CNC Machining Materials

Steel

At a glance

Processes

CNC Mill
CNC Lathe

Lead Time

As fast as 7 days

Tolerance

With drawing: as low as +/- 0.005 mm
No drawing: ISO 2768 medium

Price

$$$

Applications

Fixtures and mounting plates; draft shafts, axles, torsion bars

Alloys

4140, 4130, A514, 4340

Carbon Steel Types

1018 Low Carbon, 1045 Carbon, Zinc-Galvanized Low-Carbon

Finishing Options

Black Oxide, ENP, Electropolishing, Media Blasting, Nickel Plating, Powder Coating, Tumble Polishing, Zinc Plating, Vibratory Tumbling

About the Material

A36/1018 Steel is a mild, low carbon steel that is machinable, weldable and useful where high-strength is not required, such as fixtures and mounting plates. It is magnetic and heat treatable.

4140 alloy steel is generally harder and stronger than carbon steel. Additionally, it provides high impact resistance, fatigue strength, and torsional strength, which makes 4140 a great choice for drive shafts, axles, and torsion bars. In terms of hardening, 4140 can be hardened using a variety of methods such as cold working, or heating and quenching.

1045 Carbon Steel is stronger than low carbon steel (1018 Steel) but is easy to machine. It is heat treatable and can be used for bolts, studs and shafts.

4130 Alloy Steel is similar to 4140 Alloy Steel but offers better weldability and has a slightly lower carbon content. It is best suited for gears and other structural applications.

Zinc-Galvanized Low-Carbon Steel has an outer coating of zinc to improve corrosion resistance. It is important to note that the coating will only be present on non-machined areas.

A514 Alloy Steel is a high strength, low alloy steel that is used mainly in structural applications. It is weldable, heat treatable and is best suited for supporting heavy loads.

4340 Alloy Steel is a medium carbon, low alloy steel that is highly useful in environments involving extreme impact, heat, and wear.

12L14 & 1215 are carbon steels that are resulfurized and rephosphorized, which makes them easy to machine. However, they have a comparitively low level of carbon, so they have less strength than other cold-drawn grades of steel.

8620 Steel is a highly wear-resistant material with good strength and toughness properties. It has a low-carbon content, so is an ideal candidate for use in welding applications.

Material Properties

1018 Low Carbon Steel

Yield Strength (tensile)

60,000 psi

Elongation at Break

15%

Hardness

Rockwell B90

Density

7.87 g/㎤
0.284 lbs / cu. in.

4140 Steel

Yield Strength (tensile)

60,000 psi

Elongation at Break

21%

Hardness

Rockwell C15

Density

7.87 g/㎤
0.284 lbs / cu. in.

1045 Carbon Steel

Yield Strength (tensile)

77,000 psi

Elongation at Break

19%

Hardness

Rockwell B90

Density

7.87 g/㎤
0.284 lbs / cu. in.

4130 Steel

Yield Strength (tensile)

63100 psi

Elongation at Break

25.5%

Hardness

Rockwell B92

Density

7.85 g/㎤
0.284 cu. in.

Zinc-Galvanized Low-Carbon Steel

Yield Strength (tensile)

30,000 psi

Elongation at Break

23%

Hardness

Rockwell B65

Density

7.87 g/㎤
0.284 lbs / cu. in.

A514 Steel

Yield Strength (tensile)

100,000 psi

Elongation at Break

18%

Hardness

Rockwell C20

Density

7.87 g/㎤
0.284 lbs / cu. in.

4340 Steel

Yield Strength (tensile)

122,000 psi

Elongation at Break

13%

Hardness

Rockwell C20

Density

7.87 g/㎤
0.284 lbs / cu. in.

12L14 Carbon Steel

Yield Strength (tensile)

60,000 PSI

Elongation at Break

15%

Hardness

Rockwell B85

Density

7.86 g/cm^3
0.28lb / in^3

Maximum Temp

--

McMaster Part Number

--

1215 Carbon Steel

Yield Strength (tensile)

60,000 PSI

Elongation at Break

10%

Hardness

Rockwell B85

Density

7.86 g/cm^3
0.28lb / in^3

Maximum Temp

--

McMaster Part Number

--

8620 Steel

Yield Strength (tensile)

55,000 PSI

Elongation at Break

15%

Hardness

Rockwell B85

Density

7.86 g/cm^3
0.28lb / in^3

Maximum Temp

--

McMaster Part Number

--

A36 Steel

Yield Strength (tensile)

60,000 PSI

Elongation at Break

15%

Hardness

Rockwell B90

Density

7.86 g/cm^3
0.28lb / in^3

Maximum Temp

--

McMaster Part Number

--

Material Finish

The finish of Steel is similar to that of Stainless Steel, generally shiny in appearance and slightly darker than aluminum alloys.

Alloy and carbon steels can be media blasted, or they can be electropolished to a variety of surface finishes.

Design Recommendations

Min Wall Thickness

0.5 mm

Min End Mill Size

0.8 mm (0.03 in)

Min Drill Size

0.5 mm (0.02 in)

Max Part Size

1200 x 500 x 152 mm [x,y,z] (mill)
152 x 394 mm [d,h] (lathe)

Undercuts

Square profile, full radius, dovetail profiles

Radii : Depth

Depth must not exceed 12x drill bit diameter.
For end mills, depth must not exceed 10x tool diameter.

Cost Saving Tip

To reduce costs, limit the number of part setups, the number of inspection dimensions or tight tolerances, and deep pockets with small radii.

CNC Machining Steel FAQs

How is CNC machining steel different from other materials?

Steel is a good choice in terms of strength and durability, but its weight is the biggest drawback in comparison to other materials. There are more than 3500 grades of steel to work with and different grades behave differently when being machined. Some types of steel are specifically designed for greater ease when machining. Some steels have high work hardening tendencies and this necessitates the need to keep the machining process moving so there is no unnecessary heat build up. With CNC machining steel it is also important to keep tools sharp.

Advantages of CNC machining steel?

Steel is the workhorse of the industry because of its economical cost, wide availability, ease of processing and good mechanical properties. Most steels have good machinability and weldability and take well to heat treatments. Some are stronger and harder than others but most steels offer a combination of toughness and wear resistance.

What grade of steel is best for machining?

There are 7 grades of steel that are best for machining. The type of parts you need will dictate which grade you choose:

  • 1018 Steel is a mild, low carbon steel that is machinable, weldable and is useful where there are no requirements for high strength.
  • 4140 alloy steel is generally stronger and harder than carbon steel. It provides high impact resistance as well as high fatigue and torsional strength.
  • 1045 Carbon Steel is stronger than low carbon steel but is easy to machine.
  • 4130 Alloy Steel offers better weldability and has a slightly lower carbon content.
  • Zinc-Galvanized, Low-Carbon Steel has improved corrosion resistance.
  • A514 Alloy Steel is a high strength, low alloy steel with a yield strength of 100K PSI. It is primarily used as structural steel in construction.
  • 4340 Alloy Steel is a medium carbon that is highly useful in applications where components will experience extreme impact, heat, and wear.

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