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Bolts vs Screws 6

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ringman

ringman

Mechanical
Mar 18, 2003
385
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?
 
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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
 
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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.
 
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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
 
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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
 
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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
 
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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
 
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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
 
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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
 
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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
 
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"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>
 
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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.
 
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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.
 
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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!
 
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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.

 
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