Steel turning

Steel can be classified as non-alloyed, low-alloyed and high-alloyed, all types affecting machining recommendations for turning.

Non-alloy steel turning

Material classification: P1.1

The carbon content of non-alloy steel does not exceed 0.55%. Mild steels (carbon content < 0.25%) require special attention because of their difficulty in breaking chips and 

their tendency to stick (built-up edge).

In order to enable chip breaking and chip control, the highest possible feed should be achieved. Wiper inserts are highly recommended.

Use high cutting speeds to avoid built-up edge on the insert, which can have a negative impact on surface quality. Sharp cutting edges and light cutting geometries will 

reduce the tendency to stick and prevent edge degradation.

Low alloy steel turning

Material classification: P2.x

The machinability of low-alloy steels depends on the alloy content and heat treatment (hardness). For all materials in this group, the most common wear states are crater 

wear and flank wear. For hardened steels, plastic deformation is also a common wear condition due to higher heat generation in the cutting zone.

For low alloy steel in an unhardened state, the first choice is steel series materials and geometries. For hardened steels, it is advantageous to use harder materials (cast iron 

materials, ceramics and CBN).

High alloy steel turning

Material classification: P3.x

High alloy steel includes carbon steel with a total alloy content exceeding 5%. This group includes both mild and hardened steels. The higher the alloy content and hardness, 

the lower the machinability.

As with low alloy steel, the first choice is also the steel material and geometry.

Steels with alloying elements exceeding 5% and hardness exceeding 450 HB have additional requirements for resistance to plastic deformation and cutting edge strength. 

Consider using harder materials (cast iron, ceramic and CBN).

Stainless steel turning

Stainless steel can be classified as ferritic/martensitic stainless steel, austenitic stainless steel and duplex (austenitic/ferritic) stainless steel, each type has its own turning 

recommendations.

Turning of ferritic and martensitic stainless steels

Material classification: P5.1

This stainless steel is classified as a steel material, therefore, the material classification is P5.x. General machining recommendations for this type of steel are our stainless steel 

grades and geometries.

Martensitic steels can be machined in the hardened state, which places additional requirements on the blade's resistance to plastic deformation. Consider using CBN material 

when the hardness is greater than or equal to 55 HRC.

Austenitic stainless steel turning

Material classification: M1.x and M2.x

Austenitic stainless steel is the most common type of stainless steel. This group also includes super austenitic stainless steels, which are defined as stainless steels with a 

nickel content exceeding 20%.

The recommended materials and geometries are our stainless steel CVD and PVD materials.

For intermittent cuts or when chip impact or chip crushing is the dominant wear condition, consider using PVD grades.

Other considerations:

Be sure to use coolant to reduce crater wear and plastic deformation, and choose the largest possible nose radius. Read more about coolants

Use round inserts or small entering angles to prevent groove wear

A tendency to stick or built-up edge is a common phenomenon. They all have a negative impact on surface quality and tool life. Use sharp cutting edges and/or geometries 

with positive rake faces

Duplex (austenitic/ferritic) stainless steel turning

Material classification: M3.4

Duplex stainless steels with higher alloy content will go by names such as super or even special grade duplex stainless steel. The higher the mechanical strength, the more 

difficult these materials are to machine, especially in terms of heat generation, cutting forces and chip control.

The recommended materials and geometries are our stainless steel CVD and PVD materials.

Other considerations:

Use coolant to improve chip control and avoid plastic deformation. Use tools with internal cooling (preferably high-precision cooling). Read more about coolants

Use a small entering angle to avoid groove wear and burr formation

Cast iron turning

There are 5 main types of cast iron:

Gray cast iron (GCI)

Ductile Iron (NCI)

Malleable Iron (MCI)

Compacted Graphite Iron (CGI)

Isothermal quenched ductile iron (ADI)

Cast iron is a Fe-C composition with a silicon content of 1%-3% and a carbon content of more than 2%. It is a short-chip material that provides good chip control under most 

operating conditions.

For most cast iron materials, our cast iron grades and geometries are recommended. When machining gray cast iron at higher cutting speeds, ceramic and CBN grades are 

recommended.

High temperature alloy (HRSA) turning

Superalloys have excellent mechanical strength and resistance to creep (the tendency of a solid to move slowly or deform under pressure) at high temperatures. It also has 

good corrosion/oxidation resistance. High temperature alloys can be divided into 4 material groups:

Nickel-based alloys (e.g. Inconel)

Iron-based alloy

Cobalt based alloy

Titanium alloys (Titanium can be pure metal or have alpha and beta structures)

The machinability of high-temperature alloys and titanium alloys is poor, especially in the aging treatment state, where the requirements for cutting tools are particularly high. It is important to use sharp cutting edges to prevent the formation of so-called white layers due to different hardnesses and residual stresses.

High temperature alloy materials: When turning high temperature alloy materials, PVD and ceramic materials are often used. It is recommended to use geometries optimized 

for high temperature alloys.

Titanium alloy: Mainly using uncoated and PVD materials. It is recommended to use geometries optimized for high temperature alloys.

One form of wear common to both titanium alloys and high-temperature alloys is groove wear. Follow these guidelines for optimal performance:

It is recommended to use a leading angle less than 45°

Correctly utilize the relationship between insert diameter/nose radius and depth of cut

When using ramping or multiple passes, a depth of cut greater than 0.25 mm (0.0098 inches) is recommended

When turning high-temperature alloys and titanium alloys, always use coolant, regardless of whether you are using carbide or ceramic inserts. Coolant should be sufficient 

and correctly directed. Read more about coolants

When using ceramic inserts, pre-chamfering is recommended to minimize the risk of burr formation during entry and exit of the insert for optimal performance

Non-ferrous materials (aluminum) turning

This group includes non-ferrous soft metals such as aluminum, copper, bronze, brass, metal matrix composites (MMC) and magnesium. Machinability varies with alloying 

elements, heat treatment and manufacturing process (forging, casting, etc.).

Aluminum alloy turning

Material classification: N1.2

Be sure to use a blade with a positive rake basic shape and a sharp cutting edge. Uncoated and PCD materials are preferred.

For aluminum alloys with a silicon content above 13%, PCD materials should be used because the tool life of carbide materials is significantly shortened.

Coolant in aluminum alloy processing is mainly used for chip removal.

Hardened steel turning

Turning steel with a hardness of typically 55-65 HRC is defined as hard part turning and is a cost-effective alternative to grinding. Hard part turning ensures greater flexibility, 

shorter lead times and higher quality.

Cubic boron nitride (CBN) grade is the best cutting tool material for hard part turning of case-hardened and induction-hardened steels. For steels with hardness below about 

55 HRC, use ceramic or carbide blades.

Use CBN grades optimized for hard part turning.

Ensures good machine and clamping stability

Use the smallest possible depth of cut to achieve low entering angles and extend tool life by using the correct edge chamfers

Use wipers for optimal surface quality