You know, I knew some old fart would pop up with that, as soon as I wrote it.
What I should have said is that it all but disappeared in *print*. It migrated over to the sheet-material field, where it eventually became concentrated in plastic materials. I wrote a few articles for _Modern Plastics_ and _Plastics Technology_ (on moldmaking) in the '70s and '80s, and I noted it was being used by them.
I've seen it used for sheet metals, too, but only very rarely.
I do too, but that was in a shop that was run by people well into their 70s, back in the late 1970s.
The problem was that mil was used universally for thousandth of an inch, millivolt and milliamp.
I've been trying to figure out where I learned mil from. While I do have an electronic-ish background, it's not really a unit you'd use when repairing something. It's likely from an an older designer or engineer friend.
Circular mils are still common enough when it comes to electrical guages, such as a 500MCM cable, even though that's sort of a weird unit- "thousand circular mils." Pretty sure that's the same as a 1/2" copper rod.
A circular mil refers to the cross-sectional area of a wire with a diameter of 0.001 inch. The formula is A = d^2, where A is the area in circular mils and d is the diameter of the wire in mils. So a 1/2 inch rod is 250,000 circular mils.
It keeps you from having to use pi to calculate the cross-sectional area of a wire; if you know the current-carrying capacity in circular mils, you just use the A=d^2 formula to calculate the current-carrying capacity of a wire of any diameter.
You sure about that??? Comes out to more like a 3/4 inch copper rod (actually 0.8" diameter)
When I was at Edwards AFB they had an "Electric Spark Machine". I was there for about a year and saw it used just once. A guy made a set of dies to punch out counterfeit quarters for the Coke Machine.
Interestingly he tried a number of alloys for his counterfeit quarters and the Coke Machine rejected them all :-)
It was a LONG time ago but as I remember it they were normal sized nuts. Nothing that you couldn't buy off the shelf in the local hardware store.
But "back in the day" apprentices did not argue with the Boss, so I never asked :-)
:-)
I was stationed at an airbase near Selma, Alabama and the local folks didn't appreciate the Air Base people at all. The Base Commander arranged for us to be paid in 2 dollar bills and silver dollars one payday. There was a noticeable warming of the town's attitude toward us thereafter.
I'm curious -- what year was that?
He was too early. Today, he probably could get away with any scrap metal.
The machines I looked at several years ago only took bills. I guess they have them now that you can pay with your smart phone...
A different kind of counterfeiting required to bypass them :)
It must have been in the mid 1960's.
They also had a "tape controlled" machine there that would do things automatically. It could even change tools, or so I was told. One guy had been to school on the control system but it was never used while I was there.
I did ask the guy how it worked and it used a punched tape like a telex machine. The left column was, say longitudinal travel, and one punch was one increment of movement.
Once again, technology opens up endless entrepreneurial opportunities. d8-)
Ah, OK, that fits. Sinker-type EDMs were pretty capable by then, and you could use a quarter, say, as an electrode, to burn the end of a punch or die.
But I think you'd go through a lot of quarters doing it. Tungsten-silver was a premium electrode material, but I think that plain silver would melt off pretty quickly.
Um...that's how I learned lathe programming. We had a Sheldon 1710H controlled by a Bendix 5 NC, and a teletypewriter to key in and punch the paper tape. I could program straight cylinders and tapers, and face them off, IIRC. I never did any actual work with it; the real machinists wanted to play with it and hogged the keyboard.
For anything complex, we used a telephone-connected time-sharing system that did the programming by computer.
Mid 70's... one of my fellow shop class students figured out that he could re-size pennies using the 1 inch vertical belt sander. Schools vending machines took them as dimes. He was caught a short time later working at the belt sander :)
Imagine doing time in a federal prison for counterfeiting dimes.
After reading John's story I wonder if the pennies material helped it to be accepted. Some of those machines had pretty innovative means of detecting real coins. The thing that tripped the kid up was using the schools shop equipment. If he could have done the work elsewhere it would have taken a lot longer to catch him.
Not completely sure at this point- and it looks like there are three ideas as to what 500MCM cable is equivalent to if it was just a rod. May have to look this one up.
Very common in countries that use the metric system , 1 Mil = 1 millimeter.
30+ years ago I was takeing a "night school" Saturday morning class at the local community college. Since the winter class was held outdoors, we were happy to indulge in the mid class coffee break in the automated caffeteria. One Saturday, the coffee machine refused to co-operate. After I "thumped" it a couple times, everyone had a free coffee an I had over $5.00 in leftover coins!
We used to dip clean pennies in mercury and pass them as dimes with local merchants
Oh, right...you're a Canadian. They had to put facets on your nickels to keep you from shaving them on those long winter nights.
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