Opinions from the engineeringisti

This is one I always ponder. Nominally, if you have the weight of the car on the threaded section then it will dig into the bush, wearing it away as the car bounces up and down. Whether this will happen in a relevant timeframe is another matter!

I'm not sure what I'd do. Since there's a NutNBolt place nearby that would sell one singly I'd stagger off and buy one or it would nag away at me foreverandaday. OTOH, if I could only go and buy a pack of 25 from Screwfix then the cost would probably allay my fear and make me forget all about it!

I'd have said go for it. What stops things moving around is the friction at the faces which are clamped by the tension in the bolt, not the fact that the bolt shank is in contact with stuff. It's not like a dowel which is close fitting all the way round, the shank has a clearance in the holes so it could always move in some directions, if friction wasn't stopping it. A bolt with a shank will have better fatigue properties in more difficult applications, but I don't believe this is one which needs that. Maybe worth checking if the existing one is high tensile (numbers like 8:8 on the head) and replacing with similar if possible.

I would only replace with as near to original as possible.

High tensile M12x100mm, with a 63mm shank, £2.95 delivered:

I've been reminded elsewhere that I meant "fully threaded set screw", of course.

Anyway, no matter. A source has been found.

I've ordered some from Custom Fasteners, but it's also been pointed out to me that Namrick do 'em.

BTW, a "fully threaded bolt" isn't a bolt, it's a machine screw. A bolt has an unthreaded section on its shank by definition.

Excellent. This sort of tech pedantry is something I've missed of late :-)

I understand it's now considered an obsolete definition - the engineering definition is that a bolt is secured with a nut, but a screw is secured in a threaded hole.

Oh rlly? Pedants R Us says a set screw is entirely different from a machine screw.

And when does a threaded hole become a nut and vice versa?

When I'm ordering fasteners if I want one that's threaded all the way up I ask for set screws and specify what type of head I want on them.

I'm not sure what BSI has to say about it, but ANSI (the American National Standards Inst.,) publishes the Glossary of Terms for Mechanical Fasteners

- B18.12. It has 60+ pages of illustrated definitions. Their definition of bolt and screw is the same- "an externally threaded fastener." Most, but not all bolts are only partially threaded. Most, but not all screws are fully threaded. A set screw, rather than using clamping force on the threads, has "a formed point designed to bear on a mating part." They are commonly used on pulleys and gears, and may or may not have a head.

Both the newsgroups are in the UK, that definition has never been a common one over here.

As I've pointed out in that other post, the strict merkin definition is a bit looser. Which term is used depends on its form and usage, but a hex head bolt and a hex head cap screw can look identical.

If the part with the threaded hole performs some other function than just holding the bolt or screw, it's not a nut.

This is the UK

Which term is used depends on its form and usage, but a

Which is why I was specified it. There are many ways our languages differ, it's always fascinating to me to see where.

As they say; "Two nations divided by a single language."

One of the earliest things I learned when I first started to buy engineering fasteners to fix my SOBs was the difference between a screw and a bolt. No shortage of sources round these parts but it helps when you go in to place that supplies mainly to the trade like James Lister if you *sound* as if you know what you are talking about. I knew someone who got everything at trade price back in the days before computerised customer records. "Who shall I book it down to?" "Rees Racing International, but I'm paying petty cash."

You've been wandering round town in your pants again, haven't you?

So this is a bolt if I do this to it, but a screw if I do this to it?