Name that screw

Michael adams is a pompous ignorant prick. Ignore.

Bolts are threaded rod with a head and a plain shaft part as well as a threaded part. End of.

Screws have a head and are all threaded.

Studs have a thread but no head.

Nuts are irrelevant to the above definitions

But both coach bolts and coach screws have a plain shank at the head end ; which so it was claimed was the distinguishing feature as between screws (no) and bolts (yes).

By woodworking techniques I assume you mean joints. Entirely from memory and without looking it up might you be referring to pegged tenons among other joints ? As far from being obsolete such joints are an obvious manifestation of sound mechanical principles in a way that more modern fittings are not, being hidden away from sight. I also seem to remember that pegged tenons and similar were a feature of the knock down furniture which was popular a few decades ago, and maybe still is, in woodworking projects.

So "This is in the face of centuries of UK tradition" in building diesel locomotives is it ?

.To repeat - "centuries of tradition". Your phrase, not mine.

That raises an interesting point actually. Nuts and bolts are an off the shelf item made in standard sizes which can be expected to fit. They're one of the first large scale manifestations of interchangeable parts. The same could be said of screws bought off the shelf which can reasonably expected to fit the appropriate sized nut (when they'd be functioning as bolts) The threaded holes in components into which such screws would be threaded on the other hand are not in themselves standard off the shelf parts, although the actual components might be. Such holes are only tapped as and when required. This might mean that different standards might well apply, not necessarily to screws and bolts which are off the shelf items, but to the threads of nuts which are again off the shelf items, and the threads of threaded holes in components designed to accommodate screws which are not. Although I can't quite decide which way it should be.i.e which should be stricter

Match the hole within agreed tolerances then. Picky.

michael adams

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So that coach screws are actually coach bolts. I see.

As to studs, I'd already pointed out that "head nuts", are threaded onto "studs" as compared to "head bolts" (which actually function as screws) which are screwed into the block at 15.22 yesterday in this very thread

As with your new best friend Roger, it might actually help if you bothered to read the thread before letting your evident bitterness and resentment get the better of you.

michael adams

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Generally, a bolt (with a portion not threaded so larger) helps locate the part better than a screw threaded over its entire length. Which of course may or may not matter. I've a feeling a bolt with that shoulder is also stronger than one threaded over its entire length, made of the same steel.

Interesting point. Fitting a wheel which uses bolts rather than studs is no easier in practice IMHO. My last car which used bolts had a tool supplied - a bolt with no head which you fitted to align the wheel when changing.

As Lord Mountbatten told his mother.'You can put a boat on a ship but not a ship on a boat"

I don't recall using the words and phrases of diesels and centuries of tradition in the same sentence. You're being disingenuous.

Different area of interest.

I don't understand why you persist.

Anything else is contrary to UK convention, for decades, perhaps rather than centuries.

You are of course perfectly free to believe otherwise, but is a foolish approach and most unhelpful in making purchases in the UK of, or specifying in the UK, machine/set screws / bolts.

So the bolts (and corresponding nuts) that I bought the other day were not really bolts but screws because they are threaded right up to the head.

I imagine that the nature of the head is also a factor in the screw/bolt decision. If it has round head with a flat or cross-head notch, tightened with a screwdriver, it's a screw; if it has a hexagonal or square head, it may be a bolt depending on how far up the shank the threads continue.

There is a third category - the bastard bolt from hell! The spare wheel on my Peugeot 306 was held into a cage under the boot by a bolt-sized screw with a *round* head that had a semi-cylindrical notch in it (ie the sides were not vertical). You were supposed to use the flattened end of the wheelbrace as a crude screwdriver. This idea failed fairly spectacularly if the captive nut on the cage got seized onto the threads (it was exposed to all the water that was thrown on the underside of the car), because the curved sides of the notch in the screw head meant that the "screwdriver" end of the wheelbrace just climbed out of the notch. It took an RAC man about half an hour to free the seized thread with WD40, heat, lots of cursing and imprecations about the parentage of the person who had designed it. How much more effort does it take to cut (or die-stamp) a semi-cylindrical notch than to cut one with vertical sides using a milling machine? Or to mill/die-stamp a proper hexagonal head the same size as the wheel bolts.

Very generally speaking yes. Mr Adams was probably correct in respect of coach screws and bolts which are more associated with working in materials other than metals.

It does seem silly. A non-standard bolt/screw would have cost more than an off-the-shelf one, even for Peugeot.

I trust you're going to replace it with a standard stainless steel variant?

I would if I still had the car, but I sold it a few years ago. Until then, I made sure that I kept the exposed nut greased, and loosened/tightened it every month to prevent it seizing. It was still a crap design - I just found a workaround.

Finding an off-the-shelf replacement would not have been easy - the bolt was probably about 30 cm long. Without being able to remove the captive nut temporarily to take into a shop, it would have been difficult to make sure that any replacement I bought had the correct diameter and pitch of thread.

My present car doesn't have the problem, because the spare wheel is in a trough that it accessed from inside the boot - though it does mean that it's only big enough for one of those poxy space-saver spares. Hopefully I'll never have a puncture out of hours when I can't take the original to a tyre-repair place and I'm not about to begin a long journey (beyond the distance limit of the "toy" tyre). Going on past experience, almost all of my punctures have been discovered on a Sunday evening as I'm about to start a long journey home: the most recent one I even checked the tyre pressure (as I do routinely) only the day before when the tyre places were still open.

It's worth checking the depth of the wheel well. Sometimes a standard full wheel will fit.

Clearly the "experts" at the University of Leytonfasteners along with Professor Turnip have never heard of "roofing bolts" either.

michael adams

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especially if the boat is a submarine and 1000 feet underwater

Again, you're talking of another profession. I'm sure he has heard of them in much the same way I have come across them.

As others have said screws/bolts with a different head, in this case a dual slotted head, are sometimes referred to interchangeably.

Is it really so hard for you to accept?

How about the bolt on your garden gate? Not a thread or nut in sight. And that's before we start on bolts of lightening...

Accept what ?

Firstly there is nothing about different "professions" in any of the sources you have quoted. This is something you have made up, all by yourself.

Now you're also claiming that a differently configured head can change what was previously a screw (with a thread along its entire length) - into a bolt (which is supposed to have a partially plain shaft) but clearly doesn't.

Hint: they're called roofing "bolts" and not roofing "screws" because they're first fed through the hole, and the nut is then threaded on. Rather than being screwed into the hole. The shape of the head is immaterial. Like all bolts they're so called because of the way in which they're inserted and then tightened up.

Secondly your Leytonfasters source specifically relates to "set screws". whereas the discussion up until now has been in relation to "machine" screws. As presumably this is also the result of "centuries of tradition", a favoured phrase of yours I believe, perhaps you can explain precisely what the difference is ?

michael adams

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I thought read that the term originated with arrows and crossbows. BICBW

OED has that as it's earliest definition, for a bolt as fastening it has ...

"A stout metal pin with a head, used for holding things fast together. It may be permanently fixed, secured by riveting or by a nut, as the bolts of a ship; or movable, passing through a hole, as the bolts of a shutter."