Gave up on carbide end mills for aluminum, went back to HSS

I was running a job in 6061 last month and kept getting chatter with a 3-flute carbide end mill no matter what speeds I tried. Swapped to a 2-flute HSS rougher and the finish came out clean on the first pass at 800 RPM. Anyone else find that HSS works better than carbide in soft aluminum on older machines?

3 comments

3 Comments

daniel_martin18d ago

Huh, and here I thought carbide was supposed to be the answer to everything. @the_nathan makes a good point about coatings though, maybe my carbide just needed a shower before work.

murphy.abby17d ago

Maybe mine just needed therapy before work too.

the_nathan18d ago

Have you checked how your tool holder affects things on a lighter machine? I swapped from a standard collet chuck to a side lock holder and it made a huge difference with carbide even at lower speeds. The extra rigidity let me run a 3 flute at around 1200 rpm with no chatter on my old Bridgeport... but I still grab HSS if I need to take a heavy cut. Another thing nobody talks about is the coating on carbide can actually cause problems in aluminum if it's not polished right, the material gums up and that throws off the balance. HSS is just more forgiving when your machine isn't super stiff.