Switched my coolant mix ratio after 3 years of fighting finish quality

I always ran a 10% concentration because that's what I read online. Parts kept coming out with this weird hazy residue and I was chasing spindle speeds for months. Last Monday my tool rep dropped by and said try 7% instead. First run after the change the parts came out clean and shiny, no more haze at all. Anybody else find better luck running leaner coolant mixes on aluminum?

2 comments

2 Comments

sage_rodriguez1mo ago

Ran a 9% mix for two years on 6061 and fought the same haze issue. Dropped it to 6% on a hunch and the finish cleaned up overnight. The coolant manufactures always recommend higher ratios to cover their ass, but aluminum doesn't need that much. You might have to top off more often since the mix evaporates faster, but it's worth the trade off. Just keep an eye on the sump level especially in summer.

james_ross1mo ago

Hang on a minute, are we sure this haze was really from the coolant ratio and not something else like a bad batch of material or a worn insert? I've run 10% on 6061 for years without that problem, so it makes me wonder if the issue was just that the old coolant was getting old and funky. @sage_rodriguez I hear what you're saying, but dropping it to 6% sounds like you're asking for bacterial growth or rust if the water quality isn't perfect. Seems like a lot of people are chasing ghosts and then blaming the mix.