Why can’t we just figure out what screw -head- shape is the best and always use that. It seems pointless to have hundreds of different screw types for very similar things. Obviously this is excluding things like lug nuts or anything heavy duty.
Edit:specifying screw heads, not the threads or shape.
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Because the screw shape that is best for wood is different than the screw for plastic which is different than the screw for drywall, etc.
Emyrssentry gave a great answer about the ways there can’t be a Universal “best” screw, because the “best” design for cost will never be the “best” design for strength (how hard you can torque it without slipping), with may or may not be the “best” design for ease of use. So depending on what factors you care about, which one is “best” changes. That gives many different head designs a legit reason to exist.
**However,** I want to add that [there is also a lot of this happening.](https://xkcd.com/927/)
(To other commenters: Yes, that’s the relevant XKCD).
Some screws need high torque, some screws need to be easy to make, some screws need to be easy to screw in. You have a bunch of different competing interests, and there is no one screw head that gives the best of all worlds.
Like for example, a torx head gives high torque, but you need a pretty specialized broach to make the shape. A slotted head literally just needs a saw, but is weird to screw in with. And a Phillips head is easy to attach to the driver, but it cams out very easily.
So depending on what you need, you get different screws.
Basically, before standardization as we know it today became a thing, every company made their own screws that suited whatever purpose they needed. The first few screws were stuff like the Philips head, which is widespread in the US. This head is easy for humans to work with, though they have some disadvantages when working with machines. Still, they existed, so people used them.
Later, you get things like square heads. These were made during the industrialization, as its much easier to build a machine to use those. Later came hexagonal screws, which caused less wear on the tools, as the torque was more evenly and more effectively applied. Then along came things like Torx, which are designed to further optimize this,
Also, it should be mentioned that, as various countries industrialized, they often came up with similar screw designs. For instance, the japanese had their own screws, the JIS screws. They look a lot like Philips screws, but in fact, while you can turn a Philips screw with a JIS screwdriver, the reverse is not true, as unlike the Philips screws, JIS screws keep the inner corners in the middle of the cross, and Philips screwdrivers are designed to be shaped accordingly, thus, you cannot use them on JIS screws.
Also also, there’s companies like Apple. Apple famously makes their devices difficult to repair so they can charge service fees. For this purpose, they’ll have their own screws that cannot be turned with ordinary screwdrivers, specifically to stop you from opening their devices and repairing them yourself. Nowadays, they usually use Pentalobe screws for this purpose, as a screwdriver for these screws is hard to come by, and certainly not in every garage.
So, there’s actually a bunch of reasons!
Money is a big one.
Material is another. Screws can be made of plastic, steel, brass, stainless steel, copper, etc.
Size, is a factor.
Torque is a big one. Each of the screw designs you’re thinking of can handle a different amount of twisting force.
Head geometry. Beyond the type of driver, screws have different shapes. Pan head, flat head (countersunk), socket head, hex head, oval head.
Appearance – sometimes the designer just wants a certain look. If many screws would technically do the job, they could choose the one that is most esthetically pleasing.
There are also cases where obscure screw head shapes are used to deter people from opening it. There is speculation that Apple uses specialized screws to make it harder for non-Apple technicians to service Apple products, so that Apple can directly earn more money from repairing Apple products.
Well some people may disagree, but many believe the universal “best screw“ is the Robertson head. It is a square hole that requires a square bit on a screwdriver or a screw gun. It usually does not strip like a slotted head or a Phillips head. It is very commonly used in Canada and is very successful there. Arguably, the Torx head was designed to strip less than the Phillips head and it works really well at that. Also, the Torx head can be manufactured with a piece of metal in the middle that makes it very difficult to unscrew it in a public space without a special tool. While this is all true, one thing that prevents just one screw type from becoming the “best”is that in different places there are different traditions of screw types. This results in workers in a particular area already having bought tools that work with that particular screw. Many people don’t want to change what they are used to. Although the use of bits in electric screwguns has made this transition a lot easier because you can buy a package of different shaped screw tips for different screws. It is easy to change the bits for the different screws.
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