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A SIMPLE POINT !

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noel shelley27/08/2021 10:22:16
770 forum posts
19 photos

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 McSweeney27/08/2021 10:32:31
60 forum posts

Set screw? - Machine screw, surely.

John Haine27/08/2021 10:48:59
4188 forum posts
242 photos

????

**LINK**

noel shelley27/08/2021 10:51:27
770 forum posts
19 photos

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.

Andrew Johnston27/08/2021 10:53:33
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6283 forum posts
677 photos

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 Hurley27/08/2021 10:54:47
185 forum posts
69 photos

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 halfpenny27/08/2021 11:11:52
189 forum posts
27 photos

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 Jenkins27/08/2021 11:25:37
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2123 forum posts
582 photos

Mostly a difference between US and UK terminology I think.

Rod

Juddy27/08/2021 11:25:54
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86 forum posts

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

Emgee27/08/2021 11:42:25
2161 forum posts
265 photos

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

Emgee

Nicholas Farr27/08/2021 12:45:44
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3001 forum posts
1371 photos

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.

Shadow27/08/2021 13:02:46
21 forum posts
1 photos

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

JasonB27/08/2021 13:16:10
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Moderator
21467 forum posts
2455 photos
1 articles

Hope they were not used in conjunction with tap washers for critical jobswink 2

Martin W27/08/2021 13:56:04
901 forum posts
30 photos

Only if they were being fitted by the company drip smile p.

duncan webster27/08/2021 14:27:10
3526 forum posts
63 photos

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

JasonB27/08/2021 14:57:46
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Moderator
21467 forum posts
2455 photos
1 articles

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 B127/08/2021 14:59:26
2023 forum posts
117 photos

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.

laugh

not done it yet27/08/2021 16:20:14
6350 forum posts
20 photos
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.

laugh

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 Haine27/08/2021 16:53:11
4188 forum posts
242 photos

Well, that's cleared that up then!

larry phelan 127/08/2021 17:20:59
1095 forum posts
14 photos

Nothing in life is simple, is it ?cheeky

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