Ran a 1/4 inch bit through aluminum at 18k RPM and learned a hard lesson

I was cutting some 6061 aluminum plates for a customer job last Tuesday and figured I'd crank up the spindle speed to save time. Within about 30 seconds I hear this nasty screech and the bit basically welded itself to the aluminum. Turns out I was way over the recommended RPM and the chips weren't clearing at all, just melting into a mess. Took me an hour with a torch and a vise to get the bit out, plus I ruined a $40 part. Has anyone else found a good baseline RPM for aluminum that actually works?

2 comments

2 Comments

kimreed28d ago

Speed kills tooling every time.

benc5328d ago

18k with a 1/4 bit in aluminum is basically asking for trouble, I did the same thing with a 1/8 bit once and it welded solid in about 10 seconds. For 6061 I keep my spindle around 8k to 10k RPM with a 1/4 inch single flute end mill and a good chip load, that combo clears chips way better and keeps the heat down. You also REALLY need to use some kind of lube or mister, even WD40 helps a ton to stop that gumming up. Dropping the feed rate to let the bit cut instead of rub made the biggest difference for me, that screech is your tool screaming for mercy.