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
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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