The Science Of Small Distances

in 2010 a milestone of the post-industrial world occurred the total vehicles on earth superseded the 1 billion mark even more astounding in 2018 it was estimated that two and a half to three building internal combustion engines exist on earth the average age of the 250 million vehicles in the United States is 11 a half years depending on the vehicle in the driving conditions that 11 and a half year old engine could have seen anywhere from 5 million to 1 billion revolutions in its life but how can a machine rotate so reliably for years without failure most of us are intuitively familiar with the roller element bearing a mechanical device which carries a rotating load on rolling elements such as ball bearings or rollers we see them daily on virtually every single wheel we use as well as various other not so common places but car engines do not rotate on ball bearings or rollers their impressive reliability comes from a remarkably simple bearing device the modern Babbitt bearing in a modern engines rotating components a ground and polished metal part is rotated in a hole lined with a replaceable cap coated with a softer contact metal called a Babbitt both metals have a low coefficient of friction between them but the incredible efficiency of this design comes from between the metals machined into the dimensions of the two rotating parts is an incredibly tiny gap designed to trap a thin film of oil this thin film of trapped oil takes the entire load of the engines power and is responsible for its longevity and reliability this miniscule gap that traps oil has given us the modern industrialized world this ability to create mass produced parts with tight tolerances with efficiency and interchangeability for better or worse have changed our society in the face of this planet let's explore how small these distances actually are and what they look like this is the science of small distances [Music] [Applause] [Music] in order to make things with any precision we need dimensional units in our modern world we look to the meter and the modern derivative of the foot as the basis for all distance measurement it took over two millennia to get here the first forms of standardized length measurements were the cubit and the ancient foot archeologists believe that the Egyptians ancient Indians and Mesopotamians preferred the cubit while the Romans and the Greeks preferred the foot and what were these units based on the tools we carry around with us our arms and legs a cubit was defined as the length of the forearm while the foot was defined by the human foot the obvious problem with this was that every one is different and these sizes could vary up to 30% ancient engineering was coarse and loose by modern standards so these variances were easily tolerated they operated with an archaic version of what we now call low tolerances a modern tolerance is an allowable amount of variation of specified dimensions of a machine or part in modern tolerances the allowed range of the used unit is specified instead of the unit itself varying for example a tolerance of plus or minus one inch on a 12-inch specification allows for the actual measure dimension to be anywhere between 11 inches and 13 inches as history progressed the definition of distance shifted between various natural objects finally during the age of alignment we saw the first definition of distance through scientifically derived means the metre was invented though it was initially defined by pendulum periods in modern times the metre has now become the definitive standard of length by drawing its definition from a universal constant the modern metre is defined as the length of the path travelled by light in a vacuum in one / 299,792,458 seconds the foot has also evolved into a modern unit purely derived from the metre one foot has become 0.3048 metres exactly now that we understand the basis for units of length let's work our way down to the smallest practical mechanical distances it should be noted that this video was produced in the United States so we will use the inch as the primary unit but metric equivalents will be shown we're all familiar with one of these most tape measures divided down to 1/16 of an inch or about one point six millimeters with the exception of intricate artisan work in some highly specialized processes this seems to be the practical limit for hands-only manufacturing and construction our ability for our hands and eyes to work in tolerances lower than this without the aid of positioning tools start becoming difficult this is a micrometer it's a machinist tool used to measure lengths with high precision this specific one can be set up to an inch in increments of one and ten thousandths of an inch or 0.0025 four millimeters this will be our tape measure as we delve into smaller distances this is one 64th of an inch at one sixty-fourth of an inch or 0.3 9 6 8 75 millimeters we're at the practical limit of what our eyes can distinguish with our tools at this point fractional expression of dimensions become decimal based machinist may also refer to these distances in thousands foul or mils a unit equivalent to one one thousandth of an inch a 1:1 64th of an inch distance would be expressed as 0.15 six to five inches or 15.625 thousandths of an inch at this length hand guided work is still possible with positional tool links such as jigs and guides or through slow subtractive processes such as sanding or grinding the one 1/64 of an inch tolerance is generally the practical limit of working with wood dimensional stability is our first practical consideration of material properties when we work with small distances in the case of wood the expansion and contraction of the material based on the environment makes holding a smaller tolerance difficult if not impossible we're now entering the realm of thickness this envelope is stamped from a thick stock paper a hundredth of an inch or 0.25 four millimeters thick most thin sheets of material can be found at these sizes the fine wires that make up ethanol cables and audio cables are all here at this range of small distances our eyes have a hard time intuitively deducing sighs these are the ranges more easily recognized by touch machine tools such as mills lathes and drill presses are a requirement in order to work with these distances working at the hundredth of an inch size ranges and tolerances the concept of engineering fit begins to emerge let's say a hypothetical part pierre calls for a one inch cylinder to be fitted into a one inch hole on paper this makes sense but in real life there are other factors of play to begin with the machine making the parts can never truly be perfect it has a tolerance of its accuracy in our example let's assign the machine making our parts a realistic tolerance of plus or minus one one thousandth of an inch what this means is that no matter how hard we try it's possible the produced part will be a one point zero zero one inch cylinder and a one inch hole or a one inch cylinder and a zero point zero zero nine inch hole or any other size mismatch within that tolerance but because of the tolerance of the machine making parts that fit becomes a lucky well let's say we're able to get a perfect 1 inch cylinder and a one inch hole we now encounter a new problem assembly on paper that shouldn't be a problem just slide the part in but if you compare real-life to paper it quickly becomes obvious that to fit these parts together they have to approach each other in a perfectly aligned manner it would be virtually impossible to do this in real life with just our hands making use of positional tooling may help but at the increase of cost complexity and time of assembly engineers solved both of these problems by introducing the concept of a fit clearance if we take into account the purpose of the parts fitment a purposeful gap between components can be designed in to both accommodate for manufacturing and the accuracies as well as assembly fitting parts together can be categorized into three types Clarins fit location fit and interference fit in a clearance fit a significant gap is created between parts this may be done to aid in manufacturing and assembly this is often found in parts that are inexpensive non-critical designed for tactile use or why're simple motion such as with simple slides or rollers many of the components we interact with daily such as buttons switches knobs and other tactile controls operate with Clarence Fitz in the one hundredth of an inch range in a location fit a very tiny gap is created mostly to accommodate for manufacturing inaccuracies it's usually used for precision part fitments and generally requires tooling or force to aid in alignment and assembly and interference fit is a unique circumstance in which a smaller part is stretched with heat or tooling in order to force a larger part into it this is generally done to pin parts together with friction and can be very effective in areas where other means of component fastening aren't available in general engineers choose fit and clearance specifications by balancing the requirements of part function manufacturing costs material properties assembly cost and serviceability often that feel of quality or cheapness of a product we use can be directly attributed to the choices made in this juggling act this is a thousandth of an inch or 0.25 four millimeters the next step on our journey we are now in the realm of machine only processes how small is a thousandth of an inch this thin razor blade is four times thicker than a thousand this is the tolerance in which simple machines exist firearms quality hand tools lower in machine tools and less critical automotive parts can all be found here coincidentally this is also the rough size of the popular standard of small sizes the thickness of a human here as we approach the one thousandth of an inch mark we enter the realm of precision fit at around five one thousandths of an inch assembly by human hands only become difficult below this tolerance a combination of extreme care tooling and force may be required we can't directly see or feel changes at distances that small so measurement tools are a must at these tolerances the effects of temperature on materials require consideration for example aluminum expands or contracts one point three thousandths of an inch for every hundred degrees Fahrenheit it changes an aluminum part machined on a cold day may come out of specifications on a hot day and even more extreme but common example of this is a car engine modern engines of hoes mostly if aluminum and can have temperature swings from bitter sub-zero winter temperatures all the way to its 200 degree operating temperature engineers take this into account when choosing clearances as well as designing around expansion in general let's take a look at thermal expansion in practice this is an engine piston it channels the explosive force of an air fuel mixture into rotational energy connecting it to the rest of the engine is the steel cylinder called a RISC pin at room temperature fitting the wrist pin into the piston is almost impossible due to an extremely tight clearance but if we warm up the aluminum piston to 150 degrees Fahrenheit the holes on the piston expand to the point where the wrist pin can easily insert it by hand moving in order of magnitude down we enter the realm of one ten thousandth of an inch or 0.0025 four millimeters this is the practical limit of general machining at these tolerances not only does part temperature have to be taken into account but even the operating temperature if the equipment used to create the parts need to be considered often grinding a surface slowly is needed to hit tolerances this low but what does one ten thousandth of an inch look like well we're in the realm of surface textures now this is a one ten thousandth of an inch a size roughly similar to a tiny silt particle to put this into perspective 1200 grit sandpaper a grit used in polishing that has a surface roughness similar to leather protrudes a little more than one ten thousandth of an inch the red blood cells that run through our veins and arteries are three ten thousandths of an inch just the act of holding a piece of aluminum in your hand can expand it with body heat more than one ten thousandth of an inch astoundingly one ten thousandth of an inch is only about fifty thousand atoms of distance components holding tolerances down to one ten thousandth of an inch are typically reserved for precision machinery machine tools tooling and jigs instrumentation and are prevalent in engine components in many machines including engines clearance gaps in the one ten thousandth of an inch tolerance range are used exclusively for maintaining consistent oil films for use as liquid bearings the tolerance of this gap is absolutely critical to creating proper oil film strength from the oils viscosity these minuscule gaps allow years of engine life with minimal actual metal metal contact within an engine directly machining lengths even small that 110 thousands of an inch are possible but a reserved for highly specialized machinery usually designed for instrumentation or science working at those scales we begin transitioning into processes such as photolithography nanotechnology and other submicron processes that are beyond the scope of this video with current semiconductor manufacturing technology expected to push distances of 5 nanometers by 2020 at this level of small we are literally dealing with distances 50 atoms why [Music] [Music]

Channel: New Mind

Views: 285,012

Rating: 4.7938204 out of 5

Keywords: new mind, measurement of small length, micrometer, small measurements, machining metal, precision fixturing, width of a human hair, how do car engines work, oil clearance, oil clearance on main bearings, milling machine, tiny length, manufacturing, manufacturing engineering, how parts of a car work, how car parts are made, metal expanding in heat, manufacturing videos, metal working, cnc precision fixturing

Id: cQFTBfkqE0U

Length: 14min 16sec (856 seconds)

Published: Sat Nov 17 2018

Reddit Comments

[u/starshame]

I'm a Machinist and my favorite part is using all the gadgets we have to measure these tight tolerances. Indicators, calipers, micrometers, comparator and profilometers. A profilometer measures the SMOOTHNESS of an object. Crazy.

It's a great job with great satisfaction plus it's a skill I can take anywhere in this world and is high in demand. Love this documentary and thanks for posting this.

[u/CustomSawdust]

There is a wonderful book called « The Perfectionists » that covers the concept of measurement throughout modern history.

The invention of the caliper was fascinating.

[u/StraightOuttaMaine]

I can't believe they shamelessly stole that title from my sex tape

[u/bodhiseppuku]

I feel a little smarter from watching this...

[u/SidKafizz]

I work in this world. This guy makes it sound interesting.

[u/cavitus]

“Eh-ther-net”? (6:25) Have I been pronouncing it wrong all these years?

[u/CupiD101]

Use of metric system is very crucial. I couldn't grasp entire thing because my brain was busy converting imperial to metric in real time. I understand metric better.

[u/Someplatkid]

omg my dad is a cmm operator/programmer for aerospace parts and after years of being fascinated with how remarkable the tolerances he would check for and work with, its cool to see this get some attention on reddit!

[u/are_y0u_kidding]

I'm watching this video and each time the guy uses imperial instead of metric (and he uses it a lot) I'm getting angrier and angrier. Especially when he shows that americans started using base 10 measurements... with fucking inches. How backwards is that?