On Mon, 25 Apr 2016 19:38:27 +0700, John B.
wrote:

On Sun, 24 Apr 2016 21:50:30 -0400, Ed Huntress
wrote:

On Mon, 25 Apr 2016 08:44:12 +0700, John B.
wrote:

On Sun, 24 Apr 2016 09:53:34 -0400, Ed Huntress
wrote:

On Sun, 24 Apr 2016 20:12:37 +0700, John B.
wrote:

On Sun, 24 Apr 2016 08:48:57 -0400, Ed Huntress
wrote:

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-)

Well, this was when I was in High School and the shop was at least 2nd
generation in the same building. It was owned and operated by two
bachelor brothers who didn't talk to each other. The entire shop
except for some bench grinders operated from a single electric motor
"out back" driving an overhead shaft system. Strangely I don't
remember thinking it was an odd place to work :-)

One of the brothers had an absolutely like new Henderson 4 cylinder
motorcycle that he used to ride to work occasionally which certainly
was interesting.

As a summer hire apprentice I wasn't doing any high tech stuff, they
had me making nuts on the old lathe. Even then, making 50 cents an
hour, I can't see how the finances worked. 12 ft of hex stock in an
antique lathe, Drill, tap, part off, advance the stock a bit and do it
again. Sort of a human screw machine :-)

At least he didn't have you start with round bar stock...


But they paid every Friday afternoon at quitting time. Cash in the
hand.

When I hear stories like that, I wonder how the United States, and the
West in general, ever managed to produce anything that anyone could
afford.

Just before wire EDM came into use, I started covering tool and
diemaking, and visited a lot of t&d shops. I watched diemakers rough
out blanking dies with a bandsaw, breaking the blade, threading it
through the work (they milled out a really rough hole first, but it
usually was nowhere near the final size), and then re-welding the
blade back together. Then they'd break the blade to remove the die
from the saw, and they'd go to work with diemaker's chisels, cutting
close to the line and chiseling in some die relief. Then, possibly, on
to the die-filer. Next, hand-filing with files down to jeweler-file
size. After that, the die would go out for heat-treating.


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.

I'm curious -- what year was that?


It must have been in the mid 1960's.

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.


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.

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. g 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.

--
Ed Huntress