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Machining Stainless Steel

Can you machine stainless steel?

If you’re ever wondering if machining stainless steel is possible, well yes, it is! If there was a race to decide which material is used most often in machining precision parts, stainless steel and aluminum, would be neck and neck and trading position all the time. Machined stainless steel parts are common and a large part of business growth amongst precision parts manufacturers. Why it is so popular is just as important to know of stainless machinability. Some popular types of steel for machining are 303/304, 17-7, 16-6 and 316. Stainless steel machined precision parts are produced for countless industries for their strength, durability, resistance to corrosion and rust. It also is used for its surface quality and ability to be polished to a high luster. Producing stainless steel is a process in which elements are combined with the iron base. This melting of elements such as nickel, chromium, silicon, molybdenum, and others are combined in different percentages with iron ore to form an alloy. For example, 316 stainless steel is an austenitic alloy combining chromium, nickel, molybdenum, and iron and used in a variety of industries such as medical devices, food industry, marine environments, aerospace, and numerous others. How these parts are made likely will be done by a combination of CNC machine processes. CNC is a subtractive manufacturing process. The raw material is cut and drilled to form a high precision part. Multiple methods to machine stainless steel parts are:

  • CNC Drills-Used in machining stainless steel parts to create holes, slots, and other geometry. Cutting through or programed depths.

  • CNC Lathes– Stainless machinability is observed when using CNC lathes. This method Rotates the material while tool inserts cut the shape. Good for cylinders and similar shapes.

  • CNC Milling– Used in 3,4, and 5 axis machines. Can produce very complex machined stainless steel parts.

  • CNC Routers- Sheets of materials are cut and drilled by this method.

  • CNC Laser Cutting– Machining stainless steel by lasers is excellent when cutting sheets of materials, especially in thinner gauges of 316 stainless steel, 303/304 and 17-7.

  • CNC Plasma Cutting- Many different types of steel for machining are done with plasma technology. Used for industrial applications.

  • CNC Waterjet-Using high-water pressure and abrasives is another way to observe stainless machinability. This technology cuts various materials with no heat effect.

  • CNC machined components can be produced with a very tight tolerance of +/- .025mm or .001”. This again is repeatable and necessary for machined stainless steel parts in small runs or volume production.

Stainless steel machinability is one of the reasons it is favored by manufactures and used in so many ways from commercial goods to very high-end industry uses. Machined stainless steel parts are produced with high confidence of use and longevity of wear. It is no wonder why you will see that machining stainless steel provides many CNC shops and services providers with revenue and growing opportunities to serve the public in so many ways with precision machined parts and components.

What is the most commonly machined stainless steel?

Just like picking the right tool for the job, there’s a perfect grade of stainless steel for every machining project. But when it comes to popularity, there’s a clear champion – grade 304, also known as 18/8 stainless steel because of its composition of 18% chromium and 8% nickel. This workhorse material reigns supreme for a few reasons:

  • The ultimate shape-shifter: 304 is incredibly versatile. This grade of stainless steel boasts excellent formability, allowing it to be machined into complex shapes while maintaining its strength. So, whether you need intricate parts or something more straightforward, 304 can handle it.
  • Rust never sleeps, but 304 fights back: A key feature of stainless steel is its resistance to corrosion, and grade 304 is no exception. This fighter stands strong against moisture, chemicals, and even harsh environments, making it ideal for parts that need to stay tough wherever they go.
  • Budget-friendly champion: Let’s face it, budgets matter. The good news is, grade 304 is readily available and offered at a competitive price. This affordability makes it a fantastic choice for a vast array of projects, allowing you to get the quality you need without breaking the bank.

Now, while 304 is the MVP, there are other commonly machined stainless steel grades waiting in the wings, each with its own strengths:

  • Grade 303 (S303): This close cousin to 304 takes machinability to another level with the addition of sulfur. It’s the go-to choice for projects demanding super smooth machining, but keep in mind, its corrosion resistance is slightly less than 304.
  • Grade 316 (S316): When corrosion resistance is the ultimate champion, grade 316 steps up to the plate. This stainless steel warrior contains molybdenum, a special ingredient that gives it superior resistance to chlorides and other corrosive elements, making it perfect for marine or chemical environments. While it’s a bit trickier to machine than 304, advancements in technology and tooling mean 316 can be a viable option for many projects.

Remember, choosing the right stainless steel for your project depends on its specific needs. Think about the complexity of the part, the level of corrosion resistance required, your budget, and any post-machining processes. With this knowledge and the champion 304 by your side, you’ll be well on your way to selecting the perfect stainless steel for your next machining project.

Can you CNC mill stainless steel? 

If you ever have wondered how precision tools are made like those used by your dentist, auto engine parts, turbine blades or even kitchen utensils, the material in common will be stainless steel. Machined stainless steel parts are a large part of the world of manufacturing. It is vast in the options available to us from commercial size companies to small privately owned businesses. Each has a set of standards and processes that are used best on certain materials and designs. For machined stainless-steel parts, one of the best and most used technologies is CNC Milling. This is a subtractive process in which the raw material is shaped using computer numeric control or CNC, with spindles or bits. These tools are made of hardened steel alloys or carbide that cut into the material to shape it to the desired design. The concept is simple, but the actual process takes knowledge of materials and the tools and settings needed. Machining stainless steel and other materials by CNC uses the guides that are called the “speeds and feeds”. These settings are a combination of how fast the spindles will rotate and the rate at which the material is fed. This must be done in consideration of the final machined stainless steel part design. There are multiple grades of stainless steel available to manufactures such as:                                                

TypeCharacteristicsGradesExamples of Uses
AusteniticCorrosion and heat resistance. Is non-magnetic.303,304, 316, 310, 321Pressure vessels, piping, bolts, nuts, chemical equipment.
FerriticLower corrosion and heat resistance than Austenitic and is magnetic.409, 430, 439, 446Refrigerator panels, auto exhausts, chimney liners, fasteners.
MartensiticIs Magnetic with some corrosion resistance – not suitable for harsh conditions.410, 416,420, 440Cutting utensils, surgical instruments, dental instruments, ball bearings.
Precipitation Hardened (PH)Extreme strength and is heat treatable. High level of corrosion resistance.17-4 PH, 15-5 PH, 650, 660Turbine blades, food equipment, exhaust systems, engine parts
DuplexStronger mixture of both Austenitic and Ferritic.2101,244, 2304, 3304 2507Storage tanks, water heaters, bridges

The term “stainless machinability” is correct when referred to CNC mills. Stainless machinability allows projects requiring 316 stainless steel or 420 grades for example to result in high precision and quality with a repeatable manufacturing process. The fact that the types of stainless steel available is a strong indication of the trust from industry over this versatile material. With over 6 decades of proven credibility and sustained manufacturing methods, CNC Milling of stainless steel and other hardened alloys has a solid foundation in manufacturing for many decades to come. 

Which cutting process is best for stainless steel?  

It can be aggravating sometimes when you just don’t have the right tool for the job. I was home in the garage trying to repair a lamp by replacing the power cord. Simple project most of the time, but I had much trouble stripping the outer coating to expose the bare wire. I used what I could find, a pair of cutting plyers. Several times I used too much pressure and cut right through and watched as the cord length to this lamp gradually got shorter. Finally, after digging through my unorganized tool storage table, I found the wire strippers. The job was done, and my Saturday afternoon was saved as the right tool was eventually used. For manufacturing of machined stainless-steel parts, there is a right tool for each project as there is a variety of types of steel for machining and uses. Stainless steel was created, back in 1913, by adding chromium to iron. Machining stainless steel into precision parts positively impacted our growth in technology for over a century. This corrosion resistant material has continued to be in great demand for manufacturing. Over the years the technology used in cutting stainless steel has developed into a vast industry supporting the production of home goods, medical devices, aerospace, industrial uses, food industry, oil and gas, automotive and so on. There is a best method for cutting stainless steel, but it depends on the type of project needed to be manufactured. The following is an overview of what is the best fit: 

  • Sawing with blades is still in use today. You can cut stainless steel with a metal saw blade or band saw but is not often used in machining stainless steel. This would be to cut shapes, or bulk materials without a tight tolerance requirement. You will find smaller shops and individuals using this method. 
  • Wire EDM- Types of stainless steel machining will include wire EDM to cut many parts holding the same pattern or features, all at the same time. Stainless machinability allows this 2-axis solution to hold a tight tolerance and is good for production runs. It serves industries such as medical, aerospace, micro-electrical for example. 
  • CNC-or computer numeric control- Uses hardened steel bits- great for cutting or drilling through. This method is usually regulated in cutting thicker grades of stainless steel, and not for cutting just flat foils. Types of steel for machining by CNC are 303, 304, 17-7, 410, 420 and numerous others.  5 axis machined stainless steel parts using CNC is a great solution. 
  • WaterJet- This technology uses very highly pressured streams of water and abrasives for machining stainless steel and other materials. With no heat affected zones for projects sensitive to this. Cutting in an x/y axis, waterjet can be used for 316 stainless steel machining or grades like 304 which can be challenging to cut without any distortion to heat. Other gauges of stainless can be cut and all can be held to a +/- .005” mils tolerance. 
  • Plasma cutting- Stainless machinability does well under this technology. Using highly pressurized gases of oxygen, argon or nitrogen. For cutting very thick gauges of stainless steel, plasma is often used and is faster than other methods, keeping costs lower. The use of different gases will result in different edge quality. Consultation with the provider prior to manufacturing is recommended. 
  • Laser Cutting- Another great method for machining stainless steel is with laser technology. Using focused beams of light, including multiple laser types such as Ultraviolet, Infrared, and Fiber laser technology to name a few. Stainless machinability of precision parts manufactured by laser systems such as these are used in a variety of project needs. A great solution for thinner gauges of stainless-steel foils, from .0254mm” up to 4mm foils, and holding +/- .001” thousand. Grades like 302, 304, 17-7, 16-6, and 316 stainless steel machining supports industries including medical, defense, battery energy, nuclear science, to produce many 2axis parts. Often It is the preferred choice over other technologies for R&D and mid-level production. 

Which process is the best for machining stainless steel depends on the project and its use. For 4 or 5 axis machined stainless steel parts, you will want to go with CNC Milling technology. For machining stainless steel parts from ultra-thin foils and sheets, you want to go with laser cutting technology. For machined stainless steel parts that have no heat affected zones, waterjet systems are best. Precision parts manufacturers have many options available to them to bring your project forward. In many cases these manufacturers work to support each other by outsourcing and providing value to each other from the technologies they use. Machining stainless steel is best when utilizing the expertise and knowledge accumulated from years of experience by services providers and in turn benefits the customer.