“Righty tighty, lefty loosey” has always bothered me.
First, what does right and left mean in terms of rotating something? You have to remember the arbitrary societal choice that the top of the rotating thing should go right and therefore right means clockwise.
Second, clockwise doesn’t have meaning unless you establish a perspective. Clocks go clockwise, unless you look at one from behind. When you’re tightening a screw, it’s usually clear what the correct perspective is. Not so with something like, a home soda machine. A home soda machine involves screwing a bottle upward into the machine. Now it’s unclear what perspective is correct. You can go with the perspective that you’d actually have using the machine, looking from above, and turn clockwise, and this would be the more familiar motion. But it’s wrong. The bottle is like a screw and it doesn’t know if it’s going up or down, all it knows is tight or loose. To use “righty tighty” you’d have to imagine a perspective outside your body, figure out where the top of the bottle is, visualize that going right, and then figure out how you’re supposed to move the bottle from your actual perspective to make that happen. Lunacy.
Third, the whole thing only applies to male pieces, and oppositely to female pieces. Given a nut and bolt, the bolt obeys “righty tighty” but the nut obeys the opposite. Maybe you can glean some orientation from the bolt, so you know to flip the system over when changing from bolt to nut, and this cancels with the male/female switch. But pretend the bolt has no end. Now tight and loose aren’t even defined. How do you describe the behavior of the system?
I propose the right-hand rule (RHR) as the correct mnemonic for screwing systems.
Just a quick tangent on RHR. In case you aren’t familiar, RHR describes a way to hold your right hand to more easily reason about certain systems. I learned RHR two ways. First, the bad way: your pointer finger, middle finger, and thumb are splayed in 3 perpendicular directions. Your pointer is the +x direction, your middle +y, and the thumb is +z. Second, the good way: you make a thumbs-up and slightly unclench your fingers. Your fingers begin in the +x direction (because x comes before y) and then curve toward +y. Your thumb is +z. The second one’s easier to remember and it’s also easier for things like remembering which way our solar system goes (Venus and Uranus being exceptions) and magnetic lines created by a current.
Anyway, RHR applies to screwing systems like so: if you rotate the way your fingers go, the thing moves the way your thumb points. No exceptions; you remember exactly one thing: to use your right hand instead of your left, and this exactly lines up with our societal decision to make screwing systems obey whatever “righty tighty” means.
For example, you look at a screw and put your right hand in front of you in a relaxed thumbs-up configuration. You see your fingers emanate from your hand and turn counterclockwise. Your thumb sticks up. Therefore, if you turn the screw counterclockwise, it will go up, that is, loosen. Counterclockwise maps to “left” in “lefty loosey”.
You instead look at the thing the screw is embedded in. If you turn it counterclockwise, it would also go up, but this would tighten the system, not loosen it.
You want to put a bottle in a soda machine. You want the bottle to go up, so you stick your right hand’s thumb up. You see your fingers go counterclockwise. So that’s how you get the bottle in. Later, you forget how you got the bottle in. You want the bottle to go down, so you stick your thumb down, and see your fingers now go in a clockwise direction, so that’s the way you turn the bottle.