this post was submitted on 13 Oct 2024
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The world has a lot of different standards for a lot of things, but I have never heard of a place with the default screw thread direction being opposite.

So does each language have a fun mnemonic?

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[โ€“] [email protected] 18 points 3 days ago (6 children)

It depends which bicycle pedal you're screwing in. They have opposite threads, designed where they're self tightening on each side.

[โ€“] [email protected] 5 points 3 days ago (1 children)

Same with gas regulators that attach to the cylinders, for some reason. Oo and some hub nuts on cars

[โ€“] [email protected] 6 points 3 days ago (1 children)

I've heard flammable gas uses reverse (left hand) thread to prevent cross connection. At least for welding gases in NZ; not sure about natural gas.

[โ€“] [email protected] 1 points 3 days ago (1 children)

Acetylene does, gas lines are standard pipe.

Suppose it's cause natural gas runs at like, 1-3 psi, while a fresh tank of acetylene is 5,000?

Least in the US

[โ€“] [email protected] 1 points 3 days ago

It's also torches and everything after the regulator, which run at much lower pressure. At least in NZ

I think it might be because they're connected and disconnected regularly so misconnection is a common problem, even with colour coding. Gas work on houses involves actually putting the fittings on pipe and is done by people who should be concentrating more on that rather than on what they're about to weld/cut.

[โ€“] [email protected] 4 points 3 days ago

Exactly! Bicycle pedals have a left-hand thread on the left-hand side and "normal" threads on the right-hand side.

[โ€“] [email protected] 3 points 3 days ago (1 children)

If I remember correctly, old timey glass kerosene lanterns also have backwards threads for some reason

[โ€“] [email protected] 6 points 3 days ago

Gas threads and water threads are opposites to each other for safety reasons. Might be part of that thought.

[โ€“] [email protected] 2 points 3 days ago (1 children)

Please tell Tongshen, who manufactures the popular TSDZ2 motor. The pedal keeps coming loose because they don't do this. I keep a key on me to tighten it when it starts to loosen.

[โ€“] [email protected] 1 points 3 days ago

Oof, that's some piss poor engineering right there.

[โ€“] [email protected] 2 points 3 days ago

Bottlescrews and turnbuckles both have one end threaded in each direction.

[โ€“] [email protected] 1 points 3 days ago

And remember folks, pedal wrenches are for taking pedals off, not installing them. Except for that commenter with the e-bike.