Cross section of cemented carbide insert cutting in steel. Temperature in degrees Celsius.
There are usually three main factors that must be identified in order to determine a material’s machinability, that is, its ability to be machined.
- Classification of the workpiece material from a metallurgical/mechanical point of view.
- The cutting edge geometry to be used, on the micro and macro levels.
- The cutting tool material (grade) with its proper constituents, e.g. coated cemented carbide, ceramic, CBN, or PCD, etc.
The selections above will have the greatest influence on the machinability of the material at hand. Other factors involved include: cutting data, cutting forces, heat treatment of the material, surface skin, metallurgical inclusions, tool holding, and general machining conditions, etc.
Machinability has no direct definition, like grades or numbers. In a broad sense it includes the ability of the workpiece material to be machined, the wear it creates on the cutting edge and the chip formation that can be obtained. In these respects, a low alloyed carbon steel is easier to cut, compared to the more demanding austenitic stainless steels. The low alloyed steel is considered to have a better machinability compared to the stainless steel. The concept “good machinability”, usually means undisturbed cutting action and a fair tool life. Most evaluations of the machinability for a certain material are made using practical tests, and the results are determined in relation to another test in another type of material under approximately the same conditions. In these tests, other factors, such as micro-structure, smearing tendency, machine tool, stability, noise, tool-life, etc. will be taken into consideration.