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My Kingdom for a Bolt... or Screw.
3

My Kingdom for a Bolt... or Screw.

My Kingdom for a Bolt... or Screw.

(OP)
I’m looking for a definitive definition of a bolt and screw, as used in Engineering.

I could have posted this in “Mechanical engineering other topics”, but thought it would be more entertaining here.  Seems our vendor just stocked all of our bins with hex-head bolts with partial threads, instead of fully threaded hex-head screws.  Our descriptions don’t specify either (simply “screw”), and then the debate overflowed between what a “screw” was and what a “bolt” was.

Machinery’s Handbook defines as (p.1417, 25th ed):
Bolt- externally threaded fastener designed for insertion through holes in assembled parts, and is normally intended to be tightened or released by torquing a nut.

Screw- externally threaded fastener capable of being inserted into holes in assembled parts, of mating with a preformed internal thread of forming its own thread, and being tightened or released by torquing the head.

So a fastener used with a nut is a bolt, and the same fastener used with a flow-drilled and threaded hole is a screw...

Other definitions I hear-
Bolt- partially threaded fastener
Screw- fully threaded fastener

Ray Reynolds
"There is no reason anyone would want a computer in their home."
Ken Olson, president, chairman and founder of Digital Equipment Corp., 1977
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RE: My Kingdom for a Bolt... or Screw.

Your second set of definitions is just somone's incorrect view of the world.  You can buy partially and fully threaded bolts and screws.  

We use partially threaded bolts with retainers and there are a variety of partially threaded screws used in furniture.

TTFN

RE: My Kingdom for a Bolt... or Screw.

This question has come up before and was discussed at great length, but I can't remember the thread number. I think the confusion arises because the Machinery's Handbook definition is generally considered correct in the US, whereas in the UK, a screw is defined as a fastener that is threaded all the way to the head, whereas a bolt thread stops short of the head. Or at least that was the case in most engineering circles when I lived there. So in the UK you can tell whether it's a bolt or screw just by looking at it, but in the US you need to know the application. I guess both definitions have some merit.

RE: My Kingdom for a Bolt... or Screw.

In the US, you can also tell by looking, since the US definition implies that a screw can form its own mating threads, which requires a pointed tip to start the process, whereas a bolt would have a blunt tip, and is therefore incapable of forming its mating threads.

TTFN

RE: My Kingdom for a Bolt... or Screw.

My hardware store, in the USA, sells machine screws with blunt tips. Gurunet suggests that screws have slotted heads, but that same store sells hex and square headed lag screws. My suggestion: if it's pointy or slotted or both its a screw.

RE: My Kingdom for a Bolt... or Screw.

IRstuff: Not conclusive reasoning, since a screw intended to be inserted into a preformed  thread does not require a pointed tip and under the US definition may or may not be threaded to the head. MadMango's Machinery's Handbook excerpt should read "..or mating" not "...of mating".

RE: My Kingdom for a Bolt... or Screw.

EM:

I'm not sure that matters.  I've got lots of fasteners that are used in preformed holes where they were threaded with a machine tool, but they still use what everyone calls screws, e.g., something with a pointy end.  

Obviously, there are bound to be exceptions to every rule, and indeed, there are "bolts" with relatively pointy ends.  

But, we definitely have "bolts" that are NOT threaded all the way.  And they are definitely bolts, because they cannot form their mating threads and they are not robust enough for that in any case.

TTFN

RE: My Kingdom for a Bolt... or Screw.

(OP)
To add to the confusion, I always use the term Cap Screw and Machine Screw, were Cap Screws have partial threads, and Machine Screws have full thread.

As for bolts, I use this term when dealing with stove bolts, carriage bolts, T-bolts, etc.

Ray Reynolds
"There is no reason anyone would want a computer in their home."
Ken Olson, president, chairman and founder of Digital Equipment Corp., 1977
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

RE: My Kingdom for a Bolt... or Screw.

IRstuff: Where do you get the idea that a screw has to have a pointed end? That is not the case with either the US or UK definitions.

RE: My Kingdom for a Bolt... or Screw.

from: http://dictionary.cambridge.org/define.asp?key=70643&dict=CALD

Quote:

screw (METAL OBJECT)   [Show phonetics]
noun [C]
1 a thin pointed piece of metal with a raised edge twisting round along its length and a flat top with a cut in it, which is used to join things together, especially pieces of wood

TTFN

RE: My Kingdom for a Bolt... or Screw.

IRstuff:
 Well, I asked for it, and I got it! But if you will forgive me, I think that is a lousy definition of "screw" in general, although admittedly a good definition of a traditional wood screw. My Webster's illustrated dictionary has a much broader definition which does not mention the necessity of a point, and has five pictures of screws - two machine screws, a wood screw, a lag screw and a set screw, only two of which have points. The definition given by your dictionary, if indeed it is complete, is hopelessly narrow and would fit only one of the illustrations.
 I personally believe that from a mechanical engineering perspective, the Machinery's Handbook definition is as good as any, at least from a US perspective. It does suffer from being somewhat ambiguous in some cases since it is a "functional intent" definition, as opposed to the UK definition which is a purely physical one. But if we were to adopt the UK definition, we could not for example officially refer to socket head cap screws which are threaded only partially along their length as screws. I don't believe even people in the UK make such a distinction in that particular case. When I lived there, we called all socket head cap screws "screws", whether they were threaded all the way to the head or not. But we often were careful to make a distinction in the case of hex head bolts and screws, especially in documents such as spare parts manuals.

RE: My Kingdom for a Bolt... or Screw.

Well, I have to admit that I had to dig a slight bit to find a definition that I agreed with.

There's definitely room for confusion, but what makes it worse, sometimes, is that the fasteners are called out with their funky military designations which tell you absolutely nothing about the device, as opposed to:

1/2" 6-32

Which has its own set of confounding factors, e.g., how does a neophyte tell what a 1/4-20 is, given the above?

TTFN

RE: My Kingdom for a Bolt... or Screw.

The current edition of the IFI fastener handbook contains a rather interesting two-page summary of the history of this discussion.

The definitions of Bolt and Screw from ASME B18.2.1 - 1996 are:

Bolt:  A bolt is an externally threaded fastener designed for insertion through holes in assembled part, and is normall intended to be tightened or released by torquing a nut.

Screw:  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.

RE: My Kingdom for a Bolt... or Screw.

All pointy-ended, or tapered bodied threaded fasteners are screws, because they cannot be properly used with a nut.

However, not all screws are pointe-ended or tapered.

RE: My Kingdom for a Bolt... or Screw.

MintJulep : Well, that ASME definition is exactly the same as the one in Machinery's handbook, given in the first post in the thread, and is what I call the US definition.

RE: My Kingdom for a Bolt... or Screw.

MintJ,

ASME B18.2.1 - 1996 is the definition I have chosen to give the thumbs up  


I have been around machinery for over 45 years and the same discussion has arisen on a regular basis throughout my career --- bottom line is; what publication represents the highest authority? It is possible that your client, in some cases, will define specifically what he wants. Needless to say, he then becomes the highest authority and all else must be disregarded unless you can definitively and tactfully show that he is in error.

ietech

 

RE: My Kingdom for a Bolt... or Screw.

My basic view is understanding the difference in how they hold objects together. These ideas followed from the definitions provided earlier in the thread.

A bolt produces pressure on the mating surfaces of two parts when inserted through a smooth hole in them and tightened. This pressure holds the parts in place using the friction of the contact surface between the two parts.

A screw produces pressure between the screw and the part it is driven into due to the interaction of the screw thread with the material. It is this pressure that holds the parts together, rather than the pressure over their mating surfaces.

For example, you pass a threaded fastener though a hole in two pieces of material, and attach a nut to the other end and tighten. This fastener is being used as a bolt.

As a counter example, you tap the hole in the material and use a threaded fastener that fits those threads to hold the materials together. This fastener is being used as a screw.

xnuke

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RE: My Kingdom for a Bolt... or Screw.

English Muffin:

The original post asked for a definitive definition (does this qualify for the redundancy thread?)

The ASME as published by the IFI seems pretty definitive to me.

Xnuke:

Your definitions are application based, rather than part based.  The history of this issue that I cited in my earlier post mentions this issue.

A screw can be used in applications that call for a bolt.  A bolt cannot be used in applications that require a screw.

RE: My Kingdom for a Bolt... or Screw.

Is it not just something like the difference between a "motor" and an "engine" - very much context and popular usage dependent?  Now there's a good topic for another thread...

Bung
Life is non-linear...

RE: My Kingdom for a Bolt... or Screw.

To my recollection a screw's shank could be cylindrical or conical, and the head could be flat, recessed, slotted or rounded.

A bolt is a rod, usually of metal, with a square, round or hexagonal head at one end and a screw thread on the other. If one removes the head of a fully threaded bolt one gets a stud, right ?

RE: My Kingdom for a Bolt... or Screw.

What about a coach-bolt? This has properties of both.

JMW
www.viscoanalyser.com
Eng-Tips: Pro bono publico, by engineers, for engineers.

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: My Kingdom for a Bolt... or Screw.

jmw,
Are you sure you don't mean carriage-bolt?  Or is coach-bolt the way it is said in England?

Jesus is THE life,
Leonard

RE: My Kingdom for a Bolt... or Screw.

In Australia a coach screw has a hex head and a wood screw type of thread. It fastens metal fittings to wood.

A carriage bolt has a round head with a square boss underneath it which pulls into timber to stop it turning while the nut is being tightened. It fastens two bits of wood together.

RE: My Kingdom for a Bolt... or Screw.

notnats,

The product you described as a coach screw goes by the name of lag screw in the USA.  Carriage bolt has the same meaning in both locales.

Regards,

Cory

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RE: My Kingdom for a Bolt... or Screw.

Mint,
"A screw can be used in applications that call for a bolt.  A bolt cannot be used in applications that require a screw."

Do you mean to say that there is no such thing as a machine screw?  Machine screws function exactly like a bolt only they are smaller.  OK OK I give.  I guess if a bolt is larger than a screw then it will not fit into the hole where a MACHINE screw belongs.

I think some of the definitions given are funky.  The terminology for fasteners has evolved much like many other words in our various languages and there is not complete agreement between Machinery's Handbook vs Fastener Association of America, ect etc.  It depends to a large degree on who you choose to use as an authority.  Is it your fastener supplier (you might have a hard time correcting him/her on his/her terminology and you do want to get what you think you ordered)?  It also depends to a large degree on the specific field you are working in as context makes a difference.  Just when you THINK you've got it all figured out, someone will trump you.  And of course it depends on what country e.g. Australian coach bolts = US lag screws.  So should I go to Australia and instruct them that these things they are using to fasten coaches cannot possibly be bolts 'cause it does not fit the definition that I looked up.  Probably would be about as productive as when the US government thought they could make their constituancy convert to the metric systm.

Jesus is THE life,
Leonard

RE: My Kingdom for a Bolt... or Screw.

Metman,

Find a copy of the current IFI standards book and read the articles I cited earlier.  They answer your question.

Size, either diameter or length does matter, but not in the definitions of mechanical threaded fasteners.

RE: My Kingdom for a Bolt... or Screw.

They are one and the same and are called out depending on the method of fastening.  If you are putting a 1/4"-20 SHCS thru a part and then put a nut on it, it is a Bolt. The same 1/4"-20 SHCS put into a threaded hole is a Screw.  The term used depends on the method of fastening.  The length of the thread has nothing to do with the terminology of the part.  A 1/4"-20 x 1" SHCS will be threaded all the way up, a 1/4"-20 x 4" SHCS will not (unless ordered as such).

RE: My Kingdom for a Bolt... or Screw.

aamoroso,

Your post highlights the current state's ridiculous nature: one-part, two-names.  Your example fastener (SHCS = Socket Head Cap Screw) carries the generic name screw (in catalogs, Internet posts, etc.), yet its technical name varies whether it is combined with a nut or tapped hole.  Ludicrous.  I wish we would just start using one name for any externally threaded fastener and use specific references for geometry (e.g. thread form according to ISO 724).

Regards,

Cory

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RE: My Kingdom for a Bolt... or Screw.

Well if Metman is going to correct Australian terminology, try this:

A hex head fastener with a thread for only part of its length is a hex bolt. They are often only sold with nuts which is a nuisance if they are to be fixed into tapped holes.

A hex head fastener with a full length thread is a screw, but is always sold as a hex SET screw. Now I always think of a set screw as a fastener used to lock a collar or coupling onto a shaft, often used with a key.

I can't change convention, but I can complain about it.

Jeff

RE: My Kingdom for a Bolt... or Screw.

Hey -- that's what makes this forum so much fun.  We can complain without too much concern about getting reprimanded too nastily.

Jesus is THE life,
Leonard

RE: My Kingdom for a Bolt... or Screw.

nonats,
We have a lot to complain about.

In ANSI/ASME standards, there are:
Hex Bolt                    ASME B18.2.1
Hex Cap Screw              same B18.2.1
     (formerly called a "Finished Hex Bolt")
Hex Head Machine Screw         ASME B18.6.3
Hex Head Set Screw            ASME B18.6.2

  • Size does not differentiate: on average, the bolts and cap screw are larger while the machine and set screws smaller, but I can find 1/4inch diameter under all four names.  
  • Whether full thread or not does not differentiate: I can order partial or fully threaded cap screws.  Besides, if the screw length is shorter than a prescribed length, it will be fully threaded
  • The standards do not indicate anything about bolts being provided with a nut.  The first time I came across that was in some metric screws.
There may be slight differences in the shape or form or fit of the threads and in the bearing surface of the head.  There are definite differences in the length tolerances.

I've been floundering with this for years as I maintain an engineering database for my company so I'm trying to name the fastener correctly and consolidate usage.  It doesn't help that the database includes information collected as long as 40 years ago.

The when you order one of these, what do you get?  

Words matter.  I think.

RE: My Kingdom for a Bolt... or Screw.

Just out of interest, does anyone know how the Germans do it? Do they have a part based or an application based nomenclature? Or a mixed up mess like we have ?

RE: My Kingdom for a Bolt... or Screw.

I was going to say a screw has a point and a bolt doesn't but that might start another round of 32 replies. - VQ

RE: My Kingdom for a Bolt... or Screw.

I just use the term "Fastener" and let the drafters worry about it

Keep the wheels on the ground
Bob
showshine@aol.com

RE: My Kingdom for a Bolt... or Screw.

EnglishMuffin,

The Germans use the word die Schraube for almost all externally threaded fasteners.  This is translated to English as screw.  FYI.

Regards,

Cory

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RE: My Kingdom for a Bolt... or Screw.

Many years ago translated Japanese exploded diagrams always seemed to refer to a screw as a "vis".
No idea why. Fortunately the picture told all.
(OK, OK, in Tamia model kits)

JMW
www.viscoanalyser.com
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RE: My Kingdom for a Bolt... or Screw.

I believe "vis" is the French term for screw.

RE: My Kingdom for a Bolt... or Screw.

Don't know about that.  The French term "vis-a-vis" means " eye-to-eye," and the word "vis" obviously contributes to words like "vision."

A lot of French terms have been borrowed (or downright taken) and applied by the Anglo-Saxon (and subsequently American) military for various military terms.  "Fraise," which means "strawberry" in French, is used militarily to mean 5-foot-long pointed sticks in the ground that form bristling rings around fortifications, a passive form of defense used since Roman times to slow down or stop enemy infantry attacks.  Other military engineering terms taken from the French (without necesarily any regard for the meanings of the words in French) include "abattis" and "cheveaux-de-frise."  The 19th-Century commands for bayonet drill are all in French, and were used in the United States during the Civil War, and probably at other times as well.  The 18th-Century name for the insignia of officers - lieutenants and higher - is "gorgette," a remnant from the days of knights in armor, where the gorgette was placed between chin and chest to protect the knight's gorge, or throat.

Ah, too many things to think of!

RE: My Kingdom for a Bolt... or Screw.

Thanks sqdjlg,
and shetwynd, I understood Vis to be more properly the face as in face-to-face, the root for visage. Though cette en face means before your face. (don't pick me up on my French spelling please).

PS, as someone remarked in another thread, even bayonet is from the French town of Bayonne.

JMW
www.viscoanalyser.com
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RE: My Kingdom for a Bolt... or Screw.

"Vis a vis" actually means "as opposed to" or "opposite", in the sense of "face to face", (probably from visage a visage), rather than "eye to eye". The French word for eye is "oeil". The "a" must have a grave accent. Without that all important grave accent, however, Bable Fish translates it as "live has screw"!!!

RE: My Kingdom for a Bolt... or Screw.

jmw,

Just to clarify, the French word for an externally threaded fastener (screw) definitely is vis.

Regards,

Cory

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RE: My Kingdom for a Bolt... or Screw.

Thanks Corypad.

JMW
www.viscoanalyser.com
Eng-Tips: Pro bono publico, by engineers, for engineers.

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RE: My Kingdom for a Bolt... or Screw.

Bayonne is in New Jersey.

RE: My Kingdom for a Bolt... or Screw.

London is in Kentucky, Athens is in Georgia, so too is Rome, Birmingham is in Alabama.

Pretty soon someone will notice all this pilfering and send the cops round.

JMW
www.viscoanalyser.com
Eng-Tips: Pro bono publico, by engineers, for engineers.

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RE: My Kingdom for a Bolt... or Screw.

I grew up in Paris --- Texas.  Largest Paris outside of France.

Now that brings up another question:  What do you call natives of Paris?  [Before living in Paris, I lived in Marshall, the denizens of which were Marshallites]
  

RE: My Kingdom for a Bolt... or Screw.

Texans!

RE: My Kingdom for a Bolt... or Screw.

Texicans?

JMW
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RE: My Kingdom for a Bolt... or Screw.

jmw
I heard that they were called Texicans at the beginning of Texas history - somewhat before the fall of the Alamo [I plead ignorance of anything in the recent movie].

RE: My Kingdom for a Bolt... or Screw.

Cairo is in Illinois but around them parts they pronounces it Kayrow (even the Missourians say it that way).  Or should that be Missouriites?

Jesus is THE life,
Leonard

RE: My Kingdom for a Bolt... or Screw.

Cairo, Athens and Rome are also all in NEW York.

No originality for place names apparently.

RE: My Kingdom for a Bolt... or Screw.

Then, there's "Truth or Consequence", New Mexico.
Ya thats what I want to write as my return address on all my bills.
Were they really thinking.

pennpoint

RE: My Kingdom for a Bolt... or Screw.

How about a place just north of Houston, "Cut-n-shoot"?  It is for real.

Then there is "nip-n-tuck" a community in north central Louisiana.

rmw

RE: My Kingdom for a Bolt... or Screw.

There was a "Dime Box" in Texas.  Just down the road from "Old Dime Box".  

RE: My Kingdom for a Bolt... or Screw.

I wonder if one can buy screws in Bolt, W.V.?

Jesus is THE life,
Leonard

RE: My Kingdom for a Bolt... or Screw.

Don't agree with you, Cory. 'Vis' is not French for screw but rather the externally threaded portion of a 'boulon' this being the assembly of an externally threaded item (vis) and internally threaded item (écrou). The French therefore do not have the 'is it a bolt or a screw' dilemma.
During my engineering training (not in France) I was given as a young lad the definition as follows : a screw is torqued up by the head, whereas a bolt remains immobile while the nut is screwed onto it. Now that I work in Fasteners, it is incredible how often this simple rule is forgotten. The definition I give is no doubt the origin for another definition, which is only a corollary - screws are meant to be torqued into a tapped hole and therefore have full threads, whereas bolts are for generating a clamping force between two or more parts with the aid of a nut, and therefore have an unthreaded portion under head.

RE: My Kingdom for a Bolt... or Screw.

yates,

The English words for headed externally threaded fasteners are bolt and screw.  These are translated to French as vis.  A simple way to verify this is to look at the French words on ISO standards like ISO 898-1 or ISO 4014.  Or, use an Internet translation service (http://www.freetranslations.com).

Regards,

Cory

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RE: My Kingdom for a Bolt... or Screw.

Ha-ha all jolly good fun chaps.

To me a bolt, any bolt has a head which is gripped by having EXTERNAL flats or other shape. Usually requiring a spanner or a socket for the head.

A screw has a head gripped INTERNALLY by a slot or an internal hex or other shape. Requiring a screwdriver or a key of some sort

What is on the other end does not really matter.

RE: My Kingdom for a Bolt... or Screw.

(OP)
Warpspeed, how would you explain lag screws used in wood construction then?

"But what... is it good for?"
Engineer at the Advanced Computing Systems Division of IBM, 1968, commenting on the microchip.
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RE: My Kingdom for a Bolt... or Screw.

Lag screws ? not a common term used here in Australia ?? What do they do.

RE: My Kingdom for a Bolt... or Screw.


This reminds me of the old joke ...

A patient from an asylum for the insane rapes a cleaner, & then escapes. Headlines next day reads "Nut Screws Washer & Bolts"

from (the City of) Barrie, Ontario.

What happens if you get scared half to death twice?

RE: My Kingdom for a Bolt... or Screw.

Ha-ha-ha, good one. Also a if a Lag is an old prisoner, and a screw is a prison warder, what is a lag screw ???

And who said engineers are a dull lot with no sense of humor.

RE: My Kingdom for a Bolt... or Screw.

Thanks Kenneth,

O/k got the picture. Here in Australia we call them Coach Bolts. I think someone earlier (American ?) mentioned carriage bolts or carriage screws. Most probably the identical thing.

To me that definitely looks more like a bolt, simply because of the head. If it had a round head with a slot, it would then be a common wood screw. The threaded end of course being identical.

RE: My Kingdom for a Bolt... or Screw.

That seems to follow the external wrenching = bolt, internal key = screw philosophy fairly closely.

As you point out NA0114 is actually both a screw and a bolt using that definition.

There is also what they refer to as a Clevis Bolt NA0155 with a slotted head. Most common clevis applications might be referred to more accurately a a clevis pin, where the head typically just has a shoulder and no means to turn it, with a hole and split pin at the other end to retain it.

Interesting stuff indeed.

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