When milling, the question often arises as to which milling cutter I can use for which application. Here, opinions differ as to which of the two cutting tools is best suited for which material.
Let’s shed some light on the difference between HSS and carbide and the best way to use them.
Before we go into the question of which material is used for which purpose, let’s talk about the materials in general.
What is HSS made of and what are its properties??
HSS is derived from High Speed Steel, which means high-speed steel. It also has other names, such as high-speed steel, high-performance (high-speed) steel and high-speed steel.
HSS is an alloy tool steel with a carbon content of up to 2.06% and up to 30% of alloying elements, such as cobalt, molybdenum and titanium. There are 3 other types of HSS tools: HSS-R (shaping by rolling), HSS-G (shaping by grinding – G=ground) for low tolerances and HSS-E (like HSS-G but alloyed with additional cobalt) for materials with high strength and for long cutting channels.
To improve the various properties, HSS can also be given a surface alloy/hard coating, which is usually hard chrome plating, nitriding or carbonizing.
Due to great hardness, tempering resistance, wear resistance and heat resistance, it can easily machine soft and thin-walled workpieces accurately. HSS cutters have higher toughness and edge strength, which creates a higher rake angle and therefore a smaller wedge angle, which creates the possibility of thinner chips, but reduces cutting strength.
On the other hand, HSS has the advantage of being insensitive to shocks and vibrations, unlike carbide cutters.
How is carbide produced and what properties does it have??
Carbide, HM for short, are produced by a powder metallurgical sintering, this process involves 3 steps; grinding and mixing, shaping and the sintering. They consist of cobalt (binder) and the carbides (hard materials) embedded there, such as titanium carbide, tungsten carbide or titanium nitride. The properties of the material can be improved by reducing the grain size, but this has the disadvantage of increasing the production effort and cost. These materials are mostly used as a tool or parts of a tool in machining, chipless shaping and friction closing. A modern HM variant called Cermets (ceramic& metal) is mainly used for high speed cutting.
Their properties such as high hardness, temperature resistance and wear resistance are much higher than normal cutting materials such as HSS, but they have low fracture toughness and thermal shock resistance. Due to these good properties, a higher cutting speed is generated and even hard materials such as glass and porcelain can be machined with a carbide tool.
But when to use what now?
HSS cutters are used in applications with steel, cast iron materials, plastics and other soft materials where low speeds can be used, many shocks and vibrations occur and a sharp cutting edge is required. However, they quickly dull and then get a messy milling pattern. Due to their sharp cutting edges, they are ideal for machining aluminum and plastics.
HM cutters are used for cutting workpieces made of stainless steels, plate work, plastics and many other materials with different degrees of hardness, as they can work at very high speeds. They also have a higher hardness, temperature resistance and wear resistance than HSS, which makes them more suitable for many applications. When milling wood, only carbide cutters should be used, as they produce more precise milling in the material.
In the end, it can be said that carbide cutters are more expensive, but they are more universal and more durable than high-speed steel cutters, but if only a small amount of easy-to-mill materials are to be milled, the HSS cutters are a good choice.
High quality cutters have all the important data, such as minimum depth of cut, manufacturer’s abbreviation and maximum speed printed or lasered on the shank, if these are missing from a cutter, the purchase of that cutting tool should be avoided.
You can also find more information on this topic in our blog post "Recognizing and interpreting cutter data".
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