Why We Have Different Types of Screws

iStock/teerawut111
iStock/teerawut111

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.

Take a 40-Minute Virtual Tour of the Winchester Mystery House

BrookePierce, iStock via Getty Images
BrookePierce, iStock via Getty Images

Taking online yoga classes and watching soothing animal live-streams isn't the only way to cope with isolation. If taking a virtual tour of one of the most allegedly haunted places on Earth is more your style, now you can check out every baffling nook and cranny of the Winchester Mystery House on the landmark's website.

Along with many public businesses and institutions across the country, the Winchester Mystery House closed earlier in March in response to the novel coronavirus pandemic. A visit to the site in person normally costs up to $54, but until it reopens, anyone can take a virtual tour of the estate for free.

The Winchester Mystery House is one of the most notorious pieces of property in California's Bay Area. Constructed between 1886 and 1922, legend says Sarah Winchester built the unusual abode to ward off the vengeful spirits of people killed by Winchester rifles. (The founder of the Winchester Repeating Arms Company was her father-in-law.) The home's bizarre layout, which includes stairs that stop at the ceiling and doors that open to nothing, may reflect her fear-driven compulsion to keep building.

Today the Winchester Mystery House is an iconic California landmark. It's a bucket-list destination for ghost hunters, and it's even been immortalized as an elaborate LEGO sculpture. To see the inside of the structure, and to learn more about its history, you can take the 40-minute virtual tour here. If you're looking for more ways to support the attraction while it's closed to visitors, consider buying a discounted ticket voucher now to use when the house reopens.

Super Spreader: The Strange Story of Typhoid Mary

Mary Mallon, an unwitting typhoid carrier and unwilling hospital patient, in the early 1900s.
Mary Mallon, an unwitting typhoid carrier and unwilling hospital patient, in the early 1900s.
CBS Sunday Morning, YouTube

In the winter of 1906, Mrs. George Thompson called upon Dr. George Soper, known around New York as an “epidemic fighter,” to investigate the source of a typhoid outbreak that had occurred among renters in her Oyster Bay summer home several months prior.

After finding no issue with the well, the outhouse, the food supplies, or any other part of the property that might have generated germs, Soper considered the possibility that the carrier could have been a healthy person—an idea that wasn’t widely accepted at the time. By process of elimination, he landed on a likely culprit: the cook, a 37-year-old woman named Mary Mallon.

typhoid mary newspaper article from 1909
An article published in The New York American on June 20, 1909.
Lupo, Wikimedia Commons // Public Domain

Mallon, described by the other servants as “not particularly clean,” had arrived at the Thompson home on August 3, 1906. Just weeks later, between August 27 and September 3, six out of the house’s 11 occupants had contracted typhoid fever. Though most of her dishes were hot and prepared at temperatures that would have killed any bacteria, Mallon had served ice cream with fresh peaches one Sunday, which some of the house guests ate with gusto.

Before searching for Mallon herself, Soper followed her trail of employment all the way back to September 1900, unearthing a total of seven households in New York and Maine that had suffered typhoid outbreaks during Mallon’s tenure.

“In nearly every instance, a well-to-do and socially prominent family, soon after moving from the city to the country for the summer, experienced an outbreak of typhoid fever. In no instance had its cause been satisfactorily explained,” Soper recounted in the Bulletin of the New York Academy of Medicine. "The cook always left soon afterward. She had never been suspected."

Soper decided it was time to track Mallon down.

A Mean, Unclean Quarantine Queen

In early 1907, Soper paid Mallon a visit in Manhattan, in an old-fashioned house on Park Avenue and 60th Street where she was working, once again, as a cook.

“I was as diplomatic as possible, but I had to say I suspected her of making people sick and that I wanted specimens of her urine, feces, and blood,” Soper wrote.

Mallon seized a carving fork and chased Soper from the premises.

After another unsuccessful attempt to reason with Mallon, Soper asked New York City’s Department of Health to intervene. So Dr. Sara Josephine Baker came calling at the Park Avenue estate, and Mallon made a run for it, evading capture for three hours before police found her in a neighbor’s shed and deposited her into an ambulance.

“The ride down to the hospital was quite a wild one,” Dr. Baker recalled.

Mallon was taken to an isolation ward at Willard Parker Hospital, and doctors tested her feces three times a week between March 20 and November 16, 1907. Salmonella enterica enterica serovar Typhi, the bacterium that causes typhoid, was found in nearly every sample. Soper visited Mallon at the hospital to explain why she had been confined for so long (and also to determine the possibility of securing her release).

“When you go to the toilet, the germs which grow within your body get upon your fingers, and when you handle food in cooking they get on the food. People who eat this food swallow the germs and get sick,” he told her. “If you would wash your hands after leaving the toilet and before cooking, there might be no trouble. You don’t keep your hands clean enough.”

Mallon, frustrated and lonely, wasn’t very receptive to his advice, and refused to give doctors permission to remove her gallbladder, which they suspected was the source of the germs. There’s a good chance that this was true, since recent scientific studies have shown that many asymptomatic typhoid carriers store typhoid bacteria in their gallbladders. When their gallbladders empty bile into their small intestines, some of the bacteria goes with it, and then gets excreted in their stool.

“No knife will be put upon me,” Mallon told the doctors who requested to remove it. “I’ve nothing the matter with my gallbladder.”

typhoid mary cartoon
An illustration of unknown origin showing how Typhoid Mary spread bacteria through food.
National Museum of Health and Medicine, Flickr // CC BY 2.0

Soon after that meeting, Mallon was relocated to a bungalow near Riverside Hospital on New York's North Brother Island. Her quarters, originally built for the superintendent of nurses, were more spacious and more comfortable, but Mallon was still treated like a dangerous outcast, isolated from the rest of the island’s inhabitants.

Two years after her arrest on Park Avenue, Mallon sued the Department of Health, claiming that she had been imprisoned without due process of law—in fact, she hadn’t even been accused of a crime. Dr. William H. Park, the bacteriologist who had tested Mallon’s feces, took the stand to explain how Mallon—though seemingly healthy herself—was an asymptomatic typhoid carrier. Both sides presented compelling arguments, but the court simply didn’t want the responsibility of determining whether Mallon was fit to rejoin society.

They dismissed the case altogether, and a defeated Mallon returned to North Brother Island.

Life As a Culinary Renegade

In February 1910, Riverside Hospital finally decided to release Mallon on the condition that she promise not to work as a cook and “take such hygienic precautions as will protect those with whom she comes in contact, from infection.” She agreed to the terms and left the island.

What she didn’t do was keep her word. For the next five years, Mallon flitted from kitchen to kitchen in the area, introducing herself as “Marie Breshof” or “Mrs. Brown.” She cooked in a restaurant on Broadway, a hotel in Southampton, an inn in Huntington, and a sanatorium in New Jersey. Typhoid followed Mallon wherever she went, but she never stayed in one place long enough to rouse suspicion.

That is, until 1915, when Dr. Edward B. Cragin solicited Soper’s help in detecting the cause of a typhoid outbreak at New York’s Sloane Hospital for Women. More than 20 people had fallen ill, and the other servants had taken to calling the cook “Typhoid Mary”—a sobriquet that newspapers had used for Mallon during her solitary confinement.

After Soper positively identified the woman he knew to be Mary Mallon, the hospital alerted the Department of Health, and Mallon was whisked right back to North Brother Island. This time, she didn’t resist.

The Lonely Legacy of America’s Most Famous Asymptomatic Carrier

Mallon lived out her remaining 23 years in the lonely riverbank bungalow, processing tests in the hospital laboratory and making occasional sojourns to Queens to visit a family she was friendly with. According to Soper, “they were not particularly glad to see her.” She suffered a stroke in 1932, and passed away at age 69 on November 11, 1938. Only nine people attended her funeral at St. Luke’s Catholic Church in the Bronx.

In total, Mallon was officially responsible for infecting 53 people with typhoid—three of whom died—though there were likely many more that went unreported. While her commitment to good hygiene may have been lacking, the fact that she was so often treated like a pariah no doubt exacerbated her unwillingness to cooperate with doctors and other health officials. For many, including Mallon herself, it was simply difficult to believe that a perfectly healthy person who had never even been afflicted with a terrifying disease could somehow pass it on to dozens of others.

“It was to be Mary Mallon’s fate to clear away much of the mystery which surrounded the transmission of typhoid fever and to call attention to the fact that it was often persons rather than things who offered the proper explanation when the disease occurred in endemic, sporadic and epidemic form,” Soper wrote.

Mallon, however begrudgingly, charted a new path for scientists studying communicable diseases—and taught the rest of us just how important it is to wash our hands.

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