Valerie, Are you suggesting we launch a "counter" offensive to change that? Dewey > -----Original Message----- > From: Valerie St.Cyr [SMTP:[log in to unmask]] > Sent: Wednesday, November 05, 2003 8:38 AM > To: [log in to unmask] > Subject: Re: [TN] OFF-TOPIC: Engineering Specs :-) > > > I believe (could be wrong) that standard PCB thicknesses of 1/16, 1/4, > 3/32, 1/2 are what they are because that is what the thickness of counter > top "laminates" were when the "laminators" started supply phenolic > "laminates" to the fledgling PWB industry. Then connectors were designed > to accommodate laminates of those thicknesses, and now we are stuck with > standard thickness of .062", .093", .125" because those are the only (for > the most part) thicknesses that "standard" connectors work with .... > > Valerie > > > Valerie St. Cyr > PCB Technology > Teradyne > > 978-370-1136 > [log in to unmask] > > > > > Brian Ellis <[log in to unmask]> > Sent by: TechNet <[log in to unmask]> > > 11/05/2003 10:13 AM > Please respond to "TechNet E-Mail Forum."; Please respond to Brian Ellis > > To: [log in to unmask] > cc: > Subject: Re: [TN] OFF-TOPIC: Engineering Specs :-) > > > > Of course, this makes the metric system look stupid. It makes much more > sense to have 12 inches = 1 foot; 3 feet = 1 yard; 5.5 yards = 1 rod, > pole or perch; 4 rods, poles or perches = 1 chain (the length of a > cricket pitch between the wickets); 10 chains = 1 furlong; 8 furlongs = > 1 statute mile. In summary, 1 mile = 8 furlongs = 80 chains = 320 rods, > poles or perches = 1760 yards = 5280 feet = 63360 inches. It is this > simplicity that dictates why printed circuits are largely dimensioned in > imperial measures, rather than the complex metric system. Similarly, > imperial weights, volumes, areas etc. are equally simple. > > Brian > > Ingemar Hernefjord (KC/EMW) wrote: > > The history of length and weight is funny to read > > > > examples pasted from english history article: > > > > The foot was declared one-third yard and the inch one thirty-sixth. King > Edward II in 1324 recognising the Iron Ulna was not universally used > declared "3 barleycorns, round and dry make an inch" > > > > > > Going as far back in time as Noah's ark, the lack of a universally > understood unit of measurement was not a serious drawback. Most measuring > was done by one craftsman completing one job at a time, rather than > assembling a number of articles piecemeal to be put together later. It > didn't make much difference how accurate the measuring sticks were or even > how long they were. The cubit of Noah's time was the length of a man's > forearm or the distance from the tip of the elbow to the end of his middle > finger. > > > > For the United Kingdom, the basic English unit of length was the yard of > three feet, or the fathom of six. Half a yard was the 18-inch cubit, and > half a cubit was called a span, which was the distance across the hand > from the tip of the thumb to the tip of the little finger when the fingers > were spread out as far as possible. A hand was half a span. During the > thirteenth century King Edward I decreed the 'Iron Ulna' after the bone of > the forearm to become the main unit of measurement, which later became the > 'yard'. He ordered a permanent measuring stick made of iron to serve as a > master standard yardstick for his entire kingdom. King Edward realised > that constancy and permanence were the key to any standard. The foot was > declared one-third yard and the inch one thirty-sixth. > > > > > > Regards > > > > Ingemar Hernefjord > > Ericsson Microwave Systems > > > > > > > > -----Original Message----- > > From: TechNet [mailto:[log in to unmask]]On Behalf Of Brian Ellis > > Sent: den 4 november 2003 17:24 > > To: [log in to unmask] > > Subject: [TN] OFF-TOPIC: Engineering Specs :-) > > > > > > Origins of engineering specs > > > > Subject: Origins of engineering specs and government > > decisions. Ever wonder where engineering specifications come from? > > > > The US standard railroad gauge (distance between the rails) is 4 feet, > > 8.5 inches, an exceedingly odd number. Why was that gauge used? > > Because that's the way they built them in England, and the English > > built the first US railroads. > > > > Why did the English build them like that? > > > > Because the first rail lines were built by the people who built the > > pre-railroad tramways, and that is the gauge they used. > > > > Why did they use that particular gauge then? > > > > Because the people who built the tramways used the same jigs and tools > > that they used for building wagons, which used the same wheel spacing. > > > > Okay! Why did the wagons have that particular odd wheel spacing? > > > > Well, if they tried to use any other spacing, the wagon wheels would > > break on the old, long distance roads in England, because that's the > > spacing of the wheel ruts in the granite sets. > > > > So, who built those old rutted roads? > > > > Imperial Rome built the first long distance roads in Europe (and > > England) for their legions. The roads have been used ever since. > > > > And the ruts in the roads? > > > > Roman war chariots formed the initial ruts, which everyone else had to > > match for fear of destroying their wagon wheels. Since the chariots > > were made for (or by) Imperial Rome, they all had the same wheel > spacing. > > > > The United States standard railroad gauge of 4 feet, 8.5 inches is > > derived from the specification for an Imperial Roman war chariot. > > > > Specifications and Bureaucracies live forever. > > > > The Imperial Roman war chariots were made just wide enough to > > accommodate the back ends of two war-horses. > > > > Now let's cut to the present... > > > > The Space Shuttle, sitting on its launch pad, has two booster rockets > > attached to the sides of the main fuel tank. These are solid rocket > > boosters, or SRBs. A company builds SRBs at its factory in Utah. The > > engineers who designed the SRBs wanted to make them a bit fatter, but > > the SRBs had to be shipped by train from the factory to the launch > site. > > > > The railroad line from the factory has to run through a tunnel in the > > mountains. > > > > The SRBs had to fit through that tunnel, which is slightly wider than > > the railroad track, and the railroad track is about as wide as two > > horses' > > behinds. > > > > So.... a major design feature of what is arguably the world's most > > advanced transportation system was determined two thousand years ago > > by a horse's ass. > > > > Which is pretty much how most government decisions are made. > > > > --------------------------------------------------- > > Technet Mail List provided as a service by IPC using LISTSERV 1.8e > > To unsubscribe, send a message to [log in to unmask] with following text > in > > the BODY (NOT the subject field): SIGNOFF Technet > > To temporarily halt or (re-start) delivery of Technet send e-mail to > [log in to unmask]: SET Technet NOMAIL or (MAIL) > > To receive ONE mailing per day of all the posts: send e-mail to > [log in to unmask]: SET Technet Digest > > Search the archives of previous posts at: > http://listserv.ipc.org/archives > > Please visit IPC web site > http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 > ext.5315 > > ----------------------------------------------------- > > > > --------------------------------------------------- > > Technet Mail List provided as a service by IPC using LISTSERV 1.8e > > To unsubscribe, send a message to [log in to unmask] with following text > in > > the BODY (NOT the subject field): SIGNOFF Technet > > To temporarily halt or (re-start) delivery of Technet send e-mail to > [log in to unmask]: SET Technet NOMAIL or (MAIL) > > To receive ONE mailing per day of all the posts: send e-mail to > [log in to unmask]: SET Technet Digest > > Search the archives of previous posts at: > http://listserv.ipc.org/archives > > Please visit IPC web site > http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 > ext.5315 > > ----------------------------------------------------- > > > > > > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV 1.8e > To unsubscribe, send a message to [log in to unmask] with following text in > the BODY (NOT the subject field): SIGNOFF Technet > To temporarily halt or (re-start) delivery of Technet send e-mail to > [log in to unmask]: SET Technet NOMAIL or (MAIL) > To receive ONE mailing per day of all the posts: send e-mail to > [log in to unmask]: SET Technet Digest > Search the archives of previous posts at: http://listserv.ipc.org/archives > Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 > for additional information, or contact Keach Sasamori at [log in to unmask] or > 847-509-9700 ext.5315 > ----------------------------------------------------- > > --------------------------------------------------- > Technet Mail List provided as a free service by IPC using LISTSERV 1.8e > To unsubscribe, send a message to [log in to unmask] with following text in > the BODY (NOT the subject field): SIGNOFF Technet > To temporarily halt or (re-start) delivery of Technet send e-mail to > [log in to unmask]: SET Technet NOMAIL or (MAIL) > To receive ONE mailing per day of all the posts: send e-mail to > [log in to unmask]: SET Technet Digest > Search the archives of previous posts at: http://listserv.ipc.org/archives > Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 > for additional information, or contact Keach Sasamori at [log in to unmask] or > 847-509-9700 ext.5315 > ----------------------------------------------------- > > --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------