Parting and grooving in different materials
Parting and grooving aluminium and non-ferrous materials
Non-ferrous metals are softer types of metals such as aluminium, copper, brass etc. Aluminium with a silicon content (Si) of 13% is very abrasive. Generally, high cutting speeds and long tool life can be expected for inserts with sharp edges.
To achieve these sharp edges as on geometry -RO, the edge line usually has to be ground and the carbide needs to be uncoated, or have a thin coating.
For components demanding an extremely high surface finish, a polycristalline diamond (PCD) tipped insert is recommended. It provides the possibility for using high cutting data and ensures long tool life.
Parting and grooving heat resistant super alloys (HRSA)
HRSA falls into three groups; nickel-based, iron-based and cobalt-based alloys. The physical properties and machining behaviour of each group varies considerably. Whether the metal is annealed or aged is particularly influential on the subsequent machining properties, as the hardness varies from 150 to 440 HB.
The machinability of HRSA is generally poor compared to both general steels and stainless steels. Preferable insert geometries for HRSAs are -GF and -TF For higher cutting speeds, a ceramic insert will drastically improve productivity.
Parting and grooving titanium alloys
Titanium alloys are typically machined in the annealed or solution treated and aged conditions, when hardness can vary between 250-440 HB.
The machinability is poor compared to both general steels and stainless steels, which imposes particular demands on the cutting tools.
We recommend inserts with sharp edge -GF geometry in an uncoated grade.
To achieve good chip-breaking in long-chipping materials, such as titanium alloys, and to prolong tool life, we recommend installing a high pressure coolant in the machine.
Hard part machining
Modern manufacturing technology places increasing demands on components to be made in one set-up, creating the need for machining hardened components. Cutting tool materials such as CBN (cubic boron nitride) act as a productivity booster when turning is used instead of grinding. Both hardened, and induction hardened components with hardness between 50–65 HRc can be machined.
We recommend inserts with -S geometries for grooving and -RE for profiling. For smaller holes, CBN-tipped grooving inserts are recommended. They are suitable for both continuous and interrupted cuts and designed to achieve good surface quality and to keep close tolerances.
Workpiece material groups
In the metal cutting industry there are many different component designs and types of materials used. Each material has its own unique characteristics influenced by the alloying elements, heat treatment, hardness etc. This strongly influences the choice of cutting tool geometry, grade and cutting data. Therefore workpiece materials have been divided into 6 major groups in accordance with the ISO-standard, where each group has unique properties regarding machinability.
ISO P – Steel is the largest material group in the metal cutting industry. This material ranges from unalloyed to high-alloyed, and includes steel castings. The machinability is normally good, but differs a lot depending on material hardness, carbon content etc.
ISO M – Stainless steels are materials alloyed with a minimum of 10.5% chromium. Other alloying elements such as nickel and molybdenum may also be added. Different conditions such as ferritic, martensitic, austenitic and austenitic-ferritic (duplex), makes this alloy group large. What these types of alloys have in common is that they expose cutting edges to a great deal of heat, notch wear and build-up.
ISO K – Cast iron is, contrary to steel, a short-chipping type of material. Grey cast iron (GCI) and malleable cast irons (MCI) are quite easy to machine, while nodular cast iron (NCI), compact cast iron (CGI) and austempered cast iron (ADI) are more difficult. All cast irons contain silicon carbide (SiC) which is very abrasive to the cutting edge.
ISO N – Non-ferrous metals are softer types of metals such as aluminium, copper, brass etc. Aluminium with a silicon content (Si) of 13% is very abrasive. Generally, high cutting speeds and long tool life can be expected for this group when using inserts with sharp edges.
ISO S – Heat Resistant Super Alloys include a number of high-alloyed iron, nickel, cobalt and titanium-based materials. They are sticky, create build-up on edges, tend to work harden and generate heat i.e. similar to the ISO M materials but much more difficult to cut and shorten tool life.
ISO H – This group covers steels with a hardness between 45-65 HRc and also chilled cast iron around 400-600 HB. Their hardness makes them difficult to machine. The materials generate heat during cutting and are very abrasive to cutting edges.
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