Custom Precision CNC Machining 4140 Steel Parts From China

We specialize in high-precision custom CNC machining 4140 steel parts China for demanding mechanical applications. With advanced multi-axis machining centers, rigorous process control, and deep metallurgical expertise, we deliver custom-machined 4140 steel components that meet exact dimensional, tolerance, and surface finish requirements — all manufactured cost-effectively in our Chinese production facility. Your trusted partner for custom CNC machining 4140 steel parts China.

4140 Steel CNC Machining Expertise

Deep understanding of AISI 4140 alloy steel — equivalent to 42CrMo4 (EN) and SCM440 (JIS). We machine this versatile chrome-moly steel in annealed, normalized, and quenched-and-tempered conditions with optimized cutting parameters for each hardness state. Our custom CNC machining 4140 steel parts China service ensures consistent quality across every batch.

  • Pre-hardened stock up to 38 HRC
  • Annealed and normalized conditions supported
  • Full traceability from raw bar stock
  • Mill certificates available on request

Precision Tolerance Control

Our CNC lathes and machining centers maintain extremely tight dimensional accuracy on 4140 steel parts. We routinely hold tolerances that exceed general industry standards, ensuring your components fit and function perfectly in their intended assemblies. Count on us for reliable custom CNC machining 4140 steel parts China.

  • Standard tolerance: ±0.01 mm
  • Precision tolerance: ±0.005 mm
  • Surface roughness down to Ra 0.4 μm
  • Geometric tolerances per ASME Y14.5

Heat Treatment Coordination

We partner with trusted heat-treatment facilities to provide a full range of thermal processing for 4140 steel components — either before or after machining — to achieve the exact hardness, toughness, and wear-resistance your application requires. Ideal for custom CNC machining 4140 steel parts China with post-machining treatments.

  • Quench & temper: 28-40 HRC ranges
  • Annealing: ~197 HB (machinable state)
  • Stress relieving for dimensional stability
  • Induction hardening for localized wear zones

Surface Finish & Coating Options

Beyond precision machining, we offer a variety of surface treatments to enhance corrosion resistance, appearance, and functional performance of your 4140 steel parts — all managed under one roof for seamless supply chain efficiency. Complete your custom CNC machining 4140 steel parts China project with the perfect finish.

  • Black oxide for mild corrosion resistance
  • Zinc plating (clear, yellow, black)
  • Electroless nickel plating for wear protection
  • QPQ / salt bath nitriding for surface hardening

Industries & Typical Applications

4140 steel's outstanding strength-to-weight ratio and fatigue resistance make it the material of choice for high-load mechanical components across a wide range of industrial sectors. We manufacture custom CNC machining 4140 steel parts China for both OEM and aftermarket needs.

  • Drive shafts, axles, and spindles
  • Gears, splines, and couplings
  • Hydraulic cylinder rods and pistons
  • Tooling, die components, and fixtures

Rigorous Quality Assurance Process

Every batch of 4140 steel components undergoes systematic inspection at multiple stages of production. Our quality team uses calibrated precision measuring instruments to verify dimensional accuracy, surface finish, and material integrity for custom CNC machining 4140 steel parts China.

  • CMM inspection for complex geometries
  • Hardness testing (Rockwell & Brinell)
  • Micrometer and bore gauge verification
  • Batch-level inspection reports included
Custom CNC machining 4140 steel spline shaft parts China
Spline Shaft
Custom CNC machining 4140 steel gear shaft parts China
Gear Shaft
Custom CNC machining 4140 steel hydraulic valve block parts China
High-Pressure Hydraulic Valve Block
Custom CNC machining 4140 steel shaft bushing parts China
Shaft Bushing

International Grade Equivalents for 4140 Alloy Steel

Standard / Region Designation
AISI / SAE (USA) 4140, 4140H
DIN / EN (Europe) 42CrMo4 (1.7225)
JIS (Japan) SCM440
GB (China) 42CrMo
BS (United Kingdom) 708M40
UNI (Italy) 42CrMo4
NF (France) 42CD4
GOST (Russia) 38KhM

Typical Chemical Composition — AISI 4140

Element Weight %
Carbon (C) 0.38 – 0.43
Manganese (Mn) 0.75 – 1.00
Chromium (Cr) 0.80 – 1.10
Molybdenum (Mo) 0.15 – 0.25
Silicon (Si) 0.15 – 0.35
Phosphorus (P) ≤ 0.035
Sulfur (S) ≤ 0.040
Iron (Fe) Balance

Mechanical Properties (Quenched & Tempered)

Property Typical Value
Tensile Strength 655 – 1,100 MPa
Yield Strength (0.2%) 415 – 850 MPa
Elongation 10 – 25 %
Hardness (Annealed) ~197 HB
Hardness (Q&T) 28 – 40 HRC
Modulus of Elasticity 205 GPa
Density 7.85 g/cm³
Thermal Conductivity 42.6 W/m·K

Engineering Review

We analyze your 2D drawings or 3D CAD models (STEP, IGES, or native formats) to optimize machining strategies, fixture design, and tooling selection for custom CNC machining 4140 steel parts China.

Material Preparation

Raw 4140 steel bar stock is sourced from certified mills, cut to precise lengths, and pre-inspected for hardness and dimensional conformity before machining begins.

Precision CNC Machining

Multi-axis CNC lathes and vertical machining centers perform turning, milling, drilling, threading, and boring operations with optimized feeds and speeds for 4140 steel.

Inspection & Delivery

Finished components undergo final dimensional verification, surface finish checks, and packaging for safe transit — with inspection reports provided on request.

500+
4140 Parts Delivered Monthly
±5 μm
Precision Tolerance Achieved
10+ Years
Machining Alloy Steels
7–15 Days
Typical Lead Time