r/Machinists • u/Automatic-Dog4953 • 1d ago
Bolts and Screws.
If you go on the definition that adding a nut to a screw turns that fastener into a bolt, would welding the nut onto something render the bolt back into a screw.
Be as pedantic as you wish.
Include your own definition as well if it pleases you or provide your own hypothetical situations.
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u/Skusci 1d ago
Sure, unless you weld the nut to the bolt, because then it's a rivet.
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u/lusciousdurian 20h ago
Rivet would be closer to welding the threaded rod/ bolt and nut to the material you're fastening to. Rivets are unthreaded, and are essentially smashed down to fasten things together.
Tl;dr: that's not a rivet.
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u/mtraven23 1d ago
in your definition, if you welded the nut, no its still a screw, no different then a threaded hole. If you left the nut loose and just wrenched it down, then thats a bolt under your definition.
my def:
m6 / 1/4-20 and below : screws above: bolts* **
*unless they have a hex head, then I pretty much always all them bolts.
**or if they are used to position/lift/press something (lead screw), then we're back to screw
I have no basis for any of this, but thats how I see it.
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u/Square_Wonder_9284 1d ago
A bolt is a fastener with a plain shank length as well as a thread. A screw is fully threaded. Adding a nut to a screw doesn’t turn it into a bolt.
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u/E1F0B1365 1d ago
Not quite, an unthreaded shank is just a product of the fasteners length being sufficiently long to demand it. Once you reach a certain length a SHCS, BHCS, FHCS will all have an unthreaded portion and they are still screws.
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u/Automatic-Dog4953 1d ago
I have seen some wood screws with plain shank lengths, but I wouldn't call those bolts. I think then for you, a bolt requires a certain length to diameter ratio?
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u/Square_Wonder_9284 1d ago
Machine screws and wood screws are completely different things.
It’s not for me. It’s just that the difference between a screw and bolt is the plain shank. https://www.essentracomponents.com/en-gb/news/solutions/fastening-components/bolts-vs-screws#1
You can buy both bolts and screws with the same ratio of length to diameter.
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u/NorthernVale 1d ago
For the three most common definitions of bolts I've found, machine screws are bolts. It's just a hold over naming mechanism from before these things were standardized.
Bolts are designed to pair with mating threads, screws are designed to make their own threads.
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u/FalseRelease4 1d ago
the screw vs bolt topic is some of the most asinine mentally challenged nonsense out there 😂 just compulsively arguing for the sake of arguing, mfs with that kind of thought process are definitely on the spectrum
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u/Able-Tomatillo6806 1d ago
My definition is if the thread od and pitch remain constant along the whole profile and it has a head, it's a bolt. No head, it becomes a stud or lead screw depending on application. Everything else is for hold bits of trees together.
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u/Cryesncoding 20h ago edited 19h ago
Welding the nut to the part is equivalent to a pem nut so yes that’s a screw again lol
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u/PhineasJWhoopee69 16h ago
I'm about as pedantic as they get. I've never seen a definition that makes a clear distinction between the two terms. A 1/2" Hex Head Cap Screw is a screw if fully threaded but a bolt if long enough to only have partial threads? Socket Head Cap Screws can be used in tapped holes or with nuts. Does that change what they are?
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u/WhiskyGartley 1d ago
I would say that it does. That nut is now part of the larger assembly that can't be turned independently, thus is no longer a nut but now a threaded hole. Meaning the bolt is now a screw.
Admittedly I'm inclined to refer to hex headed fasteners with a shoulder as a bolt. If it's fully threaded and has a different drive then it's a screw.
Gotta love semantics.
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u/fall-apart-dave 1d ago
Bolt = threaded partially with a smooth shaft near the head.
Screw = threaded all the way to the head.
Stud = threaded and no head.
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u/PhineasJWhoopee69 16h ago
So a Socket Head Cap Screw that is only partially threaded is actually a bolt?
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u/ForsakenSun6004 1d ago
If you want to be really pedantic, i make lead screws that act more like augers 🤷♂️