Choice of tools: HSS or Tungsten Carbide?

Choice of tools: HSS or Carbide?

Turning of gearbox shafts

You have just acquired your new machine, lathe or milling machine, but you still need to make the most of it by using the right cutting tools with the right parameters!

The type of cutting tool depends directly on :

  • Your skill level
  • The type of machine: conventional or CNC
  • Material to be machined
  • Dry working or cooling

Basically, there is a choice between tungsten carbide or high speed steel (usually called ARS or HSS).

  • Tungsten Carbide

The case of carbide is particularly relevant when high quality surface finishes and tool durability are required (because carbide tools are not usually sharpened; they are interchangeable inserts in the case of turning and one-piece milling cutters in the case of milling) and for machining hard materials (pre-treated). However, the machine must be adapted because the cutting speeds are 5 to 20 times higher than those used for ARS machining, so the speed range of the machine must be wide enough!

Nowadays, carbide is systematically used when working on a CNC machine because the cutting parameters displayed (feed rates, rotation frequency, depth of cut) are precise and therefore conform to the recommendations of the carbide manufacturers, which allows maximum optimization of productivity.

In the case of turning (conventional and CNC), the use of tools with interchangeable carbide inserts is a real comfort: no more sharpening, dry working possible, good durability of the cutting edge, very good surface finish.

- High speed steel (HSS)

In conventional milling, on the other hand, the relevance of using carbide milling cutters is not really demonstrated insofar as it is not advisable to work downstream (except for machines equipped with ball screws), whereas all carburetors recommend working downstream except in specific cases.

HSS tools are still widely used in conventional machining, especially in milling, because they have the triple advantage of

  • From cost price
  • The possibility of resharpening with a standard grinding wheel
  • Customization of the cutting edge by grinding according to the material to be machined

But productivity is lower due to the low cutting speeds to be used and the need to regularly resharpen tools, especially when machining hard materials...

This is the reason why many HSS tools are nowadays "coated", i.e. treated after sharpening with a coating that considerably improves service life: TIN, TiAln, TiCN etc... Moreover, current HSS tools are generally alloyed with cobalt in varying percentages ranging from 3 to 10%, improving the hardness and toughness of the ARS!

Let's keep in mind that for the machining of soft and/or "sticky" materials: polyamides, engineering plastics, AU4G aluminium, copper, brass, the current HSS tools give very good results.