kone tool router bitsIndustrial engineers often ask us, "Should we use high speed steel or carbide for our solid rotary tools such as end mills, drill bits and taps?" There are no quick answers because so many factors are involved: tool size, depth of cut, required material removal rate, tool life, cycle time -- and of course cost. Each type of component also faces different challenges, including design, size, batch size, material type, and hardness.

Therefore, I thought it best to discuss both to help users understand when to use either.

HSS and cemented carbide: general characteristics

Generally speaking, the main characteristics of all high speed steels are high working hardness and excellent toughness. HSS tools also cost less than cemented carbide tools and are often a good solution for "multi-variety, small-batch" applications.

Cemented carbide is harder and therefore provides longer tool life and faster cutting data than conventional high speed steel. However, the disadvantage of this hardness is brittleness, so the cutting edges of cemented carbide tools can quickly break or shatter in some cases.

What is cemented carbide?

A carbide is a compound containing carbon and less electronegative chemical elements. There are several types of carbides, such as salt carbides, covalent compounds, and carbolic interstitial compounds (Kone Carbide Tools for Woodworking).

Hard metals are very hard and wear resistant. It's more expensive than high speed steel. Based on the chemical bonds in carbide compounds, there are the following:

  • Salt carbides
  • Covalent compound
  • Interstitial compound
  • Intermediate transition metal carbides

What is high speed steel?

High-speed steel is a type of steel that is important in the manufacture of cutting tools. This form of steel belongs to the tool steel category. This material can withstand high temperatures without losing its hardness. As a result, the steel can be used to make faster cutting tools, hence the name. In addition, the hardness and wear resistance of this material is better than that of ordinary carbon steel and tool steel. This steel is an alloy of iron, tungsten and molybdenum.

Appropriate high temperature treatment during the production of this steel gives it specific properties. We can use lasers and electron beams to do these heat treatments. When a tool made of this material is coated with the right compound, such as titanium nitride, its life is increased.

Alternatives to offset the cost of cemented carbide

When we are concerned about tool cost, high speed steel can replace hard alloy. Taps and drills last long enough and are cheap. Either way, it is important to trade off the cost of cutting speeds below what can be achieved using cemented carbide. In intermittent operations where tools are prone to damage, the performance of HSS can offset this difference with higher productivity. If we do not have replacements on hand, the cost of damaging cemented carbide tools is high and production can be shut down.

Materials and Design

KoneTool Molding KnivesWith advances in the design and materials used to make high-speed steel, its productivity has increased. Usually it contains tungsten or molybdenum, chromium and some vanadium and carbon. The HSS can be made harder by adding cobalt. Cobalt bits and tools can cut difficult materials such as titanium or stainless steel alloys. With cobalt, you can increase the cutting speed by 50%.

Coatings and Metallurgy

If we get higher hardness in high speed steel, the tool can work at higher speed and its performance will be higher. There are several coatings that can help us increase surface hardness, reduce friction, or prevent oxidation. The TiN (titanium nitride) coating produces a golden surface that keeps the edges longer to avoid oxidation. In many cases, the performance is up to 2 times higher than uncoated HSS and the cost is 25 to 50 percent higher than standard.

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