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I finally figured out why my parts kept coming out 0.003 off, and it cost me 11 days
Ran a batch of 400 aluminum brackets on the old Haas mill last month and the first 30 checked fine, then halfway through the run my micrometer started reading 0.003 under on every part. I blamed the tool holder, swapped it, re-indicated the vise twice, even had maintenance come look at the spindle, and blew four days on stuff that was not the problem. Turns out my coolant mix had drifted way too rich over time, and the chips were packing under the fixture and lifting the part just enough to matter on the deeper cuts. Spent another two days re-cutting 60 scrapped parts and dialing the mix back to where the refractometer said it should be. Eleven days total for something a $30 refractometer and a five minute check would have caught on day one. Now I check the mix every Monday before the first cut. Anybody got a go to number they run their mix at, or do you just trust the jug instructions?
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davidwilliams1mo ago
Man, this is the same story as my wife's car that kept pulling to the right and we replaced the tires, got an alignment, and it turned out to be a bent rim the whole time. We always jump to the big scary thing first when it's usually some small boring maintenance item we skipped. Same deal with your coolant, and honestly same deal with most stuff in life, the little things you stop paying attention to are the ones that bite you.
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