Is it a Bolt or a Screw?

[MensaPE]

As a young engineer, someone asked me the difference between a Bolt and a Screw. I guess the natural tendency is that Bolts are big, with a Hex head, screws are small with slots or 'phillips' heads, but NO! To tighten (or loosen) a bolt, the externally threaded 'male' element is held stationary, and the internally threaded 'female' threaded element is turned. So a bolt can be tiny, or huge. Similarly, a 'Screw' is turned to tighten or loosen it, into an internally threaded fastening element, whether a nut or 'female' threaded item, and Screws can be tiny, like for a watch, or they can be enormous.
I got this from ASME (American Society of Mechanical Engineers) resources, way before the Internet, seemingly eons ago.

 

[Forty Niner]

So if I take my #10 / 32 cap screw and put a nut on the end of it, does it become a bolt?

 

[MrWhoopee]

So if I take my #10 / 32 cap screw and put a nut on the end of it, does it become a bolt?

Depends on whether you hold the nut and turn the "fastener" or hold the "fastener" and turn the nut.

 

[RJSakowski]

Funny, in all my years working with engines, I have never heard a reference to head screws. Curiously, a bolt doesn't need to have threads. Examples are a dead bolt or a bolt from a rifle. Crossbow arrows are called bolts. I'm not sure where the bolt of lightning fits though.

Depends on whether you hold the nut and turn the "fastener" or hold the "fastener" and turn the nut.

Is a scrolt or a brew if you turn them both?

 

[SLK001]

I always considered a bolt to be something that needed a "mate" to be engaged, be it a nut, or a tapped hole, while a screw could be engaged without a "mate", as it cut its own as it is driven in.

Also, fabric comes in "bolts"!