I ran the same part 40 times before catching my zero point mistake

Set up a job last Tuesday thinking my part zero was on the left edge of the stock. Turns out I had been eyeballing the wrong corner of the vise jaws for months. The tip off came when I measured the first good piece and it was off by exactly 0.087 inches, which matched the jaw step height. I checked my notes and sure enough, I wrote down the zero location wrong back when I first got the machine. Nobody said anything because the parts were always within tolerance before, but this one was a tighter fit. Anyone else have a setup habit that just happened to work until it didnt?

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holly_reed554d ago

Read a post on a machinist forum last week where a guy found his vice was actually twisted by a few thousandths and he never checked it for years. He only caught it when he started doing a job with a really tight tolerance on a matched pair of parts. Your story reminded me of that because it is the same thing, the error was just sitting there the whole time. I had a similar thing with my tool height offset once, wrote it down one day and it worked fine until I switched to a different holder. It is wild how a wrong note can just ride along for months or years until the right part comes through.