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<p>I can relate, Jim. In May of '68 I started at Texas Instruments
right out of tech school (basic electronics). My first job was in
the Semi-automatic Testing group of Division 1 (DOD contractor). I
was given a short training period and was assigned to program a
semi-automatic component testing machine for assembled printed
circuit boards called "Fixit". This machine tested the individual
components on the assembled PCB to make sure they were the correct
value in the case of resistors and capacitors. Diodes and
transistors were checked for correct installation.
Coils/chokes/transformers were checked for continuity as well as
long etch runs and plated through holes.</p>
<p>The program was hand written on a coding form and sent offsite to
a contractor where the code was punched into IBM punch cards and a
paper tape was produced. The program was tested and modified as
needed. When the program was finalized, a Mylar tape was produced
for production boards.</p>
<p>This was at least a two week process for pretty simple PCBs, much
longer for complicated or large PCBs.</p>
<p>There was another machine called the DITMCO for testing wiring
harnesses, built by the Drive In Theater Manufacturing Company.
Yup, they used it to test out the wiring for drive-in theaters.</p>
<p>I hadn't thought about paper/mylar tape in years before this.</p>
<p>Phil in TX<br>
</p>
<br>
<div class="moz-cite-prefix">On 5/5/2019 12:17 PM, Jim Becker wrote:<br>
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<div>For some more of the Jo Block story, take a look at the
1908 Dewar Trophy story here: <a
title="https://en.wikipedia.org/wiki/Dewar_Trophy"
href="https://en.wikipedia.org/wiki/Dewar_Trophy"
moz-do-not-send="true">https://en.wikipedia.org/wiki/Dewar_Trophy</a></div>
<div>Although not explained in this article, a main reason
Cadillac was able to accomplish this was the early purchase
and use of a set of Jo Blocks. This was the genesis of
Cadillac’s “Standard of the World” slogan.</div>
<div> </div>
<div>On the subject of paper tape. Ask almost any programmer
how big a program is, he will give you an answer in bytes,
kilobytes, or these days megabytes. Ask an NC programmer
about the size of a program, he will answer in feet, as in
how long the paper tape would be if you punched it out. I
found that even in the ‘90s, long after paper (or mylar)
tape had disappeared from the shops, that was still the way
they answered.</div>
<div> </div>
<div>Jim Becker</div>
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<div style="font-color: black"><b>From:</b> <a
title="soffiler@gmail.com" moz-do-not-send="true">Stephen
Offiler</a> </div>
<div><b>Sent:</b> Sunday, May 05, 2019 5:56 AM</div>
<div><b>To:</b> <a title="at@lists.antique-tractor.com"
moz-do-not-send="true">Antique Tractor Email
Discussion Group</a> </div>
<div><b>Subject:</b> Re: [AT] OT: the inch is somewhat
metric Cast iron work on a replica cannon</div>
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<div>There is a fairly complex history leading to the
definition of 1 inch = 25.4mm exactly. There were
some troubles with parts interchangeability in WW2
because different definitions were used in different
countries. But the man who invented extreme
precision, Carl Johannson - inventory of the gage
block - arrived upon this definition while working
with Ford Motor Co. in the 1920's. It took a while
for this definition to become universal. If you find
this subject of interest, I suggest:</div>
<div> </div>
<div><a href="https://youtu.be/gNRnrn5DE58"
moz-do-not-send="true">https://youtu.be/gNRnrn5DE58</a><br>
</div>
<div> </div>
<div>The very earliest numerical-control (NC) machines
had no computer, but rather read instructions from a
punched paper tape, and these were in the research
stage in the 1940's and began to appear in practice in
the 1950's. It was not until the 1970's that
computers and digital displays began to appear on the
shop floor. Conversion from metric to inch in the
displays was not an issue. Even if it was, the
conversion could have been accomplished regardless of
the definition, because even prior to the universal
adoption of 1" = 25.4mm exactly, the errors were on
the order of 25.39993 to 25.40005 which is well beyond
the precision of the machines in those days.</div>
<div> </div>
<div>And finally, it is a rare engineering course
anywhere in the USA that does not present problems to
students using both metric and inch systems.<br>
</div>
<div> </div>
<div>SO</div>
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<div class="gmail_quote">
<div class="gmail_attr" dir="ltr">On Sat, May 4, 2019
at 9:42 PM James Peck <<a moz-do-not-send="true">jamesgpeck@hotmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="PADDING-LEFT:
1ex; BORDER-LEFT: rgb(204,204,204) 1px solid;
MARGIN: 0px 0px 0px 0.8ex">Early in WW2, the US, UK,
and Canada all had a different length inch. To
ensure parts made in the US fit into machines made
in the UK, etc., they needed a common inch. They
solved it by defining the inch as 25.4 MM. I bet one
heck of a lot of calipers and micrometers had to be
recalibrated. <br>
<br>
This made it possible for CNC machines to switch
from inch to metric on the displays. <br>
<br>
Some university courses would have test problems
using either system or both. That is the real world.<br>
<br>
[Rena Glover Goss] It has been too long since I did
this, Stephen. I used to teach this material to
engineering and engineering technology students, but
have been retired for 18 years, and gave all my
metric taps, dies, drills, and wrenches to one of my
grandsons when I downsized. <br>
<br>
I used to get criticized by faculty colleagues
because I taught my drafting and graphics courses
only in metric units. I told them the students
really didn't know how to use any of the four
systems of measurement, and that they would develop
a decent sense of at least one of them if they
didn't have to be confused by dealing with the
others. I don't think my colleagues necessarily
"bought" my argument, but I did find that things
were much simpler when students only had to deal
with a single measurement device. I think I still
have metric, architectural, mechanical engineering,
and civil engineering scales laying around--but not
nearly as many of them as I used to.<br>
<br>
So tell me-- How long is a surveyor's chain, and
what are the units in it? This is not an esoteric
question. Our family is currently dealing with a
real estate transfer that dates to the original
survey for the Wabash-Erie canal. The concepts of
Range and Township were still reasonably new at that
time, and the units of measure corresponded to the
most current technology.<br>
<br>
<br>
[ Stephen Offiler] Larry: yes, with metric threads,
you find the tap drill simply by subtracting the
pitch from the major diameter. M15 x 1.0 gives a
14mm tap drill. Using this formula, you always end
up with 77% thread engagement for any thread, any
pitch. I'm not quite following your comment about
the reduction you use.<br>
<br>
[Rena Glover Goss] THAT'S NO FAIR, SPENCER. You
were not supposed to figure out how simple those
relationships are in the metric system when compared
to any other system of threading. I used a
reduction by 1.5 millimeters so the thread
engagement came closer to 75%, as is used in the
SAE system. There are no charts for pilot drills in
the metric system--they simply aren't needed.<br>
.<br>
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