CNC Machining Materials

Stainless Steel

At a glance

Processes

CNC Mill
CNC Lathe

Lead Time

As fast as 2 days

Finishing Options

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

Tolerance

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

Price

$$$

Applications

Industrial applications, fittings, fasteners, cookware, medical devices

Alloys

303, 304L, 316L, 410, 416, 440C, 17-4PH, Nitronic 60

About the material

Stainless steel is highly resistant to corrosion and rust, making it suitable for situations where a part may be exposed to the elements for a long period of time. Stainless steel is also fairly malleable and ductile. China Manufacturing parts, Inc. offers multiple stainless steel alloys, including a food-safe variety.

The 300 series family (303, 304, etc.) are austenitic stainless steels (after their crystalline structure) and are the most widely produced grades worldwide. Austenitic stainless grades are known for their high corrosion resistance and high strength across wide temperature ranges. They are not heat-treatable except by cold working, and are generally non-magnetic.

400 series stainless steels are the martensitic family and not as common as austenitic grades. Martensitic steels are extremely strong and tough due to higher carbon content, but more susceptible to corrosion in certain environments.  They can be heat-treated to greatly increase their hardness and are magnetic.

17-4 PH Stainless Steel is a high-strength, highly corrosion-resistant material that maintains its durability up to 1100°F. The PH in its name stands for precipitation-hardened, a type of treatment it undergoes to increase yield strength. It is magnetic and heat treatable to a hardness of approximately Rockwell C50.

Nitronic 60 is an excellent all-purpose material with superior wear and corrosion resistance. It has a yield strength nearly double that of SS 304 and SS 316, as well as superior oxidation resistance. Popular applications include fasteners, valve stems, seats, pins, bushings, bearings, shafts and rings.

Material Properties

303 Stainless Steel

Yield Strength (tensile)

35,000 psi

Elongation at Break

42.5%

Hardness

Rockwell B95

Density

0.29 lbs / cu. in.

Maximum Temp

2550° F

McMaster Part Number

1243T15

304L Stainless Steel

Yield Strength (tensile)

30,000 psi

Elongation at Break

50%

Hardness

Rockwell B80 (medium)

Density

0.29 lbs / cu. in.

Maximum Temp

1500° F

McMaster Part Number

8983K213

316L Stainless Steel

Yield Strength (tensile)

30,000 psi

Elongation at Break

39%

Hardness

Rockwell B95

Density

0.29 lbs / cu. in.

Maximum Temp

1500° F

McMaster Part Number

9195K48

410 Stainless Steel

Yield Strength (tensile)

65,000 psi

Elongation at Break

30%

Hardness

Rockwell B90

Density

0.28 lbs / cu. in.

Maximum Temp

1200° F

McMaster Part Number

1316T121

416 Stainless Steel

Yield Strength (tensile)

75,000 psi

Elongation at Break

22.5%

Hardness

Rockwell B80

Density

0.28 lbs / cu. in.

Maximum Temp

1200° F

McMaster Part Number

1323T14

440C Stainless Steel

Yield Strength (tensile)

110,000 psi

Elongation at Break

8%

Hardness

Rockwell C20

Density

0.28 lbs / cu. in.

Maximum Temp

800° F

McMaster Part Number

88585K224

17-4PH Stainless Steel

Yield Strength (tensile)

160,000 psi

Elongation at Break

7%

Hardness

Rockwell C35

Density

0.28 lbs./cu. in.

Maximum Temp

1100°F

McMaster Part Number

6625K4

Nitronic 60

Yield Strength (tensile)

50,000 psi

Elongation at Break

35%

Hardness

Rockwell B85

Density

0.28 lbs./cu. in.

Maximum Temp

1800°F

McMaster Part Number

9583k21

Material Finish

The finish of stainless steel varies greatly depending on surface roughness, but it’s generally characterized as being more shiny than unfinished aluminum alloys, and slightly darker and more silver in color.

Stainless steel can also be media-blasted, sanded, hand-polished, and powder coated to achieve a multitude 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.

Stainless Steel FAQs

What is the best stainless steel for CNC machining?

There are four primary stainless steel grades that are best for CNC machining:

  • 430F grade stainless steel is a popular grade in machining industries due to the potential for good feeds and speeds. 430F stainless steel is ferritic and it’s similar to 430 with increased sulfur to improve machinability.
  • The 300 series family are the most widely used grades. 303 Stainless Steel is the fastest to machine. It maintains good corrosion resistance for industrial machining parts. 303 stainless steel is easily modified, making it ideal for a variety of parts, such as screws, nuts, bolts, gears & shafts.
  • Nitronic 60 offers superior wear and corrosion resistance making it an exceptional all-purpose material. It has a yield strength almost double that of stainless steel 304 grade and greater oxidation resistance. Popular uses include valve stems, fasteners, pins, seats, shafts and rings, bushings and bearings.
  • 17-4 PH Stainless Steel is a highly corrosion-resistant material with high strength, which maintains durability in high heats. PH, or “precipitation-hardened,” refers to a treatment the material goes through which increases its yield strength. 17-4 PH is magnetic and heat treatable for hardness.

How thin can you machine stainless steel?

Thin walls require extra care when CNC machining stainless steel. The absolute minimum thickness is 0.5mm for metals. To minimize costs and machining time, it’s recommended to increase the thickness of thin walls to at least 0.8mm. Unless weight is a determining factor thicker walls are more stable and less costly. Thin features are susceptible to vibration, creating extra complexity and requiring considerably more time in machining operations.

Is stainless steel difficult to machine?

Yes, stainless steels tend to be one of the most difficult metals to work with in CNC machining. Stainless steel gets harder over time, instead of wearing, which combined with the high-heat generation in machining stainless steel, can contribute to tool failure. Getting speeds and feeds right as well as proper tooling is key.

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