0:00 Sitting out here on the porch, you can hear a freight train rumble past the depot three miles off, and it hits you that fifty thousand tons of rolling steel is held together by pieces of threaded wire no bigger than my thumb.0:16 Last week we tracked how coiled metal springs became the hidden muscle in pocket watches and freight cars; well, today we're looking at the bones.0:27 I mean, without the humble industrial fastener — screws, nuts, bolts, and rivets — modern trade literally falls to pieces on the track.0:37 Ey up, Earl, don't go scaring folk that their bridges are falling down into the river!0:44 Though mind you, my kettle has three tiny brass screws in the handle, and if one rattles loose, tea time's an absolute disaster.0:53 People reckon empires were built on grand ideas, love, but really it's just little bits of metal clamping things tight.1:02 Now, I know how that sounds, but hang on.1:05 Before eighteen forty-one, if you bought a bolt in Manchester and took it thirty miles over to Leeds, it wouldn't fit a single nut in the county.1:16 Every blacksmith cut his own threads by hand, kind of guessing the pitch.1:21 If a carriage broke an axle bolt on the turnpike, you couldn't just fetch a spare from the livery.1:29 You had to forge an entirely new pair from scratch.1:32 Oh, like my granddad trying to fix his mangle with odd bits from his shed!1:38 It was Joseph Whitworth, wasn't it, who put a stop to all that nonsense?1:43 That's the man.1:44 Sir Joseph Whitworth sat down in eighteen forty-one, gathered sample screws from workshops all across Britain, and measured the average angle.1:55 He landed on fifty-five degrees, with a fixed number of threads per inch for every bolt diameter.2:02 Suddenly, a half-inch bolt made in Newcastle would thread clean into a nut tapped in Bristol.2:09 It was the first national standard in the world.2:13 And once you've got standard threads, you don't need a master craftsman fussing over every single wagon.2:20 You can just build things by the gross.2:23 Exactly.2:24 It cut the cost of assembling steam engines by almost forty percent in a single decade.2:30 But the real magic wasn't just screws, it was red-hot rivets.2:35 When the Industrial Revolution started throwing iron over rivers and across oceans, bolts weren't quite stiff enough for the huge shear loads.2:45 In eighteen eighty-nine, workers drove over two point five million rivets to put the Eiffel Tower up in Paris.2:54 Four men to a gang — one heating the iron in a coke forge till it glowed cherry, one tossing it with tongs, one holding the anvil against the head, and two swinging sledgehammers to mushroom the tail before it cooled.3:10 Can you imagine catching red-hot iron in a bucket hundreds of feet in the air?3:16 Gives me the shivers just thinking about it, chuck.3:19 But when those rivets cool down, they shrink, don't they?3:24 And that shrinkage pulls the iron plates together with unbelievable pressure.3:29 Swear on my tackle box, that is the honest truth.3:33 It creates friction so fierce the plates can't slide even a hair.3:38 But rivets had an Achilles' heel.3:40 If you had one bad rivet in five hundred — say, a pocket of slag or a lazy strike — the whole joint could shear under stress.3:50 That's actually what ocean divers found on the wreck of the Titanic; low-grade iron rivets in the bow plates popped like buttons when the ice bumped her.4:01 Aye, poor souls.4:02 That's the dark side of a fastener, isn't it?4:06 If the engine fails, it stops; if the bolt snaps, everything crashes down.4:11 Which brings us to the second leap: high-strength alloy bolts.4:16 During the Second World War, aircraft were vibrating so violently that ordinary threaded bolts were rattling right out of the airframes.4:26 That's when engineers figured out cold-heading and rolling threads instead of cutting them.4:33 When you roll a thread under heavy dies, you don't cut the grain of the steel — you crush it into shape.4:40 That made the bolt three times stronger against fatigue.4:44 So instead of a dozen men banging hot rivets on a skyscraper, you just need one lad with an impact wrench tightening high-tensile steel bolts.4:55 That's it.4:56 A modern skyscraper like the Empire State Building used ten million rivets, but today, a building twice that tall uses high-strength structural bolts.5:07 Today, the global market for industrial fasteners is worth over ninety billion dollars a year.5:14 A single commercial jetliner sitting on the runway has over two MILLION fasteners holding its skin and turbines together.5:23 If you piled up all the bolts forged on earth in one single year, it'd outweigh all the automobiles rolling off the assembly lines.5:33 It makes your head spin to think about it.5:36 You walk into a hospital or step onto a train, and your very life depends on a scrap of steel smaller than a thimble that nobody's thought about for fifty years.5:48 Hmm.5:48 We build these towering glass towers and high-speed rail lines, and we praise the architects and the money men.5:56 But when you get right down to the bedrock of economic history, the whole modern world is really just a mountain of standardized threads holding on for dear life.6:08 Well, as long as they stay tight, I can sleep easy.6:12 Right then, love, time to put the kettle on and check my cupboard door hinges.6:18 Night night, sleep tight, chuck.6:20 You keep that screwdriver handy, Nan.6:23 Well, out here on the porch, the creek's running quiet and that train's long gone over the ridge.6:30 That's about the size of it.
