Heating, ventilation, air conditioning, and refrigeration systems run silently in the background of modern life. A compressor in a rooftop unit might cycle on and off for 15 years. A refrigeration valve on a shipping container might see extreme temperature swings from -20°C to +40°C. A chiller in a data center runs 24/7/365. All this equipment relies on precision CNC machined parts OEM components that must hold refrigerants under pressure, maintain tight clearances for oil films, and resist corrosion from moisture and acids. China has become a major supplier of HVAC precision parts to global brands like Carrier, Trane, Daikin, Mitsubishi Electric, LG, and Gree, as well as the vast aftermarket for replacement components. This guide walks through the key machined components for compressors, valves, heat exchangers, and chillers, covering materials, tolerances, sealing requirements, and practical tips for sourcing from Chinese manufacturers.
If you've machined parts for automotive or general industry, HVAC components might seem straightforward. But refrigeration systems have particular demands that not every machine shop understands.
Refrigerant compatibility. Modern refrigerants (R410A, R32, R134a, R290) have different chemical behaviors. Some are slightly acidic under certain conditions. Some are flammable. Some operate at high pressures (R410A can reach 600 psi on the discharge side). Machined parts must be compatible—no reactions, no porosity that could leak, no materials that absorb refrigerant.
Oil management. Compressors circulate oil with the refrigerant to lubricate moving parts. Machined surfaces need specific finishes to retain an oil film and prevent metal-to-metal contact. Too smooth, and oil doesn't stick; too rough, and parts wear quickly.
Tight clearances. Scroll compressors have mating spiral parts with clearances measured in hundredths of a millimeter. Rotary compressors have cylinder bores that must be round and straight to within 0.005mm. These aren't automotive engine tolerances—they're often tighter.
Moisture and contamination sensitivity. A tiny burr or particle inside a refrigeration system can lodge in an expansion valve or score a compressor cylinder. Machined parts must be deburred and cleaned thoroughly before assembly.
High volume, cost sensitivity. The HVAC market is massive. A single compressor model might be produced in millions of units per year. Chinese CNC shops that serve this market are experts in high-volume, low-cost production with automated inspection.
Chinese suppliers that excel in HVAC machining typically have ISO 9001 (often IATF 16949 for automotive-derived processes), in-house heat treatment, honing or grinding capabilities, and clean assembly areas. Many are located in Guangdong, Zhejiang, and Jiangsu provinces, near major HVAC equipment manufacturers.
The compressor is the heart of any refrigeration system. It pumps refrigerant from low pressure to high pressure, creating the temperature difference that enables cooling. Compressor components are among the most precisely machined parts in HVAC.
Scroll compressors use two interleaving spiral-shaped parts (scrolls) to compress refrigerant. One scroll orbits relative to the other, creating moving pockets that get smaller as they move toward the center. Machined scroll components include:
Fixed scroll (machined from cast iron or aluminum, with precise spiral walls)
Orbiting scroll (similar, with bearing hub)
Crankshaft (eccentric shaft that drives the orbiting scroll)
Upper and lower bearing housings (support the crankshaft)
Seal plate (separates high and low pressure)
The most critical part is the scroll spiral. The spiral walls must be smooth (Ra 0.4μm or better), the flank angle must be consistent, and the tip height must be uniform to within 0.01mm. Small deviations cause leakage and efficiency loss. Chinese shops that make scrolls typically use 4-axis or 5-axis CNC mills with custom form tools or ball end mills. After machining, scrolls are often deburred by abrasive flow machining (AFM) to remove any tiny burrs from the spiral flanks. Material for scrolls is usually cast iron (for durability and vibration damping) or aluminum (for lighter, higher-speed compressors). Some high-efficiency scrolls use a PTFE or molybdenum disulfide coating on the spiral tips to reduce friction and improve sealing.
Rotary compressors have a cylindrical roller that orbits inside a cylinder, compressing refrigerant in the crescent-shaped space. Key machined parts:
Cylinder block (precision-honed bore, often with vane slot)
Roller piston (hardened steel, precision-ground outer diameter)
Vane (rectangular blade that slides in the cylinder slot)
Upper and lower bearing plates (support the crankshaft and seal the cylinder ends)
Crankshaft (with offset crankpin)
The cylinder block is typically made from gray cast iron or powdered metal. The bore is honed to a precise diameter (H7 or H8 tolerance) with a cross-hatch pattern to retain oil. The vane slot is broached or milled and must be perpendicular to the bore and parallel to the cylinder axis within 0.005mm. Chinese shops that specialize in rotary compressor parts have dedicated honing machines (Sunnen or similar) and broaching equipment. The roller piston is a hardened steel cylinder (58-62 HRC) with ground outer diameter (h6 tolerance) and surface finish Ra 0.2μm. The clearance between roller and cylinder bore is typically 0.010-0.025mm—small enough to seal but large enough for an oil film. This clearance is critical; too tight, and the compressor seizes; too loose, and it leaks.
Older or smaller compressors use a piston-cylinder design, similar to an internal combustion engine. Machined parts include:
Cylinder block or crankcase (cast iron, with bored cylinders)
Piston (aluminum or cast iron, with ring grooves)
Connecting rod (machined from aluminum or powdered metal)
Crankshaft (steel or cast iron, with counterweights)
Valve plate (steel, with precisely drilled ports)
The valve plate is a flat steel plate with small holes or slots for suction and discharge valves. The holes must be deburred—any sharp edge can damage the thin reed valves that open and close. Chinese shops often use CNC drilling followed by electropolishing or vibratory deburring to achieve smooth edges.
Refrigeration systems have several types of valves: expansion valves (TXV or EEV), service valves, check valves, and solenoid valves. Valve bodies for refrigeration are typically machined from brass, stainless steel, or aluminum.
A TXV meters refrigerant flow into the evaporator based on temperature feedback. Machined components include:
Valve body (brass or stainless, with inlet, outlet, and equalizer ports)
Needle and seat (precision-machined to control flow)
Power head (diaphragm housing, often brass)
Adjustment screw (for superheat setting)
The needle and seat are the most critical. The needle is a tapered stainless steel pin; the seat is a matching brass or stainless orifice. When the needle contacts the seat, it must seal completely. This requires a lapped fit with a surface finish of Ra 0.1μm or better. Chinese shops that make TXV parts often have Swiss-type CNC lathes for the needle and precision boring for the seat. They may also offer lapping or mating (running the needle into the seat with abrasive paste).
EEVs use a stepper motor to position a needle. Machined parts add:
Stator housing (plastic or aluminum)
Rotor assembly (magnets on a machined shaft)
Lead screw (stainless steel, with precision threads)
Guide bushing (brass or PEEK)
The lead screw must have low friction and minimal backlash. Threads are often Acme or custom profile, machined on a CNC lathe with thread whirling or single-point cutting. The lead screw is typically case-hardened (55-60 HRC) and ground on the thread flanks.
Service valves are used for charging and maintaining refrigeration systems. Common machined parts:
Valve body (brass or stainless, often forged then machined)
Ball (stainless steel or brass, precision-ground)
Stem and seal (with O-ring grooves)
End fittings (flare or solder connections)
Ball valves require a precision-machined ball that is round to within 0.005mm and has a smooth surface (Ra 0.2μm) to seal against PTFE seats. Chinese shops often outsource ball grinding to specialists; ask about their ball supplier.
Heat exchangers—condensers, evaporators, and coils—transfer heat between refrigerant and air or water. Heat exchanger parts include end plates, tube sheets, and manifolds.
In a shell-and-tube heat exchanger, the tube sheet holds the ends of the tubes. It's a thick plate (10-50mm) with dozens or hundreds of precisely drilled holes. The holes must be round, straight, and positioned accurately to receive the tubes (typically with a light press fit or welded joint). Tolerances:
Hole diameter: H8 or H9 (e.g., 10mm +0.022/+0.000)
Hole position: ±0.05mm for the pattern
Plate flatness: 0.1mm over the entire surface
Surface finish inside holes: Ra 1.6μm (for tube insertion)
Chinese shops use CNC drilling centers or gantry mills for tube sheets. For very thick plates, they may use gun drilling or BTA drilling to maintain straightness. Material is typically carbon steel (for water or refrigerant) or stainless steel 316 (for corrosive fluids).
Manifolds distribute refrigerant to multiple circuits. Machined parts include:
Manifold block (aluminum or brass, with drilled passages)
Distribution nozzles (small orifices for refrigerant distribution)
End caps and plugs
Manifold blocks are often machined from extruded aluminum bar or forged brass. The internal passages are drilled from multiple directions, then plugged. The intersections must be deburred—a sharp edge can create turbulence or catch debris. Some shops use abrasive flow machining (AFM) to deburr internal passages uniformly.
Industrial chillers (100+ tons of cooling) use larger components than residential HVAC. Chiller parts include compressor housings, motor frames, and heat exchanger shells. These parts are often machined from cast iron or steel and can weigh hundreds of kilograms.
Large chillers often use centrifugal compressors. Machined parts include:
Compressor casing (cast iron or steel, machined on large horizontal boring mills)
Impeller (aluminum or steel, 5-axis machined)
Diffuser vanes (precision-machined rings)
Bearing housings (with precision bores)
The impeller is a complex 3D shape with curved vanes. It's typically machined from a solid billet of aluminum 6061 or 7075 (for lower cost) or stainless steel (for corrosive refrigerants). Chinese shops with 5-axis machining centers can produce impellers, but ask to see examples—it's a specialty. Tolerances on blade profiles are typically ±0.05mm, with surface finish Ra 0.8μm. After machining, impellers are balanced dynamically.
The motor that drives a chiller compressor has a stator housing and end bells. These are large-diameter parts (300-800mm) machined from cast iron or fabricated steel. Critical features:
Stator bore: H7 tolerance, with a smooth finish (Ra 1.6μm) for interference fit of the stator core
Bearing housings: concentric to stator bore within 0.03mm TIR
Mounting feet: flat and parallel to the bore axis
Chinese shops with vertical turret lathes (VTLs) and large horizontal boring mills are equipped for chiller components. These machines have swing capacities over 1,000mm and can handle parts weighing several tons.
Material selection depends on pressure, temperature, refrigerant compatibility, and cost:
Gray cast iron (ASTM A48 Class 30-40) for compressor housings, cylinder blocks, and bearing supports. Good machinability, vibration damping, and low cost. Not suitable for very high pressures or corrosive refrigerants.
Ductile iron (ASTM A536 65-45-12) for higher-strength parts like crankshafts and connecting rods in larger compressors. Better impact resistance than gray iron.
Aluminum 6061-T6 for scrolls, valve bodies, and heat exchanger manifolds. Lightweight, good thermal conductivity, and machinable. Not for high-pressure refrigerant on the discharge side (aluminum can fatigue).
Brass C360 (free-cutting) for valve bodies, fittings, and service ports. Excellent machinability, corrosion resistance, and compatibility with refrigerants. Standard for TXV bodies.
Stainless steel 303, 304, 316 for valve stems, needle and seat, and components in corrosive environments (e.g., chillers using seawater for cooling). 303 is easiest to machine; 316 is most corrosion-resistant.
Steel 12L14, 1144 for general shafts and pins. Free-machining but not for high stress. For high-stress shafts (crankshafts), use 4140 or 4340 heat-treated to 35-45 HRC.
Powdered metal (sintered steel) for high-volume parts like valve plates, connecting rods, and bearing caps. Lower cost than machined bar stock for volumes above 50,000 pieces per year.
PEEK or PTFE for valve seats, seals, and wear pads. Chemically compatible with all refrigerants, low friction, wide temperature range. Expensive but necessary for low-leakage applications.
WARNING: Avoid brass containing lead for refrigerant systems with R32 or R290 (flammable refrigerants). Lead can react under some conditions. Use lead-free brass (e.g., C69300) instead.
Sealing is critical in HVAC parts—refrigerant leaks harm efficiency and the environment. Machined surfaces that act as seals need specific finishes:
Flare fittings: The conical sealing surface needs Ra 0.4μm or better, with no scratches across the sealing area.
O-ring grooves: Groove bottom and sides Ra 0.8-1.6μm, with no burrs or sharp edges that could cut the O-ring.
Flat gasket surfaces: Flatness 0.05mm over the face, Ra 0.8-1.6μm, with a spiral or concentric finish pattern (not a cross-hatch that could create leak paths).
Needle and seat: Lapped surface Ra 0.1μm or better for bubble-tight shutoff.
Compressor cylinder bore: Cross-hatch pattern (30-60 degree angle) to retain oil, with Ra 0.4-0.8μm.
Specify sealing surfaces clearly on your drawing. For example: "Sealing surface A to be flat within 0.03mm and finished to Ra 0.4μm maximum, with no scratches across the sealing area. Inspect visually under 10x magnification."
Quality expectations vary by component criticality. Leak-critical parts (valve bodies, compressor housings) need more inspection than brackets or non-sealing covers. Typical QC practices:
First article inspection (FAI): Full dimensional check including CMM measurement of all critical features.
In-process sampling: Check critical dimensions (bore diameters, thread concentricity) every 20-50 parts.
Leak testing: For valve bodies and compressor housings, a helium leak test or pressure decay test (e.g., 300 psi air, submerged in water). Many Chinese shops have automated leak test stations.
Surface finish measurement: Profilometer printouts for sealing surfaces.
Hardness testing: Rockwell or Brinell on heat-treated parts.
Cleanliness: For compressor internal parts, require particle count or visual inspection under UV light (to detect oil residue).
For high-volume production, Chinese shops often use in-line automatic gauging (air gauges for bores, laser micrometers for diameters) that rejects bad parts instantly. Ask about their automated inspection capability.
Here's a practical selection process:
Step 1: Look for HVAC or refrigeration experience. Ask if they have made parts for compressors, valves, or heat exchangers. Request references from HVAC customers. A shop that understands refrigerant compatibility and leak testing is valuable.
Step 2: Check their material capabilities. Do they work with brass, cast iron, aluminum, and stainless? Do they have in-house heat treatment for steel parts? Can they source lead-free brass if needed?
Step 3: Evaluate their secondary operations. Do they offer honing (for compressor cylinders), lapping (for needle/seat), deburring (abrasive flow or electropolishing), and leak testing? Shops with in-house finishing are more reliable.
Step 4: Assess their cleanroom or cleanliness procedures. For compressor internal parts, contamination is a risk. Ask to see their cleaning process (ultrasonic? vapor degreasing?) and packaging (clean bags, sealed).
Step 5: Request a sample run. Order a small quantity (50-200 pieces) of a critical part like a valve body or a compressor cylinder. Test for leaks, inspect sealing surfaces, and check cleanliness.
Many Chinese suppliers for HVAC parts are located in Guangdong (around Zhuhai, where Gree is based), Zhejiang (around Ningbo and Shaoxing), and Jiangsu (Suzhou, Wuxi). These regions have strong HVAC equipment manufacturing clusters.
HVAC parts are produced in high volumes. Here are rough benchmarks for pricing at 10,000+ pieces per year:
Brass valve body (TXV, 100g, machined from forging): $0.80-1.50 each
Compressor cylinder block (cast iron, honed bore): $2-4 each
Aluminum scroll (cast, finish-machined): $3-6 each
Steel crankshaft (turned, ground, hardened): $2-5 each (depending on size)
Heat exchanger tube sheet (steel, 100 holes, 200mm diameter): $10-20 each
Lead times: For parts requiring new castings or forgings, add 6-10 weeks for tooling. For machined-from-bar parts, first article in 3-5 weeks, production 2-4 weeks. Heat treatment, plating, or leak testing add 1-2 weeks. Shipping: air freight 3-7 days, sea freight 30-45 days.
Minimum order quantities for cost-effective pricing: 1,000-5,000 pieces for machined parts; higher for castings (5,000-20,000). Many shops accept smaller orders (100-500 pieces) but at higher per-piece prices (2-3x).
Based on real sourcing experience, here are frequent issues with HVAC parts from China:
Leaks through porosity. Cast valve bodies or compressor housings may have micro-porosity that leaks refrigerant. Prevention: require pressure testing (e.g., 500 psi air under water) on 100% of cast parts. Also specify maximum allowable leakage rate (e.g.,<1g/year helium equivalent).
Burrs on valve seats. A tiny burr on a needle seat prevents sealing. Prevention: specify "no visible burrs on seat under 20x magnification" and require inspection. Consider specifying electropolishing or abrasive flow deburring.
Incorrect surface finish on O-ring grooves. Too rough, and the O-ring abrades; too smooth, and it doesn't seal. Prevention: specify Ra range (e.g., 0.8-1.6μm) and require a profilometer report. Also specify "no scratches across the groove."
Thread galling on brass fittings. Brass threads can gall (seize) when assembled dry. Prevention: specify a lubricant or anti-seize coating (e.g., Teflon-based) on threads. Or use lead-free brass with better galling resistance.
Contamination inside compressor parts. Machining chips or oil residue left inside a compressor can cause failure. Prevention: specify a cleaning process (e.g., ultrasonic with detergent, followed by DI rinse and hot air dry). Require cleanliness verification (particle count or visual under UV).
The HVAC industry is evolving, and Chinese shops are adapting:
Lower GWP refrigerants. New refrigerants (R32, R454B, R290) have different pressure and flammability characteristics. Machined parts for these systems need tighter sealing and sometimes different materials. Shops are investing in better leak testing and alternative materials (e.g., lead-free brass).
Inverter-driven compressors. Variable-speed compressors run at different speeds, changing oil circulation and wear patterns. Scroll and rotary compressor parts are being redesigned for wider speed ranges, requiring more precise machining.
Microchannel heat exchangers. Aluminum microchannel coils are replacing copper tube-and-fin designs. Machined manifolds and headers for microchannel coils require precise hole patterns and clean drilling.
Additive manufacturing for complex parts. Some expansion valve bodies and compressor components are being 3D printed (metal laser sintering) to create internal passages that can't be drilled. This is still niche but growing for high-performance systems.
Automated inspection and assembly. Chinese shops are investing in inline vision systems and robotic assembly to reduce labor costs and improve consistency.
Sourcing HVAC precision parts from China is a well-established, mature practice. The supply chain is deep, costs are competitive, and quality can be excellent if you choose a shop with relevant experience. The key is understanding the unique requirements: refrigerant compatibility, sealing surface finishes, leak testing, and cleanliness. Start with a trial order of a critical component, verify their processes, and build a long-term partnership.
Need help sourcing precision machined parts for HVAC or refrigeration equipment? Send us your drawings and annual volume estimates. We work with a network of Chinese CNC shops that specialize in compressor components, valve bodies, heat exchanger parts, and chiller components—with in-house honing, leak testing, and cleaning. Free DFM feedback and quoting available.
A: Gray cast iron (Class 30-40) is standard. It retains oil well (the graphite flakes act as reservoirs) and has good wear resistance. For higher-pressure or higher-speed compressors, some use ductile iron or even steel with a special coating. But for most HVAC applications, gray iron is the proven choice.
A: Specify the surface finish (Ra 0.1μm max for a lapped metal-to-metal seat), the flatness or roundness (e.g., 0.002mm for a needle seat), and require a leak test (e.g., helium leak rate<1x10^-5 scc/s). Also specify that the seat must be free of scratches, burrs, and tool marks when inspected under 20x magnification.
A: Yes, many have 5-axis machining centers and specialized CAM software for scroll profiles. However, not every shop has experience with the thin walls and precise tip heights. Ask for sample parts or case studies. Also ask about their deburring process—scroll spirals often require abrasive flow machining to remove burrs from the flanks.
A: For small refrigeration compressors (1-5 hp), the radial clearance is typically 0.010-0.020mm. For larger compressors, 0.020-0.030mm. The clearance must be uniform around the circumference (roundness of both parts within 0.003mm). Chinese shops with honing and grinding capabilities can achieve these clearances.
A: R32 is mildly flammable and operates at higher pressures than R410A. Standard materials (cast iron, aluminum, brass, steel) are compatible, but avoid materials that can spark (e.g., beryllium copper). Also, ensure that any plastic seals or gaskets are R32-compatible (standard EPDM or HNBR is fine). The bigger concern is ensuring that machined parts can handle the higher pressure (discharge up to 600 psi).
A: Specify the drilling method (e.g., CNC drilling with peck cycle), deburring (e.g., light chamfer or abrasive brush), and inspection (e.g., go/no-go pin gauge for hole size, borescope for burrs). For very thick tube sheets, specify gun drilling or BTA drilling to maintain straightness. Ask the supplier about their hole quality control process.
A: If the valve body is machined from bar stock (no forging), MOQs of 500-2000 pieces are typical. If it's forged first (for better material properties and lower machining cost), the forging die costs $3,000-8,000, so MOQs of 5,000-20,000 are needed to amortize the die. For low volumes, stick with bar stock machining.
A: Yes, many have helium leak test equipment (mass spectrometer type). They can test to very low leakage rates (e.g., 1x10^-6 scc/s). Specify the maximum allowable leak rate and the test pressure. Also ask for a calibration certificate for the leak tester. This is common for automotive AC components and is widely available in China.
A: For a steel shaft running in a sintered bronze bearing, Ra 0.2-0.4μm is typical. For a shaft running directly in a cast iron bearing (some small compressors), Ra 0.1-0.2μm is better. The shaft should be ground (not just turned) to achieve the roundness and finish. Specify "grind after heat treat" and require a profilometer report.
A: Search for "large CNC machining China" or "horizontal boring mill China." Look for shops with VTLs (vertical turret lathes) with swing over 1,000mm and HMCs with travels over 2,000mm. Ask for photos of their large machines and examples of chiller parts they've made. Regions like Shanghai, Suzhou, and Dalian have heavy machining capabilities.
Ready to source precision machined parts for HVAC or refrigeration equipment? Contact us with your drawings and annual volumes. We'll match you with qualified Chinese CNC shops that specialize in compressor, valve, and heat exchanger components—with leak testing, honing, and cleaning capabilities. Free quoting and DFM feedback available.
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