stainless steel machining

Slaying Stainless Steel: Machining Guide

Stainless steel can be as common as Aluminum in many shops, especially when manufacturing parts for the aerospace and automotive industries. It is a fairly versatile material with many different alloys and grades which can accommodate a wide variety of applications. However, it is also one of the most difficult to machine. Stainless steels are notorious end mill assassins, so dialing in your speeds and feeds and selecting the proper tool is essential for machining success.

Material Properties

Stainless steels are high-alloy steels with superior corrosion resistance to carbon and low-alloy steels. This is largely due to their high chromium content, with most grades of stainless steel alloys containing at least 10% of the element.

Stainless steel can be broken out into one of five categories: Austenitic, Ferritic, Martensitic, Precipitation Hardened (PH), and Duplex. In each category, there is one basic, general purpose alloy. From there, small changes in composition are made to the base in order to create specific properties for various applications.

For reference, here are the properties of each of these groupings, as well as a few examples of the popular grades and their common uses.

Category Properties Popular Grades Common Uses
Austenitic Non-magnetic, outstanding corrosion and heat resistance. 304, 316 Food processing equipment, gutters, bolts, nuts, and other fasteners.
Ferritic Magnetic, lower corrosion and heat resistance than Austenitic. 430, 446 Automotive parts and kitchen appliances.
Martensitic Magnetic, moderate corrosion resistance – not for severe corrosion. 416, 420, 440 Knives, firearms, surgical instruments, and hand tools.
Precipitation Hardened (PH) Strongest grade, heat treatable, severe corrosion resistance. 17-4 PH, 15-5 PH Aerospace components.
Duplex Stronger mixture of both Austenitic and Ferritic. 244, 2304, 2507 Water treatment plants, pressure vessels.

Tool Selection

Choosing the correct tooling for your application is crucial when machining stainless steel. Roughing, finishing, slotting, and high efficiency milling toolpaths can all be optimized for stainless steel by choosing the correct style of end mill.

Traditional Roughing

For traditional roughing, a 4 or 5 flute end mill is recommended. 5 flute end mills will allow for higher feed rates than their 4 flute counterparts, but either style would work well for roughing applications. Below is an excellent example of traditional roughing in 17-4 Stainless Steel.

 

 

Slotting

For slotting in stainless steel, chip evacuation is going to be key. For this reason, 4 flute tools are the best choice because the lower flute count allows for more efficient chip evacuation. Tools with chipbreaker geometry also make for effective slotting in stainless steel, as the smaller chips are easier to evacuate from the cut.

stainless steel machining

Finishing

When finishing stainless steel parts, a high flute count and/or high helix is required for the best results. Finishing end mills for stainless steel will have a helix angle over 40 degrees, and a flute count of 5 or more. For more aggressive finishing toolpaths, flute count can range from 7 flutes to as high as 14. Below is a great example of a finishing run in 17-4 Stainless Steel.

 

High Efficiency Milling

High Efficiency Milling can be a very effective machining technique in stainless steels if the correct tools are selected. Chipbreaker roughers would make an excellent choice, in either 5 or 7 flute styles, while standard 5-7 flute, variable pitch end mills can also perform well in HEM toolpaths.

stainless steel

HEV-5

Helical Solutions offers the HEV-5 end mill, which is an extremely versatile tool for a variety of applications. The HEV-5 excels in finishing and HEM toolpaths, and also performs well above average in slotting and traditional roughing. Available in square, corner radius, and long reach styles, this well-rounded tool is an excellent choice to kickstart your tool crib and optimize it for stainless steel machining.

stainless steel machining

Running Parameters

While tool selection is a critical step to more effective machining, dialing in the proper running parameters is equally important. There are many factors that go into determining the running parameters for stainless steel machining, but there are some general guidelines to follow as a starting point.

Generally speaking, when machining stainless steels a SFM of between 100-350 is recommended, with a chip load ranging between .0005” for a 1/8” end mill up to .006” for a 1” end mill. A full breakdown of these general guidelines is available here.

Machining Advisor Pro

Machining Advisor Pro is a cutting edge resource designed to precisely calculate running parameters for high performance Helical Solutions end mills in materials like stainless steel, aluminum, and much more. Simply input your tool, your exact material grade, and machine setup and Machining Advisor Pro will generate fully customizable running parameters. This free resource allows you to push your tools harder, faster, and smarter to truly dominate the competition.

In Conclusion

Stainless steel machining doesn’t have to be hard. By identifying the proper material grade for each part, selecting the perfect cutting tool, and optimizing running parameters, stainless steel machining headaches can be a thing of the past.

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7 replies
  1. Stanley D Holland
    Stanley D Holland says:

    I have a need for a 6.5 inch long 11/64ths (.171 inch) end mill or drill/mill that I can use to drill holes in steel then begin the side-to-side milling process. I do engraving work and I sometimes need to make my own jigs to hold various items to be engraved.
    I made my own drill tool using one of my broken cutters and it worked, but I am certain there has to be a better more efficient way of doing business.

    Reply
    • Jeff Rauseo
      Jeff Rauseo says:

      Hi Stanley,

      I would recommend giving our tech team a call to talk through this application and see how we can help. You can reach them by calling 800-645-5609 or by emailing to [email protected]

      Reply
  2. Jasmine Paulos
    Jasmine Paulos says:

    This is really very very interesting and informative too, You contain a lot of information in a single article regarding this, Thank you for sharing your knowledge. Keep updating us with your knowledge.

    Reply
  3. Dylan Peterson
    Dylan Peterson says:

    It’s awesome that stainless steel is designed to resist corrosion due to their high chromium content. My boss has been telling me about how he wants to build a new machine this quarter for use outside, and he wants to make sure that it can stand up to the weather. I’ll pass this information along to him so that he can look further into his options for using stainless steel.

    Reply

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