Old timer at a shop swore by not using coolant on aluminum...

I was about 6 months into my first CNC job at a little shop near Portland, and there was this guy named Rick who'd been running mills since the 80s. He told me coolant just makes a mess with aluminum and you're better off running it dry with really sharp tooling and high RPMs. I thought he was crazy because every manual I read said coolant is essential for chip evacuation and keeping temps down. But he let me watch him cut a whole batch of 6061 parts on a Haas mini mill, no coolant at all, just a stiff air blast. The finish was actually better than anything I'd gotten with flood coolant, and the tool life seemed fine for the run. I still run coolant on steel and stainless, but for aluminum I've been experimenting with dry cutting based on that one interaction. Anyone else try ditching coolant for certain materials, or is Rick just an old-school outlier?

2 comments

2 Comments

mason7981mo ago

Oh man, "coolant just makes a mess with aluminum" - that's the kind of line that gets you either a fist bump or a blank stare depending on who you're talking to. I tried going dry on aluminum once after watching some YouTube video and I swear my endmill started sounding like a dying cat halfway through the first part. But Rick sounds like one of those old guys who's been breathing in cutting fluid fumes for so long he's immune to everything. I think the real trick is having the right tooling and feeds, not just turning everything off and praying. Still, if it worked for his parts on that Haas, maybe there's something to it for certain setups. Just don't try that on 7075 or anything gummy unless you want to scrape aluminum off everything within a 10 foot radius for the next week.

jade8851mo ago

Wait, did you just say "dying cat halfway through the first part" because I heard it too and it made me want to cry? I think that's the universal sound of regret right there. But honestly, Rick probably keeps that Haas so dialed in he could machine butter with a dull bit and still get a mirror finish. You're dead on about 7075 though, that stuff is like the diva of aluminum alloys, one wrong move and it's gumming up everything like a toddler with playdough. People forget that dry machining works great until it doesn't, and then you're spending an hour with a scraper and a can of brake cleaner. At least with coolant you can pretend you're a pro while your chips are getting blasted out of the way.