By Jonathan 
Steelmaking in the modern era dates back to the 1850s during the time of Henry Bessemer. Over time, steel has cemented itself as one of the most popular metals in CNC machining, alongside aluminum, titanium, and several soft metals.
The fascinating story of this metal in manufacturing is now at the stage where steel CNC machining is showcasing the versatility and reliability of the metal. In CNC machining, grades such as 1018 steel, 1215 steel, 1045 steel, and 4140 steel undergo a subtractive process under computer control.
Steel blocks for machining are the ideal raw materials, enabling manufacturers to provide the required parts. The resulting precise, durable, and versatile parts are utilized in various industries, including medical, automotive, transportation, and aerospace.
This blog introduces CNC machining for steel, surveying the steel grades involved and other details.
Different Grades Of Steel For CNC Machining
Experts in steel processing will confirm that there are over 1000 different types in the market. This can be confusing, so engineers prefer to categorize this material into four classes, namely alloy steel, carbon steel, stainless steel, and tool steel.
Carbon Steel
Carbon steel grades that can be CNC-machined from this class are 1045 steel, 1018 steel, and 1080 steel. These are some of the best steel for machining because they are easy to machine and cost-effective.
Carbon steel precision machining
A popular category of carbon steel is free machining steel or free-cutting steel, which is specially designed for enhanced machinability. Additives such as lead and sulfur promote chip breakage, making machining easier.
1215 steel, 1144 steel, and 12L14 are the most popular grades of free machining steel.
Alloy Steel
The machinable grades of steel under this category include 4140 steel and 4340 steel, both of which are renowned for corrosion resistance, strength, and hardness.
Stainless Steel
Users turn to stainless steel CNC-machined parts for corrosion resistance. The steel grades in question here are 303 stainless steel, which is the most machinable, 304 stainless steel for food-grade items, and 316 stainless steel.
303 stainless steel parts
Tool Steel
True to their name, tool steels are typically CNC-machined for tools and other hard parts, such as dies and molds. These grades of steel are designed to manipulate other metals and materials. As expected, machining tool steel can be a strenuous affair due to the extreme hardness.
Steel tools
The American Iron and Steel Institute (AISI) performs most of the categorization for these steels, thus the common prefix A for these materials. Examples are A286 and A582. Indeed, these grades of steel are extremely challenging to machine.
Pros And Cons Of Steel CNC Machining
Steel CNC machining provides strong, versatile, and durable parts for different industries. With the right grade, excellent surface finishes can be attained by ProleanTech. However, there are also limitations to consider, including the difficulty of machining for some grades and high prices for some parts.
Benefits of Steel In CNC Machining
- Good machinability
- Wear resistance
- Corrosion resistance
- Compatibility with many surface finishes
Limitations Of Steel In CNC Machining
- Some grades are difficult to machine
- Different heat sensitivities
- Some steel grades are too expensive
Post-Processing Options For Steel Parts
Steel CNC machining is one of the most precise types of machining, but it is often complemented by post-processing steps such as heat treatment, surface finishing, passivation, and case hardening. The choice of post-process depends on elements such as the steel grade and expected surface finish.
Anodizing: After the steel CNC milling machine process, the parts can be anodized to achieve increased surface hardness, enhanced aesthetic appeal, improved corrosion resistance, and better surface adhesion.
Steel anodizing process
Coating and Plating: Plating, the addition of a thin layer of another metal on the CNC-machined part, can enhance electrical conductivity, wear resistance, corrosion resistance, and appearance.
Grinding: Precision grinding of steel parts creates refined surfaces from rough ones, resulting in parts with higher accuracy, a better surface finish, and the capability for complex geometries.
Heat Treatment: Heat treatment can make steel parts harder, stronger, and more corrosion-resistant. The process can also be used to relieve internal stresses.
Laser Engraving or Etching: Some CNC-machined steel parts require identification, permanent marking, or customized aesthetics. These can be achieved through etching or engraving.
Polishing: Polishing removes tool marks, surface imperfections, and roughness from the steel parts.
Powder Coating: Powder coating is an ideal method to enhance the mechanical properties and visual appeal of steel CNC machining products. It entails spraying electrically charged powder particles on the part, followed by curing.
Steel CNC Machining Compared To Other Metals
Steel is undoubtedly a renowned material for CNC machining, but it is not always the best CNC machining material. Aluminum, brass, and other alternatives present their advantages, so it is always worthwhile to check if they offer better than the steel machining properties.
For instance, steel is usually stronger and more durable, but it can be compared to other metals in other elements.
| CNC machined Metal | Strength | Machinability | Corrosion resistance | Cost | Common use |
| Steel | Average to high | Average to difficult | Varies with grade | Moderate | Machinery, structures, tools |
| Aluminum | Average | Superior | Good | Low | Automotive, aerospace, electronics |
| Brass | Low to average | Superior | Superior | High | Electronics, fittings |
| Copper | Low | Poor | Superior | High | Heat exchangers, electrical parts |
| Titanium | High strength-to-weight ratio | Poor | Superior | Very high | Aerospace, medical parts |
Applications Of CNC-Machined Steel Parts
There are many steel grades to make CNC machined parts, and so are the different areas you can use them in. For a narrower search, the common grades are outlined below, together with their most popular applications.
| Type of steel | Application of CNC-machined parts |
| SS303 | Aircraft parts, screws, electronic parts, bushings |
| SS416 | Bolts, nuts, gears, valves, shafts |
| SS304 | Food-grade parts, screws, heat exchanger parts, automotive parts |
| 1045 | Connecting rods, gears, bolts, axles |
| 1018 | Spindles, pins, tie rods |
| 1144 | Pistons, nuts, gears |
| 4140 | Bolts, nuts, automotive parts, machinery parts |
| 8620 | Fasteners, gears, camshaft |
| 8630 | Connectors, crankshaft, connecting rods |
4140 steel fasteners
In Conclusion
Steel CNC-machined parts are in high demand for their high tolerances, high durability, strength, and versatility. With a quality surface finish, these parts can suit even the demanding aesthetic requirements in some industries.
Having identified the different steel grades, the applications of machined parts, and the comparison to competing technologies, the next step is probably to order steel parts. But if there is still confusion, experts in CNC machining services can help