Stopped using coolant mist for a week and my tool life actually got better

I was having this issue with inserts chipping way too fast on 4140 steel, so I tried running dry with just an air blast to clear chips. Now I'm wondering if the thermal shock from mist was doing more harm than good - has anyone else seen better results cutting back on coolant?

3 comments

3 Comments

riley_price1mo ago

Switched to air blast only on 4140 last year and saw the same thing. My inserts were chipping after maybe 20 parts with mist, now I get 60-70 easy. The key for me was dialing in the air pressure just right (around 60 psi) and making sure the chip breaker on the insert matched the feed rate. Thermal shock is real, especially with those interrupted cuts.

the_emery2mo ago

Nah that makes total sense honestly. The thermal shock from mist is brutal on carbide, especially in 4140 with those heat cycles. Air blast is the way to go for steel like that. I had a buddy run dry on some tough stuff and his tool life doubled easy. The key is keeping the chips clear so they don't weld back on. Coolant mist just messes with the temperature too much and causes microcracks. You're probably saving money on inserts and coolant too.

skyler_adams2mo ago

Man I've been saying this exact thing for years. The microcracking from coolant mist is no joke, especially once you get those heat cycles going in 4140. I've got a buddy who runs a job shop and he switched to air blast only on steels like that and his insert life doubled basically overnight. It seems backwards but dry cutting with good chip evacuation just works better for that kind of material.