Why Are There so Many Types of Screws?!


This episode of Real Engineering is brought
to you by CuriosityStream, watch over 2,400 documentaries for free for 31 days at curiositystream.com/realengineering. We have all been there, visiting your local
hardware store like a kid in a candy shop. You arrive at the pick and mix screw section
and you are just overcome with excitement. How could you possibly pick just one type
of screw. Woooooow look at all these screws. Amaaaazing. You have sultry slotted screws, rowdy robertsons,
playful phillips, oh and look at this one a hex screw. You naughty polygon. In your excitement you pick the largest bag
you can find and fulfill your childhood dreams to buy 2 of every kind of screw. Mother can’t stop you now. You arrive home with the glee of a spring
lamb. Oh the assembly that awaits. What joy. Then, to your horror, you open your toolbox
to discover you only have a fat flat head screwdriver that doesn’t even fit the flat
head screws your bought. Your life is a lie. You spent your life studying theory and never
learned practical application. You are no real engineer. Shhh it’s all going to be okay, dry those
existential crisis tears. We are going to learn what all these screws
are for, and how they came into existence. The humble screw is a technology so old that
we cannot easily determine who first invented it, but the answer as best we can tell is
Archimedes who used the helical screws ability to turn rotational motion into linear force
to pump water, though he probably stole the idea from the Egyptians. You can imagine how a screw works fairly simply
by viewing the cross-section at the bottom. This part is essentially a wedge, and when
you force a wedge under something it will lift it up. This wedge shape spirals all the way up the
screw, allowing that force to be applied along the full length of the screw. This idea was used for centuries to pump water,
dig holes, and for pressing the shit out of grapes to make some wine. Then some unknown person had a bright idea. If we can apply an opposing force, we could
create compression to hold two parts together, and so someone slapped a head on one of these
screws that would press down while the threads pulled upwards. Creating an incredibly useful fastener. This idea didn’t really take off until a
method of mass manufacturing them came about in 1797, when Henry Maudsley invented this
metal cutting lathe that allowed for the consistent and precise cutting of screw threads. He even set up a standard screw thread geometry
for his machine shop , and cut all his nuts and bolts to fit those threads, and thus the
chaos started. Several decades of differing standards resulted
in headaches far worse that your annoyance at new phone not fitting your old charging
dock. Perhaps the most notable incompatibility occured
during the great boston fire of 1872 when fire departments from neighbouring regions
arrived to help, only to discoverer their fire hoses didn’t fit Boston’s fire hydrants. [Maybe show XKCD comic] Most of the world has now accepted ISO metric
threads as a standard, although one country is still holding onto the inch as the standard
unit of measurement. A measurement that was legally defined as
the length of “three grains of barley, dry and round, placed end to end, lengthwise”
for 8 centuries until it was redefined as 25.4 millimetres. Because, as we all know, the best in class
is always defined by the second best, but I digress. We can now generally trust that a nut and
bolt with the same diameters will fit, even when mixing freedom units and metric, but
what’s the story with all these different screw heads. Why can’t we just agree on one shape so
we don’t need a toolbox full of screw drivers? The simple slotted screw head was likely the
first type used as it’s easy and cheap to manufacture with a cutting tool, but is a
pretty terrible design for anything other than manual screw driving into wood. Screwdrivers can slip out of sides and you
can turn the screw off its centre axis, which causes it drive into the material at an angle. This was not acceptable for mass production
methods, which as we explored previously, needed a foolproof production method. So Peter Lymburner Robertson designed a manufacturing
process for this square bit screw-head. Which was designed to be easily and quickly
driven home, without danger of the screwdriver slipping out and damaging either the screw
of the workpiece. 700 of these bad boys were used in the Model
T, and it saved Henry Ford about 2 hours of manufacturing time on each and every vehicle. Henry Ford was so happy with the design that
he wanted to licence it and manufacture them himself to ensure he had a reliable and steady
supply of the fastener, but Robertson wasn’t about that money making life and said no. He continued doing this with other manufacturers
for some bizarre reason and now the design is mostly just used in Canada, and so in stepped
Henry F Phillips with his infuriating screw design. He licensed out the design to Henry Ford and
many other people. This conical cross design allowed for a single
screw driver to fit many sizes of screws, was self-centering, and was designed to cause
the screwdriver to slip out of the slot at a certain torque and thus prevent workers
from over tightening it and damage the screwdriver or workpiece. It also prevents you from getting the blasted
thing out of a workpiece with even the slight bit of rust. By 1939 this design was licenced to nearly
every automotive, airplane and rail manufacturer in the US, just in time for the boom in manufacturing
created by World War 2 [1] With the lend lease act, many American designs were sold to their
Allies, and thus the screw design spread even further. Now that most screwdrivers can automatically
limit torque the phillips design is pretty much just a pain in the ass, so other designs
have come to the fore in more recent years. Specifically designed to stop that slipping
called cam-out, like hex screws and torx screws. Let’s compare these two types of screw to
see how their design came into existence. These two screws have the same diameter tool. Both have six points of contact between the
screw and tool. However we can see when we rotate our hex
tool it contacts the screw at a greater radius. Allowing it to applying more torque with the
same force, but the plane of contact is not perpendicular to the circle and that means
some of the force from the rotation of the screwdriver is being applied outwards radially
to the screw. This can damage both tools. With the torx screwhead the angle of contact
is near perpendicular, meaning it can applied more torque without fear of damaging the screw. But ironically, even though this is a great
screwhead design. It was designed to not be used by the general
populace. It was used in Apple’s first personal computer
[2] to make it harder for the average guy with a phillips head screwdriver from opening
up the machine. But thanks to it’s design, Torx screws started
proliferating, and more and more people had the correct tool to loosen it. So someone decided to place a pin in the middle
to make it even harder. Bringing us to an age where our right to repair
is questioned and many random screw designs have appeared to make it harder for us to
take apart our gadgets . Why? Because screw you that’s why. If all these nuts are driving you crazy, you
might just be a squirrel and being a worldly squirrel you probably learn about all the
other types of squirrels around the world. There’s ones with wings, ones with cute
little ears and tails. Look at this ginger one, class. If you want to learn more about them. I highly recommend watching this documentary
titled “Going Nuts” on curiositystream. It’s a beautifully shot documentary that
I really enjoyed. For a slightly more on-brand recommendation,
they also have an exclusive, original documentary series premiering on the 13th of June about
the new race to the moon called ‘Return to the Moon’. You can watch it for free, by signing up to
curiositystream using the code realengineering, or using the link the description. This will give you a month of completely free
access to over 2,400 documentaries and nonfiction titles from some of the world’s best filmmakers. After that first free month you can continue
your access for just two dollars ninety nine a month. As usual thanks for watching and thank you
to all my Patreon supporters. If you would like to see more from me, the
links to my instagram, twitter, discord server and subreddit are below.

100 Comments

  1. Shlomo Spitzer said:

    most screw drivers today can limit torque? never used one in my life

    July 19, 2019
    Reply
  2. swng said:

    wat

    July 20, 2019
    Reply
  3. BreakCoreGivesMeWo0od said:

    but why do you have an electric oil radiator when you seem to have central heating?

    July 20, 2019
    Reply
  4. Slim Tony said:

    The torque limiter on my screwdriver is my weak arm :c

    July 20, 2019
    Reply
  5. Kart G said:

    I hope you're not losing your mind

    July 21, 2019
    Reply
  6. B B64 said:

    I thought this was about the Kama Sutra.

    July 21, 2019
    Reply
  7. The Captain said:

    Class

    July 21, 2019
    Reply
  8. SuperMegaJew said:

    The intro was actually hilarious

    July 21, 2019
    Reply
  9. Che knauss said:

    Best transition ever XD!!!!!!!!!!!

    July 22, 2019
    Reply
  10. Numb Nutz said:

    Robertson. Genius inventor. Idiot business man. Shame the world doesn't have the Robertson screw. For wood work they are king here in Canada.

    July 22, 2019
    Reply
  11. Zack Hanna said:

    Me, managing the hardware department at a hardware store:

    July 22, 2019
    Reply
  12. d0st said:

    Thank you for random laughs. This is Educative and fun.

    July 23, 2019
    Reply
  13. The El Diablo said:

    "Perts"

    July 23, 2019
    Reply
  14. Akinie Garraway said:

    "Freedom units" cracked me up lol

    July 23, 2019
    Reply
  15. שקד בר אוריון said:

    Screw you!

    July 23, 2019
    Reply
  16. Warbear William said:

    Now that’s screwed up.

    July 23, 2019
    Reply
  17. Devin Heida said:

    As a Canadian, I can tell you Robertson screws are king and the world is missing out on use beauty.

    July 24, 2019
    Reply
  18. Daniel Black said:

    What do squirrels have to do with it? I think a better Segway would be something about learning about different types of screws. Was that arbitrarily chosen?

    July 24, 2019
    Reply
  19. Herman Böök said:

    All you need is Torx.

    July 24, 2019
    Reply
  20. Amateur Asian said:

    I have never seen someone so pissed over a fucking screw

    July 24, 2019
    Reply
  21. helmsplitter0233 said:

    Screw your metric LOL

    July 24, 2019
    Reply
  22. The Dolphin said:

    You didn't mention the Pozidrive Screw Head — that bastard cousin of the Phillips head. Why oh why did we need both to constantly get them mixed up? I swear, if ever I meet the inventor of Pozidrive I will kill him.

    July 25, 2019
    Reply
  23. Anthony Tuttle said:

    My favorite video yet. Well done!

    July 26, 2019
    Reply
  24. gluino said:

    This video isn't as good as most of his other work.
    Not much info that most people don't already know.
    Feels incomplete.

    July 27, 2019
    Reply
  25. sparkythebuilder said:

    Impact drivers. Phillips screws best friend.

    July 27, 2019
    Reply
  26. marouane jamal said:

    real engeneering lost his shit

    July 27, 2019
    Reply
  27. Kevin Bellingham said:

    great video! And didn't go on and on, like the endless screw choices, the torx might be a better design in theory, but in practice… blows chunks. May as well use a slice of wonder bread to turn that screw

    July 27, 2019
    Reply
  28. G G said:

    1 minute into talking about squirrels I realized he wasn't talking about screws anymore lol

    July 28, 2019
    Reply
  29. Vilém Beránek said:

    Why are there so many types of sctues?
    CZ someone screwed up 😅

    July 28, 2019
    Reply
  30. Miuzik 8OP said:

    Well so much for watching your videos with my children to expose them to the world of engineering. I'm not sure why you, a person clearly of a higher education, can't refrain from multiple instances of profanity, or slamming the U.S.
    Grow up…

    July 28, 2019
    Reply
  31. shoshenkis said:

    Also the more models, the more tools and the more you spend.

    July 28, 2019
    Reply
  32. blueckaym said:

    Hmm, one of the most important aspects of screws (and esp. bolts) is their loosening under vibrations, and the ways to deal with it … not that this video mentions it at all :/

    July 29, 2019
    Reply
  33. blueckaym said:

    So I still didn't get which holds stronger – a hammered down screw, or a nail screwed with a screwdriver?

    July 29, 2019
    Reply
  34. Bagel said:

    Does anyone notice that he has a TierZoo button in his tool chest?

    July 29, 2019
    Reply
  35. Nathan Mc Cormack said:

    You videos are forever engaging and entertaining and every other positive work I can think of, but this was the first video I've seen that had all those and the ability to make me piss myself laughing 🤣 I love it

    July 29, 2019
    Reply
  36. Nina Schaefer said:

    Interesting history

    July 30, 2019
    Reply
  37. please help me i am hacked ONURHD said:

    its to rape people

    July 30, 2019
    Reply
  38. Thomas Brand said:

    No philips head has ever annoyed me more than literally every other hex or torx screw I've ever dealt with.
    Oh, let me do this minor repair on my Jeep. Well fuck me, I guess I need to go to Home Depot to get a damn torx screwdriver. Of course they don't have any, but the clueless employee is looking at me like I'm the idiot. Bitch, I just asked you about a screwdriver with a six pointed star for a head and you handed me what you called "a plus sign screwdriver." That's a goddamn philips head ffs!

    July 30, 2019
    Reply
  39. Matthew Sylvester said:

    That first minute was to detailed

    July 31, 2019
    Reply
  40. Cryzk said:

    the worst thing is when a single item has differing screw sizes on the same section

    August 2, 2019
    Reply
  41. Lexicon Devil said:

    Funny how you can just use a flat blade driver on the fancy pants torx ….
    Even the “tamper proof” ones .

    August 2, 2019
    Reply
  42. Mark Overcash said:

    CGP Grey at 3:40 !

    August 3, 2019
    Reply
  43. sleekEDITINGco said:

    Look I like the idea of a good universal screw but there's always one person that wants to make more money than the rest of the world and will make it as hard as possible for anyone to do anything other than continue coming back to them for repairs/replacements so they can charge them more than once for a single product.

    August 5, 2019
    Reply
  44. Abhinav Girish said:

    Allen Nuts are superior

    August 5, 2019
    Reply
  45. Prajwal Pingali said:

    Cgpgrey!!!!!

    August 5, 2019
    Reply
  46. Some Asshole said:

    I definitely hate hex far more than Phillips heads. I would love if everything moved to metric torx.

    August 5, 2019
    Reply
  47. JP Labs said:

    ‘Pressing the shit out of some grapes to make wine.’

    Crisis wine?

    August 5, 2019
    Reply
  48. Igors Jakimenko said:

    I was waiting for "Screw you" 😀

    August 6, 2019
    Reply
  49. J Privacy said:

    Upvote for "Crisis Wine".

    August 6, 2019
    Reply
  50. Q.D. White said:

    English captions at 2:57 👍

    August 7, 2019
    Reply
  51. Q.D. White said:

    3:30 “Freedom units” and metric. I can’t tell if this is a snarky American or cynical European.

    August 7, 2019
    Reply
  52. Nicholas Ratliff said:

    Is the real engineering logo a single tooth of an Involute Gear?

    August 8, 2019
    Reply
  53. HuntingTarg said:

    I am just here to upvote the use of "Freedom Units"

    Because the Anglosphere used their odd, wacky, antiquated agriculture-derived measurement system to overcome better-made NAZI tanks, planes, artillery, and rifles; and better made Imperial Japanese warships; and rescue all of Eurasia from despotism.

    August 10, 2019
    Reply
  54. Harm Hoeks said:

    Torx is basically best right?

    I wonder how ot performs after rust!! Regular ones can screw you.

    August 10, 2019
    Reply
  55. Ali Hamza said:

    the given code curiosity stream is invalid

    August 10, 2019
    Reply
  56. The-Mike_D said:

    Loved the humor in this one. Very entertaining

    August 11, 2019
    Reply
  57. Chance McClendon said:

    HAHA i didn't know Robinsons were mostly in Canada. there so good

    August 12, 2019
    Reply
  58. rtrThanos Ezekyle Abaddon said:

    Passed out drunk in the living room. Woke up at 1:49am, heard “hex screw”, and immediately got mad while thinking about those stupid hex screws with the post in the middle for “security”. I must have passed out again for a minute because the next thing I see on the screen are squirrels.

    August 12, 2019
    Reply
  59. Nathan Frey said:

    Why so many types of screws? Because people have been screwing for a very long time…

    August 14, 2019
    Reply
  60. Carlos O'Gorman said:

    3:41 cpg gray logo in the background

    August 14, 2019
    Reply
  61. Luca Veronese said:

    freedom units… haha..

    August 15, 2019
    Reply
  62. Eric Sell said:

    "Crisis Wine" in the bottom of the toolbox…HAHAHAHAHAHA!

    August 16, 2019
    Reply
  63. victor hugo sanchez cordova said:

    Curiously, there seems to be a relation between most of your videos with unfair ammount of dislikes and refering to the "not metric" meassurement system
    Hmmm I wonder why..
    nobody in the world uses that stupid archaic stuff anymore why would somebody be angry because of it?

    August 17, 2019
    Reply
  64. Kaijin said:

    Archimedean spiral

    August 17, 2019
    Reply
  65. lord pickle said:

    "Six grains of barley, dry and round, placed end to end, lengthwise" eh? I'll have to use that instead of bragging about the whopping two inch stiffy I'm packin'. Literally sounds three times as large.

    August 18, 2019
    Reply
  66. Logan Strom said:

    Phillips bits are horrible. Square bits are where it's at.

    August 18, 2019
    Reply
  67. 813 said:

    Because, screw you.

    August 18, 2019
    Reply
  68. Mac Gyver said:

    if everyone could adjust to torx, that would be great

    August 19, 2019
    Reply
  69. Eric Bouchard said:

    As an office furniture installer working around Boston, MA, I can confidently say that square-headed screws (which we universally call "Canadians") constitute 99% of our "attach desk base/ped/legs to wooden surface" hardware usage. Dat stuff ain't limited to Canuckastan.

    August 20, 2019
    Reply
  70. bastol said:

    Everyone: ahh i finally got a torx driver i can fix my macbook.

    Apple: pentalobe.

    August 22, 2019
    Reply
  71. Kaihu said:

    Because screw you. That’s why.

    August 23, 2019
    Reply
  72. matt allwood said:

    I'm just commenting so the you tube algorithm makes you more money

    August 24, 2019
    Reply
  73. ZimmMr said:

    No worries, we technicians are here to save the day!

    August 28, 2019
    Reply
  74. Andreas Dünser said:

    "Freedom units" Ahahaha that's hilarious!

    August 28, 2019
    Reply
  75. Januschka Steinuschka said:

    aaaaaaaaaaaaaaaaaaaaaaallllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll that fucking stupid pointless talk about stopping climate change and using our ressourcess responsibly. All that talk, while companies do their best to prevent us from repairing our electric devices. Devices that are designed to be thrown away every two years.
    ==>> Politicians that talk about stopping climate change dont mean it, as long as they dont even mention this "designed to NOT be repaired" absurdity.
    Yeah. Mention. Thats it. That where we are at. Far from expecting them to make legislation to ACTUALLY change the industry and force them to design specifically to be repairable.

    September 1, 2019
    Reply
  76. James S. said:

    Don't you just love engineers! I'm just glad someone a 100+ years ago had the wherewithal to standardized the screw system we have. At least we're only dealing with SAE and Metric. Can you imagine the bedlam we would have in industry if every manufacturer of hardware decided to have their own standard of what screw threads are? It would be exactly like the software industry today! 🙄

    September 1, 2019
    Reply
  77. James S. said:

    I have a better subject. Why are there a 100 different size automotive oil filters? They all do the same thing. Only need 3 different sizes. 🤔

    September 2, 2019
    Reply
  78. Walter's Guides said:

    3:40 :Thinking:

    September 2, 2019
    Reply
  79. Volcanoman said:

    Love it. As a Canadian, I never knew that Robertson screws were pretty much unique to here now. I mean, I did know that their inventor was Canadian, but I just assumed that being a superior product to Phillips screws (and infinitely better than slot-type screws), they would have found worldwide acceptance. They're just…normal here, available everywhere, used by pretty much every contractor at least some of the time. Of the three main types of screw heads, they're by far my favourite (it's crazy how something over a hundred years old can be so high quality even today). Also, apparently, P. L. Robertson had a really good reason why he was unwilling to license his screws to Ford. He had entered such an agreement with an English licensee company whose parent company intentionally drove the licensee into bankruptcy so that they could buy the English rights at a reduced price from the trustee. Robertson spent a fortune getting the rights back, and from that point on, he refused to license his design to anyone else, which made Ford look elsewhere. That he went with the VASTLY inferior Phillips shows how desperate he was to have the supply chain under his control (which is weird…if the product is worth it, why not just sign a contract requiring Robertson to supply him with X amount of screws a year, for Y amount of years, at Z price, thus ensuring that he would always have access to what he needed?).

    As good as Robertson screws are however, they take 2nd place overall to Torx in my opinion, which are really quite wonderful to use. I've been using Torx wood screws for a few years now on various projects, and if I have the option, I'll always choose them.

    September 3, 2019
    Reply
  80. 108johnny said:

    Was the ginger squirrel from Germany?
    I got those kind on my lawn, drives my dog nuts…..

    September 3, 2019
    Reply
  81. TJ LABBEE said:

    Square or Robertson screws are far superior, speaking as a Canadian carpenter. I hate Phillips heads.

    September 3, 2019
    Reply
  82. Curtis said:

    I think the left hand thread Phillips screw would be even more infuriating than the normal one. 4:52

    September 3, 2019
    Reply
  83. Fuzzy Johnson said:

    It's not going to be OK! It's not!!

    September 4, 2019
    Reply
  84. Rob Knapp said:

    Fractional inches are much easier to deal with than decimal BS.

    September 4, 2019
    Reply
  85. TheColdZephyr said:

    I was immediately reminded of CatDog, the episode where Dog becomes the smart one. He mentions one 'John Jacob Jingleheimer Flathead.'

    September 5, 2019
    Reply
  86. Miguel Valero Arcia said:

    This is perhaps my favorite video on this channel. Ever. Period.

    September 5, 2019
    Reply
  87. Texlith Graves said:

    Hears satirical banter about Imperial and Metric- "Hmm? Is that the sound of the nearly conquered making a fuss over measurements again? Oh you poor sweet innocent child, come talk with us on the moon when you grow up."

    Ha ha, in all seriousness though, great video and thanks for confirming that I'm not the only one with a few loose screws.

    September 5, 2019
    Reply
  88. James England said:

    I like the humorous change of pace!

    September 6, 2019
    Reply
  89. Galen Ferrara said:

    Did you buy the wrong screw again?

    September 7, 2019
    Reply
  90. flabbertoe said:

    We use inches, bitche$! We set the standard. USA all the way!

    September 7, 2019
    Reply
  91. Chase Assaker said:

    "a nut and bolt with the same diameter will fit, even when mixing metric and freedom units" Amazing. Beautiful. This is why I love your videos

    September 7, 2019
    Reply
  92. Phil Carroll said:

    “Just been into B&Q for a bag of tungsten-tipped screws. Never gonna use ‘em…… Never gonna use ‘em.”

    September 7, 2019
    Reply
  93. Synthetase2 said:

    But why are all the threads still so different?

    September 8, 2019
    Reply
  94. DDC ll said:

    So the answer to why we have so many screw designs today is because people are saying fuck you to each each other eh.

    September 8, 2019
    Reply
  95. wayne thomas said:

    Torx is pretty good but hex usually has a deeper engagement. Torx would probably be far superior if they tool went deeper. The other problem is the tool. The torx bit's outer points may be many but are not a very deep engagement. An example is GM truck brakes that used have head torx screw for the mounting of brake calipers. With very little rust the bit just rounds out the inside of the screw just like a philips screwdriver or snaps your hardened torx bit off in the screw. It's a trainwreck of a repair and I always use the torches to ease removal and throw the fucking things away and use a hex head cap screw, ie a bolt. With hex you can apply much more power to the tool and screw before it rounds out. Improvement could probably be made to torx but, as a mechanic, it's just another pain my ass set of tools I needed to buy but the fasteners are NOT superior to hex and are way inferior to actual hex head screws, ie than you use a socket or wrench on. What you called a hex screw is actually called a socket head cap screw and uses an Allen wrench. In tight quarters I understand the use to SHCS or Torx but where space is not an issue, lets just use bolts! Much more force can be applied because it engages the entire outside of the head head.

    September 9, 2019
    Reply
  96. Grant Trotter said:

    Phillips heads are supposed to slip out at a certain torque. 🤯

    September 9, 2019
    Reply
  97. Javier Lopez Zavaleta said:

    4:21 those are models A not Ts >:v

    September 10, 2019
    Reply
  98. Tuning3434 said:

    The worst kind of screw is the un-lubricated / non-zinc plated screw.

    September 11, 2019
    Reply
  99. Scott Rettie said:

    You forgot to mention about a plain straight drive can only be applied every 180 degrees (phillips is every 90 and a hex is every 60) Also would of been to stat reason fir counter sunk and internal vs external drive. Plus phillips has a pozi drive (extra cross) allowing more torque to be applied improving the classic cross shape.

    September 11, 2019
    Reply
  100. VZ_ 342 said:

    Here I was, happily watching about different screws and screw heads, when suddenly I see…SQUIRREL!!1! And I am distracted…two minutes later I realize the purpose of the distraction: Damn, it’s a commercial! But…IT HAS SQUIRRELS! So I keep watching. I was curious, and waded into the stream.

    👍🏼🙂

    September 12, 2019
    Reply

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