Originally Posted by 270 MKV
Mil is actually unitless
Paw Bear is 100% correct. the term mil can be applied to anything you desire. Unfortunately, many people like to use slang terms more than I care for. It can often be confusing just as it has been for the original post.
I worked for 46 years as a machinist, toolmaker, instrument maker, tool & cutter grinder and 25 of these years were as a working shop supervisor in a research facility at the University of Illinois.
I grew to hate that term mil, simply because almost everyone that uses it seems to believe it has only one application and they are the absolute authority on what's correct. In a previous post someone mentioned it isn't a linear measurement.
Well, they've never talked to as many mechanical engineers as I have (which is in the hundreds) because I've met only a handful that didn't use the term to mean anything other than 1/1000 of an inch or .001 inches. I've also dealt with hundreds of students looking to have something fabricated. 30-40% of them were foreign. Metric was their way of measuring. At least 50% of the foreign students were also well versed in mechanical engineering. They used the term to mean millimeter, which is 1/1000 of a millimeter or .03939 inches, which approaches 40 times the accepted US .001 inches.
Although not as often, 3rd in line from my experiences, I've heard a student or professor use "mil" when they're referring to a millionth of an inch.
I'd like to further point out that decimal degrees is as fast as anything else used for calculating.
I was however surprised to read that it also had something to do with dividing a circle into something other than units different that 1/1000th. I'm 71 and still learning. This term "mil" seems to include 5 times more than I first suspected.
Since I'm darned sure I don't know everything and I'm not the absolute authority on all the ways the term mil (lowercase BTW) is acceptably used, I darned certain what my experience is & I've had 46 years of it. I've often wished the term "mil" didn't exist because of the confusion it seems to cause.
A few of you need to swallow their pride. For myself, I've been humbled more than I care for in my life.