The ideal machining on a CNC machine tool is the golden intersection between the minimum machining time, the minimum possible decline on the tools used, and the achievement of the desired dimensional accuracy.

To achieve this, however, each machinist must use their knowledge and experience to choose the ideal tool for each machining in terms of machining ability, hardness, precision, morphological characteristics of the final geometry, the containment method and the capabilities of his/her machine tool.

After the selection of the right tools, the appropriate cutting conditions must also be selected.

The most widely used cutting conditions are axial and radial cutting depth, cutting speed and propulsion speed.

It is generally stated that:

• Cutting speed (m / min) is the instantaneous speed of the main cutting motion that acquires a tool cutting point relative to the workpiece.
• Propulsion velocity (mm / min) or propulsion is the instantaneous velocity of the secondary propulsion motion that acquires a tool cutting point relative to the workpiece.

In conclusion, it could be said that the purpose of any machinist working on machining is to optimize the machining procedure, namely those conditions which lead to:

1. the desired quality of the processed parts
2. as little damage as possible to cutting tools
3. fast processing, therefore high productivity

High-performance cutting tools

The development of material technology, as well as extensive investment by cutting edge manufacturers in the research and development of new materials and coatings, led to the creation of high-performance tools which allow higher cutting speeds with higher radial and axial depth, while at the same time increasing robustness and maintaining a satisfactory lifetime.

Usually, an experienced machinist is capable to select the appropriate cutting conditions taking into consideration the material to be worked, the strength of the retention, and the type of machining.

However, with modern tools, this is not necessary, as reliable cutting manufacturers generously give their customers all the necessary cutting conditions for each possible machining.

Specifically, they provide in detail:

• the recommended cutting speed depending on the tool, material and the type of machining (whitening, finishing, etc.)
• the proposed axial and radial cutting depth.
• the proposed adaptation of all of the above, taking into account the robustness of the machine tool, the retainer and the general machining conditions (tool cooling method, peripheral or vertical machining, homogeneous or reverse machining, method of initial immersion, plunging, creation of insert hole etc.).

Therefore, it is economically advantageous to have the cutting conditions provided by the individual manufacturer.

If the proposed treatment conditions are ignored, there is a risk of immediate destruction of the cutter or a drastic reduction in its service life.

As new coatings and new innovative geometries of modern tools are likely to allow cutting conditions that are quite different from those widely used in terms of hardness and material type, there is no absolute reason not to use the average value provided, but to prefer arbitrary experimentation.

Obviously, along the way, there is the possibility for the machinist to utilize his experience of adapting the machining conditions provided to the upper or lower recommended limits.