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
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
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RE: My Kingdom for a Bolt... or Screw.
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.
RE: My Kingdom for a Bolt... or Screw.
TTFN
RE: My Kingdom for a Bolt... or Screw.
RE: My Kingdom for a Bolt... or Screw.
RE: My Kingdom for a Bolt... or Screw.
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.
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
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RE: My Kingdom for a Bolt... or Screw.
RE: My Kingdom for a Bolt... or Screw.
TTFN
RE: My Kingdom for a Bolt... or Screw.
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.
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 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.
However, not all screws are pointe-ended or tapered.
RE: My Kingdom for a Bolt... or Screw.
RE: My Kingdom for a Bolt... or Screw.
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.
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.
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.
Bung
Life is non-linear...
RE: My Kingdom for a Bolt... or Screw.
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.
JMW
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RE: My Kingdom for a Bolt... or Screw.
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.
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.
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.
"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.
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.
RE: My Kingdom for a Bolt... or Screw.
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.
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.
Jesus is THE life,
Leonard
RE: My Kingdom for a Bolt... or Screw.
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.
RE: My Kingdom for a Bolt... or Screw.
RE: My Kingdom for a Bolt... or Screw.
Keep the wheels on the ground
Bob
showshine@aol.com
RE: My Kingdom for a Bolt... or Screw.
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.
No idea why. Fortunately the picture told all.
(OK, OK, in Tamia model kits)
JMW
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RE: My Kingdom for a Bolt... or Screw.
RE: My Kingdom for a Bolt... or Screw.
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.
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
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RE: My Kingdom for a Bolt... or Screw.
RE: My Kingdom for a Bolt... or Screw.
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.
JMW
www.viscoanalyser.com
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RE: My Kingdom for a Bolt... or Screw.
RE: My Kingdom for a Bolt... or Screw.
Pretty soon someone will notice all this pilfering and send the cops round.
JMW
www.viscoanalyser.com
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RE: My Kingdom for a Bolt... or Screw.
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.
RE: My Kingdom for a Bolt... or Screw.
JMW
www.viscoanalyser.com
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RE: My Kingdom for a Bolt... or Screw.
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.
Jesus is THE life,
Leonard
RE: My Kingdom for a Bolt... or Screw.
No originality for place names apparently.
RE: My Kingdom for a Bolt... or Screw.
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.
Then there is "nip-n-tuck" a community in north central Louisiana.
rmw
RE: My Kingdom for a Bolt... or Screw.
RE: My Kingdom for a Bolt... or Screw.
Jesus is THE life,
Leonard
RE: My Kingdom for a Bolt... or Screw.
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.
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.
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.
"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.
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"
RE: My Kingdom for a Bolt... or Screw.
And who said engineers are a dull lot with no sense of humor.
RE: My Kingdom for a Bolt... or Screw.
Picture of a lag "screw" (or lag "bolt", if you prefer): http://www.boltdepot.com/lag-bolts.aspx
RE: My Kingdom for a Bolt... or Screw.
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.
This is what typically be called a carriage bolt over here: http://www.boltdepot.com/carriage-bolts.aspx
Regading internal vs. external wrenching for bolt/screw definition. Take a look at NA0114
(http://www.reidproducts.com/na_series.htm#NA0114) and note that the head has both internal and external wrenching features. A good number of other parts share this head configuration (NAS1802, et. al.)
RE: My Kingdom for a Bolt... or Screw.
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.