How to Determine the Direction for Loosening or Tightening a Screw?

[DelElliana]

Standard screws have left-handed threads, where left means loose and right means tight. Turn counterclockwise to loosen and clockwise to tighten. Over-tightening screws can cause damage to the car. There is no fixed rule like left-loose-right-tight or right-loose-left-tight. It depends on the rotation direction. Generally, loosening follows the rotation direction, while tightening goes against it.

[OscarFitz]

I usually follow the right-hand rule when tightening screws, imagining my right hand holding a screwdriver: turning clockwise tightens, and counterclockwise loosens. This rule applies to most household items, like chairs, tables, or appliance casings. But a motorcycle chain mechanic told me that some mechanical parts, like engine flywheel screws, are reverse-threaded, so you need to pay special attention to the labels. When working, it's best to wear cotton gloves for better grip and to protect your hands in case of slippage. If a screw is rusted and stuck, spray some rust remover first and use an extended wrench—forcing it can easily strip the screw.

[DelRylee]

Having repaired cars for over a decade, I judge screw direction mainly by three points: First, remember the rule - regular screws tighten clockwise and loosen counterclockwise. Second, observe the thread angle - hold the screw in your right hand and the direction the threads spiral upward is the tightening direction. Third, test by hand - gently turn counterclockwise half a turn first; if you feel any loosening, immediately stop and switch directions. Especially for screws on aluminum alloy engines, they're particularly fragile - applying too much force and stripping the threads would be disastrous. Just last week, I encountered a customer who broke a bolt while installing a seat themselves, ultimately requiring re-tapping.

[SanEleanor]

When disassembling and cleaning my old washing machine at home, I once got the directions mixed up. Remember that standard screws tighten to the right and loosen to the left, just like twisting a bottle cap. However, in some special cases, such as fan blade fasteners or bicycle pedal axles, reverse threads are designed to prevent self-loosening during operation. Once when replacing an electric vehicle motor, I almost twisted the shaft off. After that, I learned my lesson: take a photo first, look up the model online, and then proceed. I recommend beginners use a reversible electric screwdriver at low speed for a trial turn, so even if it's wrong, you can stop in time.

[VanCaleb]

Found a handy trick when assembling IKEA furniture: Hold the tool in your right hand and mimic the tightening motion—the direction your thumb points is the way the screw moves. This prevents confusion. Note that different screw materials require different approaches; for instance, wood screws should be turned slowly in the final half-turn, and plastic screws must never be tightened with power tools. Last time, my son cracked a computer mount by overtightening. I recommend buying a precision screwdriver with torque measurement, especially useful for small items like glasses or phones.