So, I’m at work, which is a machine shop. I’m running one of the mills (hence the screen name, BTW). I’m making these rectangular parts out of stainless steel. They need to be an inch and an eighth, or 1.125 inches long. The tolerance for the stuff we’re making is plus or minus .005, so a finished part could measure anywhere between 1.120 and 1.130 and still be acceptable.
I take the first blank, clamp it in the vice, and run it past the end mill, which carves off the ugly saw marks and puts a nice machine finish on it. I take the part out, flip it over, and start to machine the other side, which is when I realize I’ve screwed up. I forgot to measure it before I made the second cut, so I don’t know how much I needed to take off: I’ve probably blown it and taken off too much, so that the part will be too short.
Well, since I’m half-way through with the cut, I finish it, in the hopes that it might still be salvageable. I blow the part off, take it out of the vice, and grab my trusty digital calipers, and check how badly I’ve screwed up. I clamp them on and check the read-out: 1.1250 inches.
I measure again: 1.1250 inches. I carefully wipe down the part, making sure there aren’t any chips on it that might throw off the calipers. Still 1.1250. I clean the jaws of the calipers. Still 1.1250. I got the part dead-on accurate, to within [sup]5[/sup]/[sub]10,000[/sub]ths of an inch. That’s .0005. By way of comparison, a human hair is .002. And I did entirely by chance.
You know that feeling you get when you go to the store and buy a bunch of random stuff, and when the guy rings it up, it comes out to a round number? Like you buy fifteen different things, and the price is exactly thirty bucks? And you get this little feeling that there’s some sort of higher order to the universe? Multiply that feeling by a factor of fifty: that’s what I felt right then. Heck, this was two days ago, and I’m still jazzed up about it. I mean, what are the odds that I’d just happen to hit the exact size I was going for, on my first try, without even measuring? I gotta start buying lottery tickets.
