Certain things like bikes, cars, and furniture use hexagonal bolts for fastening. Hex bolts can only be used with the right diameter key and they don’t slip like Phillips and Flatheads. Also, the hexagonal tip keeps bolts from falling so you don’t need a magnet to hold your fasteners. Furthermore, it’s easy to identify which Allen key you need for each fastener, and you can use ballpoint hex keys if you need to work at an angle.
Since the hex bolt design is so practical, why don’t we use this type of fastener for everything? Why don’t we see hex wood screws and hex drywall screws ?
Edit : I’m asking about fasteners in general (like screws, bolts, etc)
In: Engineering
I always figured that it was planned. It’s hard to to over tighten flat head screws. A bit easier for Phillips and far easier for torx and hex. I always figured the manufacturers knew how much torque to apply to get it to sit correct but not strip the threads and specd what to use.
Philips head screws were designed to be fastened by automatic machinery on production lines. The machine can push the driver head into the screw and it will find the proper alignment and turn without slipping out.
When I used to work on F-16s, we used all types of fasteners. For doors that were frequently opened, it was 9/64 hex drive. They absolutely do get stripped, and we’d have to frequently get them drilled out. Part of our problem were lazy people that, instead of replacing one that was starting to round out, they’d angle the bit to tighten it, and it was the next guys’ problem. The ball-end bits made them strip quicker (there’s a pun in there somewhere, I’m sure).
Hence why NASA adheres to this logic and solely use hex bolts on every element of spacecrafts
You question is actually kind of interesting. The answer lies in torsion and the strength of the head or grooves used to turn the screw. Basically, engineers want you to have a simple enough head to turn, but won’t be damaged in application by the torsion you might *reasonably* apply to the screw. So a slotted screw is ideal for simplicity’s sake, but a Philip’s or “Cross” adds more torsion, and so on, moving the points of contact from the inside of the screw head to the outside.
I personally like ECX bits. They’re a combination of Roberts and flat head. So you get the none slip out of Phillips/Roberts but the higher torque of a flat head.
https://toolguyd.com/milwaukee-ecx-screwdriver-bits/
They are much more expensive as the equipment to produce them needs to be much more complicated and precise. You can make a slotted screw with a hand drill, file and metal saw. Good luck making a hex or torx screw.
They are also not as good as torx and strip easier. And they are newer than ph and pz, so less equipment in general.
Im contributing here because i don’t like the existing answers, not because i think i’m 100% right.
There’s a lot of history as to why we use one fastener vs another. why do we have 50 different types? There’s hex, torx, Phillips, flat, Robertson (the square one), Posidriv, JIS (Japanese Industrial Standard), and even weird stuff like tri-wing, and security variations of each of these. The reason for each of these, other than trying to make it difficult of the users, is that they do all fit very niche roles and have benefits over the others. If you’re interested, look up the history of screwdrivers. but it comes down to how the screw is intended to be used and when it was invented, with each new one coming in trying to set a new standard for all others. They’re interested in factors like:
Ease of production:
Flat is a clear winner here which is why it was one of the first invented (1744). someone manufacturing simple screws with purpose needed to make many of them. Carving a simple slit in the heads of each was the most economic way to achieve this.
Ease of torque application:
The next clear invention was the Phillips head (1935). basically 2 flat heads at right angles to each other, but quite a bit more complicated. This style provided specifications for depth, angle of sides, ease of production, and other things like cam-out which is the screwdrivers ability to slip out of the head. There are certain needs where given a particular downward force, you WANT the screwdriver to slip and no longer apply torque and “cam out” of the head of the screw to avoid over-tightening.
Posidriv/JIS/Robertson(my personal favorite) each evolved to fit a niche at the time they were invented and each had requirements for compatibility/cam-out/torque ability/consistency that the others didn’t quite meet.
As a personal aside, FUCK posidriv. these are the ones that look like phillips, except you can’t help but tear them out with a phillips head. Ideally, they allow for less cam-out for higher torque with similar manufacturing difficulty, but as someone maintining things, fuck these things.
I’m not going to into the rest because i don’t want to finish the research, but the point is that there’s more than just twisting the screw head. For a long time manufacturing en masse a hexagonal hole was just expensive and impractical when other options were almost as good. Various standards were created because they solved problems in the industry they were trying to solve them within. And as technology improved making various types more frequent vs another, there’s still the issue of all OLD stuff that needs to be maintained and replaced and/or updated. Old flat screw heads are incredibly cheap to produce now, and if a more expensive variant (such as hex) is impractal at the quantities needed. why not just produce a bunch of flat head?
The Robertson head is the best overall screw head.
NOT that awful American square head with the lack of taper and crappy fit.
The tapered square hole Robertson has excellent contact area between driver and screw, lots of forgiveness with size tolerance for both the driver and fastener as long as you get the taper correct, and only 5 sizes of driver to go from very large to very small fasteners. In practice, only three sizes (Red, Green and occasionally Yellow) cover just about every likely scenario. Screws rarely strip, because the tool force on the screw is well distributed over the screw’s entire hole.
The screw is securely held by the driver in almost any orientation, and if the driver is slightly magnetic, those screws never fall off.
But back in the day, the inventor was just a bit too greedy, so US manufacturers introduced a square drive *without* that critical taper (to avoid patent issues) resulting in a shitty combination that results in stripped screwheads and pissed off users. The square drive completely spoiled the market for the much better Robertson.
In Canada, the construction and electrical industry is quite dominated by Robertson applications, but it never caught on in the states.
Every time I have to drive a Phillips or slot screw, I fervently wish that the damn thing was a Robertson.
clearances are way better for alan or torx bolts, fitting a long skinny alan in a space, internally into a bolt requires way less room than a hex bolt where a socket needs to fit around it
Latest Answers