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steel cnc machining

Steel CNC Machining: A Comprehensive Guide

Steel is a good choice for various CNC machining operations because of its excellent machinability and homogeneity. It also offers strong workability, weldability, high ductility, and formability to fulfill any project's specifications and is well-suited to your particular machining demands.

Steel has emerged as one of the more common industrial alloys for CNC machining projects due to its favorable physical qualities. The metal has a high tensile strength and excellent corrosion resistance, adding to the durability and part longevity of the product. This comprehensive guide explains all you need to know about steel CNC machining, including its surface finishes.

What Is Steel CNC Machining?

Many manufacturing processes depend on the process of machining. It used to be that the entire procedure was done manually, but that required a lot of time and work. Computer Numerical Controlled (CNC) machining is one of the automated machining services available today.

CNC machining, which forms designs from metal and plastic material, entails using a computer to control the movements of a particular tool. Because of its speed, accuracy, and production effectiveness, this automated technique has become highly widespread in the industrial sector.

Steel is one of many materials that are suitable for CNC machining. One of the most widely used materials for custom-made parts and prototypes is CNC steel.

Grades of Steel for CNC Machining

Steel CNC Milling

There are various steel options for CNC machining, and they have their unique property. Here are some common grades available:

1018 Steel

This steel grade, which contains iron, carbon, manganese, phosphorus, and sulfur, is frequently referred to as mild carbon steel. The best selling point of 1018 steel in metal CNC machining is its high weldability, which makes it the standard choice for carburized CNC steel parts. But keep in mind that welding is only advised after carburizing.

In addition to being exceptionally weldable, 1018 steel possesses exceptional machinability. This is the rationale behind its application in CNC precision machining operations, such as turning and milling steel. Manufacturers use it for forged connecting rods, spindles, shafts, and other CNC machined parts. This low carbon steel grade’s main drawbacks are its price and incompatibility with various finishing techniques.

Its mechanical properties are:

  • Density (g cm-3)- 7.87
  • Elongation at Break- 15%
  • Yield Tensile Strength (MPa)- 310
  • Hardness (Brinell)- 131
  • Shear Modulus (GPa)- 78

1215 Steel

Iron, carbon, manganese, phosphorus, and sulfur are all found in this type of steel. Because of this steel type’s comparatively high sulfur content, it is referred to as free-machining steel. Due to its employment in automatic screw machine processes, it is also frequently called screw stock.

1215 steel creates tiny chips during machining, enabling faster cutting rates and preventing machine tangling. It could be more weldable, though. Its relatively low carbon concentration also makes it less strong than other cold-drawn grades.

It is appropriate for automatic projects requiring extensive machining in the industrial setting. It can be used for couplings, hose fittings, studs, pins, and screws.

Mechanical Properties

  • Density (g cm-3)- 7.87
  • Elongation at Break- 10%
  • Yield Tensile Strength (MPa)- 415
  • Hardness (Brinell)- 167
  • Shear Modulus (GPa)- 80

1045 Steel

steel 1045 blue zinc plated auto parts
Steel 1045_Blue Zinc Plated_Auto Parts

This steel has a medium carbon content and contains iron, carbon, silicon, manganese, and sulfur or phosphorus. This one is one of the most adaptable steel manufacturers use for CNC steel parts. Due to its strength and toughness, 1045 steel is frequently used in CNC steel machining applications where water resistance is crucial.

Furthermore, 1045 steel is weldable and machinable, which are crucial aspects manufacturers consider when processing steel. This grade can be used for shafts, studs, bolts, gears, and ales. In essence, manufacturers favor it for tasks that demand extremely fast speeds.’

Despite being a relatively robust steel grade, its use is not recommended for extremely strong goods because its tensile strength and hardenability are at most moderate.

Its mechanical properties:

  • Density (g cm-3)- 7.87
  • Elongation at Break- 12%
  • Yield Tensile Strength (MPa)- 450
  • Hardness (Brinell)- 170
  • Shear Modulus (GPa)- 60

4130 Steel

The levels of alloying elements in 4130 steel are higher than in regular steel. Iron, carbon, chromium, manganese, molybdenum, phosphorus, silicon, and sulfur comprise its composition. These components charge this steel grade’s toughness, machinability, and thermal compatibility.

Due to its resilience to extreme stress, it is frequently utilized for various building tasks. It is also employed in the installation of aircraft engines. Because it is less expensive and just as strong as aircraft-grade steel, manufacturers frequently choose 4130 steel. 4130 steel is simple to heat treatment; however, it is difficult to weld.

Its mechanical properties are:

  • Density (g cm-3)- 7.87
  • Elongation at Break- 20%
  • Yield Tensile Strength (MPa)- 460
  • Hardness (Brinell)- 217
  • Shear Modulus (GPa)- 80

4140 Steel

custom cnc machined 4140 steel parts
Custom CNC Machined Steel Parts

This type of steel is a low alloy steel with minimal amounts of chromium, molybdenum, and manganese. The strength, flexibility, and toughness of the steel grade are improved by its chemical composition. Additionally, the addition of chromium increases the corrosion wear resistance of this grade.

Due to its superior machinability and abrasion resistance, it is utilized in various industries. 4140 steel, however, requires pre- and post-heat treatment and is not the most straightforward metal to weld. This grade is frequently used to make CNC steel couplings, spindles, bolts, nuts, and automobile parts.

Its mechanical properties are:

  • Density (g cm-3)- 7.87
  • Elongation at Break- 19%
  • Yield Tensile Strength (MPa)- 655
  • Hardness (Brinell)- 197
  • Shear Modulus (GPa)- 80

Pros of Steel CNC Machining

steel cnc turning and milling
Steel CNC Turning &Milling

Most CNC steel parts on the market today have good machinability, which is the ease with which metals can be cut or shaped to produce a satisfactory outcome. Machinability for steel CNC machining is influenced by factors such as hardness, energy, horsepower, and shear stress.

Another advantage of CNC steel machining for machine parts is the strong resistance to corrosion and wear. Furthermore, steel parts are often compatible with a wide range of surface finishes.

Cons of Machining Steel

1045 steel cnc turned and milled parts
1045 Steel CNC Turned and Milled Parts

Despite the obvious advantages, there are some drawbacks to using CNC to machine steel parts. For one thing, not all steel pieces are easily machined. As a result, some steel grades may be problematic to use for geometrically complex projects.

Furthermore, different steel grades have varied heat sensitivities. Some grades are not ideal for CNC steel parts that will be subjected to high temperatures because they may melt and become distorted.

Options For Post-Processing And Surface Finishes On Steel Parts

steel milling machining
Steel Milling Machining

As the name suggests, surface finishes are procedures carried out after the standard manufacture of metal items. The goal is to make these mold components more aesthetically pleasing and functional. However, various metals need various surface treatments. Below are the common surface finishes applicable:

Carburizing & Nitriding

Carburizing hardens metal surfaces by heating steel metal with carbon-containing compounds such as carbon monoxide and charcoal. Carburizing also improves the wear resistance of CNC steel parts.

Nitriding Exposing steel to ammonia gas while heating to introduce nitrogen. Creates a very hard surface layer able to withstand wear and abrasion.

Powder Coating

The powder coat finish includes putting dry powder on the steel’s surface. The thickness of the finish is generally between 0.15 and 0.3 mm. The obvious advantage is that the CNC steel parts are more corrosion-resistant.


Coating the steel surface with a thin layer of metal like chromium, nickel, or zinc via electroplating. This enhances corrosion resistance, wear properties, and aesthetics. Chrome plating provides a shiny decorative finish. Nickel improves wear and corrosion resistance.


Treating the steel surface using a nitric acid solution to increase corrosion resistance. Improves the formation of a protective oxide layer. Common for stainless steel parts.

Differences Between Steel and Iron

MachinabilityModerate to difficult depending on carbon contentExcellent machinability
Cutting SpeedGenerally 100-350 SFM for most gradesCan be machined at higher speeds around 400 SFM
Tool WearCauses more rapid tool wear compared to ironLess tool wear
StrengthMuch higher strength due to carbon contentLower strength than most steels
HardnessUp to Rockwell C 60 for hardened high carbon steelSofter than steel, about Rockwell B 80 at maximum
CostGenerally higher cost than ironLower cost material
Corrosion ResistanceProne to rusting without protectionHigher corrosion resistance over regular steel
ApplicationsStructural parts, tools, weapons, machinery, automobilesLow carbon steel, cast iron products

Here are some of the differences between steel and iron:


Machinability is determined by a number of elements, including the metal’s hardness and strength. The harder a metal is, the less machinability it has. That idea also applies to aluminum.

Steel has a wider range of Brinell hardness (80 to 600) than aluminum (about 15). Steel also has greater tensile and yield strength than aluminum. As a result, steel is stronger but less malleable.


Machinists can work faster on aluminum since it is lighter than alloy

steel. Furthermore, after heating, aluminum cools faster than steel. This suggests that manufacturing cycles are longer when machining steel.


Many times, the choice between steel and aluminum comes down to price. This is especially true when both materials are appropriate for a given job. While there are many types and grades of these metals, stainless steel CNC machining is normally more expensive than aluminum.

Applications of Steel Machining

custom cnc precision machined steel parts
Custom CNC Precision Machined Steel Parts

Steel metal CNC machining is utilized to make various parts in the medical, robotics, food, and beverage industries, aerospace, and other areas that demand high-strength applications.

Steel is an excellent material for a variety of uses, including:

  • Medical equipment
  • Machine components
  • Gears
  • Tractor components
  • Heavy construction machinery
  • Aircraft engine mountings

Steel has exceptional machinability, homogeneity, and resistance to corrosion and oxidation, resulting in longer product life and reduced total cost of CNC machined parts.


at machining steel cnc machining services
AT-Machining Steel CNC Machining Services

Steel is a good choice for making strong and durable components. It provides a perfect blend of qualities at a reasonable price. Producers concerned about machining efficiency can choose a machinability-enhancing alloy such as Steel 1018. While steel can be more challenging, the rewards are frequently well worth the effort.

As a result, designers should work with a reputable CNC machine shop like AT-Machining to produce high-quality steel goods at a reasonable price. Contact us today, and let’s discuss your project.

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Hey there, I’m Sam!

From AT-Machining, I’m a CNC Machining Expert in this field for more than 20 years.  We offer cost-effective machining services from China. Ask for a quote for your ongoing or upcoming projects now!

Best Regards, Sam, Co-Founder

AT Machining

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