Although Aluminium is usually seen as an easier material to machine (compared to, for instance, Stainless or Exotics), there are more general problems associated with machining “sticky” or “long chipping” materials like Aluminium.
You can expect to encounter various issues with these materials like unmanageable swarf, built up edge on your cutting tool and subsequently low tool life or poor surface finish. There are a few things to bear in mind when selecting the right tools that can help to combat this.
Although some advanced coatings are suitable for machining aluminium, the best option is usually an uncoated cutter with polished flutes. This is because when you’re machining any material a lot of heat is generated, but with aluminium this heat can cause the cut material to weld itself to the cutting edge.
Commonly this is referred to as a “built up edge”, which can make the tool blunt and prematurely causes you to have to regrind the tool or throw it away (even though the cutting edge is still intact!).
The best tools for cutting aluminium will also have a sharp cutting edge, high rake angle and a positive approach:
In turning applications, a smaller corner radius can be used for better surface finish without compromising on tool life.
In milling applications, tools with deep flute pockets and a high helix angle can be beneficial for dealing with swarf and avoiding tools clogging up with swarf (built-up edge).
For aluminium substrates with a high silicone content or abrasive properties, you should select a cutter with either a DLC (diamond like carbon) coating or a PCD tip (polycrystalline Diamond).
Getting the best out of your tool
It is important to select the correct cutting speed and feed when machining Aluminium. Commonly, a failure to push the tool as hard as it is designed to be pushed can be as bad as pushing the tool too hard. If your feed rate is too low, you can generate too much heat when cutting and increase the chance of getting a built-up edge on the tool. Conversely, if your feed rate is too high then you are likely to get clogged up flutes and cause the tool to break.