"Fredxx" wrote in message ...
On 22/10/2020 11:47:10, michael adams wrote:
"Fredxx" wrote in message ...
On 22/10/2020 08:27:31, michael adams wrote:
"soup" wrote in message
...
But then much like the difference between a ship and a
boat, I don't think it has ever been detailed when a machine screw
becomes a bolt.

A bolt is threaded into a nut to tighten it,

A screw is threaded into a female thread, or as in the case of woodscrews
creates it own female thread.

Because a bolt can be used to join components through an unthreaded hole
there's no necessity for the thread to go all the way to the end. However
this is purely incidental.

The convention is that a bolt is not wholly threaded along it's length. If it is,
them
it would normally be called a machine screw.

It's not normally considered 'coincidental'?

It is purely "incidental". The different threading on nuts and bolts is a
direct result of the different functions they were designed to perform.

I wouldn't call two entirely different functions 'coincidental'.

Nobody decided to produce fasteners where the threading only
went three quarters of the way along and then worked out what they
could be used for - joining components through unthreaded holes
which could then be tightened with a nut.

I don't get your point. Bolts are generally cheaper to make and many bolts I have come
across are intended to provide an element of location. A good example is attaching two
castings together. There need be no nit where one is threaded and the other plain and a
close fit to the bolt.

What they needed to produce was something which could join
components through an unthreaded hole which could be tightened
with a nut - which is what we call a bolt.

The fact that the threading on this fastner doesn't need to cover the entire
length is purely incidental. The bolt could work equally well if it was threaded
over its entire length,

What defines nuts and bolts is the way they're used, not their appearance

My previous explanation was entirely OTTOHM. However logical sounding
definitions. once encountered, seem to stick in the memory..

quote

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.

Machinery's Handbook

quote

https://en.wikipedia.org/wiki/Screw#...bolt_and_screw

Which I have already stated is USA centric.

It's very simple really and there's nothing USA centric about it.

A bolt is something you push through a hole with a thread on the end. That's it.
It doesn't move after that. You shove a nut on the other end and you turn the
nut to tighten the bolt.

A screw is something you er screw into a threaded hole until you can't screw
it in any further.

Spot the difference ?



Standard pattern woodscrews are plain at the end but are still screws.

Whereas machine screws can be used with nuts through unthreaded holes,
in which case they're functioning as bolts.

I have always believed that bolts were designed to assist in location, apart from
being
cheaper to make than machine screws.

Eh ? Its precisely the opposite. Provided the nut and the bolt head are big enough
there's no necessary connection whatsoever between the bolt diameter and the hole
through which its put, Even more so, if oversize washers are also used at either end.

Ah, I can see the problem.

I can assure you a bolt, with a non-threaded portion can be used for location, whereas
the indeterminate true diameter of a thread is going to be a sloppy fit.

I can assure you a bolt can be used in castings and made captive without a nut. As Dave
has said it seems you haven't worked much on cars.

They're screws not bolts.

Like Dave and all the other "experts" you're understandably confused because they
do admittedly look like bolts. However that's only going by appearences

However like Dave, when you were screwing these "bolts" into these cylinder heads
did you never stop and think "hold on, if I'm screwing these bolts into this cylinder
head rather than just pushing them in and tightening them on the other side with a nut,
like I do with all other bolts, why are they called "bolts" and not "screws" ?


There is usually a very strong correlation between the hole size and bolt/screw.
Anything else would be considered a bodge.

But at least it *is* possible bodge with genuine bolts whereas it clearly isn't with the
kind of nuts which you insist on calling bolts based solely on their appearance.


michael adams

....