What steel grades are best for CNC machining?

12L14 offers the best machinability and is ideal for screw machine parts. 1018 is excellent for general-purpose welding and machining. 4140 is the most common alloy steel for shafts and gears.

What is the difference between carbon steel and alloy steel?

Carbon steel contains primarily iron and carbon with minimal alloying elements. Alloy steel adds chromium, molybdenum, nickel, or vanadium to improve strength, hardenability, and toughness. Alloy steels like 4140 and 4340 are used for high-stress applications.

Can you machine hardened steel?

Yes, hardened steels up to 60 HRC can be machined with carbide tooling. However, most machining is performed in the annealed condition with heat treatment applied after machining. Tool steels are typically machined soft then hardened.

What surface finishes are available for steel parts?

As-machined, ground, polished, bead blasted, zinc plated, electroless nickel plated, hard chrome plated, black oxide, and powder coated.

How do you prevent corrosion on steel parts?

Zinc plating provides basic protection. Electroless nickel and hard chrome offer superior corrosion and wear resistance. Black oxide provides mild protection with a dark finish. Powder coating provides durable decorative protection.

What tolerances can steel machining achieve?

Standard milling and turning hold ±0.02-0.05mm. Precision work holds ±0.01mm. Grinding achieves ±0.002mm on critical features.

CNC Steel

CNC steel machining is the precision processing of steel workpieces using computer-controlled cutting tools to produce high-strength, durable components. Steel offers exceptional mechanical properties—high tensile strength, hardness, wear resistance, and fatigue strength—making it the most widely specified material for load-bearing and high-stress applications. The material is available in multiple grades: carbon steels (1018, 1045, 12L14) for general-purpose parts, alloy steels (4130, 4140, 4340, 8620) for high-strength components, tool steels (A2, D2, O1, S7, M2) for dies and cutting tools, and stainless steels for corrosion-resistant applications -5.

CNC steel machining encompasses milling, turning, drilling, boring, and grinding operations. Tolerances range from ±0.02mm to ±0.05mm for standard work, with precision grinding achieving ±0.002mm on critical features -1 -4. Surface finishes as-machined reach Ra 1.6–3.2μm, with grinding achieving Ra 0.2–0.8μm. Industries served include automotive, aerospace, heavy equipment, oil and gas, and industrial machinery.

Our CNC Machining Services

From prototype to production — reliable quality, on-time delivery

We provide precision CNC machining services for a wide range of materials including aluminum, steel, stainless steel, copper, brass, titanium, PEEK, PTFE, acetal, nylon, and other engineering plastics. Our manufacturing capabilities cover 3-axis, 4-axis, and 5-axis CNC milling, as well as CNC turning, suitable for both prototype development and high-volume production runs.

With ISO 9001:2015 certification and a commitment to quality, we serve customers across aerospace, automotive, medical, electronics, industrial equipment, and consumer goods industries. Our in-house capabilities include surface finishing, anodizing, powder coating, heat treatment, and inspection with CMM and optical measurement equipment.

We offer competitive pricing, flexible lead times, and full material traceability. From simple brackets to complex precision components, we deliver parts that meet your specifications with reliable quality and on-time delivery.

Case StudiesMore+

SLINAR - Precision 304 Stainless Steel Test Fixture Block: High-Stability Milling for Semiconductor Test Equipment

Precision 304 Stainless Steel Test Fixture Block: High-Stability Milling for Semiconductor Test Equipment-stainless_steel

SLINAR - Precision 304 Stainless Steel Semiconductor Cavity Component: High-Accuracy Milling with Strict Perpendicularity and Flatness Control

Precision 304 Stainless Steel Semiconductor Cavity Component: High-Accuracy Milling with Strict Perpendicularity and Flatness Control-stainless_steel

SLINAR - Precision D2 Tool Steel Fixture Fastening Component: High-Accuracy Milling with Superior Flatness for 3C Assembly Tooling

Precision D2 Tool Steel Fixture Fastening Component: High-Accuracy Milling with Superior Flatness for 3C Assembly Tooling-stainless_steel

SLINAR - Precision 304 Stainless Steel Liquid Cooling Adapter: Milling + Turning Solution with Passivation Treatment

Precision 304 Stainless Steel Liquid Cooling Adapter: Milling + Turning Solution with Passivation Treatment-stainless_steel

SLINAR - Precision 304 Stainless Steel Knurled Micro-Adjustment Handle Shaft with Passivation and TIR Control for Medical Equipment

Precision 304 Stainless Steel Knurled Micro-Adjustment Handle Shaft with Passivation and TIR Control for Medical Equipment-stainless_steel

SLINAR - CNC Machined Stainless Steel Precision Gear Components - Group Overview

CNC Machined Stainless Steel Precision Gear Components - Group Overview-stainless_steel

Materials

Alloy Steel 16MnCr5

Alloy steel 1.7131 | 16MnCr5

Steel 1.7131 has a high surface hardness and wear resistance with good machinability.

Understand Alloy Steel 16MnCr5

Alloy Steel 4140

Alloy steel 4140 | 1.7225 | EN19 | 42CrMo4

Alloy steel 4140 (CNC) has good overall properties, with good strength and toughness. Suitable for many industrial applications. Not weldable.

Understand Alloy Steel 4140

Alloy Steel 4340

Alloy steel 4340 | 1.6511 | 36CrNiMo4 | EN24

Alloy steel 4340 (CNC) can be heat treated to high strength, while maintaining good toughness, wear resistance and fatigue strength. Weldable.

Understand Alloy Steel 4340

Alloy Steel 1215

Alloy steel 1215 | EN1A | 1.0715

Alloy steel 1215 is a low tensile, low harden-ability carbon steel. Can be machined at higher speeds.

Understand Alloy Steel 1215

Applications

Automotive

Transmission shafts, gears, and axle components
Engine brackets, mounts, and structural parts
Suspension components and steering linkages
Brake system components and fasteners

Aerospace

Landing gear components (4340 alloy steel)
Engine mounts and structural brackets
Hydraulic actuators and manifold bodies
High-strength fasteners and fittings

Industrial Equipment

Pump shafts, impellers, and valve bodies
Gear housings and drive system components
Machine tool components and fixture plates
Heavy equipment structural parts

Tool & Die

Stamping dies and forming tools (tool steels)
Injection mold components
Cutting tools and wear parts
Jigs, fixtures, and gauges

Oil & Gas

Valve bodies and wellhead components
Connectors and high-pressure fittings
Downhole tool components

Capabilities

We machine all common steel grades including carbon steels (1018, 1045, 12L14), alloy steels (4130, 4140, 4340, 8620), and tool steels (A2, D2, O1, S7). Equipment includes 3/4/5-axis CNC milling centers, CNC turning centers with live tooling, and surface and cylindrical grinding. Turning handles diameters up to 600mm and lengths to 1,500mm. Milling handles parts up to 2,000mm x 800mm x 600mm -8. Tolerances are held to ±0.02–0.05mm standard, with precision grinding achieving ±0.002mm on request. Heat treatment and surface finishing available in-house. ISO 9001:2015 and AS9100D certified.

Finishes

Plating

Zinc Plating: Basic corrosion protection for carbon steel
Electroless Nickel: Uniform coating with hardness and corrosion resistance
Hard Chrome: Wear-resistant coating for shafts and bearing surfaces
Black Oxide: Mild corrosion protection with dark appearance

Coating

Powder Coating: Durable polymer finish in any color
PTFE / Teflon: Low-friction non-stick surface
Phosphate Coating: Base for paint adhesion, corrosion protection

Heat Treatment

Quench & Temper: Increases hardness and strength
Case Hardening: Hardened surface with tough core
Nitriding: Surface hardening with minimal distortion
Annealing: Softens for improved machinability

Mechanical Finishes

Grinding: Precision surface finish with tight tolerances
Polishing: High-gloss reflective surface
Bead Blasting: Uniform matte texture
Tumbling: Edge deburring and surface smoothing

Technical Specs

Steel Grade	Type	Tensile (ksi)	Yield (ksi)	Hardness	Machinability	Common Uses
1018	Carbon	63	53	126 HB	Excellent	General purpose, shafts, pins
1045	Carbon	91	77	179 HB	Good	Gears, axles, bolts
12L14	Carbon	78	60	163 HB	Excellent	Screw machine parts, fittings
4130	Alloy	97	63	197 HB	Good	Aircraft, motorsport, tubing
4140	Alloy	95	60	197 HB	Good	Shafts, gears, tooling
4340	Alloy	108	68	217 HB	Fair	Landing gear, crankshafts
8620	Alloy	90	60	180 HB	Good	Gears, camshafts, pins
A2	Tool	230	—	57-62 HRC	Poor	Dies, punches, tooling
D2	Tool	248	—	58-64 HRC	Poor	Cutting tools, dies, wear parts
O1	Tool	200	—	57-62 HRC	Fair	Gauges, jigs, knife blades
S7	Tool	210	—	54-58 HRC	Fair	Impact tools, chisels
M2	HSS	230	—	60-65 HRC	Poor	Drill bits, end mills, taps

Parameter	Capability
Max Part Size (Milling)	2,000mm x 800mm x 600mm
Max Part Size (Turning)	600mm diameter x 1,500mm length
Standard Tolerance	±0.02 – 0.05mm
Precision Tolerance	±0.01mm
Grinding Tolerance	±0.002mm
Surface Finish (As-Machined)	Ra 1.6 – 3.2μm
Surface Finish (Ground)	Ra 0.2 – 0.8μm
Max Part Weight	1,500kg

FAQs

What steel grades are best for CNC machining?

12L14 offers the best machinability and is ideal for screw machine parts. 1018 is excellent for general-purpose welding and machining. 4140 is the most common alloy steel for shafts and gears.
What is the difference between carbon steel and alloy steel?

Carbon steel contains primarily iron and carbon with minimal alloying elements. Alloy steel adds chromium, molybdenum, nickel, or vanadium to improve strength, hardenability, and toughness. Alloy steels like 4140 and 4340 are used for high-stress applications.
Can you machine hardened steel?

Yes, hardened steels up to 60 HRC can be machined with carbide tooling. However, most machining is performed in the annealed condition with heat treatment applied after machining. Tool steels are typically machined soft then hardened.
What surface finishes are available for steel parts?

As-machined, ground, polished, bead blasted, zinc plated, electroless nickel plated, hard chrome plated, black oxide, and powder coated.
How do you prevent corrosion on steel parts?

Zinc plating provides basic protection. Electroless nickel and hard chrome offer superior corrosion and wear resistance. Black oxide provides mild protection with a dark finish. Powder coating provides durable decorative protection.
What tolerances can steel machining achieve?

Standard milling and turning hold ±0.02-0.05mm. Precision work holds ±0.01mm. Grinding achieves ±0.002mm on critical features.

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