Tooling is one of the most exciting aspects of machine tools. The history of mankind is about developing shaping and cutting tools through the material ages. For the last 100 years or so high carbon steels (HCS) and high speed steels (HSS) have been at the frontline of cutting. Tooling is a high volume consumable in the machine tool industry and sales also are a good indicator of economic health and recovery.
Tooling not only has to be hard is subject to heat, stress and rubbing and a variety of vibrations from the machining process (frequencies). To cope and resist with the heat created tooling needs to have ‘hot hardness’ as well as the following:
- Toughness and impact strength
- Thermal shock resistance
- Wear resistance
- Inert behaviour
Often these different properties overlap or can be at odds with each other. For example: a diamond coated or tipped tool might well prove the hardest tooling and ideal for cutting, however it also has poor shock /impact strength when compared with say, HSS.
High Speed Steels (HSS) as the name implies are run/cut at higher speeds than carbon steels; they contain either Molybdenum or Tungsten and other trace elements like cobalt, chromium and vanadium.
Cast cobalt –was an early cutting material and is now used for heavy, rough cutting (Stellite). Cobalt tipped tools and are in common use in schools and colleges.
Carbide tooling or cemented / sintered carbides developed from the 1930’s increased the high speed and high temperature cutting range further. They are often the most versatile, productive and cost effective tooling choice.
Carbide inserts are also made from Tungsten and titanium (TiC) are screwed onto tooling and holders and can have several cutting faces. This means only the inserts are replaced. The moulded (sintered) shape of the insert features chip breaking forms and generally they are used for high speed cutting.
Coated tooling is now commonplace (TiN) (TiC) (TiCN) giving improved performance and lower running costs due to longer life. Recent developments have given us Diamond and Cubic Boron Nitride along with Alumina based ceramics and the hardest cutting tools.
Tool holders and changers mean that the right tipped tool for the task can be selected and programmed into a CNC sequence.