Just realized my tool offsets were wrong for 4 months straight

I was chasing a .005 tolerance on some aluminum parts last Tuesday and couldn't figure out why every part was coming out slightly oversized. Checked my tool holders, double checked my speeds and feeds, even swapped out the end mill. Finally went back to basics and measured my tool offsets with a height gage instead of just trusting the presetter. Turns out the presetter was off by .003 from a build up of cutting fluid residue and I never caught it. I had been comping feeds in the wrong direction for months thinking the machine was drifting. Had to re-evaluate about 60 parts from the last batch and scrap maybe a third of them. Has anyone else had a presetter get that far out of whack without noticing?

2 comments

2 Comments

the_sage9d ago

Four months of fighting a .003 ghost is rough, but @burns.brooke hit on the real issue - most shops don't run a basic height gage check on their presetter daily. A quick five minute verification every morning would have caught that buildup before the first batch went sideways. Spending 30 seconds on calibration could have saved you from scrapping a third of those parts and four months of second guessing every setup.

burns.brooke9d ago

Takes a special kind of pain to realize you've been fighting ghosts for four months. My buddy had a similar thing happen with his tool presetter, except it was off because he kept storing it right next to the coolant mister. Took him three weeks of chasing a .002 tolerance on some stainless before he cleaned the glass and got a good reading. Scrapping a third of a batch hurts, but at least you caught it before it got worse. Consider it a very expensive lesson in calibrating your gear more often. That .003 will haunt you more than any scrap report ever will.