Second point first: Just because a metal is soft does not guarantee that you can cut it at a high surface feet per minute so you cannot safely generalize and say soft equals go fast. I am thinking about metals such as brass and copper which are soft but which cannot be machined at the same speed as aluminum.
Regarding the advantage of carbide over HSS for aluminum when you do not have a high spindle speed available? That is a good question; if you could get pre-ground HSS tools with all the shapes available for carbide insert tools, at a cost less than carbide quite likely if your maximum rpm was 2000 it would be sensible to use the HSS. If it is a case of having to grind your own HSS tools I think it is much easier to use carbide.
Of course as soon as you consider machining cast aluminum then carbide is the way to go because high silicon aluminum alloys are very abrasive.
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An open mind is a virtue...so long as all the common sense has not leaked out. |