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Screw This, Screw That: Why We Have Different Types of Screws

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If you've ever mistakenly grabbed the Phillips head screwdriver when you needed a flat head, you've probably asked yourself why there are different types of screws. Let's start at the beginning.

The screwdriver, originally called a screwturner or turnscrew, entered the world inconspicuously and kept a very low profile until its 300th birthday. Historians believe it was invented in Germany, but aren't sure exactly when. The Medieval Housebook of Wolfegg Castle, the oldest known written reference to the tool, has a hazy publishing date somewhere between 1475 and 1490. Considering the invention likely predates the book by at least a few years, the mid to late 15th century is about as exact a birthday as it gets. For about 300 years, the persistent presence of screws is the only solid evidence that screwdrivers even existed. Then, suddenly, documentation of screwdrivers exploded across Europe, particularly in France.

Early screwdrivers had pear-shaped handles and were made for slotted screws. Metal screws as we know them today have been in use since at least the 15th century for cabinetry work and to secure plates on jousting armor. Before that, wooden screws were used in wine and olive oil presses as far back as the 1st - 3rd century BC (how they turned them for so long without a screwdriver, I haven’t been able to figure out).

These early metal screws were prohibitively expensive. It wasn’t until several advances in screw making – among them, Jesse Ramsden and Henry Maudslay's screw-cutting lathes and David Wilkinson’s and Job and William Wyatt’s mass production of screws on assembly line-like systems – occurred around the beginning of the First Industrial Revolution that the screw became easy enough to produce to become popular and widespread. This increase in popularity, of course, led to the refinement and diversification of the screwdriver. The tool took on many different shapes and sizes, though for a long time every version was still for flat slotted screws, which were the only type around.

Better Heads

This changed in 1908, when Canadian P.L. Robertson patented the “first recess-drive type fastener practical for production usage,” a recessed square-drive screw that bears his name. Robertson screws became a standard in Canada and gained a buzz in the U.S. when the Ford Motor Company, one of Robertson's first customers, used over seven hundred of them on each Model T. The square-drive head on Robertson screws had an advantage over slot heads because the driver was relatively easy to get situated on the head and stayed put during installation once it was there. A screw like Robertson’s became crucial as American manufacturers moved increasingly toward mass production methods. The time it took to align the driver with the slot, multiplied across thousands of workers in a factory and across hundreds, if not thousands, of screws per worker per day, became a significant loss of time and money. Additionally, the automated screwdrivers used on assembly lines often slipped out of the screws’ slots and into whatever component was being assembled or stripped the screw once it was driven all the way. [Image credit: Saforrest]


The American automobile industry was especially in need of a screws screw that could stand up to the torque of their automated drivers and be fitted and tightened quickly, but a bad break in Robertson’s past doomed him just when his invention was needed most. Dealing with dishonest parties while licensing his screw in England, Robertson wound up losing the rights to his invention and had to spend a small fortune to buy them back. When Ford, wanting to protect his assembly advantage (the screws saved his workers two hours of assembly time per vehicle), asked for a licensing agreement from Robertson so that he could manufacture and control the distribution of the screws, Robertson turned him down and he refused to allow anyone to make the screws under license. After their run on the Model T, Ford had to limit the use of the screws to his Canadian division and the widespread adoption of the Robertson screw in the U.S. fizzled and failed.

Enter Portland, Oregon-based businessman Henry F. Phillips and the patent for a screw with a deep X-shaped slot, which he had purchased from friend and inventor J.P. Thompson. Phillips refined the design of the fastener, today known as a Phillips screw, for automated screwdrivers. The X-shape of the slot and pointed tip of the Phillips head screwdriver made the driver self-centering and unlikely to slip out when it wasn’t supposed to. The recessed slot was shallow enough, though, that the driver did pop out when the screw was fully tightened, which prevented over-torquing and damage to the screw, the driver and the product being assembled.


The American Screw Company began mass-producing Phillips’ design. A successful trial on the 1936 Cadillac helped it proliferate through the U.S. auto industry. By 1940, 85% of the screw manufacturing companies in the U.S. had a license to produce the Phillips screw design. Usage spread from the auto manufacturers as the Phillips drive system was used during the Second World War on many wartime products and vehicles. Though originally meant for automated, industrial applications, Phillips screws and handheld screwdrivers found their way into the toolboxes of handy men and women across the country by the turn middle of the century. [Image credit: U.S Patent and Trademark Office.]

Other Ways the World Turns

Most anyone who’s had to fix anything at home or put together an IKEA couch has heard of slotted and Phillips screws and maybe even hex sockets. The world of screws is vast, though, and plenty of other types of screw heads and drives exist, like the Mortorq, the Pozidriv and the Bristol. You can take a crash course in the different types of screws here, and if you want a more in-depth history of screws and drivers, check out Witold Rybczynski’s One Good Turn: A Natural History of the Screwdriver and the Screw.

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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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8 Common Dog Behaviors, Decoded
May 25, 2017
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Dogs are a lot more complicated than we give them credit for. As a result, sometimes things get lost in translation. We’ve yet to invent a dog-to-English translator, but there are certain behaviors you can learn to read in order to better understand what your dog is trying to tell you. The more tuned-in you are to your dog’s emotions, the better you’ll be able to respond—whether that means giving her some space or welcoming a wet, slobbery kiss. 

1. What you’ll see: Your dog is standing with his legs and body relaxed and tail low. His ears are up, but not pointed forward. His mouth is slightly open, he’s panting lightly, and his tongue is loose. His eyes? Soft or maybe slightly squinty from getting his smile on.

What it means: “Hey there, friend!” Your pup is in a calm, relaxed state. He’s open to mingling, which means you can feel comfortable letting friends say hi.

2. What you’ll see: Your dog is standing with her body leaning forward. Her ears are erect and angled forward—or have at least perked up if they’re floppy—and her mouth is closed. Her tail might be sticking out horizontally or sticking straight up and wagging slightly.

What it means: “Hark! Who goes there?!” Something caught your pup’s attention and now she’s on high alert, trying to discern whether or not the person, animal, or situation is a threat. She’ll likely stay on guard until she feels safe or becomes distracted.

3. What you’ll see: Your dog is standing, leaning slightly forward. His body and legs are tense, and his hackles—those hairs along his back and neck—are raised. His tail is stiff and twitching, not swooping playfully. His mouth is open, teeth are exposed, and he may be snarling, snapping, or barking excessively.

What it means: “Don’t mess with me!” This dog is asserting his social dominance and letting others know that he might attack if they don’t defer accordingly. A dog in this stance could be either offensively aggressive or defensively aggressive. If you encounter a dog in this state, play it safe and back away slowly without making eye contact.

4. What you’ll see: As another dog approaches, your dog lies down on his back with his tail tucked in between his legs. His paws are tucked in too, his ears are flat, and he isn’t making direct eye contact with the other dog standing over him.

What it means: “I come in peace!” Your pooch is displaying signs of submission to a more dominant dog, conveying total surrender to avoid physical confrontation. Other, less obvious, signs of submission include ears that are flattened back against the head, an avoidance of eye contact, a tongue flick, and bared teeth. Yup—a dog might bare his teeth while still being submissive, but they’ll likely be clenched together, the lips opened horizontally rather than curled up to show the front canines. A submissive dog will also slink backward or inward rather than forward, which would indicate more aggressive behavior.

5. What you’ll see: Your dog is crouching with her back hunched, tail tucked, and the corner of her mouth pulled back with lips slightly curled. Her shoulders, or hackles, are raised and her ears are flattened. She’s avoiding eye contact.

What it means: “I’m scared, but will fight you if I have to.” This dog’s fight or flight instincts have been activated. It’s best to keep your distance from a dog in this emotional state because she could attack if she feels cornered.

6. What you’ll see: You’re staring at your dog, holding eye contact. Your dog looks away from you, tentatively looks back, then looks away again. After some time, he licks his chops and yawns.

What it means: “I don’t know what’s going on and it’s weirding me out.” Your dog doesn’t know what to make of the situation, but rather than nipping or barking, he’ll stick to behaviors he knows are OK, like yawning, licking his chops, or shaking as if he’s wet. You’ll want to intervene by removing whatever it is causing him discomfort—such as an overly grabby child—and giving him some space to relax.

7. What you’ll see: Your dog has her front paws bent and lowered onto the ground with her rear in the air. Her body is relaxed, loose, and wiggly, and her tail is up and wagging from side to side. She might also let out a high-pitched or impatient bark.

What it means: “What’s the hold up? Let’s play!” This classic stance, known to dog trainers and behaviorists as “the play bow,” is a sign she’s ready to let the good times roll. Get ready for a round of fetch or tug of war, or for a good long outing at the dog park.

8. What you’ll see: You’ve just gotten home from work and your dog rushes over. He can’t stop wiggling his backside, and he may even lower himself into a giant stretch, like he’s doing yoga.

What it means: “OhmygoshImsohappytoseeyou I love you so much you’re my best friend foreverandeverandever!!!!” This one’s easy: Your pup is overjoyed his BFF is back. That big stretch is something dogs don’t pull out for just anyone; they save that for the people they truly love. Show him you feel the same way with a good belly rub and a handful of his favorite treats.

The best way to say “I love you” in dog? A monthly subscription to BarkBox. Your favorite pup will get a package filled with treats, toys, and other good stuff (and in return, you’ll probably get lots of sloppy kisses). Visit BarkBox to learn more.

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