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Author Topic: So, why are there different types of screws?
Oualawouzou
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Heya there,

Well, we just got the baby's furnitures and spent most of the day yesterday wrestling with the proverbial unhelpful assembly instructions.

At one point, we got stuck with a particular type of screws who, for whatever reason, ended up requiring a specific Allen key to work. I can't help but wonder why the NFBSK we need different types of screws. It was 4 screws out of several dozens that did not require an Allen key to screw in. So why these 4?! Is there a logic reason behind this?

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Le champignon arrive.

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timbobmc
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Um.. to make it as difficult as possible?

I've wondered that myself just when the choice is between phillips and regular.

Good luck with the baby.

Do the heads of the allen screws lie flush with the surface or do they poke out?

I do know phillips screws were designed so it would be easier to use a power driver.

But I'm like you, why mix up a bunch of different type screws in one little piece of furniture? [Confused]

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Die Capacitrix
We Three Blings


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Better question. Why does the same type of screw have so many names. Allen key, Unbrako, or Inbus screw.

I am so ticked off right now. I though Inbus was some sort of special screw, and now I've found it it was just an Allen screw. [Mad]

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Niner
Deck the Malls


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And of course hex key, which I prefer since it's nice and descriptive.

As to why there's so much variety in sizes of hex keys, there are two things. One, someone thought it would be good to have metric and standard sizes, so you've always got that set that won't fit everything. Two, a lot of hex keys are "flush" style or otherwise embedded in something where they have to be smaller than the shaft of the bolt. Thus, you have sizes that correspond to every shaft size.

What really irks me is larger flat-head screws. I see no reason not to use the much more friendly Phillips head on anything but the tiniest of screws. Flat heads are so hard to center and keep in place, so even hand screwing doesn't work well. Philips is self centering, and because of it's depth, a partially stripped head can still be used.

And don't get me started on Torx or other "security by obscurity" heads.

Henry

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Wizard of Yendor
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quote:
Originally posted by Niner:
And don't get me started on Torx or other "security by obscurity" heads.

I thought Torx was supposed to have some actual advantages. But yeah the "security" screws are pretty silly. I bought I set of secruity bits just in case I ever need to tamper with soemthing they don't want me to. [Wink]
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Niner
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I believe Torx is actually designed to be a mix of the best of hex and phillips (the flat faces of a phillips with more faces like a hex, and design that's less prone to slipping). However, I tend to see them used in places as sort of a security measure based on the idea that you won't have the right screw to take it out - two examples are car seats and hard drive screws.

There is an actual "secure" Torx that has a pin in the bolt and a hole in the bit, but again it relies on the fact that it's rare (and I've heard it's easily defeatable by simply breaking the pin out).

Henry

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abbubmah
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Don't forget the Robertson bit. I have some, but have never had a Robertson-head fastener.

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Jay Temple
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Isn't it funny how often "screw" and "Robertson" come up in the same topic at snopes--and we're not even discussing religion!

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Jenn
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quote:
Originally posted by timbobmc:
Do the heads of the allen screws lie flush with the surface or do they poke out?

It depends on the design of the head and if you have a countersunk pre-drilled hole. Most of my furniture is from IKEA so nearly everything is put together with allen screws and bolts; some are flush and some aren't.

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Silas Sparkhammer
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As one of Jeff MacNelly's characters said in the comic strip "Shoe," "One of these days I'm gonna find that Phillips guy and wring his neck."

So...is he still alive?

(Oops; no, Henry F. Phillips died in 1958. Oh, well. I'll break a thumbnail in his memory.)

Silas

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Nion
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I've always wondered about all this security stuff.

I used to have a truck with a fairly-nice set of wheels on it, so I went out and bought a set of four "security" lugs for it. After I put them on, something occurred to me: How many "unique" designs could these things really have? I'd think a determined thief could just take a pic, go to the hardware store, find the same "style" lugs, buy them, and BOOM! I have no wheels.

Fortunately (unfortunately) I don't have that truck anymore, so it is a moot point. Still, I have to wonder how much protection they ever really offered.

Also, am I the only one that thinks that new Craftsmen bit-set is a thief's godsend? I mean, if it can easily remove stripped screws, couldn't it remove odd-shaped screws as well?

Relic "Screwed" Man

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snopes
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quote:
I can't help but wonder why the NFBSK we need different types of screws.
Because we have different types of holes.

- snopes

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Kabouter
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*shrug* I've removed "security" screws with a paperclip before, when I was a PC tech and noone knew where the bits went.

Kabouter
...insecure...

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Delta-V
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quote:
Originally posted by Ole Pappy:
Don't forget the Robertson bit. I have some, but have never had a Robertson-head fastener.

The screws on my deck are Robertson-head. That's the only place I've ever seen them used...exterior decking and fencing.

The reason for the different styles is cost and torque.

The slotted head screws are cheap and easy to make. But they're completely useless for powered screwdrivers and you can't put much torque on the screw without it either slipping out or stripping the head (and maring the surface of whatever you're screwing). [Mad]

Phillips screws are self-centering, making powered screwdrivers possible. They're somewhat more expensive to produce than slotted-head. They tend to 'cam-out' easily under torque, making it hard to apply much torque. I've heard they were designed that way to prevent overtightning. However, it's not good for exposed fasteners to look stripped.

Robertson-head and allen-head fasteners can handle more torque than phillips-head fasteners, but are more expensive. Because the bottom of the hole is flat (unlike the pointed end of the phillips), there's more contact area and so it's less likely to cam-out. The robertson-head is cheaper than the allen-head, but the allen-head has six points of contact rather than 4, making it less prone to rounding out the hole.

The Torx-head fasteners solve the problem of rounding/stripping by having the flat bottom of the robertson/allen that reduces cam-out, but it has much better contact with the driving bit to prevent stripping the head. The points of the 'star' on the driving bit engage the recesses on the screw at nearly right angles, so it has a very positive contact. Torx is becoming more and more popular because of that, particularly in assembly-line work.

Because they're less likely than a phillips to be damaged when tightening, the allen (internal hex) heads are often used for exposed ('decorative') fasteners on 'some assembly required' furniture. It's also very cheap to make the allen keys, so they usually include one with the fasteners. I suspect that those 4 fasteners are allen-head because they're more visible than the rest.

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Oualawouzou
Angels Wii Have Heard on High


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quote:
Originally posted by Delta-V:
I suspect that those 4 fasteners are allen-head because they're more visible than the rest.

That would have made sense, given the explanations you provided (many thanks, btw). However, these four screws are 100% invisible (as in, you won't see them unless you tear apart the furniture). And screws serving the same purpose on different pieces of furniture from the same set were just "regular" screws.

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Le champignon arrive.

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1958Fury
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Oh, you mean the tools. I thought it was going to be something about the Kama Sutra.

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Purple Iguana
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I imagine they're all supposed to have their purpose. The kind of screws that always baffled me were the ones I most often see in bathroom stalls. It's a flat-head TYPE of screw, except it looks funny... like it's made that you can screw it IN, but you can't UNscrew it. What's supposed to be the benefit of that??? Has anyone else seen these?

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Die Capacitrix
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quote:
Originally posted by Purple Iguana:
I imagine they're all supposed to have their purpose. The kind of screws that always baffled me were the ones I most often see in bathroom stalls. It's a flat-head TYPE of screw, except it looks funny... like it's made that you can screw it IN, but you can't UNscrew it. What's supposed to be the benefit of that??? Has anyone else seen these?

Anti-vandalism. There are standard removal tools for these so-called security screws, but they are more expensive.

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"Strength is the capacity to break a chocolate bar into four pieces with your bare hands - and then eat just one of the pieces." Judith Viorst

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abbubmah
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You should carry a book or magazine to keep your mind off the hardware. JMHO.

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DemonWolf
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quote:
Originally posted by Niner:
What really irks me is larger flat-head screws. I see no reason not to use the much more friendly Phillips head on anything but the tiniest of screws. Flat heads are so hard to center and keep in place, so even hand screwing doesn't work well. Philips is self centering, and because of it's depth, a partially stripped head can still be used.

I actually prefer flathead scews because if the come loose I can easily find an object to substitute for a screwdriver to fix it until I can do a better job later.

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Don Enrico
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quote:
Originally posted by Die Capacitrix:
I though Inbus was some sort of special screw, and now I've found it it was just an Allen screw. [Mad]

I, on the other hand, was wondering what an Allen screw might be, until I learned from your post that it is just a plain old Inbus screw. [Smile]

quote:
Originally posted by Niner:
(...) someone thought it would be good to have metric and standard sizes, (...)

But, but... metric is standard! [Razz] [Wink]

Don "screw imperial!" Enrico

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followsthewolf
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quote:
Originally posted by snopes:
quote:
I can't help but wonder why the NFBSK we need different types of screws.
Because we have different types of holes.

- snopes

And, of course, we need different tools to adequately screw those holes.

[fish]

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Shadowduck
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I've long suspected the reason designers have a seemingly pathological need to avoid using the same size / type of screw more than once in any given design can only be a deep and abiding hatred of maintenance engineers... This can also be seen in their tendency to position screws in such a way that removal of several unrelated subassemblies (usually with much skinning of knuckles) is necessary to get at them.

On an unrelated note, one of the best cases of nominative determinism I ever came across was an engineer I used to work with many years ago - Mr. Allen Key [lol]

Shadow 'why yes, I am a maintenance engineer - why do you ask?' Duck

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WildaBeast
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What I want to know is why does GM insist on using those "star" head screws? I had to go out and buy a new screwdriver just to replace a tail light.

And what's the actual name for that "star" scraws? I remember I learned it once, and that they're named after a person, but I can't remember the name.

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RangerDog
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Those are the Torx heads previously mentioned

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Purple Iguana
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quote:
Originally posted by Die Capacitrix:
quote:
Originally posted by Purple Iguana:
I imagine they're all supposed to have their purpose. The kind of screws that always baffled me were the ones I most often see in bathroom stalls. It's a flat-head TYPE of screw, except it looks funny... like it's made that you can screw it IN, but you can't UNscrew it. What's supposed to be the benefit of that??? Has anyone else seen these?

Anti-vandalism. There are standard removal tools for these so-called security screws, but they are more expensive.
Hmmm... s'pose that makes sense, but I can't imagine why anyone would want a door to a bathroom stall... but then I don't understand why people do half of the things they do anyway, so it rarely surprises me when things like this happen. [Smile]

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asnakeny
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Unsurprisingly, there's even a book about this topic:

One Good Turn by Witold Rybczynski. (It is subtitled, "A Natural History of the Screwdriver and the Screw."

It has a nifty chapter about why Phillip's screws have become so ubiquitous (and Robinson's much less so).

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FuzzDuckie
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Good grief....all the old screws and nails sitting in my father's garage are outdated now! (many of them are also from my GRANDFATHER when he used to do a lot of tinkering in his workshop...)

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ct
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quote:
Originally posted by Purple Iguana:
Hmmm... s'pose that makes sense, but I can't imagine why anyone would want a door to a bathroom stall... but then I don't understand why people do half of the things they do anyway, so it rarely surprises me when things like this happen. [Smile]

You'd be surprised. I saw a hobo tear out a bathroom stall with his bare hands once.
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nod
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The security screws in public lavatories (sorry, I'm English - a bathroom has a bath in it!) over here are to prevent people stealing the fixtures and fittings, especially the stainless steel splashbacks in gents.

As for all the other screw standards..

There are several different philips head sizes, each needing its own driver - the wrong driver will cam out. There are also Pozi-drive screws - very similar to philips but less prone to cam out.

Torx head bolts can (as their name suggests)transfer more torque without rounding or cam out than plain hex/allen bolts.

Some manufacturers use their own pattern heads for screws to stop unauthorised access to the heart of the appliance as well.

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GenYus
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quote:
Originally posted by RubberDuckie:
Good grief....all the old screws and nails sitting in my father's garage are outdated now! (many of them are also from my GRANDFATHER when he used to do a lot of tinkering in his workshop...)

Nails are outdated? Is there a new type of hammer that I'm not aware of?

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abbubmah
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quote:
Originally posted by RubberDuckie:
Good grief....all the old screws and nails sitting in my father's garage are outdated now! (many of them are also from my GRANDFATHER when he used to do a lot of tinkering in his workshop...)

You'd be surprised - I bet your grandfather screwed the same way everyone else does.

ole "living proof" pappy

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