The answer to this question is a lot more complicated than one might think. There are many different types of steel, and each has its own properties and uses.
For example, there are four main types of steel: low-carbon steel, high-carbon steel, alloy steel and stainless steel. Low-carbon steels are used for applications in which the metal will not be subject to great stress or wear; they are also used in applications where the metal must be easy to machine. High-carbon steels have a higher carbon content than low-carbon steels, which makes them harder and stronger; they are also less prone to rusting. Alloy steels contain elements other than iron (e.g., nickel) that provide added strength or corrosion resistance.Stainless steel is less common because it is more expensive and requires more care when machining.
Carbon Steel:
– Low cost
– High hardness
– Lower corrosion resistance
– Easy to machine
Stainless Steel:
– Higher cost
– Lower hardness (but still hard)
– Higher corrosion resistance
1. Stainless Steel
| General Characteristics | Alloy | Common Applications | Tolerances for a 1/2″ Dia. Bar |
| Designed for machining, non-magnetic | 303 | Electronic hardware, automotive, aerospace, medical instruments, and many applications requiring corrosion resistance | Cold finished |
| +/- .002 | |||
| Better weldability and formability, slightly more corrosion resistant | 304 | Applications needing formability or weldability | Cold finished |
| +/-.002 | |||
| Better corrosion resistance | 316 | Medical implants and surgical instruments, aerospace | Cold finished |
| +/-.002 | |||
| Corrosion resistance and high electrical resistivity | 430 FR | Excellent corrosion resistance in fresh water, gaseous, moderately acidic, and low chlorine environments | 0.002 |
| High carbon, can harden to RC 60 | 440 | Applications requiring stainless steel with highest hardness | 0.002 |
| Excellent corrosion resistance and heat treatable | 17-4 PH | Medical, aerospace, applications needing corrosion resistance and hardness | +/-.002 |
2. Steel
| General Characteristics | Alloy | Common Applications | Tolerances for a 1/2″ Dia. Bar |
| Moderate strength and low-stress applications. | 1008 | Good matte surface finish that makes it suitable for exposed parts | 0.002 |
| Plain low carbon steel, poor machinability but good formability and weldability. Case harden only | 1018 | Rivets and parts requiring strong welds | Cold drawn |
| 0 | |||
| Strength, impact resistance and higher tensile strength. | 1045 | Responds to heat treatment extremely well, but it not recommended for case hardening | 0.003 |
| Higher carbon, higher strength, direct hardening | 1137 | Higher stress applications, gears, shafts, studs, etc. | Cold drawn |
| 0 | |||
| Strength and machinability | 11L37 | Easily machined and can be annealed, quenched, tempered, and heat treated | 0.003 |
| Strength and hardness and a more uniform surface hardness | 11L41 | Axles, shafts, bolts, and pins | 0.003 |
| Designed for excellent machinability. Case hard only | 12L14 | Endless commercial products; probably more pounds used in turned products than any other bar stock | Cold drawn |
| 0 | |||
| Designed for good machinability. Case harden only | 1215 | Parts needing better formability or weldability than 12L14 | Cold drawn |
| 0 | |||
| Strength, toughness, and fatigue resistance | 4130 | Military and commercial aircraft parts | Norm AQ |
| HT Condition F4 | |||
| Popular general-purpose alloy. Direct hardening | 4140 or 4142 | Gears, shafts, pins, bolts and nuts, pump and valve components | Cold drawn |
| 0 | |||
| Designed for better machining w/lead additive; direct hardening | 41L40 | Couplings, shafts, tooling, bolts | Cold drawn |
| 0 | |||
| .55% Ni, .50% Cr, .20% Mo, heat treatable and case hardening | 8620 | Shafts, bushings, pins, gears, bolts | Cold drawn |
| 0 | |||
| Very high 1% carbon, .25% Ni,1.4% Cr, .08% Mo | 52100 | Bearing applications | Cold drawn |
| Spheroidize annealed | |||
| +/- .006 |
What Type Of Steel Is most popular For CNC Machining?
Carbon Steel: Carbon steel is the most common type of metal used for CNC machining because it has the highest level of ductility and toughness. Carbon steel has less resistance to corrosion than stainless steel but can be more easily welded than stainless or tool steels.
Stainless Steel: Stainless Steel is also a popular choice for CNC machining because it’s resistant to corrosion, rusting, tarnishing, and other chemical reactions with air or water, and it’s food grade material that can be used food processor and storage containers/equipments.
