A SIMPLE POINT !

[noel shelleyParticipant @noelshelley55608]

[noel shelleyParticipant @noelshelley55608]

If a bolt has thread all the way to the head and is longer than about 1" or 25mm then it is NOT a bolt – it's a set screw ! If there is plain rod between the head and the thread it's a bolt. This simple point may save some one trouble when ordering set screws or bolts. Good luck, Noel.

[Rob McSweeneyParticipant @robmcsweeney81205]

Set screw? – Machine screw, surely.

[John HaineParticipant @johnhaine32865]

????

**LINK**

[noel shelleyParticipant @noelshelley55608]

Depends on which school you went to I think ? Set screw is a more descriptive term but the importany think is to get the right part for the job ! Noel.

[Anonymous]

Set screw is the correct technical term. But unfortunately sloppy definitions mean that set screw can also be used to mean a grub screw. Machine screws imply a non-hexagon head.

It's almost as bad as describing a milling machine as universal just because it has horizontal/vertical capability.

Andrew

[Mike HurleyParticipant @mikehurley60381]

Always known them as set screws, but the term machine screw is just as ' correct ' to my knowledge. Either way, distinctly different to a bolt.

regards Mike

[john halfpennyParticipant @johnhalfpenny52803]

I was taught (and it seems logical to me) that a macine screw is the generic term, and so called to distinguish from other types, such as wood screws. A bolt is one subset of machine screws, with plain portion of shank. A set screw is another.

[Roderick JenkinsParticipant @roderickjenkins93242]

Mostly a difference between US and UK terminology I think.

Rod

[JuddyParticipant @juddy]

Isn't a bolt used in conjunction with a nut (& washer etc.) and a screw (machine, set, grub, shoulder etc.) is fitted to a threaded hole although there will be as many opinions on this as there are types of screws and bolts

[EmgeeParticipant @emgee]

Looks like Wiki has it wrong on this topic, not the first error on that platform. !!!!!!

Emgee

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I've always known set screws to be hex head that are fully threaded, a bolt has a plain shank between the head and the thread and the head doesn't have to be a hexagon e.g. coach bolt or even square head bolt, machine screws normally require a screwdriver to tighten them up. of course, all of these can and are used with or without nuts.

Regards Nick.

[ShadowParticipant @shadow]

At the bolt supply company I worked they were called tap bolts.

[JasonBModerator @jasonb]

Hope they were not used in conjunction with tap washers for critical jobs

[Martin WParticipant @martinw]

Only if they were being fitted by the company drip .

[duncan webster 1Participant @duncanwebster1]

In case anyone is wondering what the fuss is about, if loaded in shear a bolt with a plain shank has a much better abutment against a round hole, and has a significantly higher shear load capacity. This implies that the plain bit should be just less in length than the thickness of the 2 bits that it is going through

[JasonBModerator @jasonb]

You may also run into problems if you order a coach screw using Noel's definition of a bolt/screw as this is a coach bolt

And this is a coach screw

Edited By JasonB on 27/08/2021 14:59:31

[Mick B1Participant @mickb1]

In the colloquial-speak I'm used to, anything with a round head – machine or wood thread, domed, cheese, flat, c/sk or cap, and slotted,Phillips, Pozi, hex socket, torq or other drive – is a screw.

Anything with a hex head is a bolt, however high or low up the shank the thread goes.

I'm not saying this is right, just that it's common parlance. I've seen enough variations – such as setscrew/grubscrew conflation as above – to think that the only way to be certain to get the right screw is to

• buy from shops, where you can check any important features such as threaded length;
• from suppliers who specify their wares exhaustively;
• or make 'em yerself.

[not done it yetParticipant @notdoneityet]

Posted by Mick B1 on 27/08/2021 14:59:26:

In the colloquial-speak I'm used to, anything with a round head – machine or wood thread, domed, cheese, flat, c/sk or cap, and slotted,Phillips, Pozi, hex socket, torq or other drive – is a screw.

Anything with a hex head is a bolt, however high or low up the shank the thread goes.

I'm not saying this is right, just that it's common parlance. I've seen enough variations – such as setscrew/grubscrew conflation as above – to think that the only way to be certain to get the right screw is to

• buy from shops, where you can check any important features such as threaded length;
• from suppliers who specify their wares exhaustively;
• or make 'em yerself.

Well, for a start, I differentiate between cap-screws and cap-head bolts. The bolts have a plain section of shank. Screws are made to be screwed all the way in and secure the part on the head – that can be a hex or round. Cap heads are particularly useful when counter-bored below the surface. Bolts are generally tightened with a nut, or threaded into a different member to that which is being secured by the bolt.

I specify dependent on the situation in which the fixings are to be used. There are often alternatives, but also some specific fixings (coach head bolts are one example that are never going to be screwed in!) for some applications.

I don’t think I have ever seen a coach bolt/screw threaded completely to the head.

In summary, all is not simple when specifying a fixing. There are always going to be exceptions to the basic ‘rules’. Some bolts even have square heads, after all.🙂

[John HaineParticipant @johnhaine32865]

Well, that's cleared that up then!

[larry phelan 1Participant @larryphelan1]

Nothing in life is simple, is it ?

[Howard LewisParticipant @howardlewis46836]

Being trained in UK, I was taught:

Bolt – Threaded upto a plain shank beneath the square or hexagon head

Setscrew – Threaded all the way to the head

Machine screw – Tightened by a screwdriver of some type.

Capscrew – Tightened with an Allen key..

Coachbolt – Dome headed bolt or setscrew with square under the head.

Coach screw – Square or hexagon headed screw, with tapered coarse thread, to go into wood.

Howard

[noel shelleyParticipant @noelshelley55608]

And it all started with a simple point ! N

[Brian GParticipant @briang]

We know we want bolts, but are they bolts, fitted bolts or driven bolts?

Talk of fasteners is bringing back some VERY bad memories about interactions with buyers who couldn't understand that the length of a bolt or screw is how far it goes below the surface which may or may not be its overall length depending on the head (as well as dealing with qualified engineers who specified brass self-tapping screws, but that is another sad story).

I'm also pretty sure that based on their failure rate, somebody in China took an order for "cheese head" machine screws a little bit too literally. At least our buyer asked me why a drawing for woodscrews didn't specify what type of wood they should be made from before placing an order.

At least screws and bolts are less prone to confusion than rivets.

Brian G

[Nick WheelerParticipant @nickwheeler]

Lets not forget everybody using '10mm bolts' because they need a 10mm spanner to turn the actual M6 fastener…..

[Author]

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