The Difference Between High Speed Steel & Carbide End Mills

by startoolinc | Last Updated: February 11, 2020

When deciding on which kind of end mill to use in computer numerical control (CNC) machining, part of the process will involve weighing high speed steel vs carbide.

While carbide end mills have largely replaced HSS in CNC machining over the past several years, a HSS end mill still has plenty of uses in machining. These occurrences usually involve softer materials and specific applications.

Before outlining the benefits and uses of each material, let’s first briefly recount the history of the use of HSS and carbide end mills.

The History of High Speed Steel & Carbide End Mills

The origins of high speed steel are traced back to the turn-of-the-century and the experiments of Frederick Winslow Taylor and Maunsel White at the Bethlehem Steel Company. The first alloy formally classified as “high-speed steel” appeared in 1910 and was composed primarily of tungsten. By 1930, molybdenum-rich high speed steels began to come into use, with development motivated by material shortages and increased costs due to World War II. Since that time, cobalt was introduced to molybdenum high speed steels to provide additional heat resistance and hardness.

Around the same time that molybdenum started to replace tungsten in HSS alloys, the German company Friedlich Krupp began to sell products composed of cemented carbide. General Electric in the United States and various Japanese companies also pushed development forward. The rapid increase in quality of carbide over the last several decades has corresponded with a growing rate of adoption in CNC machining, as now a vast majority of cutting applications opt for carbide over HSS, with some notable exceptions.

Uses and Benefits – High Speed Steel vs Carbide

Now let’s examine the respective benefits of HSS and carbide and the most common applications of each in metalworking.

High Speed Steel

HSS is known for its ability to withstand high temperatures while maintaining its hardness. While HSS suffers from much slower cutting speeds than carbide, it is less prone to drill breakage and can perform well for a considerable length of time. HSS has proven cheaper and more effective in use with multi-toothed form cutters, with re-sharpening after a lengthy duration of use a snap.

HSS end mills find regular use in drilling small diameters or large depths, where the material’s strength at withstanding cutting force makes it an asset despite natural limitations in cutting speed. HSS can also be used for milling cutters, tool bits, saw blades, and other cutting tools used for low-speed applications, where its high hardness can be best put to use.

Carbide

Carbide tooling comes with high efficiency in use and retains its cutting edge well at high machining temperatures. Compared to HSS, carbide tools boast a higher cutting speed range and improved rigidity. Carbide tools are known to provide exceptional surface finish quality.

Due to these advantages, carbide finds use in most cutting applications, from boring to face milling and beyond. Carbide is often used when machining on cast iron, plastics, and other nonferrous materials.

Summary

To recap, carbide end mills are used for tools in a majority of machining applications, while HSS comprises a smaller but vital segment of the market. If you prioritize cutting speed, carbide blows HSS out of the water.

On the other hand, HSS provides ample durability and strength for high-pressure operations or in low power machines. Tool breakages can be costly and cause inconvenient production slowdowns, making HSS a more economical option than carbide in applications involving substantial feed rates. Now you know the difference in high speed steel vs carbide end mills when it comes to your CNC machining jobs.