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Bolts vs Screws
6

Bolts vs Screws

Bolts vs Screws

(OP)
ASME Y14.5 'tends' to differentiate between bolts and nuts in the Fixed and Floating fastener formula section.

Is there a consensus amongst engineers/designers/cad operators as to the technical correctness of the definition of bolts verses screws?

RE: Bolts vs Screws

This terminology debate has been around for a while.  There is no technically compelling reason to differentiate externally threaded fasteners into the two groups of bolt and screw.  French and German languages use a single word (vis and schraube) so why can't English?  Since the helical pattern is called a screw thread, I think screw is the natural choice.

Regards,

Cory

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

RE: Bolts vs Screws

http://euler9.tripod.com/bolt-database/boltdef.html

Quote:

Bolts are defined as headed fasteners having external threads that meet an exacting, uniform bolt thread specification (such as M, MJ, UN, UNR, and UNJ) such that they can accept a nontapered nut.  Screws are defined as headed, externally-threaded fasteners that do not meet the above definition of bolts.


http://everything2.com/index.pl?node_id=1272695

Quote:

The short rule is, if it has a nut, it's a bolt. If it doesn't, it's a screw. I hope this clears things up, but expect that I won't change common usage.


http://www.bicyclesports.us/id193.htm

cheers

RE: Bolts vs Screws

Your original post comments on Bolts and Nuts which are externally vs. internally threaded fasteners, but your question asks about bolts vs. screws.  Technically, the term is "Threaded Fastener"...no differentiation between bolt or screw.

RE: Bolts vs Screws

Pins are actually "bolts", bolts are actualy "screws".

RE: Bolts vs Screws

(OP)
Looks like their aint no consensus.   

RE: Bolts vs Screws

(OP)
ctopher,

Thanks, that helps a lot.  Mon I will research the B18 standard for screws.

RE: Bolts vs Screws

Wow that seems like a simple question so why cannot I think of a simple answer?

The problem as I see it with the answer from Corblimeylimey and ctopher is that if you use say a M6x20 countersunk screw/bolt to clamp a plate to two other plates one thick and one thin, in one instance you use a thread and in the other a nut and washer so the same fastener becomes both a M6 countersunk screw and a M6 countersunk bolt.

My personal preference is bolts have external drives on them, be that hexagonal or even square (like a coach bolt) whilst screws have internal drives on them, like Phillips or Allen, however I am sure there is a very good reason why that is wrong.

I am sure this thread will have a few more twists and turns in it.

RE: Bolts vs Screws

The general rule of thumb as I learned it (for what it's worth) is that the difference is which part is being torqued.  A screw is torqued through the screw head, a bolt is torqued through a nut.

When the people fear their government, there is tyranny; when the government fears the people, there is liberty. - Thomas Jefferson
 

RE: Bolts vs Screws

I believe the US customs or whoever it is has a definition as bolts & screws are taxed differently but I can't remember the reference.

CBLs first link http://euler9.tripod.com/bolt-database/boltdef.html sounded very definitive but didn't appear to give any kind of reference as to where that definition was obtained from.

Plus based on several of the definitions, where do set screws fit in?

I long ago gave up trying to work out the difference and if I care for an application make sure the threaded fastener I call up has an adequate description, preferably a spec.

KENAT, probably the least qualified checker you'll ever meet...

RE: Bolts vs Screws

Fastenal is not completely consistent w/ its terminology.  For hex head threaded fasteners it's about 90% "Hex Head Cap Screw" & 10% "Hex Bolt".

Most of the old-school heavy-metal places I worked at in WI use "screw" for anything w/ threads, including hex head.

RE: Bolts vs Screws

ringman,

   Try working out positional tolerances from first principles.

   A bolt, a cotter pin or a non-countersunk rivet can be assumed to be located exactly at nominal position.  Your clearance holes must clear an area at least the diameter of the fastener, located exactly at nominal position.  As the hole gets larger, it can shift off nominal, hence the MMC specification.

   A screw, a dowel pin or a fabricated feature is located by a positional tolerance.  The clearance hole located excactly at nominal position, must clear an area equal to the diameter of the fastener plus the positional tolerance.  Again, an increased diameter allows positional error.

                                JHG

RE: Bolts vs Screws

Um, in your original post, ringman, "ASME Y14.5 'tends' to differentiate between bolts and nuts in the Fixed and Floating fastener formula section."

I believe you mean they differentiate between bolts and screws ?

I.e. between floating fasteners (threaded fasteners with nuts) vs. fixed fasteners (fasteners threaded into tapped holes on a single parent body).  The tolerances required for position of the fasteners will change depending on those circumstances, as you know having read that section.  

Or maybe I am misreading things...it is Monday after all.

RE: Bolts vs Screws

I am with AJACK1 on this subject. If I can turn it with a wrench, it's a bolt. If I need an allen, torqs or screwdriver, it's a screw.
 This was generally how the old MS specs seemed to categorize them.  

RE: Bolts vs Screws

What about Lag Screws? There are both types, install with a screwdriver or a wrench.

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Jul 13, 2008)
ctopher's blog

RE: Bolts vs Screws

ctopher and CheckerRon,

   How about cap screws, as opposed to socket head cap screws?  Cap screws have hexagonal heads.

   There is a contect to this terminology that has nothing to do with how we turn the fastener.  

                          JHG

RE: Bolts vs Screws

Some people call them lag bolts.
I thought about hex head cap screws, but was kind of ignoring them. I didn't say it was a hard rule, I said that's how I think of them.

 It seems from the concensus of this post, that there is a context to the termminolgy, but no one is really sure what it is.

Again, ignoring the anomoly of the Hex Head Cap Screw, I like my Dad's definition best:
"Bolts are big and screws are little."

RE: Bolts vs Screws

Yes, terminology is screwed up. With the mix of different languages these days, who knows what's correct anymore?

I agree there are 'lag screws' and 'lag bolts', but if you order a 'lag bolt', most likely you will get a piece of hardware in a bag or box labeled 'lag screw'.

Yes, there are 'socket head cap screws', but not 'socket head cap bolts'. thumbsup2

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Jul 13, 2008)
ctopher's blog

RE: Bolts vs Screws

I can share the swedish definition if someone is interested. We define a bolt as a screw without any threads. A screw is everything else. Still many people name screws as bolts, mostly when the screw is of a large dimension.

RE: Bolts vs Screws

   Okay, how about this?

   A bolt is 25 to 50 yards of fabric, as supplied to a wholesaler.

   I challenge you all to solve a GD&T problem with this information.  :)

                        JHG

RE: Bolts vs Screws

or...

"Bolt out the door after being scr.."

never mind...

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Jul 13, 2008)
ctopher's blog

RE: Bolts vs Screws

vims: A screw without any threads is a blank, or a pin.

RE: Bolts vs Screws

I would checked Machinery's Handbook and my Engineering Drawing and Design... Both had the same defination, which has already been discussed and is mentioned in CBL's first link.

I agree that having screws/bolts be able to "morph" depending on useage is unacceptable. I hate to disagree with what I have considered an infalliable resource (Mach. Handbook), but this is where I'm making my stand!

My definition is going to be: If it will not accept a nut or is installed with a screwdriver, it is a screw. Otherwise, it's a bolt. And before we get into another debate, screwdrivers are flathead or phillips. I don't want to hear about "screwdrivers" with sockets for hex heads. Those aren't screwdrivers in my book. I don't know what they are. I guess boltdrivers.

I'm also not sure where other configurations of internal driving mechanisms fall (i.e. square, star, etc). I suppose since I definately would say that socket heads are bolts, then those would be bolts (unless they will not accept a nut of course!).

-- MechEng2005

RE: Bolts vs Screws

A "screwdriver" is not called that because it only installs 'screws', it is because of its 'twisting' motion.
Therefore, no matter what type of head it has on it, it's a screwdriver. There are also 'nut drivers', same family as the screwdriver, but with a permanent socket end.

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Jul 13, 2008)
ctopher's blog

RE: Bolts vs Screws

ctopher,

   A screwdriver is also a mixture of vodka and orange juice, ideal for removing the bolt of cloth your female companion has wrapp...  oops!

   The original post asked about how ASME Y14.5M-1994 differentiates between bolts and screws.  The final question was "Is there consensus...".  Evidently, the answer to that is "No!"

                 JHG

RE: Bolts vs Screws

Those are my favorite screwdriver! lol

I agree...no consensus. Which is OK, as long as we know how to pick the correct screw or bolt for our designs.

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Jul 13, 2008)
ctopher's blog

RE: Bolts vs Screws

I go with my gut but to be technical I would look at ASME B18.12-2001, "Glossary of Terms for Mechanical Fasteners".

Marcelino Vigil
GDTP T-0377
CSWP

RE: Bolts vs Screws

Well, I think historically, a screw is a threaded rod-like object that uses mechanical advantage to displace or move something else as a function of its being turned, such as  Lead screws, Archimedes' screw, threadforming screws of various types, ballscrew, thumb screws, and screw propeller.

A bolt is simply a rod whose function involves being placed into something else that is meant to receive it, such as the bolt of a lock, a door hinge bolt and the traditional definition for a bolt.

The confusion might come from the fact that screw drivers are called screw drivers, even they are also used for bolts, which would explain the non-functional distinction I've and others have learned (use a wrench on a bolt, and a driver on a screw)...and the rest is history.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

RE: Bolts vs Screws

Very good explanation Matt.
Thanks!

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Jul 13, 2008)
ctopher's blog

RE: Bolts vs Screws

"A bolt is simply a rod whose function involves being placed into something else that is meant to receive it..."

Yup.  Then some nut put a screw thread on one, and things got screwy.  Like this thread <bolting for the door>
 

RE: Bolts vs Screws

I met a guy once that was screwed up by a lightning bolt hit!

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Jul 13, 2008)
ctopher's blog

RE: Bolts vs Screws

There is no standard to justify this but I have noticed often that the difference between a bolt and screw depends on it's size, and were you work.

My last employer was a pipe foundry.  The smallest fastener we had was a 3/8 SHCS.  Everything there was a bolt.  If you asked for a screw you would get a wood screw.

Now I work at for a semiconductor company were a 3/8 fastener is considered very large.  We go down to a '0' on some applications.  Everything here is a screw.

I will add that personally I go with the Machinery Handbook definition based on what the hardware is going into.

RE: Bolts vs Screws

There you go JamesBarlow, I too went from pressure vessels, piping and structural, to optics and lasers and experienced the same thing.

In CPI work, all is 3/4" bolts and studs. In optics, it's all small screws, down to #00, or 1 to 1.5 UNM.

So we really go by 1)our industry, and 2) whatever the screw/bolt standard calls the fastener.

RE: Bolts vs Screws

ctopher - I said I didn't want to hear about it! ;P

Maybe your screwdrivers can have something besides phillips and flathead, but mine don't! I'm putting my foot down on this. You can't change my tools!

RE: Bolts vs Screws

Thanks to virgildesign I looked up and copied these definitions from ASME B18.12-2001:

3.1.1 Bolts
3.1.1.1 bolt: an externally threaded product designed
for insertion through holes in assemblies to mate
with a nut and normally intended to be tightened or
released by turning that nut. The only bolt that has a
washer face is the heavy hex structural bolt.

3.1.2 Screws
3.1.2.1 screw: a headed and externally threaded
mechanical device having capabilities that permit it to
be 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 wrenching
its head. Refer to Table 2 for a listing of type designations
for tapping screws and metallic drive screws.

 

RE: Bolts vs Screws

MechEng, you don't have hex drive or torx/star drive screw drivers?  Not even exchangeable bits for a ratchet or electric driver?

What kind of an engineer are you?winky smile

KENAT, probably the least qualified checker you'll ever meet...

RE: Bolts vs Screws

Well CheckerRon you were typing as I was.

I think that's probably the answer the OP wanted, is ASME B18.12 referenced (directly or indirectly) by 14.5?

KENAT, probably the least qualified checker you'll ever meet...

RE: Bolts vs Screws

Thanks, CheckerRon, that pretty much jives with the rule of thumb I posted, so  think I'll stick with it.

When the people fear their government, there is tyranny; when the government fears the people, there is liberty. - Thomas Jefferson
 

RE: Bolts vs Screws

Time was when I asked for a box of 1/4-20 screws I got a box of devices that may have hex heads or some variety of screwdriver heads. If I asked for a box of 1/4-20 stove bolts I got a box of devices that were designed to be turned or held by a flat blade screwdriver and an equal number of square nuts. Usually unplated.
When installing the heads on my old flathead Ford V8, I never screwed "head screws" into the block. In fact I have never heard of "head screws"  I have heard bikers threaten to do something similar to their enemies.  

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Bolts vs Screws

"Why not the best?"
 Jimmy Carter.

Then why have we gotten the worst from Jimmy Carter?

RE: Bolts vs Screws

Kenat - I have the tools that perform the same function as you mentioned, but the ones I have are hex/torx/star BOLT drivers. Certainly not screwdrivers... I don't know where you shop that you get "screwdrivers" that are used on bolts. Maybe if it's manufactured in a foreign country it is a translation mistake.

-- MechEng2005

RE: Bolts vs Screws

MechEng,

Screwdrivers is the common term.  I've never even seen bolt drivers as a term before.  I hope you are being sarcastic.  If so, sorry for not catching on.  If not, do a search on McMaster-Carr for screwdriver to see.  The do one for bolt driver.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

RE: Bolts vs Screws

fcsuper,

Yes, I was being sarcastic. Just trying to have a little fun with the topic. The fact is that if you ask me for a screwdriver to put in a socket head, I'll hand you the right tool. If I asked you for a bolt driver for a socket head, I suspect I would get the proper tool. =)

It's just sometimes fun to "play" with a topic. Engineer's don't get enough "play" time (at least where I work). It's either right or wrong. Sometimes I think things should be "technically wrong, but fun/amusing."

-- MechEng2005

RE: Bolts vs Screws

So, is an allen wrench a screw driver?

RE: Bolts vs Screws

No, it's an Allen Key

KENAT, probably the least qualified checker you'll ever meet...

RE: Bolts vs Screws

I'd call it a socket head cap screw driver.  smile

Joe
SW Office 2006 SP5.1
P4 3.0Ghz 1GB
ATI FireGL X1

RE: Bolts vs Screws

An allen wrench could be termed as an allen wrench. It would be USED to torque a socket head BOLT though, not a socket head screw.

In my opinion anyways

-- MechEng2005

RE: Bolts vs Screws

Just curious, how do you get torque out of an allen wrench? There may be a way, I have not seen it.

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 08
ctopher's home (updated Aug 5, 2008)
ctopher's blog
SolidWorks Legion

RE: Bolts vs Screws

ctopher
It's the verb, not the direct object.
How do you torque a socket set screw?
(which our friend MechEng2005 might call a socket set bolt)

 

RE: Bolts vs Screws

To my Good Buddy KENAT:
As I recall "allen key" tried unsuccessfully to run for president, and to beat Barack out of the Illinois senate seat---or was that keyes?

 

RE: Bolts vs Screws

btrueblood had the right idea back on 25 August ... the standard talks about fixed vs floating fasteners, not screw vs bolt.  Beyond that, the mental extension to screws & bolts is natural because a nut & bolt work together as a pair to secure mating components between them, whereas a screw is threaded directly into the workpiece ... which is how fixed & floating fasteners work respectively.

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

RE: Bolts vs Screws

I love it when I win.

:)

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