Model Boat Mayhem
Mess Deck: General Section => Chit-Chat => Topic started by: supersonic on October 28, 2007, 09:57:05 pm
-
OK ENGINEERS !,Big discussion tonight at the pub, regarding bolts and screws and the difference between the two
I maintain that a scew can only be tightened by its head.
A bolt cannot be tightened by its head. ( eg. coach bolt )
A coach screw can be tightened by its head
A bolt requires a nut to be tightened
A hexegon head screw tightened with a nut therefore becomes a bolt !
Engineers only reply !
sorry for this post but this has got my back up
Come on lads lets get it sorted.
Dave.
-
Ha ha ha,,, Funny this one... Forgotten the full problem but the landlord did say nthat a screw has a point and a bolt dont.... But then the landlord has never had a point...lol
So if a screw has a point why does a a coach bolt have a point also why does supersonic post this on a thread....lol.... Beat ya to it dad......
Come on I see a big debate coming on here and a fun one..... ;D
-
What do do landlords know about engineering ?
This post was specifically for ENGINEERS !
Dave.
-
Only my opinion, but a screw has a cutting thread, whereas a bolt has a dull edge on its thread ready for the NUT. :)
Cheers...Ken
-
I was taught that a bolt has an unthreaded portion of shaft, the thread of a screw runs right up to underneath the head
-
Hi gys.....i was always told that anything with a slot for tightening up or undoing (cross or straight ) was a screw a bolt had either a square or hexagonal head to be tightened with a spanner or socket.......but i have to admit that i was never exactly certain
regards..bob..
-
:) Humm this is going to be a LONG THREAD.....lmao
-
Differences between the two -
A bolt is a bolt, a screw is a screw - simple.
The differences are largely empirical in my mind.....
If it is above about M6, then by and large it is a bolt.
If it has a hex head then it is a bolt
If is is slotted, pozi or torx it is a screw.
Wom
-
Sorry Wombat -------- Totally wrong,
A coach bolt cannot be tightened by the head but a coach screw can, whatever the size ! :)
-
Generally, if it has a hexagon head it is a bolt, no matter what size it is. Screws are available in a variety of head configurations, i.e. countersunk head, round head etc. and with a range of slots, i.e. straight slot, pozi-drive, hexagon slot (the Allen screw)etc. That's the accepted convention. The exceptions are coach bolts which have plain low domed heads and coach screws which can either have a hexagon head or a square head!
-
Sorry Wombat -------- Totally wrong,
A coach bolt cannot be tightened by the head but a coach screw can, whatever the size ! :)
Actually not totally wrong - merely an incomplete list. The information that is there, I challenge you to find fault with it, if you cannot then it is not wrong. Unless there is nothing correct in it then it cannot be totally wrong.
Part of the problem here is that you are crossing disciplines - Coach-screws/coach bolts are for woodworking, where the difference is that the screw cuts its own thread while the bolt is passed through a clearence hole and retained with a nut. But by this definition a machine screw is not a screw but a bolt, unless of course it is a tap-tite - but by popular usage it is a screw.
Wikipedia offers this definition of the difference between bolts and screws, which I think is what you are hinting at:
A bolt passes through a hole of larger diameter than its thread, and is held in place by a nut or similar device; it is not designed to be turned. What is often referred to as a bolt is in fact a cap screw, which is designed to be turned (or screwed). Cap screws may, or may not be used with nuts. The distinction is subtle, but significant in the design of the fastener. If threaded all the way to the back of the head a cap screw becomes a machine screw. (http://A bolt passes through a hole of larger diameter than its thread, and is held in place by a nut or similar device; it is not designed to be turned. What is often referred to as a bolt is in fact a cap screw, which is designed to be turned (or screwed). Cap screws may, or may not be used with nuts. The distinction is subtle, but significant in the design of the fastener. If threaded all the way to the back of the head a cap screw becomes a machine screw.)
This, though, is a flawed definition because there are cases where the definition of what is a bolt or a screw depends on how it is used - by this definition, if I pass an item through a clearance hole and lock with a nut then it is a bolt, but if I fasten the identical object into a threaded hole it is a screw.
I suspect any rigorous attempt at a definition will end up in problems.
-
I always thought that a bolt was what you did if you inadvertently put a screw in the wrong socket. But then I'm not an engineer.....
-
I am reminded of the newspaper report that appeared after a lunatic broke into the asylum laundry, raped several of the workers and then escaped. The headlines read..... (wait for it!)....
NUT SCREWS WASHERS AND BOLTS
Rick
PS I have to agree with the earlier definition - I was taught that bolts have an unthreaded portion of shank, machine screws are threaded up to the head.
-
From a site where the author is bitching about sloppy definitions from "credible" authorities
Having "credible" sources such as Machinery's Handbook, ASME, ISO, and military specification sheets misusing and arbitrarily misdefining the words throws the whole world off.
They give the definition of a bolt as:
Bolts are defined as headed fasteners having external threads that meet an exacting, uniform bolt thread specification (such as M, MJ, UN, UNR, and UNJ) such that they can accept a nontapered nut. Screws are defined as headed, externally-threaded fasteners that do not meet the above definition of bolts.
So by their definition a bolt is a bolt if it is made to a bolt standard otherwise it is a screw.
http://euler9.tripod.com/bolt-database/boltdef.html (http://euler9.tripod.com/bolt-database/boltdef.html)
By and large it seems to me that the distinction between a bolt and a screw is largely arbitrary - we can agree at the extremes - we konw what a bolt is and we know what a screw is, but where you transition from it being a bolt to it being a screw is largely a matter of common usage. For instance Rick comments
PS I have to agree with the earlier definition - I was taught that bolts have an unthreaded portion of shank, machine screws are threaded up to the head.
I thought these were "shanked bolts"
-
If you go into a reputable engineering supplier and ask for a low tensile, hex head (or any other shaped standard head), 1/4" BSF, 3" long screw, you will be supplied with a screw that is threaded to just underneath the head, if on the otherhand you ask for a bolt, you will be given a bolt that has a plain portion under the head with a standard length of thread on the bottom end (varies with diameter and type) but on this size would be about 1" long.
John
-
Machine screws usually have a minimum thread length according to the relevant standard. This can be dependant on nominal thread diameter or length of screw (shank). For instance metric machine screws up to M1.4 and screws of larger diameters that are too short for the specified minimum thread lengths, are threaded as far as possible up to the head. All other machine screws are normally supplied with shanks that have an unthreaded portion.
-
Engineering Bolts do not have their thread all the way to the top but have a plain shank (I can not remember thr formula to work it out)
Engineering Set Screws have the thread all the way to the top
I deliberately did not say what the top would be as you can get both hex head and allen head bolts the same with set screws. You can also get specialised bolts and set screws that have a slot or crosspoint.
Coach bolts and coach screws follow the same rules as above, with the exception of slots and cross point heads. I have never understood why a wood screw is called that when it can have a plain shank or threads all the way to the top ???
Brian
-
Left to itself, this one will run for ever!
When Whitworth sat down in the 1840s and devised a standard for "threaded fasteners", his main aim was to make the things interchangeable, so that Joe the village blacksmith could go down to his B&Q (or whatever they had then) and buy some "threaded fasteners" which he knew would fit the Squire's traction engine when it came in for repairs. Whether he called them bolts or screws is immaterial and academic - he knew what he wanted and his only concern was that they would fit the job in hand.
Over the years other standards and designs have come along. Metric, ISO, Unified and many more. The hexagon head has been joined by slotted, cross-head, Allen and no end of others. Definitions have come and gone too, and common usage has blurred what was probably once an easily-described item of hardware. For instace, all bolts have screw threads. You screw a nut onto a bolt.
Whatever definition we now use for "threaded fasteners", someone will come up with an exception to prove it wrong. It makes for an entertaining discussion on the forum, but in the end we are just like Joe the blacksmith - we know what we need for the job, and as long as what we get fits, it really doesn't matter what its called.
Rick
-
Dear All,
Rick, I completely agree with what you say.
May I add something just for the benefit of others who possibly might not know - which will be very few I know. The purpose of the unthreaded shank on engineering bolts, is quite simply to ensure the smoothest and tightest fit between the metal being joined. Should the metal being 'joined' be under stress/vibration from any direction, wear to both thread/bolt and hole will result if the joins be in contact with the threaded part of the bolt - thus slackness in any assembly will likely result - and things can start moving with expensive consequences! The same applies to non-engineering bolts, as wood, plastic, etc. will obviously wear in the same way. Thus washers are used to raise the nut to the level of the thread above the level of the metal or wood being joined. Obviously, if any material being joined is threaded right through then obviously full contact results and there is no problem. Most of our modelling applications are more tolerant of course, but, with motors other than elec. it might be wise to conform with the status quo - I am only familiar with elec. myself, and have no knowledge of other modelling power sources. I know all this is very basic but it is intended only to be a very brief descrip. of possible interest to one or two who might not know.
This is also not intended to start a long conv. on bolt usage/application! - I don't want the blame for instigating same under this Topic! :)
Regards, Bernard
-
Actually, I'm finding it quite interesting. Some good explanations on a subject that a lot of us have probably never really thought about. Whitworth did a good job considering just how much his system is still used today.
-
Hi all, I think I already gave my definition in another thread and I agree with the previous simple definition. Screws have the thread along the whole length, bolts are threaded for only a proportion of the length. Graham, C Eng O0
-
You're a technological Luddite Colin, NO such thing as Whitworth anymore, everybody in the world (except the
descendants of the Pilgrim fathers on t'other side of pond ) changed to Proper sizes in late 60's. We got them
out of the excreta in the 40's but they still dumped on us in the 60's .
Machine screws change sex to become Bolts beyond a length to diameter ratio, someone with access to relevant
BRITISH STANDARD (Oh buns) ISO STANDARD should be able to elucidate. (WOOOOOOO)
-
You're a technological Luddite Colin
You're dead right there! Kako motors and Mighty Midgets for me every time! O0
I think what I meant to say is that there is still a lot of stuff in use which uses Whitworth. The owner's association of my 1:1 scale boat reckon that the keel bolts have Whitworth threads. They probably hold Blackpool Tower and Hungerford Bridge together too - maybe?
-
Ok, put simply:
If a nut fits on --> it's a bolt.
-
Oh Oh - I feel a ship versus boat tide rising here :o
-
THANKS FIREBOAT O0,
NOW ISNT THAT WHAT I SAID 24 POSTS AGO ;D
REGARDS DAVE
-
::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::)
Here we go... some rumpy old git with a shed is going to take this back to the pub now....
Its still not sorted tho. There are a few posts out there which I personaly think are true...
I think somewhere down this Thread we lost a bolt...... Its still open for discussion.... Cant spell..... Never could... What you say pops....lol O0
-
Fireboat, coachbolts don't have nuts!!! :D
-
I definitely bought a BOLT for my back gate which I fixed on with screws and nerry a nut in sight - which given that this is a family forum - is a good job!
Bolt - A bolt is the term used for a threaded fastener, with a head, designed to be used in conjunction with a nut.
Screw - A headed threaded fastener that is designed to be used in conjunction with a pre formed internal thread or alternatively forming its own thread. Historically, it was a threaded fastener with the thread running up to the head of the fastener that has no plain shank. However this definition has largely been superseded to avoid confusion over the difference between a bolt and a screw.
Straight from
http://www.boltscience.com/pages/glossary.htm#s (http://www.boltscience.com/pages/glossary.htm#s)
Until I looked it up, I'd have sworn that a screw was threaded all the way up! Where's my Luddite membership card :o {-)
Danny
-
An when i called SWMBO a rude word I defiantly made a bolt for the door!
-
Fireboat a nut will fit on a Engineering Set Screw, but it is not a bolt
Brian
-
Chingdevil, when you put a nut on an engineering set screw, an amazing thing happens !
Its SEX changes and turns instantly into a BOLT
Dave. :D
-
Afraid not it is still a set screw with a nut on it ::) ::)
Brian
-
NO, NO ,NO -- It only thinks its a screw, but by having sex with the nut,
it really is a ---- Bolt,
screwey isnt it ?
Dave.
-
I am afraid to ask this but what does a bolt become when you put a nut on it, other than tight ??? ??? ???
Brian
-
Brian , exactly, You have to put a nut on it to make it become tight, which is what started this off
GOOD EH ? {-) {-)
Dave.
-
For goodness sake! Please take a look at the attached picture, it shows a small sample of Allen (Socket Head Cap) Screws that my organisation currently uses on its products. Note that in each case the thread does not go up to the head. So much for one of the definitions previously used.
-
Hi
Meridian, Thanks for your pic, the shank is designed to stop any lateral movement between the two parts
that you are fastening together. If the shank was threaded to the top of the screw it would allow more tolerance
for the two parts to move. By having a push fit shank it removes the possibility of movement
O0
Dave.
-
The other thing that causes me real confusion (and I sell them) is carriage/coach bolts/screws. Generally, a coach bolt is taken to be a cup square bolt with a thread for a nut, whereas a carriage screw has a hex head and wood thread.
You don't have to look very far, however, to realize that the terms are actually completely confused, even by the people who make them.
And, if you are not very careful, we'll be into etymology and origins in Old French and Latin.
-
Hi Supersonic.
Yes, I know the purpose of an unthreaded portion of shank, but the point I was trying to make was that by definition, a screw does not necessarily have to have a thread that extends up to the head, as suggested by some people.
Cheers,
Andrew
-
CORRECT! O0 O0 O0 O0 O0
Supersonics Son has gone quiet, must be too much for him, or , it could be long words .
Dave {-)
-
It is a rather strange language we speak isn't it, we SCREW bolts into things just the same way we screw woodscrews into things. If we use bolts, the thing is said to be BOLTED together and if using screws, is Screwed together. If we tend to use small 'bolts' for model engineering, we tend to call them screws but when the item is assembled, it is said to be BOLTED together.
The general trend with our language seems to imply anything with a woodscrew type thread is definately a screw. Anything with a machined thread is called a bolt.. unless it has a screwdriver slot in the top, in which case it becomes a screw!
I know this is not gospel and I don't speak as an expert by any means but this seems to be the general speak amongst most people when they request fastenerswith which to put things together.
As an aside, it is my guess that the first rotatable fastner would have been the screw and when a question was recently put about which invention has been the most significant in mankinds history, I dont remember anyone mentioning the humble screw (bolt). Without it, none of the engineering miracles would have been created and the whole world would have fallen apart.
Just my tuppence worth.
Chris
-
Hi Sheerline,Well said,shall we post about "rotatable fasteners" ?
Dave.
-
Have a look at this site
http://www.boltdepot.com/fastener-information/type-chart.aspx
You are right meridian they are called screws, but using the definition of engineering fixings bolts do not have the thread all the way to the top while screws do. As an aprentice I got many a telling off for going to the stores for a bolt and coming back with a screw
Brian
-
Nobody has properly explained the set screw yet - it seems to be a bolt on which the thread runs up to the head. And the clockmakers seem to have done very well without screws, using pins and wedges to hold quite complex mechanisms together. And hoorah for Whitworth and the Lord Chancellor.
-
It's the letters what gives it away, stoopids!
B is for bolts what is Big; S is for screws what is Small.
What is you like? Din't you guys learn nuffink at school?
FLJ (B.Tech; M.Inst.Prod.Eng; M.Inst.Mech.Eng; C.Eng; ................failed da lot but I is still fightin', innit?) O0
-
There is another range of fasteners not listed in the engineering books, these are known by a number of different names but relate to the same thing, for example: Bluddy screws, f--k--g screws, sodding bolts and the general term used for all unyielding fasteners....'the bast-d'!! >:( These latter types have been around since the first ever fastener was installed and found reluctant to release. It was at this point in history that the cold chisel and hammer were invented, closely followed by the cutting torch.
It also began to dawn on young apprentices that there was indeed a god out there of whom they had no knowledge and indeed their mothers and schoolteachers had omitted from their education. ::) Only engineers and technicians knew of this greater being.... his name was f--k! They were always thankful to him when at the end of a massive struggle, the battered, bent and red hot smoking remains of a bolt was extricated from its hole because they always thanked him and lit a cigarette in his honour.. O0
I know the above to be true because I have witnessed it and practiced it all my life.
I have received the best of education, the school I went to was truly excellent.... I know this cos my Mum said it was approved!! {-)
-
And why is it that when removing a number of screws, it's always the last one that refuses to budge?
-
Thats the one that was born a B-st-d! ;)
-
Sods law applies to the removal of the last bolt. Can anyone define sods law? :-\ Graham
-
And why is it that when removing a number of screws, it's always the last one that refuses to budge?
The Law according to Mr S*d, or "Left-Hand Fred" as he's known to his engineering friends, states a number of things. My favourite is "It is not possible to overestimate the stupidity of even the average apprentice". You can substitute anyone you like for "apprentice"!
FLJ
-
Sods law simply : 'If it can, it will'
I know this to be true, I rebuilt an Austin Sheerline and the designer worshipped at the temple of SOD!
-
Have a look at the following!
http://foldoc.org/?Murphy's+Law
-
I am sorry about this shocking pun but going on the original subject matter being discussed here, 'we may have screwed the thread up' as we have wandered off a bit. Possibly my fault, sorry chaps. ::)
-
Not to worry Sheerline it lightened things up a bit as I think I detected a few 'cross threads' in there somewhere. ;D Graham
-
Ah Ha crossed thread eh does this mean a screw has been used into a hole where a bolt should go or even vice versa O0
Stavros
-
I think the diversion was probably my fault, I just couldn't resist it! Apologies. :embarrassed:
-
Ther are a few 'nutters' on here I think. Several of them should make a' bolt' for the door before others become 'bored'
AAh, the old ones are the best eh!
-
Stop stealing lines Sheerline (reply 29) and FLJ don't critisize us lfet huders ( Oh regg3b)
-
Well, I only use ummms when I work with either, alltogether now, Bu**er-um thats good enough....
-
It must be my age Circlip, I'm 58 so you have to make allowancies for my advanced state of senility! :P
-
Nobut a lad
-
Speakin' of left-and freds, what about wire wheel spinners? Woe betide the bod who forgot "left-and fred on the right of the car and t'other way about", and mixed up the front hubs.
First inkling that something was wrong was the spinner bouncing down the road. And you knew the wheel would be not far behind it!
-
F1 , ESTORIL , NIGEL MANSELL , Rear tire rejoined race track before he did.
-
And why is it that when removing a number of screws, it's always the last one that refuses to budge?
The Law according to Mr S*d, or "Left-Hand Fred" as he's known to his engineering friends, states a number of things. My favourite is "It is not possible to overestimate the stupidity of even the average apprentice". You can substitute anyone you like for "apprentice"!
FLJ
Well Mr FLJ, you've really upset me now. I'm keggie handed and I consider your remarks somewhat below the belt. My mum gave me a Christian name and it only became 'little sod' much later on life........................... >>:-( >>:-( >>:-(
-
Via email to mayhem ....
Dear [Mayhem],
My name is Jesse and I’m an Editor at Happy DIY Home (https://happydiyhome.com/).
I was doing research on screw head types and just finished reading your wonderful piece [here]
In that article, I noticed that you cited a solid resource that I’ve come across in the past: http://www.boltdepot.com/fastener-information/type-chart.aspx
We just published an updated, comprehensive guide on screw head types. It is completely free and you can find it here: https://happydiyhome.com/screw-head-types/ (https://happydiyhome.com/screw-head-types/)
If you like the piece we’d be humbled if you cite us in your article. Of course, we will also share your article with our 100k newsletter subscribers and followers across our social platforms.
Either way, keep up the great work!
Warmly,
Jesse
-
It is a pity that they don't include JIS.
I purchased a set of JIS screwdrivers after seeing them on a James May TV show & I am amazed how many things I have that need JIS drivers. The difference with Pozidrive is night & day when in use even if they look very similar. I got them right down to minute (sent from Japan) so I can now get into those tiny camera etc screws that previously looked imposible.
I must get some for my impact driver which will work well as they don't cam out.
If only I had known this when I butchered Japanese motorcycle screws all those years ago.
-
Phillips, JIS, and Pozidriv screwdrivers explained: https://bike.bikegremlin.com/10583/phillips-vs-jis-vs-pozidriv/