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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 screw.
Woooooow look at all these screws. Amaaaazing.
You have sultry slotted screws, 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.
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 can not 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,
多个世纪以来 这个原理被应用于抽水 挖洞
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.
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,
甚至在混合自由度 单位 度量标准时也匹配
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 or 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 slightest bit of rust.
By 1939 this design was licenced to nearly every automotive, airplane and rail manufacturer in the US
到1939年 这种设计几乎被授权给美国每个汽车飞机 铁轨的制造商
Just in time for the boom in manufacturing created by World War 2 ,
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.
然而我们可以看到 当我们转动六角扳手时 它接触螺丝钉的半径更大
Allowing it to applying more torque with the same force,
but the plane of contact is not perpendicular to the screw
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 
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 level 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 want to 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.
我强烈推荐去curiositystream网站 观看标题为“Going Nuts”的纪录片
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 them for free, by signing up to curiositystream using the code realengineering,
你可通过code realengineering 注册curiositystream网站来免费观看
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.
下方是我的Ins twitter discord server 和 subreddit 的链接