On Sun, 24 Apr 2016 18:21:21 +0700, John B.
wrote:
On Sun, 24 Apr 2016 06:43:15 -0400, Ed Huntress
wrote:
On Sun, 24 Apr 2016 14:21:47 +0700, Good Soldier Schweik
wrote:
On Sat, 23 Apr 2016 20:00:29 -0700, Gunner Asch
wrote:
On Sat, 23 Apr 2016 23:23:18 +0000 (UTC), Cydrome Leader
wrote:
Gunner Asch wrote:
On Fri, 22 Apr 2016 16:27:05 +0000 (UTC), Cydrome Leader
wrote:
I indicated 3/8" barstock to "close enough" of about 3 mils in a 3 jaw,
centerdrilled and used a livecenter.
3 mils????
0.003"
Oh..you mean 3 thousandths. NOBODY says 3 mils when machining..least
not in the US.
Only in plastic sheet making will you find it..and thats not
machining..thats extruding
Slang would be 3/1000s, 3k, an RCH, etc etc
I hate to agree with you but I never heard the term "mil" until very
recently and I worked in and around the business since I was in High
School. It was always 3 thousandths (.003) or 3 tenths (.0003) for
smaller dimensions.
Before the late 1930s, "mil" was used commonly in machining, too.
Well, I wasn't around the shops in the "late 1930's" :-)
But I did for a couple of weeks run a lathe that the cross slide was
calibrated in 1/128th of an inch. The owner of the shop reckoned it
dated from "Civil War Days".
When they're that old, you should sell them to interior decorators for
use as foliage planters. They look nice with a Wandering Jew twined
around the bedways, standing between a miniature palm and a ficus
tree. d8-)
In 1977, I was one of the writers for American Machinist's 100th
Anniversary issue. For a year, we all poured through the old AM
archives, going back 100 years. The term "mil," for thousandth,
appeared all of the time in the old volumes, as a slangy shorthand,
like the way we use the term "tenths" today.
Then, I'd say roughly in the late '30s, the term "mil" all but
disappeared. Universal use of gage blocks, sub-thousandths accuracy,
aircraft and military specs combined to add another decimal point to
required accuracies. American Machinist adopted a style point of using
numerical values to express accuracy, with a zero before the decimal
point for metrics, and with no leading zero for inch-based dimensions.
Written out in English, we used "thousandths," "ten-thousandths," and
"microinches." Metrics were a problem child, as we first used
"micron," and then, when SI came in vogue, "micro-meter."
Anyway, the point is that no one here is old enough to remember the
use of "mil" for thousandths of an inch, but some of us who were
deeply involved in metalworking history have seen it used a lot in the
deep past.
BTW, don't get me started on "gage" versus "gauge." That one has a
history, too. There used to be an important distinction, but that
distinction has been lost in time.
--
Ed Huntress
Here's a little history of how we express "thousandth of an inch":
https://en.wikipedia.org/wiki/Thousandth_of_an_inch