The day a coolant line split and taught me to check everything

I was running a big aluminum job on our old Haas, about 4 hours into a 6 hour cycle. Heard a weird hiss and saw a fine mist, but the pressure gauge looked fine. Kept going for 20 minutes until the pump started screaming. Turns out a cheap plastic T fitting on a secondary line had a hairline crack. The gauge only read the main line, so I missed it. Lost the whole batch and a $200 end mill. Anyone else have a story about a small part causing a huge crash?

3 comments

3 Comments

casey_barnes3mo ago

Watched a buddy's lathe eat itself because a single set screw backed out on a boring bar holder. Thing was just chattering for a bit, then it dug in and snapped the bar right off. Took the insert with it and put a nasty groove in the part.

robinson.holly3mo agoTop Commenter

Okay, but "ate itself" feels like a stretch. A set screw coming loose is a basic shop mistake, not a machine meltdown. It wrecked the tool and the part, which totally sucks and is expensive, but lathes are tough. That's a bad day, not a total breakdown. The machine itself is probably fine after a cleanup and a new tool holder.

hugow301mo ago

Yeah I've seen this happen more than once. First thing you gotta do is check the taper on your spindle bore. If that set screw backed out and the bar shifted, it might have put a little wobble in the holder that you can't see by eye. Take a test cut with a fresh insert on some scrap before you trust it again. Also check the threads on the set screw hole itself. Sometimes when they let go like that they strip out the threads and you end up chasing them with a tap. A little Loctite on the new screw goes a long way too, I use blue 242 for stuff like that.