No mention of Mr Nettlefold and his wonderful patent?
1: These Are Screws Screws Yup. 2: These Are Not Nuts and bolts How can you tell? They have big nuts but no prick!!! LOL!!! 3: Screws Are Traditionally Driven Like This... A screwdriver driving a screw 4: ...Except In Birmingham!!! A hammer and bent screw Classic Brummie builder joke! Excellent!! 5: Did …
My father worked for GKN Automotive Fasteners so this article was catnip to me. I am pleased that Nettlefold's contribution is remembered beyond the association of his name with tose of Guest and Keen. My father's former employers, Steel Nut & Joseph Hampton sank with Woden tools at the end of the 60s.
I did not down vote you, but the person that did could have just advised you that this is a regular el reg feature. El reg recognises that the el reg commentards having to constantly deal with the worlds, political, technological and scientific problems, just need a break from time to time :-)
Why! when you put a screwdriver down right beside any computer or rack equipment. The bugger decides to move and you physically have to get up and look elsewhere for it!
Happened to me this morning, working on a laptop, put screwdriver to the right of the main body, and next thing I know it's moved itself behind the screen!
How do they do that?
It is not just when working on computers. Screw drivers are a vindictive lot with a sense of humour. They watch for the time when you have just spent 15 minutes lining up the most darned difficult set of bits and need to drive the screw to hold it from collapsing. Normally the driver is to be found in another room, or if assisted by a wife in the tool box in the tool store as it you "have finished with that thing".
The circuit board from which I am regularly - every few minutes - prying an IC using a small screwdriver is on my left. That's where the wires go; it has no choice.
When I remove the IC, I place the screwdriver next to the circuit board, on my left.
And yet here it is, snuggling up to the soldering iron on my right.
How does it do that?
aha, does yours 'tidy up' tools that originated in a tool bag/box into any nearby cupboard/receptacle, but
DOES NOT TELL YOU....
Then when you ask X days/weeks later if she has seen your [insert name of tool], you are either asked where you had it last, OR it is suggested that you improve your 'tidying up' skills.
Apparently it is logical.
Have a swifty on me,
It's because they don't exist.
From a production engineer's point of view a screwdriver, especially a flat blade one, must be a boring old thing to make. So they don't bother. They hire squadrons of mystical oriental gurus and swami types to 'put the fluence on' a lot of scrap material. They hypnotise old rags, torn trousers etc. into thinking they are screwdrivers.
(1) all modern screwdrivers bend rather than getting the lid off the paint pot.
(2) when the magic wears off they revert. So you leave a screwdriver on the bench and when you come back you can't find it, but there is a stained scrap of polka-dot fabric that bears no resemblence to any clothing you have ever written off.
I recently cleared out one of our sheds! I found screwdrivers from my youth, perhaps they actually went back to the screwdriver phase after becoming rags from a bag that had disintergrated.
Why is it that I can never find a screw of the correct size, when I know they were in a pot, specifically used for rogue laptop screws and I know there were loads in there!
Is there an unwritten rule that states 'you will always have left over screws' or do they multiply overnight if left unattended?
You'd expect a set screw to have a machined end to the thread and usually a blind head (i.e. a grub screw). It would also not be used with a nut. You could have said machine screw and I wouldn't have disagreed with you - the distinction that one particular style of head makes it a bolt rather than a screw always seemed very artificial to me.
You're all wrong. My extensive research in this area leads me to believe the screw is in a state of quantum flux.
The behaviour of screws and screwdrivers while superficially similar are actually different processes, the screw as has been frequently observed is driven by pure malice and will strive to hide itself in the most awkward place and if possible will cause pain when located and does employ quantum effects to relocate without passing through the intervening space.
Screwdrivers however employ dimensional gyroscopy where the turning action generates a force at right angles to the axis of rotation but as it is unable to rotate along either of the other 2 normal axes the force builds up until the screwdriver can not store any more energy and it moves at right angles to all the normal 3 dimensions which results in it jumping forward in time.
No can of worms, it's a set screw in the picture. I grew up reading two sets of literature: books on diseases of the eye thanks to my Mother's training as a nurse at Wolverhampton Eye Hospital and the sales material that my Dad, sales manager of GKN Automotive Fasteners, brought home with him. I memorised symptoms and torque tables. No wonder I wound up it IT.
A set screw holds something in position with friction against the point, without a hole - a set screw "sets" the position. The classic example is to fix a gear on an axle. A set screw will invariably have a finished point - on the "not a screw" picture it's clearly what is left after casting and thread cutting.
"A set screw will invariably have a finished point - on the "not a screw" picture it's clearly what is left after casting and thread cutting."
Used to work in the manufacture of these things.. Only handled a few million of them personally.
The ones pictured are absolutely definitely called "Set Screws". And Set Screws, quite variably, do not always have a finished point. Sometimes a finished point would actually be a very bad idea in these sorts of things, sometimes you want a larger active surface area.
And speaking from experience in automotive and engineering (electrical and mechanical) industries, sometimes the set screw acts on a mechanism, not directly on the item being "set" or held. Again, in many of these cases a point would be pointless.
</post 3hr sleep rant :) >
A very good article I thought. I hope this sort of thing gets a regular 'Slot' it would be a 'Pozi'-tive contribution to the knowledge of El Reg readership.
So much so that I showed it to a couple of Brummie colleagues Mr 'Philips' and Mr 'Robertson' who took exception to the hammer-thing and ended up being right 'Cross-Heads'. Both saying that this happens in 'Bristol' more often and the p*** shouldn't be taken out of a 'Clutch' of West-Midlander's. That's quite normal for Mr 'Philips' though 'cos he 'Torx' & 'Torx' and but we can usually calm him down 'One-Way' or another and you have to draw a 'Line' somewhere but then as he said he was just making a 'Tri-point'
Bored now, someone else can have a go I've got some work to nail.
I'm looking forward to part 2, which I hope will cover screw habitats. I've seen some that prefer metal, and some that make their home in wood, but I've heard that there are some rare breeds with other predilections. There's also one, I believe, where the head breaks off the male after mating.
that would be [in all likelihood], the 'jumbo' boxes of screws that one can mistakenly purchase in big DIY shoppes.
In my experience they are invariably crap, so crap that one has even broken the heads off with my leccy screwdriver.
Anyone seriously into screwing know that you need a Stanley 'Yankee' if you want to apply some serious torque, btw the one[s] to purchase are from second-hand/vintage tools shops, they are the mutts nuts.
You need a screwdriver with a hex shank, or (slightly less good) with a flat on the shank, or (much less good) with a hexagonal handle. You apply an adjustable spanner to the flat part, press the end of the handle hard onto the screw head with one hand and torque via the spanner with the other.
Unscrewing (or shearing the head off) is guaranteed.
You can also improvise with a hex screwdriver bit, a spanner, and a flat piece of metal with which to press down. With this arrangement you can rotate a screw with barely an inch of vertical clearance above its head, as I once had to do to get a swollen UPS out of a rack before it exploded. OK, that was technically a bolt.
I think electric drills with torque "control" meant Yankee screwdrivers fell out of favour. Stanley don't do them anymore. Still they did the job at the time, and had replaceable tips.
But for real torque that you can get your weight behind, put a screwbit into a "brace and bit" drill.
I checked. Our Photoshop operator is campaigningly left-handed, which is why he pushed his sinister agenda. We've tied his left arm behind his back for a month, so that should keep things rightly right-handed for a while.
As for the 0.02%, that's compiled from aggregating screw stats from 2.4 million websites. Feel free to provide an alternative figure, with exhaustive proof, naturally.
"I checked. Our Photoshop operator is campaigningly left-handed, which is why he pushed his sinister agenda. We've tied his left arm behind his back for a month, so that should keep things rightly right-handed for a while."
You should make him sit on his left hand. Errrr, no hang on, knowing Photoshop people that might force him to take him self in hand in an unwanted and inappropriate manner. Could you not perhaps break a few fingers on the said hand?
I was surprised, neigh shocked, that I noticed that those LH screws "looked wrong" before I even read what they were. Considering I'm one of those people who has to spend about 5 minutes working out which way is clockwise on an upside-down screw, I'm actually quite chuffed with this newly identified skill of mine.
> Not once you include right-side wheel lugs on old Chrysler products.
Lots of vehicles had those, not just Chrysler. I remember spending a couple of hours with increasingly large spanners trying to take the back wheel of an ambulance, with mate standing on one side of a bloody great big spider while I hauled up on the other side... nothing till in frustrate thumped the spider in the other direction and it span free.
Incidentally all cars with knock off wheels have spinners going in the opposite direction to wheel so the trundling effect tightens then rather than coursing the wheel to drop in the first 50feet.
Though I was disappointed there was no explanation about why a dropped screw *always* finds its way either into the deepest, darkest crevice or is attracted by the universe's strongest force which ensures it ends up electrically shorting the two most sensitive (and expensive) exposed current-carrying pieces of metal in the room?
The strongest is that which binds quarks together into hadrons. It has the well-nigh pathological property of increasing with distance, which is why quarks are only ever found in pairs and triples (and theoretically, in one-point-something solar-mass chunks denser than neutronium but still not quite big enough to collapse into a black hole).
Judging by the picture you have an odd idea of popular.
Perhaps that explains some articles
I would have been happier with the wine press (or even olive oil press)
Icon: well you don't have a wine glass
Riddled with inaccuracies, as usual for The Register.
A "Brummie Screwdriver" is NOT a common-or-garden clawhammer, but rather the old-fashioned cast-iron Stillson's-type plumber's monkey-wrench, 15-18 inches long, traditionally painted red on the handle.
The hammering face is usually the back of the monkey-screw housing.
Also, picture number 2 *is* a screw, specifically a "Machine Screw".
The bolt, which the author seems to have confused this with, is easily distinguished by a smooth, threadless section near the head. You can *use* a machine screw as a bolt, but there are penalties for doing so without using a bushing as any proper engineer would know.
Wrote :- "You can *use* a machine screw as a bolt, but there are penalties for doing so without using a bushing as any proper engineer would know."
An equivalent thing is modern wood screws which are threaded up to the head as opposed to traditional ones the upper half of which are plain. So the modern ones don't have the positive shear location that the traditional ones do - instead of having a tapered pin drawn into it, the upper piece is held only by the tips of the thread, assuming it has a pilot hole.
But apparently Joe Public likes the modern type because more thread looks stronger; he is also more likely to get away with drilling no pilot holes, especially as modern timber is crap (or isn't even proper timber), never mind that the two workpieces can end up being held slightly apart because both get a thread cut in them, but out of phase with each other.
No, Joe Public likes them because they are self-piloting and self-recessing when used for their intended purpose: hanging drywall aka sheetrock or, in the case of the galvanized or resin coated version, building a deck or fixing a fence. The thin shank is designed for displacing the minimum of the material being fastened in place so you *don't* need to drill a pilot hole.
Before you wade in, you are exchanging words with someone who drove about two hundred of the resin-coated type last Saturday in a marathon fence-repairing the likes of which hasn't been seen since the last marathon fence repairing at Chateau Stevie (gale force winds, carpenter ants - who against all reason are actually not real carpenters at all but bloody vandals that gnaw holes in wood instead of getting a proper house - termites and rot. I have some of each in The Fence of Go Away Neighbours).
Ordinary woodscrews, which absolutely require a pilot hole to sink, will shear as you drive them under these conditions, especially is using an electric drill-driver.
These are known as three pointed or tri-wing, but to answer your question; they are used on any piece of equipment that is in front of you when you don't have a tri-wing screwdriver.
I have just spent the whole day screwing in 31 degrees of sun, putting a fence up.
Thank god for my 12v cordless and a 2 litre flask of slowly melting crushed ice.
I have noticed here in Spain that if you have to take the hinges off a door, they are invariably fitted with old slotted wood screws that have such a fine slot that no existing screwdriver can remove them, not even an old Spanish one.
Which brings me to what the article calls a Brummy screwdriver. In my day we always called a hammer an Irish screwdriver and believe me I have seen Paddies on site driving screws in with a well placed whack from a claw/club/ballpein/sledge hammer, something Spanish chippies must have been good with.
A cold beer 'cos that's what I need tonight!
Not a huge exaggeration ... maybe not exaggerated at all.
Typically ten lengths in five guages. Times two (imperial, metric). Times four commonly available patterns (slot, philips, pozi, at least one of many others). Times two head styles (countersunk, raised). Times three common materials (mild steel, brass, zinc-plated).
That's 2400 permutations. I'm sure some of the permutations are unobtainable, but I've also left out a lot of variants (stainless steel, green organic, black lacquer ... huge ones and minuscule ones .... tri-wing and many other obscure drive patterns ... single and double helix ... with or without a cutting or ripping flat on the sharp end ....) Then there are the many families of self-tappers for use on metal sheeting ....
I could cheat, by including all the evolutionary culls ... I've found occasional headless screws, slotless screws, threadless screws, banana-shaped screws, pointless screws, you name it, in boxes of usable ones. And of course there are what we might call Apple specials ... if you buy by the million, they'll make them the exact length and guage you specify, slightly lighter and slightly cheaper than a million standard-size ones.
BTW did you see the size of the woodscrews that they were assembling Canary Wharf Crossrail station with, on the TV last night? Something like 60cm by 40mm. (is that 24x80 guage in imperial? )
You may jest, however back in the 80's when I started at a well known luxury car manufacturer in Coventry, I was issued with a 10mm socket, a 3/8" brace and a hammer. If it didn't fit, hammer it home.
Few years later on I was fitting fuel tanks in the wheel arches of said luxury vehicle, however on the left side I had to belt the crap out of a seam to make the tank fit. reason? the Mk3's body was 5mm shorter on the nearside than the offside!!
Ah English manufacturing at its finest! We found a similar issue when replacing the rotted out fenders on an MGB. The new manufactured replacement panel was fully 3/4" longer than the one that came off. When queried, the manufacturer said this was normal to allow for variations in the originals and we should just cut it down to fit. Our gap was "a bit bigger than usual but by no means extreme".
I heard a lovely story about those fender mounted fuel tanks from a bloke who ran a car radio and electrics workshop back when carphones were the in thing for smart executives. A bloke brings in one of these anonymous Coventry build luxury cars to have one fitted. The installer has never done one in these before so he looks around for a good spot to mount the box-o-tricks. On the wheelarch behind the back seat looks like a good spot. Cue drilling followed by wondering why he can smell petrol...
My summer job (1970s) was making the stuffing for the seats on those vehicles. Although notionally the material used was flameproof cotton, the actual stuff used contained a high proportion of what fell on the factory floor. So a good quantity of broken wooden pallet plus the unusual "gifts" that were put into cotton bales in Hong Kong and other warehouses around the world. I saw such things as the South China Morning Post, gloves, chopsticks and even a full meal in takeaway containers going down the conveyer belts to be packed for sending to the seat manufacturer. British industry at its finest.
Picture this, a spacious newly built double garage with a superbly smooth screeded floor. There are two steps up into the house and the garage is totally empty. In theory any item dropped would be easily found in seconds. But wait, there is one brick missing where some pipes go under the house.
From the top of the step ladder I watch as the screw I drop hits the bottom step, goes horizontal and vanishes forever through the only possible exit.
I think that light fitting still only has one screw holding it up :(
I do computer repairs and servicing, and my business partner and I visit customers' premises a lot. Screwdrivers are consumables to us, like toner, ink, pens, whatever. No matter how many we buy, I never have one in my van when I need one, or the workshop. They just seem to go missing. So every time we order a Draytek router for a customer, we order a half dozen of their promotional screwdrivers. They come with two flat blade sizes and two pozis and they're only a quid each.
Perhaps they're related to biroid life forms....
we had to ship some products to military stores wrapped up in waterproof covers and sealed in wooden crates which were built to an unnecessarily high specification.
By way of venting our frustration in complying with the crating requirements we used square-socketed Robertson screws (Picture 9, centre top row) that frustrated the hell out of the recipients.
Moral of the story: Specify EVERYTHING!
Look it is easy. Screws are used with screwdrivers, bolts with wrenches.
No more arguing.
Me? I keep a nice adjustment screwdriver (with a magnet on its antipode) at the ready in my shirt pocket (it has a nice clip). Of course it is in reality a "multi-tool" used for all sorts of things (broaching shipping tape is but one).
Oh, there are a lot more confusing differences waiting in the spanner drawer of the toolbox for the unwary ex-pat doing the in-driveway-engineering thing than that obvious and well-known one.
Upside: awesome tools that often would be banned in the EU, like gasoline-powered chainsaws mounted on 10-foot poles and portable hydraulic pincers only the fire brigade is allowed to have elsewhere.
Land of the Red Man. Land of the Free. Land of Husqvarna and Tecumseh. Praise the lord and pass the two-stroke oil.
As an ex-pat Brit living in Canada, it seems to me that everything mechanical here has to have a 2-stroke attached for extra noise. Other than the obvious that the country is big and there isn't often somewhere to plug anything electrical in, it seems to me that there is an addiction to noise here that is built into the psyche of the place, perhaps a US influence.
Oh and what is it about Harley Davidson bikes anyway? Why do some people feel that sitting on a mechanical fart machine is cool?
Harley-Davidsons are so heavy that they don't get blown off the road by semis. US driving is war by other means, hence the constant vehicular size arms race.
The Harley is the only bike I have ever encountered where it is necessary to replace the factory pushrods with uprated ones just to get the thing to rev a bit, because the factory ones bend at medium speed (no risk of getting to high speed). But the average Harley in the US never goes over 55, because at that point everything starts to vibrate loose.
skelband, may I recommend you seriously consider purchasing a large (7500 KW peak load or better) "worksite" generator and mount it in the flatbed of your King Cab pickup truck (having family in Alberta I know that all Real Canadians have a King Cab truck)?
That way if you need to use a namby-pamby electric tool you can fire up the earsplitting generator and experience the thrill of go-anywhere electricity AND the proper amount of decibels for the job at hand.
My generator sounds like a badly maintained ice-cream truck has parked in my garden, and during the aftermath of hurricanes and other weather annoyances gives me the double joy of internet and lights AND neighbor annoyance in one earsplitting package.
Can El Reg please expose the spanners please?
Last year i purchased a full set 5mm - 30mm Open & ring ended, now in the box are 5 left, and I haven't had the need to use any. (points accusingly at son)
Son swears blind he put them back in the box after use, so now i'm left with 5mm, 9mm, 27mm, 28mm & 30mm sizes that i have no idea what they might fit!
The rest appear to have de-materialised or turned into carpet mats for an Astra!
Wrenches and spanners .. another biroid life-form.
I once dropped one into the sump-shield of my car. Could see it but could not reach it with any tool. So I thought, get up to 10 mph or so and slam the brakes on, it'll shoot out by inertia ...
Which it did. Hit the road, bounced sideways, straight down the drain that materialized out of nowhere. Sigh.
The 10 mm one is still jammed on an inlet manifold bolt of his car. The 12 mm one is dangling from one of the battery terminals where it will eventually cause a short and arc-weld itself across the terminals. It will then be interesting to see whether the battery electrolyte will boil away *before* the battery explodes violently or whether the heat of this process sets the various plastic parts and rubber hoses on fire.
The rest of the "complete set" are scattered over the roadways of your home town as they were inadvertently left on various cross members and handy ledges in the engine compartment after the last job.
Kids. Love them, feed them, educate them, but never ever ever lend them your tools.
The rest appear to have de-materialised or turned into carpet mats for an Astra!
It's simple. They, like socks, are the larval form of wire coathangers. That's why houses like mine are full of wire coathangers even though I never brought them into the house and there were none there when I moved in, whereas my tools and socks go missing despite careful management of them.
Husqvarna is Swedish and a chainsaw on a stick has been an essential item in Southern part of Europe for years, used to trim palm trees!
To an old Brit like me any of https://www.google.es/search?q=pipe+wrench&client=firefox-a&hs=CxI&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&tbo=u&source=univ&sa=X&ei=v2nZU4mPMOHb0QX72YGwAg&ved=0CD4QsAQ&biw=1024&bih=442
the above would be a wrench but something with open fixed jaws at either end or a combination of jaw and ring or rings at each end wold be a spanner. An 'L' shaped hexagonal bar would be an Allen Key not a hexy wrench etc.
A monkey wrench is what you get when one of the so called Barbary Apes (really a type of Macaque monkey) on Gib steal your bloody camera and chuck it off the Rock!
It's more subtle than the time travel and teleporting that has been observed above.
They agree, well in advance of comming into contact, years some time, that as soon as they touch, one, or both, will slightly change dimension or angle of attack, so that the attempt of transferring torque by the user will be rendered useless. So no screwing takes place.
A self sacrificial part of the pact is that the screw agrees to shed just enough material so that each subsequent attempt of torque-transfer will be increasingly futile.
At the advent of mechanised screw drivers the rate of material shedding was upped to instant from the screw community. So the first attempt is also the last.
My maths textbook at school had a practice question in the statistics section. It involved machines producing screws and sampling for quality control. One of the questions was guaranteed to result in an entire class of 14 year olds dissolving into ROFLs for the rest of the period. "What is the chance of getting a good screw?"
I have still got the same red handled philips screwdriver I bought 26 years ago when I first hit the world as a Customer Service Representative, (technician/engineer was a dirty word).
It works exactly as it did back then, no upgrades, no reboots, no bugs. Nowadays its all green tabs and flimsy clips.
I'd be gutted if I lost it.
Any Canadian boy can tell you for just about any purpose, but especially if you're using some kind of power drill to drive screws home, the Robertson is the one and only choice.
I still can't imagine why the easily stripped and screwed up Phillips, or the "Whoops damn it slipped out of the slot" regular screw are so popular. Especially in the US of America.
Then again, a country that so solidly refuses to move into the modern age of screw technology would probably also refuse steadfastly to accept metric measurement....
On the question of the actual screwdrivers, I once worked for a guy who had a set of insane Swiss made screw drivers. Seventy-Five Dollars Each!
They NEVER slipped. Ever. And you could use them all day with no hand fatigue.
(Mine's the one with the red Robbie in the pocket!)
Wrote :- "I still can't imagine why the easily stripped and screwed up Phillips, or the "Whoops damn it slipped out of the slot" regular screw are so popular."
Never heard of Robertson. A square socket : looks like it's been around a long time in America but no-where else much. Looks a bit crude and similar in function to an Allen (hexagon).
I hope you are not lumping Pozidriv in with "Phillips". From Wikipedia :- "The chief disadvantage of Pozidriv screws is that they are visually quite similar to Phillips, thus many people are unaware of the difference" Pozidriv screw heads have as a visual marker of four radial ticks at 45deg to the main slots.
Pozidrivs are brilliant and Phillips are awful. Phillips screwdrivers are meant to slip out of the screw when "sufficient" torque is reached! They were invented specifically for automated assembly so that the driver would cam out and spin harmlessly when the screw was tight - but in the hand they can of course slip sideways after cam-out, and ruin the adjacent surface (or your other hand), especially as they require a great deal of end force to try to keep the driver in the screw. Even before the point of cam-out, Phillips screws and drivers are made to much lower tolerances than Pozidriv, often being quite sloppy, typified by their use in toys and cheap electronics of Far Eastern design. All leading to a poor and frustrating experience.
OTOH Pozidrivs will not cam out and are an excellent fit. Assembling stuff in awkward places, like up a ladder where I can use only one hand, I often carry a Pozidriv screw just fitted onto the end of the screwdriver; the driver will hold it that way in a horizontal position, and even downwards with a bit of magnetism or grease.
Never heard of Robertson? It's a 'square socket' done right, before the square made the scene; the Robertson has a Morse taper that allows the driver, holding the screw, to be held vertically, downward-pointing, and to be used one-handed (left or right, according to taste).
Barry, the reason why Phillips and slotted screws are so popular in the US is ultimately due to Robertson’s refusal to license his patented design to foreign manufacturers. (Phillips was willing to license his design to anyone, and eventually sold his patents to Ford. Slotted screws were unencumbered by IP issues.)
The US accepted metric measurement in 1866.
My Dad was a Brummie and he always called it a Yankie screwdriver. He owned a couple of Yankie screwdrivers (which I now have) but he always called those pump screwdrivers. One of our favourite pastimes was seeing how many No 8 S/Ts we could get spinning like tops on the bench. I don't think we ever counted them, but I guess we got around 30 going at once. When I show this trick to people they are amazed but most can't do it.
The way I was taught, the thread has nothing to do bolt verses nut. Something is a bolt if it is fitted by applying torque to the nut and a screw if torque is applied to the head. So the bolt in picture no.2 is a bolt in most applications, but it would be a screw if it was being screwed into a threaded hole.
Wrote :- "I was taught .. Something is a bolt if it is fitted by applying torque to the nut and a screw if torque is applied to the head."
It is true that with a nut and bolt the first option is just to do up the nut if possible, but often you need a spanner on both the nut and the bolt head - when your definition breaks down.
There is some truth in what you say, but in my experience it depends on context. In the store room, a screw is something threaded up to its head and a bolt is only threaded part-way. (Except wood screws). However, once the bolt/screw is in use your definition is partly right - anything with a nut on the other end tends to be called a bolt - if for no better reason than you just cannot tell how far it is threaded once fitted. Like on a ship (I have been a ship's engineer) you might tell a fitter to "take the bolts out of those pipe joint flanges", even if they turn out (though unlikely) to be what the storeman would call screws.
A fully threaded screw in a tapped hole tends to be called a machine screw, and a set screw is a machine screw in a tapped hole protruding beyond it so that its tip locates something, like engaging in a hole in a shaft (eg securing a wheel hub to the shaft). A set screw may of may not be a grub screw (ie a screw with no head, driven by a socket or slot in its body).
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