Had a collet chuck let go mid-cycle and it scared me straight about maintenance checks

It was last Tuesday morning about 10am, running a batch of stainless steel shafts on a Haas VF-2. Heard a weird vibration for maybe 4 seconds before the whole 3/4 endmill flew out and smacked the enclosure window. Thank God nobody was nearby. The collet nut was tight when I checked it at setup an hour earlier, but I think some coolant had gotten in there and softened the grip over time. I used to just wipe down the collets quick between jobs, but now I'm pulling them apart and drying them with compressed air before every single run. Has anyone else had coolant cause a collet to lose grip like that, or was it probably something else I'm missing?

3 comments

3 Comments

wade_kelly7715d ago

Blame the tool holder not the collet, that was likely a clamping issue from the start.

gracethomas15d ago

Start by checking the tool holder bore with a good indicator. I've seen more collet walkout from a dirty or worn holder bore than from the collet itself. If the bore has even a tiny nick or some leftover crud, the collet can't seat right. A quick clean with a paper towel and some brake cleaner usually fixes it for me. Also, make sure your collet nut threads are clean and you're not overtightening it, that can pull the collet off center too.

wilson.olivia15d agoMost Upvoted

Are you sure the vibration wasn't just a loose endmill from the start? I get being careful, but pulling collets apart every run seems like overkill for a one-off freak thing. @wade_kelly77 might have a point too, but I'd just blame the coolant getting in there and call it a day.