What are the best carbide inserts for cutting aluminium?

The best inserts for cutting are specially dedicated aluminium inserts such as CCGT060204 AK H01, that are uncoated carbide, highly polished, with a sharp ground edge, aluminium specific chip breaker and a positive rake angle, all of which are required features to get the best performance on aluminium.

What makes these features important for cutting aluminium? Read on.

Design features of aluminium cutting carbide inserts

Uncoated

As a rule, aluminium cutting inserts lack any kind of coating. This is both because aluminium is soft enough not to require one, and also because coatings reduce the smoothness of the insert surface which can impede cutting finish. Coatings containing aluminium can also chemically react to aluminium, causing adhesion and a build up of aluminium on the cutting edge.

High Polish

Aluminium cutting inserts are polished to a mirror finish. this isn't just too look shiny, a highly polished cutting surface improves cutting finish by facilitating the smooth flow of swarf over the cutting edge. This also reduces surface area for adhesioin, preventing built up edge of aluminium on the cutting edge which would reduce cutting efficiency and finish.

Chip Breaker

As as soft ductile metal, aluminium tends to form long ribbons of swarf, rather than small chips. The chipbreaker geometry on aluminium cutting inserts allows for continuous removal of material at the cutting surface which improves finish.

Ground edge

Aluminium cutting inserts have a precisely ground cutting edge, which makes them sharper than carbide inserts just formed by sintering tungsten carbide. A sharp edge is advantageous when cutting softer materials like aluminium, where the robustness of a blunt edge to absorb cutting forces is not required, and the sharpness increases both the ease of cut and quality of finish, by cleanly shaving material off the workpiece rather than rubbing it off.

Positive Rake

As you may know from our guide on rake angles and why they matter positive rake angles perform better on small lathes in almost all materials. But even on large powerful lathes that can utilize negative rake tooling to full effect, positive rake aluminium cutting inserts are still the preferable option.

This is because aluminium is soft enough that the benefits of negative rake in reducing cutting forces on the insert aren't required. A positive rake insert, ground, uncoated and polished, can remove large amounts of material fast without concern for generating excess cutting forces. The sharper, positive rake geometry helps peel off material at greater depth of cut than would be possible with a neutral or negative rake insert.