View Full Version : Bolts & screws
shumway76
5th Sep 2011, 17:32
How would you differentiate between a bolt & a screw?
There is no universally accepted distinction between a screw and a bolt. The Machinery's Handbook describes the distinction as follows:
A bolt is an externally threaded fastener designed for insertion through holes in assembled parts, and is normally intended to be tightened or released by torquing a nut. A screw is an externally threaded fastener capable of being inserted into holes in assembled parts, of mating with a preformed internal thread or forming its own thread, and of being tightened or released by torquing the head. An externally threaded fastener which is prevented from being turned during assembly and which can be tightened or released only by torquing a nut is a bolt. (Example: round head bolts, track bolts, plow bolts.) An externally threaded fastener that has thread form which prohibits assembly with a nut having a straight thread of multiple pitch length is a screw. (Example: wood screws, tapping screws.)
dixi188
5th Sep 2011, 18:41
My understanding of aviation fasteners is a bolt has a plain shank between the threaded part and the head and a screw is threaded all the way.
The difference is that a bolt can take tensile and shear loads (on the plain shank) and a screw can only take tensile loads.
So bolts hold stressed parts together and screws only hold un-stressed parts together.
hope this helps.
I'll go with dixi. It's what we were taught many years ago.:ok:
easaman
7th Sep 2011, 13:39
Besides the above mentioned differences between bolts and screws, bolts are used where more strength is required. To tighten a bolt, you turn the nut, whereas on a screw you turn the screw head. Screws have more threaded portions than a bolt.
Some books say that screws are below 5 mm and bolts above 5mm in diameter.
Cheers easaman
You use a screwdriver on screws and a spanner on bolts - simples:-)
Kengineer-130
16th Sep 2011, 00:17
Agree with Dixi on this one.:)
westhawk
16th Sep 2011, 03:24
You use a screwdriver on screws and a spanner on bolts - simples:-)
That it is! The other explanations seem reasonable and in keeping with my training as well.
However I always found it interesting that the HS125 manuals consistently called bolts "screws". "Fasten the attachment screws and install split pins." I likened it to my fellow US mechanic's penchant for calling engines "motors" or pilots calling jet fuel "gas". And it's definitely more fun to do when someone objects!
And Allen seems to favour screws; probably because he didn't use a spanner on them.:)
easaman
17th Sep 2011, 17:33
When you are Reading all the above infos, allen's are screws, not to forget set screws.
cockney steve
27th Sep 2011, 17:28
Allen? That'll be a Parker-Kalon cup-head safety set-screw then! :8
Genghis the Engineer
27th Sep 2011, 20:18
Allen? That'll be a Parker-Kalon cup-head safety set-screw then! :8
I was taught as an apprentice that they are hexagonal socket cap-head screws.
On the whole, I go with the majority: plainshank=bolt, full-length=screw.
G
FlightPathOBN
28th Sep 2011, 08:39
Bolts are defined as headed fasteners having external threads that meet an exacting, uniform bolt thread specification 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.
according to ASME
jucylucy
28th Sep 2011, 13:16
Bolt is something you do after the screw!:}
grounded27
28th Sep 2011, 18:12
What a silly "THREAD"!?!
Bus429
1st Oct 2011, 02:51
Concur with plain shank and full thread notion; 'twas what we woz taught during apprenticeship. (Mind you, when I started my apprenticeship, Mr. Whitworth had only just retired).
ArthurR
1st Oct 2011, 18:37
A bolt is a externally threaded fastener designed for insertion through holes in assembled parts, and is normally intended to be tightened or released by torquing a nut.
A screw is an externally threaded fastener capable of being inserted into holes in assembled parts, and mating with a preformed internal thread or forming its own thread and of being tightened and released by torquing the head.
also most bolts have a flat head, where screws have a point.
Perrin
2nd Oct 2011, 09:18
Ah, sorry to change track but good story. When I started working in Scotland at Scottish Avaition at Prestwick coming from the USA (ex USAF) they said I would have to get not only a set of Witworth but BSF along with my AF tools.
Did so, many many years later working for BRAL at Glasgow I became a hero because I had the spanners to change the brake contol valve on the much loved ATP. Ah those where the days.
Keep them up boys
Peter :D
If you have to come on a forum for Professional aircraft engineers & ask this question, just maybe you should think about another occupation
For F**K sake....
If it has a nominal length its a Bolt....no nominal length....SCREW.
END OF STORY...GET BACK TO WORK!!
Screws.....Yet another stupid thread along the lines of opening a can of oil....100+ threads on opening a can of Oil?? I ask you.....WTF??
Come on guys....stop acting like twats eh??
YOUR SUPPOSED TO BE PROFESSIONAL.....ACT LIKE IT
Pilots read this crap.....lets at least look intelligent?
Shame you didn't follow your own advice.
Bravo!:ugh::ugh:
Pilot DAR
3rd Oct 2011, 01:43
If you have to come on a forum for Professional aircraft engineers & ask this question, just maybe you should think about another occupation
Having found "screws" in places where a "bolt" would be the required part, I would rather that someone come on here and ask, rather than guess!
Though, of course, were' putting in the proper fastener, because we're referring to the parts catalog... right?
I agree with Dixi's explanation. Added to that, is that if will be common to find design data, and strength information for bolts, driven in part from the precision, and specific manufacturing techniques associated with the formation of the threads (they will never be "cut" on an aircraft structural bolt).
Though "screws" could have a "machine" thread, they might even more likely have a thread which cannot accept a nut, and is made to a much more poor quality. Aircraft screws do not thread into aircraft nuts. So, every time I see one butchered nto an anchor nut, I wish the installer had asked first!
grounded27
4th Oct 2011, 22:41
Though "screws" could have a "machine" thread, they might even more likely have a thread which cannot accept a nut, and is made to a much more poor quality. Aircraft screws do not thread into aircraft nuts. So, every time I see one butchered nto an anchor nut, I wish the installer had asked first!
This is a rediculous thread (pun inteanded). What I have seen a variety of nuts used on screws. Bottom line is the only difference between a bolt and screw is that screws are used for 2 purposes, aerodynamic cleanlyness and supposed quick extraction as a standard. The A-holes at MDC and Airbus who deviated from the standard phillips made money on their endeavour to make these parts more likely to replace as they are crap designs, they hide behind thier higher shear strength (bus coppied MDC).
Now a bolt allows for a higher torque value due to it's increased impact area on 6 or 12 points. Frikin parts changers need to get back to work, both of these mechanical devices are nothing more than a nuisance to me when trying to fix an aircraft. not getting Holly, but God bless the quick release fastener.
Saint Jack
6th Oct 2011, 03:32
It never fails to amaze me how such seemingly simple topics like this one result in so much divisiveness. JAYMEE BEE in his apoplectic Post #13 referred to an earlier thread which discussed whether or not there is a proper method of opening a can of oil, his not-so-well-chosen words were:
"....Screws.....Yet another stupid thread along the lines of opening a can of oil....100+ threads on opening a can of Oil?? I ask you.....WTF??...."
I say divisive as replies generally fall into one of two groups, the first are those among us who are prepared to listen to alternate thoughts and explanations and give them due condsideration. Then there is the second group who instantly dismiss anything they weren't taught in there training or have heard of previously. The saying "There are none so blind as those who will not see" springs to mind.
We are working in an industry where progress is fast-paced and we must contantly re-train and adapt to these changes with an open mind or risk being left behind - and this includes being able to discuss bolts and srews plus opening a can of oil, in a responsible manner.
Absolutely correct Saint J.
This topic was being discussed quite professionally (IE without any slanging going on) until Jamie Bee stuck his oar in.
AVIOCHAP, no, just a problem with that particular post. :ok:
Perrin
6th Oct 2011, 14:17
Yes i agree get a life and smile, hate to work with someone with not able to go with the flow.
Could this now start anothe thread?
Sorry about the caps but being a oap no lights in the house till the street lights come on, some rewire that was.
Keep them up boys and girls
peter:):):)
grounded27
6th Oct 2011, 14:33
We are working in an industry where progress is fast-paced and we must contantly re-train and adapt to these changes with an open mind or risk being left behind - and this includes being able to discuss bolts and srews plus opening a can of oil, in a responsible manner.
If you have not refined these standard maintenance practices shortly out of school, I would not to work anywhere around you. There is no need to debate what a bolt or screw is and it has no practical application whatsoever. Bottom line is aside from the most obvious of applications, when in question use what the manufacturer has specified.