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?
Photo credit: https://3.bp.blogspot.com/-Giy8OrYJTjw/Tfm9Ne5o5hI/AAAAAAAAAB4/c7uBLwjkl9c/s1600/scan0002.jpg
One mnemonic is to imagine yourself opening a jar.
I use the right hand rule - ball up your fist with your thumb sticking out, and turning in the direction of your fingers curling will result in the screw going the rest your thumb points.
Right hand for right-handed threads and left hand for left-handed. If unsure, it’s most likely right-handed.
The assumption in this whole post is that it’s right-thread, since left is so uncommon.
Most common example would be a bicycle, I think - your pedals tighten on “in the same direction the wheel turns” as you look at them. So your left pedal has left-hand thread, and goes on and comes off backwards.
The effect of precession also means that you can tighten the pedals on finger tight and a good long ride will make them absolutely solid - need to bounce up and down on a spanner to loosen them.
Oh God I hate those sneaky left-thread bastards lol.
Me learning this about electromagnetism: huh, neat.
Me learning this about something I actually use in day to day life: 🤯
It’s especially helpful when you’re looking at screws (or nuts!) from the back or any other weird frame of reference.
Your door is a jar.
Is it a jar of jam or jelly?