efficient cold forming and extrusion of brass rods into intricate shapes without compromising material integrity. Furthermore, brass’s non-sparking nature makes it ideal for use in fuel system components and safety-critical applications.

Plumbing Systems

One of the most widespread applications of brass rods is in the plumbing industry, where they are machined into valves, pipe fittings, connectors, and faucet components. Brass offers superior strength, leak resistance, and compatibility with high-pressure water systems, making it a top choice for residential, commercial, and industrial plumbing.

Modern brass rod production lines incorporate automated threading, chamfering, and polishing units to ensure leak-proof seals and smooth flow dynamics. The antimicrobial properties of brass also contribute to improved water hygiene, reducing bacterial growth in potable water systems—an advantage increasingly valued in health-conscious building codes.

Aerospace Industry

While the aerospace industry primarily uses lightweight alloys like aluminum and titanium, brass still holds a niche in non-structural but mission-critical components. Brass rods are used to fabricate small yet vital parts such as fittings, bushings, relay contacts, and instrument housings that require excellent corrosion resistance and dimensional stability.

These components often operate in confined spaces with limited maintenance access, so their durability and reliability are paramount. Brass production machines equipped with micro-machining capabilities ensure the precision required for aerospace-grade tolerances, often within ±0.01 mm. The material’s compatibility with various plating and coating processes further enhances its performance in extreme temperature and humidity conditions.

Electronics and Electrical Engineering

Brass rods are extensively used in electrical and electronic manufacturing due to their high electrical conductivity (approximately 28% IACS), mechanical strength, and ease of plating. They serve as raw material for terminals, connectors, switch components, relay pins, and circuit breaker parts.

Automated brass rod processing systems enable high-speed production of stamped and turned contacts used in consumer electronics, industrial control panels, and power distribution units. The oxidation-resistant surface of brass ensures stable electrical contact over time, minimizing resistance buildup and preventing system failures. Its compatibility with tin, silver, and nickel plating further improves conductivity and solderability.

Medical Equipment Manufacturing

In the medical field, brass rods are utilized in the production of surgical instruments, diagnostic devices, dental tools, and imaging equipment components. The material’s ability to withstand repeated sterilization cycles—via autoclaving, chemical baths, or radiation—makes it ideal for reusable medical devices.

Brass production machines produce components with smooth, burr-free finishes that minimize contamination risks and facilitate cleaning. Additionally, lead-free brass alloys (such as C36000 or DZR brass) are commonly used to meet stringent health and safety regulations. The combination of precision machining and biocompatible materials ensures that medical devices perform reliably in critical care environments.

Other Industrial and Specialty Applications

Note: While brass offers numerous advantages, proper alloy selection (e.g., lead-free vs. free-machining brass) is crucial depending on the application—especially in potable water systems and medical devices. Always ensure that brass rod production machines comply with ISO, ASTM, and industry-specific standards to guarantee product quality, safety, and regulatory compliance.

Specification & Requirement of Brass Rods Production Machines

The production of high-quality brass rods relies on advanced machinery designed to handle the demanding processes of shaping, forming, and finishing. These machines must meet strict technical specifications and operational requirements to ensure consistent dimensional accuracy, surface finish, and material integrity. Understanding both the capabilities and maintenance needs of this equipment is essential for maximizing efficiency, minimizing downtime, and producing rods that meet industry standards.

Extrusion Machines

Extrusion is the primary method for forming brass rods from heated billets. These machines apply extreme pressure to force the molten or semi-solid brass through precision dies.

• Equipped with high-capacity hydraulic systems (typically 100–2000 tons of pressure) to deform dense brass alloys
• Dies crafted from hardened tool steel or tungsten carbide to withstand temperatures up to 750°C and resist wear
• Integrated temperature control systems maintain optimal billet heating (650–750°C) for uniform flow and reduced defects
• Automated billet feeding and cooling conveyors improve throughput and safety

Key insight: Proper die design and alignment are critical to prevent warping and ensure consistent rod diameter.

Drawing Machines

Drawing refines the diameter and surface quality of extruded rods by pulling them through progressively smaller dies.

• Powered by variable-speed electric motors allowing precise control over drawing speed (10–60 m/min)
• Equipped with multi-stage die blocks for incremental size reduction and improved dimensional accuracy
• Hardened tungsten carbide or diamond-coated dies reduce friction and extend service life
• Tension control systems prevent rod breakage and maintain straightness during high-speed operation

Performance tip: Lubrication systems using oil or soap-based drawing compounds minimize heat and die wear.

Cutting & Threading Equipment

After shaping, rods are cut to length and may be threaded for specific applications such as plumbing or electrical connectors.

• Circular saws or shear cutters with carbide-tipped blades ensure clean, burr-free cuts at high speeds
• Automatic bar feeders allow continuous processing and reduce manual handling
• Threading machines use precision chasers or rolling dies to create accurate threads (NPT, BSP, metric)
• Digital length sensors and programmable logic controllers (PLCs) enable tight tolerances (±0.1 mm)

Quality note: Regular blade sharpening and tool calibration prevent dimensional drift and surface imperfections.

Polishing & Finishing Systems

Surface finish is crucial for aesthetic, functional, and corrosion-resistant properties of brass rods.

• Rotating abrasive belts or wire brushes remove oxidation and smooth surface irregularities
• Multi-stage polishing lines progressively refine finish from matte to mirror-like shine
• Replaceable brush heads and abrasives designed for different grit levels (120–600+) allow customization
• Dust extraction systems maintain air quality and prevent contamination of finished products

Efficiency tip: Automated feed systems integrate with polishing units to maintain consistent speed and pressure.

Packaging & Handling Machinery

Final packaging ensures safe transport and storage while maintaining product quality.

• Bundling machines group rods into standard lengths using steel or plastic straps
• Vacuum sealing or anti-tarnish wrapping protects against moisture and oxidation during storage
• High-speed labeling systems apply barcodes and specifications for traceability
• Robotic arms or conveyor systems handle heavy bundles (up to 1000 kg) with minimal labor

Operational benefit: Automated packaging reduces damage and improves inventory management.

Control & Monitoring Systems

Modern brass rod production lines incorporate advanced automation for consistent quality and data tracking.

• PLC-based control panels manage machine sequencing, speed, and fault detection
• Sensors monitor temperature, pressure, alignment, and dimensional accuracy in real time
• SCADA systems provide remote monitoring and historical performance analytics
• Statistical Process Control (SPC) software detects trends and alerts operators to deviations

Digital advantage: Integration with ERP systems streamlines production planning and quality reporting.

Best Practice Recommendation: Invest in modular, scalable machinery with digital diagnostics. This allows for future upgrades, easier troubleshooting, and better integration across production stages. Always verify machine compatibility with your specific brass alloy (e.g., C36000, C26000) and desired rod dimensions (diameter range, length, tolerance).

How to Maintain Brass Rod Production Machines

Effective maintenance is vital to ensure machine reliability, product consistency, and operational safety. A structured maintenance program extends equipment lifespan and minimizes unplanned downtime.

• Lubrication: Apply high-temperature grease and hydraulic oil to moving parts (bearings, chains, guides) to reduce friction and prevent premature wear. Follow OEM schedules for oil changes and filter replacements.
• Cleaning: Regularly remove brass shavings, dust, and coolant residues from machine surfaces, conveyors, and cooling systems to prevent clogging and overheating.
• Inspection: Conduct daily visual checks and weekly detailed inspections of critical components such as dies, blades, belts, and sensors for signs of wear, misalignment, or damage.
• Calibration: Use precision gauges and digital tools to verify alignment, tension, and dimensional accuracy. Recalibrate control systems monthly or after major repairs.
• Component Replacement: Proactively replace consumables like cutting blades, polishing brushes, and seals before failure occurs. Keep spare dies and chasers on hand for quick changeovers.
• Filter Maintenance: Replace air and oil filters regularly to protect pneumatic and hydraulic systems from contamination and ensure smooth operation.

Pro tip: Implement a Computerized Maintenance Management System (CMMS) to schedule tasks, track repairs, and analyze failure patterns for predictive maintenance.

Long-Term Strategy: Combine preventive maintenance with operator training. Well-trained staff can identify early warning signs—such as unusual noises, vibrations, or inconsistent finishes—enabling timely interventions. This proactive approach not only improves machine uptime but also enhances the quality and marketability of the brass rods produced.

Quality and Safety Standards in Brass Rod Production Machinery

Ensuring high-quality brass rods and safe working environments in manufacturing facilities relies on adherence to comprehensive quality and safety standards. These standards are established through international frameworks, national regulations, and industry-specific guidelines. By complying with these protocols, manufacturers not only produce reliable, precision-engineered brass rods for mechanical, construction, and industrial applications but also safeguard employee well-being and minimize environmental impact.

Important Note: Non-compliance with quality and safety standards can lead to product defects, workplace injuries, regulatory penalties, and environmental harm. Regular audits, employee training, and process documentation are essential for sustained compliance.

Quality Standards in Brass Rod Manufacturing

Quality assurance in brass rod production is governed by a combination of international standards, material specifications, and rigorous testing protocols. These standards ensure consistency, reliability, and performance across batches and applications.

• ISO/IEC 17025:2017 – General Requirements for Testing and Calibration Laboratories
  This internationally recognized standard ensures that laboratories conducting material testing (e.g., tensile strength, hardness, chemical composition) operate with technical competence and generate valid, traceable results. It mandates strict control over equipment calibration, personnel qualifications, and test methodologies.
• IATF 16949:2016 (formerly ISO/TS 16949) – Automotive Quality Management System
  Widely adopted in metal manufacturing, this standard emphasizes defect prevention, continuous improvement, and reduction of variation in the supply chain. It applies particularly to brass rods used in automotive components such as connectors, fittings, and transmission parts.
• RoHS (Restriction of Hazardous Substances) Directive
  While not an ISO standard, RoHS compliance is critical for brass products used in electronics and consumer goods. It restricts the use of lead, cadmium, mercury, and other hazardous substances. In brass production, this influences alloy composition—especially in lead-free brass formulations like C36000LF or C46400.
• Material and Dimensional Standards (ASTM, DIN, JIS)
  Brass rods must meet specific mechanical and dimensional requirements defined by national and international bodies:
  • ASTM B488 – Standard for electrodeposited coatings of gold for engineering uses (relevant for plating)
  • ASTM B16 – Standard specification for free-cutting brass rod, bar, and shapes
  • DIN 17660 / EN 12164 – European standards for copper and copper alloys in general engineering applications
  • JIS H3250 – Japanese Industrial Standard for brass rods and bars

Key mechanical properties monitored during production include:

• Tensile Strength: Typically ranges from 300–500 MPa depending on alloy and temper
• Elongation at Break: Measures ductility; usually 10–30% for common brass alloys
• Hardness: Measured in Brinell (HB) or Rockwell (HRB); varies by alloy and heat treatment
• Dimensional Tolerances: Diameter accuracy within ±0.05 mm to ±0.2 mm, depending on grade and application

Modern brass rod production machines are equipped with integrated sensors and automated inspection systems that continuously monitor:

• Rod diameter and roundness via laser micrometers
• Surface finish quality (roughness, cracks, pits)
• Threading accuracy and pitch consistency (for threaded rods)
• Length precision using optical encoders
• Chemical composition via inline spectrometry (in advanced facilities)

Safety Standards in Brass Rod Production Facilities

Safety in brass rod manufacturing involves protecting workers from machinery hazards, chemical exposure, and environmental risks. Compliance with occupational health and environmental regulations is mandatory and enforced through regular inspections.

• OSHA (Occupational Safety and Health Administration) – USA
  OSHA regulations are foundational for workplace safety in U.S. manufacturing plants. Key requirements include:
  • Machine Guarding (29 CFR 1910.212): All moving parts of lathes, cutters, rollers, and extrusion machines must be enclosed or guarded to prevent contact.
  • Lockout/Tagout (LOTO) – 29 CFR 1910.147: Ensures hazardous energy sources are isolated during maintenance to prevent accidental startup.
  • Personal Protective Equipment (PPE) – 29 CFR 1910.132: Mandates use of safety glasses, hearing protection, gloves, and steel-toed boots in production areas.
  • Exposure to Metal Fumes: Monitoring and ventilation required for zinc oxide fumes (from brass heating), which can cause "metal fume fever."
• MSHA (Mine Safety and Health Administration) – USA
  While not directly applicable to rod production, MSHA oversees safety in copper and zinc mining operations—the raw material sources for brass. Ethical and sustainable supply chains often require MSHA-compliant sourcing documentation.
• Local and National Safety Guidelines
  Regional agencies provide additional guidance on:
  • Safe handling of cutting oils, coolants, and lubricants
  • Fire prevention in areas with flammable coolants or dust accumulation
  • Emergency response plans for chemical spills or equipment failure
  • Worker training programs on hazard communication (HazCom) and machine operation
• EPA (Environmental Protection Agency) Regulations
  The EPA enforces environmental compliance in metal manufacturing:
  • Air Emissions: Control of particulate matter and metal fumes via filtration systems (e.g., baghouses, scrubbers)
  • Hazardous Waste Management: Proper disposal of spent coolants, metal shavings, and cleaning solvents under RCRA (Resource Conservation and Recovery Act)
  • Wastewater Discharge: Treatment of coolant runoff to remove heavy metals before release
  • Reporting: Submission of Toxics Release Inventory (TRI) reports for certain chemicals

Expert Tip: Implement a Quality Management System (QMS) like ISO 9001 alongside IATF 16949 to streamline compliance, improve traceability, and enhance customer confidence. Similarly, adopting an Environmental Management System (EMS) such as ISO 14001 helps standardize sustainability practices and reduce regulatory risk.

Best Practices for Compliance and Continuous Improvement

• Conduct regular internal audits of both quality and safety procedures
• Invest in operator training for machine-specific safety and quality checks
• Use automated data logging to track rod dimensions, machine performance, and defect rates
• Establish a corrective and preventive action (CAPA) system for non-conformances
• Partner with certified third-party labs for independent material verification
• Monitor regulatory updates from OSHA, EPA, and international standards bodies
• Engage in sustainability initiatives such as coolant recycling and energy-efficient machinery

By rigorously adhering to quality and safety standards, brass rod manufacturers ensure the production of high-performance materials that meet the demands of aerospace, automotive, plumbing, and electrical industries. These standards not only enhance product reliability but also foster a culture of safety, responsibility, and operational excellence across the entire production lifecycle.

Frequently Asked Questions About Brass Rods and Their Industrial Applications

Brass rods are versatile engineering materials known for their excellent machinability, corrosion resistance, and electrical conductivity. They play a critical role in a wide range of industrial and manufacturing sectors due to their durability and aesthetic appeal.

• Plumbing Industry: Brass rods are commonly used to manufacture valves, fittings, faucets, and pipe connectors due to their resistance to water corrosion and ability to maintain structural integrity under pressure.
• Automotive Sector: Components such as bushings, connectors, sensors, and transmission parts are often made from brass rods because they withstand high temperatures and reduce friction.
• Electrical & Electronics: Thanks to their good electrical conductivity, brass rods are ideal for producing terminals, switch components, sockets, and various types of connectors.
• Ammunition Manufacturing: The cartridge cases in rifle and pistol ammunition are frequently made from brass due to its ductility, strength, and ability to expand and seal the chamber upon firing.
• Marine & Shipbuilding: Marine hardware such as propeller shafts, fasteners, and underwater fittings benefit from brass’s resistance to saltwater corrosion.
• Civil Construction & Architecture: Decorative elements, door handles, railings, and architectural fixtures often use brass rods for both functional and aesthetic purposes.
• Mechanical Engineering: Used in gears, screws, bearings, and other precision-machined parts where low friction and wear resistance are essential.

Overall, brass rods serve as a foundational material in applications requiring a balance of strength, corrosion resistance, and ease of fabrication.

To ensure consistent performance and reliability, brass rods must meet stringent quality standards defined by international and industry-specific specifications. These standards govern material composition, mechanical properties, dimensional accuracy, and surface finish.

• Dimensional Tolerances: Diameter, length, straightness, and roundness must conform to precise tolerances (e.g., ASTM B453 or ISO 426) to ensure compatibility with machining and assembly processes.
• Alloy Composition: Common brass alloys include C36000 (free-cutting brass), C26000 (cartridge brass), and C28000 (naval brass). Each has specific copper-zinc ratios and may include lead or tin for enhanced machinability or corrosion resistance.
• Mechanical Properties: Key metrics include tensile strength (typically 300–500 MPa), yield strength, elongation (10–50%), and hardness (measured in Brinell or Rockwell scales).
• Surface Quality: Rods should be free from cracks, pits, seams, and excessive oxidation. A smooth surface finish is crucial for applications requiring tight tolerances or aesthetic appeal.
• Certifications: Reputable suppliers provide mill test certificates (MTCs) confirming compliance with standards such as ASTM, ASME, ISO, or DIN.

Adherence to these standards ensures that brass rods perform reliably across demanding industrial environments and meet regulatory requirements.

The production of brass rods involves high-temperature processes, heavy machinery, and exposure to metallic dust and chemical agents. Therefore, comprehensive safety protocols are essential to protect workers and maintain operational integrity.

• Machine Guarding: All moving parts of lathes, extruders, cutters, and drawing machines are equipped with protective shields to prevent accidental contact and reduce injury risks.
• Personal Protective Equipment (PPE): Workers are required to wear heat-resistant gloves, safety goggles, face shields, ear protection, and respirators when handling molten metal or fine particulates.
• Chemical Exposure Control: Proper ventilation systems and fume extraction units minimize inhalation of zinc oxide fumes (which can cause "metal fume fever") and other hazardous substances during melting and casting.
• Dust Management: Regular cleaning and use of HEPA-filtered vacuums control brass dust accumulation, which is combustible and potentially harmful if inhaled over time.
• Waste Disposal Protocols: Spent lubricants, metal shavings, and contaminated materials are disposed of according to environmental regulations to prevent pollution and ensure workplace hygiene.
• Training & Emergency Preparedness: Employees receive regular training on equipment operation, emergency shutdown procedures, fire safety, and first aid response.

These measures collectively create a safer working environment and help companies comply with OSHA, EPA, and other regulatory bodies.

Maintenance is a cornerstone of efficient and high-quality brass rod manufacturing. Production machines operate under intense conditions—high pressure, heat, and continuous motion—making regular upkeep essential for optimal performance and longevity.

• Lubrication: Ensures smooth operation of moving parts, reduces friction, and prevents overheating in drawing benches, extruders, and rolling mills.
• Residue Removal: Metal shavings, scale, and coolant buildup are cleaned regularly to avoid contamination and maintain precision in machining operations.
• Wear Inspection: Technicians routinely check dies, rollers, guides, and cutting tools for signs of wear or deformation that could affect rod dimensions or surface quality.
• Component Replacement: Worn or damaged parts are replaced promptly to prevent machine breakdowns and maintain production consistency.
• Calibration: Machines are calibrated periodically to ensure alignment, dimensional accuracy, and repeatability—critical for meeting tight tolerances in high-precision applications.

Preventive and predictive maintenance schedules not only extend equipment life but also reduce downtime, lower repair costs, and ensure the consistent production of high-quality brass rods.

The manufacturing of brass rods involves a series of specialized machines designed to shape, size, finish, and package the final product. Each machine plays a distinct role in transforming raw brass billets into precision-engineered rods.

Modern brass production facilities often integrate these machines into automated production lines, enhancing efficiency, reducing human error, and ensuring consistent product quality from batch to batch.