Bolt or screw?

[FulmenParticipant @fulmen]

I feel there is a sex joke here somewhere, but I just can’t find it. Something about a lady with nuts perhaps?

[Robert Atkinson 2Participant @robertatkinson2]

They are not the same. Aircraft have crashed because a screw was used in place of a bolt.
The FAA have a good description:
Generally, bolts are used where great strength is required, and screws are used where strength is not the deciding factor. Bolts and screws are similar in many ways. They are both used for fastening or holding, and each has a head on one end and screw threads on the other. Regardless of these similarities, there are several distinct differences between the two types of fasteners. The
threaded end of a bolt is always blunt while that of a screw may be either blunt or pointed.
The threaded end of a bolt usually has a nut screwed onto it to complete the assembly. The threaded end of a screw may fit into a female receptacle, or it may fit directly into the material being secured. A bolt has a short threaded section and a comparatively long grip length or unthreaded portion, whereas a screw has a longer threaded section and may have no clearly defined grip length. Turning the nut on the bolt generally tightens a bolt assembly; the head of the bolt may or may not be designed for turning. Turning its head always tightens a screw.”

https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/amtg_handbook.pdf

Which has a lot of other good engineering information by the way.

They are clerly in the “bolt has a plain shank” camp. The plain shank is called “grip length” in aviation. This is a hang-over from rivets.

Robert.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for that link, Robert … 677 pages duly downloaded for occasional reference.

MichaelG.

[Martin KyteParticipant @martinkyte99762]

Bit of guesswork here but for what it’s worth  here is my take on this. Back in the days of wooden ships the timbers were fixed together with spikes, tree nails and copper bolts. Generally speaking the spikes and tree nails were of square section and were driven home directly into timber. Copper bolt were of round section and were driven into bored holes often at angles to each other to form the composite mass of structures like the keel, stern timbers etc.

My notion is that a bolt describes a large cylindrical rod fitted in a bored hole in order to create a fixing. It can be plain like a dowel or perhaps fitted with washers and riveted over at the ends. With the advent of screw threads and nuts the ends could be fixed fixed this way to prevent movement of the bolt.
So in my scheme a bolt is defined as a round rod for fastening.

If it’s left plain it’s a dowel bolt.

If the ends are beaten over to prevent movement it’s a rivet bolt.

If one or both ends are screwed it’s a screw bolt.

Easy to see how the common terms then develop sometimes omitting the bolt bit and sometimes the screw bit.

I would love to know if this is anywhere near the mark from someone who is more of a historian than me.

regards Martin

[Fulmen]

On Fulmen Said:

I feel there is a sex joke here somewhere, but I just can’t find it. Something about a lady with nuts perhaps?

If you must … there was one decades ago [and probably no-longer acceptable]
… It related to events in a Launderette, and  punch-line was the “News Headline”

Nut screws washers and bolts

MichaelG.

[Mark RandParticipant @markrand96270]

Deleted! Replied to post on first page, which had already been shredded on second page. 😀

[BazyleParticipant @bazyle]

It is rather important if you don’t have a picture and are trying to order the right item for a particular job.

[Howard Lewis]

On Howard Lewis Said:

My understanding has always been that a fastener with the thread extending right up to the head, is a Setscrew.

If there is a plain section between the underside of the head and the end of the thread, it is a Bolt.

If the fastener has a parallel thread, it can accept a nut, and in smaller sizes can be described as a Machine Screrw..

Grubscrews have no head, and the thread is continuous

Otherwise, to me a screw, implies a wood screw with a tapered thread.

A fastener intended for tapping its own thread is in my definition of a Self Tapping Screw, colloquially a Self Tapperer.

HTH

Howard

.

Howard has nailed it — must have been to the same school !!

This is the nomenclature I was taught in the late 50’s & 60’s both as an apprentice and at Tech college.  One addition is Fitted Bolts which are made to a closer tolerance with ground shanks, plain section.

John

 

[JohnF]

On JohnF Said:

On Howard Lewis Said:

[…]

.

Howard has nailed it —

 

Surely that’s cheating 🙂

MichaelG.

[JA]

On JA Said:

… Rather like “How many angels can sit on a pinhead?”.

JA

I think that very topic has been debated on here several times before. Can’t remember a consensus ever being reached though.

[peak4Participant @peak4]

My I refer you back to my post on the previous page.
It referred to an ISO standard, though hosted on a suppliers site.
From everything I’ve managed to find, spread across various ISOs, it seems a fair indication of the intended usage of the terms screw and bolt.
One of the previous links fails has moved, but this seems to work
https://regbar.com/wp-content/uploads/2019/09/ISO-1891-2009-ÖNEMLİ.pdf
(ISO225 also seems relevant, but I’m struggling to find a free source for it.)

Round about P 29 onwards.
Very broadly, external drive fasteners such as hex or square heads, seem to be subdivided into fully threaded screws, and partially threaded bolts.
Round heads, some countersinks etc, with some form of built in anti-rotation feature such as a square section or a nib are also called bolts.
Internally driven fasteners, such as Allen, Torx, Philips, slot heads, etc, are mainly called screws, regardless the thread length.

See also the tensile testing rigs in ISO898 staring about P26
https://pppars.com/wp-content/uploads/2021/07/ISO-898-1.pdf

If anyone here is legitimately studying, or lives in NI, then they may have free access to ISOs; also I think folk in Lancashire can gain free ISO access via their library cards.

[FulmenParticipant @fulmen]

Or do a search for Indian standards. A lot of them are just copied from ISO and are freely available.

[SillyOldDufferModerator @sillyoldduffer]

In an ideal world, all engineers would abide by the modern definition, unpolluted by the slack alice terminology of the past!   Unfortunately, technical English existed long before the importance of standardisation was realised, and even when the leadership understand the need, it’s extremely difficult to get a workforce to adopt anything new.

So today, we live in a world in which mixes formally defined technical terms, often international, with rafts of historic equivalents inherited from different trades, regions, and nations.   The past was a god-damned mess, the present isn’t much better, and the future unlikely to fix it because most people hate change.

History matters in another way too,  Many definitions have changed over time, thus what an apprentice was told in 1960 might have been obsolescent at the time, and is now plain wrong.   But it’s hard for individuals to keep up to date, and even harder to overwrite what we were taught in our youth.  Plus, those who need to understand the formal difference between a machine screw and a bolt are hugely outnumbered by ignorants who don’t care because their needs don’t require any extra understanding.

Yet another problem is the way technical English reuses the same words for other purposes.  ‘File Handle’ is a cracking good example.   In my workshop, this is a ‘file handle’:

 

This however is not only meaning of ‘file handle’, or even the most common!   Googling ‘file handle’ is unlikely to find ‘our’ definition, instead much more likely to find a definition like this:

A file handle, in the context of technology, refers to a unique identifier for a file or a data resource used by an operating system or a software application. It is typically an integer value that allows programs to access and manage files efficiently without directly interacting with the file system. By using a file handle, the program can read, write, or manipulate the file, depending on the permissions granted.

My workshop probably has less than 30 handles attached to files.  Typing this post, my computer  currently has 277,337 open files, each of which is managed internally by the operating system with a file handle.  Computer file handles are big business, what they do under the bonnet is complicated, and all computers and the internet depend entirely on them.

May not be sensible to conflate wooden file handles with software file handles, and yet here we are!   The computer usage of the term is derived from ‘our’ workshop meaning in that ‘handle’ suggests a way of controlling a tool.   It’s just that the computer tool is a hideously complicated software artifact, not a length of steel with hardened teeth cut in it.

Dave

 

 

 

 

[Fulmen]

On Fulmen Said:

Or do a search for Indian standards. A lot of them are just copied from ISO and are freely available.

I tried that, but couldn’t find ISO225, or anything with the same title.

Bill

[FulmenParticipant @fulmen]

Try this: https://law.resource.org/pub/in/bis/S01/is.8536.1987.pdf

[File HandleParticipant @filehandle]

Its almost like you know that I once worked in computing.

[Author]

Posts