What is it: A BOLT or a Screw?

[Kern Dog]

Maybe it is a regional thing, but I've wondered before which the proper word for certain fasteners.
The torsion bar adjuster on the lower control arm: Is it a screw or a bolt?
Is a screw merely a fastener that has no threaded nut?

I am not completely serious on this, its just that I have heard some smart people use the word screw in applications where I would have used bolt.

[jaak]

I would say a torsion bar adjuster is a bolt. I consider any fastener you use with any type of screwdriver, a screw. If you gotta use a socket or wrench, it is either a nut or bolt.

Jason

[Dino]

I think it's more about the application than the actual item.  If it needs a nut on the end it's a bolt, if it doesn't it's a screw.  Now machine screws, those are tricky little bastards.   

[68X426]

A screw has a point end, a bolt has a flat end. 

[Mytur Binsdirti]

I think it's more about the application than the actual item.  If it needs a nut on the end it's a bolt, if it doesn't it's a screw.  Now machine screws, those are tricky little bastards.   

A screw has a point end, a bolt has a flat end. 

Then why is this called a bolt?   

[BSB67]

.....and this a screw?

[440]

I would say anything that uses a phillips or flat head would be a screw. Anything smaller then roughly 1/4-20 thread is a screw. Anything that bears a heavy load or is larger then roughly 1/4-20 I would call a bolt.

[JB400]

A screw is a clamp that uses an object to thread into, to compress another object against it.

A bolt is a clamp that has to use a nut to compress 2 objects together.

By definition, some fasteners can be classified both as a screw and a bolt.  In the case of the torsion bar adjusting bolt, it is a bolt.

[XH29N0G]

I won't attempt to describe the difference, but I'll know it when I see it.

[ht4spd307]

you screw the pink one and you bolt the silver one .it aint rocket science

[440]

 

[68X426]

Then why is this called a bolt?   

That's a lag screw.  You can call it a bolt I suppose, but it responds to lag screw when you call it.

[b5blue]

Here, let me Google it for you.........http://www.brighthubengineering.com/machine-design/31077-guide-to-fasteners-part-i-overview-of-bolts-and-screws

[HANDM]

My big wonderment is why some people call an engine a motor when clearly a motor is electric.

You wouldn't say"my drill engine quit working", you would say drill motor
You would say "my motor quit running in my Charger"
Then you have motorcycle which confuses the issue even more   

[John_Kunkel]

To avoid confusion I always use the factory terminology...the parts book calls the TB adjuster a bolt.

[Kern Dog]

Holy crap, that woman in Pink is a goddess. I'd be amazed if I lasted long enough to undress.

[375instroke]

My big wonderment is why some people call an engine a motor when clearly a motor is electric.

Neither dictionary definition, nor common usage agrees with that.  Detroit Motor City, motor boat, outboard motor, Harley-Davidson Motorcycles, Department of Motor Vehicles, motorhead, Motor Trend, eBay Motors, General Motors, Ford Motor Co., Federal Motor Carrier Safety Administration, Texas Motor Speedway, Indianapolis Motor Speedway, on and on.

[375instroke]

Bolt: A wrenchable fastener with external threads and a full size shank diameter that is not fully threaded. For a protruding head bolt the length number defines the length from the bearing surface of the head to the end of the unthreaded shank. For a flush head bolt the length number defines the length from the top of the head to the end of the unthreaded shank. Bolts are capable of transmitting shear loads.

Screw: A wrenchable fastener with external threads that is typically fully threaded. For a protruding head screw the length number defines the length from the bearing surface of the head to the end of the thread. For a flush head screw the length number defines the length from the top of the head to the end of the thread. Screws are not typically used for transmitting shear loads.

So this would be a lag bolt because it has an unthreaded shank, and can transmit sheer loads, and that's the most defining part, where other aspects such as not using a nut, are secondary.

Then why is this called a bolt?   

I would still call this a bolt because of the shank.  We use many fasteners in my profession, and we have screws with hexes on them and Phillips recesses, so you can use either, but bolts generally only have hex heads unless they are countersink, but the bolts have an unthreaded part, and that's the part you measure for the length.  Screws are measured by their entire length.

.....and this a screw?

[crj1968]

Screw bolts! Use nails

[djcarguy]

     Baling wire an coathangger make quicker fasteners for repairs,dont they??   

[JB400]

Don't you know that duct tape is the best fastener there is?

[djcarguy]

    No you have to have clean hands an surfaces for that duck tape stuff to work,,who has time to wash AN clean everything,,or anything before the next test drive,HAHA     

[djcarguy]

Don't you know that duct tape is the best fastener there is?

  Duck tape is for that pink SCREW above.HAHA HO..............................................

[maxwellwedge]

When people tell me to screw off I usually bolt for the door.

[Nacho-RT74]

this is an interesting language learning to me.

In Spanish, both, screw and bolt are calls "tornillo". I have allways make difference between screw and bolt, but just repeating what you say and I read, not really knowing why you call it different. ( same about motor and engine difference... spanish got same word for both: "motor", but with accent at the end )

[Kern Dog]

I like tornillo chips and salsa, Nacho...