The HIDDEN Screws of PRECISION

you don't normally think of simple everyday  items like say a pretzel being the result   of screws i mean sure the machines that  make pretzels have screws in them used   as fasteners but there's a much bigger and  important story here about screws were used in   measurement to make those machines  and the pretzels ultimately possible   screws have been used in measurement probably  much longer than you can imagine and the story of   how and what they unlocked with their simple  helical magic is absolutely incredible in a previous video i already talked about  hero of alexandria's incredible dioptra   which is recognized as using screws in a very  clever surveying device amazingly way back in   the first century a.d also in that same video i  mentioned drawings of canons from the 1480s which   used screws to carefully regulate their firing  angle if you haven't watched that video check it   out in the 17th century in england an important  leap using screws for precision measurement was   yet again not where you'd expect it as in  measuring the length of things but in astronomy in   one of the world's happy accidents around 1639 a  spider crawled into william gascoigne's telescope   the web that it spun in there was in just the  right place between the elements such that the   spider web itself was in perfect focus as well  as the very distant objects he was looking at   this meant for the first time ever an astronomer  had a truly beautiful reference right inside   his telescope gascoigne is credited with first  creating something you may have used yourself   the telescopic site these were first used in  telescopes but had been adapted way beyond those   then gascoigne took it a step further and  put a screw driven measuring device inside   his telescope by turning a handle attached to a  screw he could move two vertical arms with very   thin wires back and forth so he could measure the  width of objects he saw in the sky by also knowing   the focal length to the object he could calculate  the size of objects with unprecedented accuracy   it was also useful for calculating angular  distances at resolutions just not possible before   this was a huge leap forward in our understanding  of astronomical objects and gascoigne well not   a household name is recognized as having  made significant advancements in astronomy   thanks to help from a screw and a spider in his  screw-driven device gascoigne ended up using thin   wires not spiderweb though later spiders  would be farmed for exactly this purpose   and used widely in telescopic sites because  spiderweb is thin strong and resists change in   temperature and humidity well which is especially  useful in long overnight astronomy viewings and while it's easy to imagine how screws are  important when directly used in measurement   like gascoin's telescope they are also indirectly  important as well in the latter part of the 18th   century jesse ramsen was the preeminent instrument  maker in britain the pieces he made are surely   some of the best of the period to solve a vexing  problem an award was offered how to accurately   mark out the dials on instruments in particular  the curved ones like on sextants while there have   been various techniques used over the years they  tended to suffer from a few different problems   notably being slow error prone and expensive  i mean how good is your instrument if the   dial you're reading from isn't accurate what was  needed was some kind of machine that could solve   all of these problems and that's what ramsden  created building upon some previous work and   taking it much further rams then invented an  innovative dividing engine able to accurately and   quickly divide a circle such that a sliding scribe  could make a very accurate line on the scales of   instruments it worked very simply a huge 2160  tooth worm wheel ran around the entire outside   a foot lever could be stepped on to rotate a  worm screw six rotations exactly which would be   one degree then a scribe on a sliding sled could  be used to mark the work piece as it was clamped   in the engine this drove the price of marking  out a sextant down by 50 times and it made it   more accurate as well rams didn't want a prize  for his engine and as a condition of doing so   had to publish the plans for how to make it in  addition to the very innovative screw-cutting   lathes he invented to make it accurate and  i'm happy i get to share those plans with you   and so this design was copied and even  improved upon which means that suddenly   there were many more instruments made  that had much better scales on them   so in this case you don't see the precise  measuring screw in the finished project   it's not there at all except as a core component  of the machine that made your sextant more   accurate and much cheaper and this led to improved  instruments of all kinds which helped tremendously   with navigation and other kinds of scientific  instruments and think how important that is   whenever you can measure better you can do just  about anything better and if you're thinking   what's ramsden's dividing engine done for me  lately the dividing head that i have in my   machine shop that i use to make the timing clutch  for the marble machine x has a worm wheel inside   of it that uses the exact principle just in a more  compact form so ramsen's basic design lives on then allegedly in about 1776 finally the first  end measurement device that i know of using   screws was created i say allegedly because  there is some doubt and research continues   but more on that another time supposedly made by  one of the giants of the industrial revolution   james watt the man that greatly increased the  efficiency of the steam engine and then even   more importantly set up a business with  a partner to make engines for anyone who   could pay if there's any one person when you  think industrial revolution it's usually what   a couple years ago i was privileged enough to  travel to london to examine the micrometer first   hand and take it apart to help answer a lot of the  questions about it i have a whole video about that   amazing experience that you should watch for sure  and at its center as the main element is a screw   driven by a crank on the back cleverly as the  screw is turned it slowly moves a sliding jaw   forward in small amounts and a high resolution  dial on the back allows for precise measurements   to be read the screw serves a second purpose  too which is to also turn a worm wheel which   is a lower resolution display one line  per complete turn of the wheel on the back   this way between the two dials you should be  able to read both the number of turns and a   high resolution display of a partial turn and this  lets you calculate the measurement really easily   keep this in mind as we're going to see a  refinement on this idea a little later i love   this idea so much i made a 3d printable version of  it and you know what it actually works really well   stick around to the end to find out more and how  you can get the files this micrometer isn't known   to have any descendants it's like it was made in  a vacuum with no obvious device that inspired it   and nothing known to have come after it if watt  ever used it in anything there's no record of it   did this micrometer play a vital role in the  precision of the creation or manufacture of   watts famous steam engines or play none  at all we may never know but if it did   did this screw this very screw contribute to  the success of watts engines that powered huge   factories that generated vast fortunes and was  a key trigger for our modern world it blows my   mind even considering it so while we don't know if  watt's supposed micrometer played any role in the   industrial revolution we do know that without  precision his engines simply weren't possible but we do know of one man and his inventions who  for sure brought precision to the world and in   a very meaningful way and precision screws are  a big part of that story enter a certain henry   maudsley describing the full breadth of mosley's  talents inventions and impact would take us   all day so for now i have to just stick  to one small part of what he is known for   measurement an incredible precision freak he  had a particular interest in screws and worked   tremendously hard to make them as precise as  possible famously in the display window of his   shop he displayed a single item a five foot long  brass lead screw that was incredibly precise for   the time in a statement no one else could match  no doubt there were other precision machines and   screws made by others before modsley but as far  as i can tell they were pretty isolated and in   low numbers and for singular specialized tasks  like clock making while precision may indeed be   the child of many parents mothsley took it all  to a whole other level and he started building   true precision machines for industry at scale  with such an interest in precision and having   harnessed the power of precise screws it's  no accident around 1805 he invented his own   bench micrometer with a very precise screw at  its core reportedly able to measure reliably   down to ten thousands of an inch nicknamed after  the highest appointed officer in great britain   the lord chancellor monslee's bench micrometer  was the ultimate authority and used to settle   any dispute in his shop and at the science  museum london they have a bench micrometer   made by mogsley which is incomplete but thought  to be similar to his famous lord chancellor   and we can't talk about modsly and screws without  also mentioning his famous screw-cutting lathe   one of the first screw cutting lathes by using  one master screw he could cut new screws that   could go into other precision machines  so the precision could easily be copied   cleverly different gears could be swapped between  the master screw and the spindle so you could cut   screws of different pitches as well this lathe  shows up in many of the history books about   machine tools often incorrectly described as the  first screw cutting lathe but we'll talk about   the problems with that in screw cutting in general  another time but you don't have to look at it just   in the history books amazingly it's in the london  science museum in the back of a display case   sitting there as if it wasn't one of the most  important pieces of machine tooling ever made modsly is famous not only for the work that he  himself did but also for incredibly talented   engineers that he trained and then themselves went  on to do amazing things not only did modsly make   machines that duplicated precision but he himself  trained many men that would go on to do it as well   sometimes at even greater scale ever increasing  the amount of precision in the world one of them   joseph whitworth is again someone we could  do several videos on it we will surely talk   about him another time in fact a couple of years  ago with destin from smarter every day i did a   collab video with him on whitworth to talk about  one of the accomplishments of what whitworth was   able to do supposedly measured to a millionth  of an inch in the 1840s check that video out   in an era where measuring to a sixteenth  of an inch was considered pretty precise   this was light years ahead he made a couple  different versions of bench micrometers but   the most famous was a very clever device to take  advantage of two different kinds of screws the   worm wheel and the conventional screw watch  the video i made with destin to find out more   whitworth claimed his millions machine could  easily tell the difference in a work piece just   by momentarily touching it with a finger and that  was really the problem temperature could it really   accurately measure to a millionth of an inch  modern testing says no and you can understand what   whitworth's problem was he had no way to control  for temperature and without a thermometer at least   as accurate as your measuring device you have no  way of knowing how accurate those incredibly small   measurements are speaking of screws whitworth's  influence over screws was so strong he was able   to standardize them across all of britain  in 1841 in a world where just about every   shop had their own standards for making screws  and few were truly interchangeable whitworth's   incredible manufacturing influence was able to  unite the country behind his thread standards   and they would stay the standard for decades  even while there were many other competing thread   standards over the years they would survive  in some specialized areas even into the 1960s while whitworth's effort and his screw  standardization was a success his millionths   machine didn't fare well at all but someone  across the channel around that same time was   working on something to put pretty high resolution  measurement into everyone's hands or should i say   palms as in jean lauren palmer of paris or palmer  for us english speakers in 1848 the familiar hand   micrometer was patented by frenchman palmer the  micrometer had finally left the benchtop and   was now in your hand this simple relatively  inexpensive device first designed by palmer   meant anyone could measure accurately to small  amounts though obviously in millimeters at first   one story i've read as the inspiration was to be  able to measure a stack of thin sheets of metal   and know the count really easily much faster  than doing it by hand these devices are now so   ubiquitous who knows maybe made in their millions  by now and are in machine shops everywhere and my   shop is no exception used every time i'm in there  making chips even though this design is over 170   years old the operation is as simple as it is  clever and is entirely based around a precision   screw i don't have time to go into how to use it  or read a micrometer right now but it boils down   to this once the screw has been turned to the  dimension you want to measure on the work piece   you can read the full turns of the spindle on the  sleeve and then add the amount the spindle has   partially turned with a tiny bit of mental math  you can easily add the two together and get a   really high resolution measurement really really  quickly if you want to know more i'll link to a   video on how to read one by using the screw in two  different ways at once first by how far it moves   along the axis and then by how much of a circle it  turns if you remember back to the watt micrometer   this is the same idea measuring full turns and  partial turns but in a much more compact and   clever way and this is the gift that palmer gave  us a simple device in our pockets that allows   us to quickly easily and reliably peer into tiny  bits of measurement as important and revolutionary   as these palmer micrometers are the original  ones are exceptionally rare in fact only four   are known to exist one at the smithsonian and  three others in private collections and here's   me holding one of those four what a privilege a  couple years back i had the chance to examine one   and that was a real treat the original ones  were likely made in relatively low numbers   so how did they get to be made in their  millions and start showing up everywhere   at the paris exposition of 1867 palmer's invention  was seen by the american industrialists brown and   sharp who promptly bought the patent and a year  later released their first sheet metal gauge based   on the same design and yeah i got to examine one  of those as well from the same private collection   shout out to tom at ox toolko for introducing me  to someone with those historically valuable pieces   if you don't know tom check out his brilliant  machining channel he will surely forget more   than i will ever know about machining and i've  spent countless hours learning a ton from him and   you will too and so micrometers like these became  incredibly widespread and often the first choice   of machinists everywhere in the old analog form  or now sometimes the fancy digital ones and over   time to get better and better measurements the  screws had to get more and more precise the most   precise ones i know of were able to make repeated  and accurate measurements down to 20 millionths of   an inch or for my metric friends that's about  half a micron which is absolutely incredible   that's about the size of an average particle of  smoke from a purely mechanical screw but then   in another revolutionary step they were  paired with rotary encoders in linear scales   suddenly the precision didn't just have to come  from the screw but from the electronics the screw   was driving no longer was it necessary to strive  for near perfect mechanical accuracy with the   screw which was very expensive and time consuming  now the magic could come from the electronics and   look what it did in both the cheap version and  the highly respected brand which is even traceable   back to national standards so you know they're not  messing around for insanely small amounts of money   and under the right temperature conditions of  course you can now get micrometers which can   measure down to 1 micron or about 40 millionths of  an inch and that absolutely blows my mind and of   course electronics just didn't find their way into  micrometers but into all sorts of ways to measure   which we're going to talk about in an upcoming  video but in the centuries before we had   help from electronics measuring with screws was  an incredibly important and influential part of   everything industrial i want you to pause for  a moment and think about all the screws to use   in measurement that we touched on in this video  which is only really part of the story like those   pretzels we saw at the beginning you don't see the  screws of precision in the pretzels just like you   don't see them in all the things i just mentioned  but they're surely there bringing precision to all   kinds of things you would normally never think  about they're there just sometimes invisible and   in the background so what do you think maybe  i changed your views on how screws are used   let me know what you think in the comments the  next stop on your journey is to hit the subscribe   thumbs up and bell button if you like this  it's great to get that kind of feedback and   it really helps keep me going if you didn't  like it give it the old double thumbs down   i can't stand advertisement interruptions are  putting other people's words in my mouth so i   don't do mid-roll ads or take money from sponsors  instead i'm supported by the lovely people over   at my patreon who are helping bring more content  like this would you consider joining us with every   video i publish i also have a patreon companion  video that goes a bit further and has more detail   on the things that i had to cut or things that  i found really cool but just didn't quite fit   and even if i don't publish a video on my  channel in a month i still publish a patreon   video with updates and show behind the scenes  and more how i'm just putting all this together   at most patron levels with this video people will  get the 3d printable watt micrometer i showed the   video and also blender files with some of the  animations i did as well it's cool stuff and   there for you to play around with as always  thanks for watching i'll see you next time

Channel: Machine Thinking

Views: 32,545

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Id: isVQMHmzHNo

Length: 19min 53sec (1193 seconds)

Published: Sun Oct 03 2021