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Cutting Tool

Machining cutting tools: Types of material

December 03, 2019
Machining cutting tools: Types of material

In Yamazen Mexicano we want to support Mexican companies that use machining cutting tools so that they can select the best option that allows them to obtain the best results in quality, precision and duration.

At first glance it seems simple to be able to choose cutting tools for certain machining processes, but various mechanical manufacturing jobs require high precision and quality. We find a great diversity of options in cutting tools and it can be difficult to make a good choice. Therefore, we present below a list of the different types of cutting tools that are frequently used in the industry and we will mention the types of materials in which they perform best.

A cutting tool must meet the following characteristics:

Hardness: The ability not to alter its geometric shape (elastic deformation) under mechanical pressure and high temper.

Toughness:  The ability to absorb energy with or without elastic deformation without fracturing.

Wear resistance: The time that passes before the tool needs to be replaced by wear (abrasion), adhesion or oxidation.

Each type of machining cutting tools has a combination of these characteristics depending on the material with which it will work. Very hard materials tend to have less resistance, and all materials lose hardness as the temperature rises.

Efectos de la temperatura en diferentes herramientas.

Figura 1: It shows the decrease in hardness as the temperature of some tool materials increases.

TYPES OF MATERIALS IN CUTTING TOOLS

CARBON STEEL CUTTING TOOLS

The most common and old, known for hundreds of years. They are tools used for the operation of low speed and temperature machining, and are goog enough to machine other steels. Usually with a concentration of coal around 1%, with some other components in minimum quantities (Mn, Cr, V, Si). Its life time is short but also it's low-cost and it is the most common material for helical bits. They lose their hardness around 200 ° C.

 

 

Common types of carbon steel tools: drill bits, rhymes, milling tools, turning and forming tools, serrated and abrasive discs and bands.

Types of materials: brass, aluminum, magnesium, other steels, mechanizable plastics.

Appropriate processes:

  • Low production.

  • Machining in which not very high temperatures develop.

  • Finishing at low cutting speed, in very delicate jobs.

  • A fin sharp edge, which is difficult to obtain with igh-speed steels (HSS).

  • Low speed steel cutting (5 m / min)

 

HIGH SPEED STEEL CUTTING TOOLS (HSS)

High speed steels (HSS) are a type of steels developed around 1900 that allow to increase cutting speeds considerably compared to the materials known up to that time. They are alloys of carbon steel with other materials (cobalt, niobium, molybdenum and tungsten mainly) that increase their hardness and heat resistance. The initial hardness of HSS cold is similar to that of tempered steels, but while carbon steels lose hardness from 200 ° C, fast steels keep it up to 600 ° C, in addition to supporting higher cutting speeds . HSS steels tend to be more expensive for alloys and recently because coatings such as nitrides or oxides of titanium or chromium, or nitrates of titanium and aluminum are added.

Common types of HSS steel tools: drill bits, rhymes, strawberries, punches, discs and serrated bands, punches, jaws and dies.

Types of materials: Other steels, iron (with certain coatings), soft metals (aluminum, bronze, brass, copper, magnesium), mechanizable plastics.

Appropriate processes:

  • Low to medium production
  • Precision machining at low cost.
  • High speed machining at low volume.
  • Higher cutting speed.

 

CEMENT CARBIDE AND CERMET CUTTING TOOLS

Cemented carbide cutting tools (important, not to be confused with CERMET tools) are extremely hard. They are made using the powdered metallurgy technique, with carbide particles (carbon and metal composites) cemented inside a compound composed of some metallic element as a means of attachment, such as cobalt. Tools of this type that have high cobalt are used for rough cutting, while these tools with low cobalt are used for finishing operations.

They can withstand cutting operations at very high speed and the carbide tool does not lose its hardness up to 1,000 ° C. Some of the most common materials are: tungsten carbide (WC), titanium carbide (TiC) or tantalum carbide (TaC). Despite their relative fragility, they offer acceptable toughness, not only for finishing materials, but also for milling and turning stainless steels. They are usually used in the form of small inserts.

The CerMet is also a type of cemented material. CerMet is the name assigned to ceramics based on titanium carbide (TiC), titanium nitride carbide (TiCN) and / or titanium nitride (TiN), but the binder is nickel or molybdenum. Its name comes from CERamic METal. Moderately expensive, it provides greater resistance to abrasion compared to tungsten carbide, at the expense of some resistance. It is also chemically much more inert and has a very high resistance to abrasion. It has a high resistance to wear in incidence, high chemical stability and heat resistance, and also little tendency to regrowed edge and oxidation wear.

To increase the life-time or modify the cutting properties of cemented carbide tools, coatings of other ceramics or even diamond carbon (DLC) are usually added.

Common types of cemented carbide and CerMet tools: Cutting inserts, straight cutters, drill bits, discs and serrated blades, machuelos.

Types of materials: Aluminum and non-ferrous metals, hard materials (iron, stainless steel, titanium), steel alloys.

Appropriate processes:

  • High production volume
  • Rough and fine cutting.
  • High precision with moderate costs
  • Machining of special materials.

CERAMIC CUTTING TOOLS

Ceramic cutting tools are similar to cemented carbide but harder, yet  less resistant. They are chemically inert and have great resistance to corrosion. They have a high compressive strength. They are stable up to 1,800 ° C. They are ten times faster than those of HSS. The friction between the face of the tool and the chip is very low and has a low thermal conductivity. Generally, no collant is required when used and they provide an excellent surface finish.

These cutting tools are made from ceramic powder, compacted in the form of insertion and sintered at high temperature. The most common ceramic materials are aluminum oxide and silicon nitride. 

Aluminum oxide or alumina (Al2O3), also called Corundum which is also used in grinding wheels, has a hardness superior to tungsten carbide, but its fragility is also greater, which makes it sensitive to shocks and vibrations, so its use is limited to continuous machining operations and on robust, stable, powerful and high structural rigid machines. In this case, the design of the tool holders is especially important, which should be as rigid and robust as possible. It is important to note that ceramic tools have their own cutting rules; the ceramics, having no metal alloys, do not produce welding of chip particles on the face of attack of the tool, so they do not form sharp growths, and for this reason surface finishes of very good quality are achieved, this is possible due to to the fine granulometry and the high hardness that allows to obtain edges of very good quality and duration, that allow to make passes of 0.01mm deep.

Common types of ceramic tools: Cutting inserts.

Types of materials: hard materials (iron, stainless steel, titanium), steel alloys, special materials.

Appropriate processes:

  • Fine finish.High accuracy.
  • Machining of special materials.

POLYCRYSTAL DIAMOND CUTTING TOOLS (PDC)

Important! We must not confuse PDC (Polycrystaline Diamond deposit Composite) diamond cutting tools with the PCD (Poly Crystaline Diamond) type of sintered diamond.

Of the tools with greater hardness, they are ceramic tools (usually cemented carbides) covered by layers of microscopic grain of polycrystalline diamond (PCD) very similar in hardness to that of the monocrystalline natural diamond. Therefore, it has high wear resistance and is widely used as an abrasive for grinding wheels.

This cutting material has some critical points: The temperature in the cutting area must not exceed 600 ° C. It cannot be used for ferrous metals due to its affinity, nor for tough materials with high tensile strength. This excludes the PCD from most machining applications.

Yet, these cutting tools are perfectly suited for non-ferrous abrasive materials and non-metallic materials that require high precision and high quality surface finish. It is also used for turning and milling abrasive alloys of Si and Al. In fact, the uncoated fine-grained hard metal and PCD are the two materials mainly used for machining aluminum.

Other materials that can also be machined through PCD are: Compounds, special alloys, graphite, other ceramic and sintered, soft metals.

Due to their great chemical stability, the friction of these cutting tools with the workpiece does not affect their cutting edge. The PCD does not leave burrs and the life of the tool is many times longer, but due to its high fragility, very stable conditions and very rigid tools and machines working at high speeds are required, and fluid must be used to cool the work process.

Common types of PDC tools: Cutting inserts, straight cutters, bits, discs and serrated blades.

Types of materials:Compounds, Resins, Plastics, Coal, Ceramics, Pre-synthesized hard metals, Bronze, Mg Alloys, Zn Alloys, Pb and brass.

Appropriate processes:

  • Finishing
  • Semi-finished turning and boring.

MONOCRISTALINE DIAMOND CUTTING TOOLS

The monocrystalline diamond is functionally identical to the PDC, but with a greater hardness and a precision of finishing of radius less than 1µm, so it reaches roughness less than RZ 0.02µm.

CUBIC BORON NITRIDE CUTTING TOOLS (CBN)

Second in hardness after the diamond, it has a high hardness at high temperatures (2,000 ° C.), excellent wear resistance and good chemical stability during the machining process. It is more tenacious than ceramic tools despite its greater hardness, but is lower in thermal and chemical resistance..

A low CBN content with ceramic binder has more abrasion resistance and chemical stability, suitable for steels and hardened cast iron. A higher CBN content improves toughness and is indicated for steels and hard foundries and also for heat-resistant alloy steels.


These are the groups where you can group almost every machine cutting tool. In the next part we will talk about the mechanical characteristics of the main materials that are currently machined.

And remember, when machining with any of the types of cutting tools it is very important to take care of safety. And that is why our recommendation is that at all times you do not get your Personal Protective Equipment (PPE): glasses, cap, gloves, safety shoes and appropriate clothing as appropriate: Safety comes first!

If you have more questions or questions about the subject, or would like to find the right solution for your machining need, do not forget to contact your Yamazen sales agent.

We will continue talking about other introductory topics in the next entry.

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