Origins of Precision

so the other day I was working in the shop making some chips and I got to thinking where does all this come from like straight lines regular intervals you know that kind of stuff now I'm no scholar a professional machinist for that matter and like you do I started having a look in the story in history of how he got to where we are today and it's pretty amazing it took thousands of years and the work of people all over the world and I found a lot of things that surprised me I think the best way to think it through is to imagine you have nothing and you start all over again so let's say you're stranded on a desert island and one day you decide you know just the thing that'll get you back to civilization a time machine I mean not only do you regret the three-hour boat tour but you might as well fix all that other stuff too as everyone knows a time machine is made up of lots of complex precise parts like the parametric fam in the turbo and cab you later but it's a desert island everything around you is organic shapes to get started you need something straight with accurate mark dimensions a ruler how would you get there where would you even start get three reasonably flat pieces of cast iron or granite and mark them a B and C if you rub a and B together they'll get flatter but also run the risk of one becoming concave and the other convex either just a little bit the trick comes when you rub B and C together and then C an a the only common plane between three or more surfaces has to be one that's practically perfectly flat this is how you on remote desert island with a lot of effort but no external reference make a perfectly flat surface from which all the dimensional precision of the modern world comes from with that flat surface or surface plate you can make the rest the tools you need to create things like squareness parallelism flatness how round something is and make tools for accurately dividing a circle then you can make portable straight edges which are just as flat as your surface plate to transfer that nearly perfect geometry into other machines like lathes or milling machines to make precision parts everything precision around you can be traced eventually back to the surface plate oh you don't see the surface plate in say your car or phone but if you follow the champ tools backwards it's there your phone was made by machines which got their final precision from straight edges which in turn got their precision from the surface plate it's like bricks in a building all bricks are relative to the first one that was laid so it is with tools in the shop to the surface plate there every machine shop and factory throughout the world and they are regularly inspected resurfaced when necessary and certified to attest to their accuracy and serve as the final authority and foundation for precision surfaces mine came from the Alameda Naval Air Base where was in the machine shop that rebuilt jet engines from at least the mid-60s until the base closed in 1997 it's old and beat up but it's good enough for me and I think the history is pretty cool so now we have a perfectly flat surface but what a surface plate can't do for you though is giving unit distance of measure something like the regular marks on a ruler this has to be an arbitrary amount and historically the differences between the next town or parish over have played trade and commerce from Malaya France at the time of the French Revolution was estimated to have over 250,000 units of weights and measure throughout the country and that was a problem in no way unique to France so with your surface plate you can make a straight edge to start a ruler and now you have to mark it at regular intervals what unit do you use where does that unit come from could you accurately recreate those marks if you lost your ruler since history was units of measurement have been taken from nature often the human body a cubit was elbow to fingertips the inch was the width of a thumb and the span was taken from the hand Edward the first of England declared that three barley corns dry and round make an inch don't laugh about using barley corns for measurement US and British shoe sizes are still measured in barley corn to this day the obvious problem is your barley corns might be a different size than mine or mine might even dry out and change over time though for a long time that was good enough but eventually a more accurate universally accepted measurement system was needed the dream has always been to find a natural measurement that was uniform everywhere that anyone could reproduce at high accuracy so in 1824 England created a standard yard based on a pendulum length beating seconds in London at sea level and a vacuum thus being a natural measurement it can be recreated if lost or destroyed and in 1834 was destroyed in a fire when Parliament burned problem was the calculations used to create it were found to be erroneous and by then it was well understood that gravity is not geographically uniform and that standard was abandoned thankfully copies of the previous 1760 yard were still available and from those a new standard was made to which all measurements were standardized all the way until the weights and measurements Act of 1963 or where I said about France having hundreds of thousands of measurements in the 1790s the French had been working to sort the whole mess out what would become the metric system they too wanted it based on a natural system that anybody could reproduce the measurement of one ten-millionth of the earth between the North Pole and the equator and they would call it the metre it wasn't just measurement they were trying to make decibel the 360 degree circle inherited from the ancient Babylonians became 400 degrees the metre in the 400 degree circle would make calculations far easier and synchronize astronomy and navigation 100 kilometres would be one degree of latitude on earth 40 million meters in circumference so getting the length of the meter right was incredibly important as so many other measures derived directly from it for example one milliliter of water is one cubic centimeter weighs one gram and requires one calorie of heat to raise its temperature one degree centigrade which is a 1% difference between freezing and boiling the amount of hydrogen winning the same amount is exactly one mole of atoms in it by comparison in the American system the answer to how much energy does it take to boil at room temperature gallon of water is go fly a kite [Music] [Applause] [Music] to get the measurement needed for the meter in the earliest 1790s the French Academy of Sciences charged two men to the top astronomers at their time but also very familiar with surveying to plot the Meridian distance from Dunkirk through Paris to Barcelona the remainder of the distance the equator in North Pole would be extrapolated originally the mission was supposed to take less than a year however after some delays when the expedition was finally underway the country was convulsing from the French Revolution and everything was a mess to say the least instead of a year or less it took six years to determine that single number and is truly an amazing story you know everything that possibly could go wrong did even with all their hard work a tiny error was introduced that we still live with today the story that expedition and methods is so amazing it deserves its own video and that'll come later with a measurement finally done in 1799 the French legislated the metre is the official standard the France had a rocky on-again off-again relationship with it until 1875 when an international convention made the standard across several countries official bars were sent to countries to serve as their reference the u. s. received what is called the number 27 national prototype meter bar made of platinum with a touch of eridium in annex shape to keep maximal dimensional stability speaking of which getting back to freedom units in 1866 the US Geographic survey stated that there after the u.

s. inch was equal to just a tiny fraction of a hair over 25. 4 millimeters starting in 1893 all the way until 1960 every calibrated device made in the u.

s. intermet wreck from the most sensitive scientific instruments to schoolchildren's rulers were all traceable back to that number 27 meter bar sitting in Washington DC it was at that moment over a hundred fifty years ago in 1866 the u. s.

inch was linked to the meter and every time in later years the meter was further refined so was the inch with it but in the late hundreds the English imperial yard was such that 1 inch equaled a fraction of a hair under twenty five point four millimeters even worse compared to the meter the English yard artifact was slowly shrinking [Music] so having your flat surface and now agreed-upon international standard is useless unless you can actually get it into the hands that who have manufacturing high-precision products and that's exactly the situation a Swede named Karl Edouard Johansson found himself in he was inspection chief at a Swedish factory making American and German guns unlicensed when they started making a new gun there was no way for him to quickly make new gages the tools to quickly check the size of machined items in this footage from a World War 1 UK munitions plant notice she's checking the dimension with gauges of a fixed size the obvious problem is they're gonna wear be difficult to adjust and not super precise what was needed was a system where the gauges could be adjusted but even more importantly checked and set correctly at regular intervals and that's what Johansson invented notice now the gauges are adjustable but even more profound and far-reaching was the system used to set and check them for that - Hanson invented a set of very precisely made metal blocks size such as they could be combined together to make many many thousands of dimensions quickly and accurately in doing so he made a universal measuring system that underpins the industrial world today he made his first gauge set in 1896 with the help of his wife selling machine to carefully lapped the very hard steel blocks his first sets were so expensive they cost more than his annual salary at the gun factory in 1914 a set cost about $21,000 in today's money and were accurate to three millionths of an inch making the block so they kept dimensional stability at that accuracy proved very difficult and Johansson had to experiment many different kinds of Steel but also cycles of freezing and heating letting them sit for many months before finally being lapped a final dimension the entire process takes about a year at the outbreak of World War one the u. s. War Department declared Johansson's blocks as the standard of measurement for all war materiel however the German submarine blockade of neutral Sweden caused near panic line ditional gauge block sets were not available the chief of the US Bureau standards was able to get you a Hansons u.

s. sales manager released from army duty and sent to Sweden he stayed there until he was able to get 128 sets made and successfully smuggled them past the German inspectors back to the US [Music] city of s kosuna Sweden is famous for steel and machine tools near its historic main square our factories with products requiring the finest craftsmanship here over 300 years ago Sweden's tool-making had its origin and in this ancient town world industry was revolutionized a half-century ago by incredibly accurate products of the Johanson factory at the fathers of son bacon molten metal is transmuted into the finest steel driving like giant serpents at the Johansson plant fully processed steel bars of all required dimensions move from vast storerooms to machines cutting them into proper lengths for milling [Music] here master machinists shape marks of Steel that made modern industrial science possible for they are the world standard engineering measure the unbelievably precise Johanson gauge blocks these operations may appear quite simple but the cutting and polishing procedures demand utmost skill the creation of perfect flat planes of steel is one of the greatest achievements of industrial science each gauge block must pass rigid spectroscopic tests and be completely perfect for it is the final authority and all highly accurate measurements this device developed by the company's founder detects an error of 125 millionths of an inch in these blocks which check accuracy of gauges making high-precision mass production possible now engineer Johansson demonstrates an amazing property of these blocks first bringing several together although non-magnetic they adhere he attaches top and bottom blocks to cables of the tensile strength tester which indicates their remarkable cohesion possibly the result of molecular attraction the blocks cannot be forced apart even with a tencel full of 120 kilos or 570 pounds per square inch only with such amazingly fine measuring units could our modern machine age come into being gates blocks in various combinations are exceedingly sensitive to temperature changes here a cylindrical gauge is being tested now the gauge is slightly warm with this result that may seem hardly more impressive than a box of children's flocks but with them we have built our complex industrial world endless combinations provide all needed dimensions gauges of all types everywhere are tested with these blocks produced in a little Swedish town where half a century ago modern industrial science was born in the economic depression that followed the war Johansson was about to go out of business so we contacted Henry Ford who promptly bought the company Ford and Joe Hansen were fast friends only Ford's son Etzel and Johansson were allowed into Ford's office without knocking in Ford's 1931 book moving forward there's a whole chapter on Johansson's blocks Ford rights before Johansson's blocks they pretty much didn't know where an inch was but now could calibrate and check their gauges often multiple times a shift and could consistently maintain three ten thousandth of an inch accuracy on critical parts this greatly increased production and profitability click on the link to read that chapter starting in nineteen twenty three Johansson and Ford co-brand engage blocks were sold in the heavy bakelite box here's a period brochure detailing the different options and grades when new the a grade set cost about five and a half thousand dollars in today's money the 81 block set is said to be able to make over a hundred thousand combinations but I can't find a precise number mentioned anywhere and that really annoys me but more on that later production reached its peak during World War two when Ford was shipping 200 sets a week Ford had ensured the US would never be short on gauge blocks again and companies all over the United States involved in the war effort were buying them as fast as he could make them and you know what the blocks have an amazing property if you carefully slide or ring them together they'll actually stick together on the very precision lap sides is it because of intermolecular forces cold welding where the electrons are crossing between the blocks or maybe because the atmosphere is crushing down on them and all the air is squeezed out or I don't know the debate rages on and no one seems to know for sure but it's probably a combination the problem of different inch standards became a real issue in World War two when the inch based countries discovered their parts were not truly interchangeable as there was at least three different standards for the inch following the war in 1951 the Canadian sensibly legislated that one inch was equal to twenty five point four millimeters exactly and shortly after the US and UK followed suit but Johansen had beat them all to it he had split the difference between the US and English standards and set one inch to exactly twenty five point four millimeters long ago in 1923 when he started working with Ford he had effectively already shifted over entire industries which were using his blocks as their definitive basis of measurement what was then called the industrial inch I'm glad that sink in for a moment the u. s.