When it comes to end mills, they can be either coated or uncoated. Both have their own advantages and disadvantages, but which one is better and how should you choose between them?
What Are Coated End Mills?
Coated milling cutters have a thin layer of coating applied to their surface. This can be applied via CVD (Chemical Vapor Deposition) or PVD (Physical Vapor Deposition) methods. This coating can be made from various combinations of materials, such as titanium nitride (TiN), titanium carbonitride (TiCN), titanium aluminum nitride (TiAlN) or diamond-like carbon (DLC), among others.
The purpose of the coating is to increase the hardness of the tool and provide better wear resistance during machining. Coated tools have a lower coefficient of friction. This means that they have a longer service life and can cut through material faster.
What Are the Disadvantages of Coated End Mills?
Limited material compatibility: Some coatings may not be suitable for machining certain materials, so their application may be limited. For example, aluminum (and other non-ferrous metals) may adhere to certain coatings, resulting in the formation of sticky chips. This can lead to faster tool wear, complete tool burnout or workpiece damage.
Not suitable for slow cutting speeds: Coated end milling cutters are prone to chipping or coating peeling when used at slow speeds, so they are not suitable for use in slow machining.
Higher cost: Coated tools are usually more expensive due to the additional coating process. So if you are on a limited budget and do not need high machining performance/tool life. Then uncoated tools may be a better choice.
What Are Uncoated End Mills?
Uncoated milling cutters, as the name suggests, do not have any coating on the surface of their tool substrate. They are usually used for low-cost general-purpose milling operations of ferrous metals. Or they are the first choice for high-performance machining of non-ferrous metal applications such as aluminum.
What Are the Advantages of Uncoated Milling Cutters?
Ideal applications for machining non-ferrous metals: Polished, uncoated milling cutters can be used for high-performance machining of non-ferrous metal applications such as aluminum. Some coatings can stick to these types of materials, which can cause problems that affect tool life and workpiece finish.
Cost effective: Uncoated milling cutters are usually more affordable than coated milling cutters for general-purpose applications. Therefore, this is an ideal choice for budgets.
Versatility: They can be used in a wide range of materials and in general economical machining.
Easy to resharpen: Uncoated tools are relatively easy to resharpen when the tool becomes dull.
What Are the Disadvantages of Uncoated end mills?
Lower tool life: Uncoated tools may have a shorter life compared to coated tools. This is especially true when machining harder or more abrasive materials.
Cannot withstand higher temperatures: The lack of a coating results in higher cutting temperatures, which can affect tool life and surface finish.
Unsuitable for higher speeds and feeds: The increased risk of tool wear for uncoated tools makes them unsuitable for high-speed or high-feed milling applications.
Which is Better, Coated or Uuncoated End Mill?
The answer to this question depends on the specific cutting application and the material being machined. Coated milling cutters are used for high-speed machining and cutting hard materials, such as stainless steel or titanium. The coating gives the tool better wear resistance and longer tool life, which can save money in the long run. However, coated tools are more expensive than uncoated tools, so the cost-benefit analysis must be carefully considered.
Uncoated milling cutters are typically used for softer materials, such as aluminum or brass. They are cost-effective and can be used for a wide range of general-purpose machining. However, they are not as durable as coated tools and may need to be replaced more often.
In summary, both coated and uncoated milling cutters have their place in a shop. The wise choice depends on the specific cutting application and the material being machined.
For machining softer materials, such as aluminum, you would typically use an uncoated milling cutter. Aluminum chips tend to be sticky or form long chips. As a result, you may encounter a variety of problems, and the wrong choice may reduce your tool life or affect your surface finish.
