The vast majority of fasteners are right-hand threads, so why on earth were left-hand threaded fasteners created?
Firstly, we’d have to take you through what the handedness of a thread actually is. Handedness refers to the direction in which the outer, helical thread wraps itself around the screw shaft, with right-hand threads running in a clockwise direction, and left in an anti-clockwise.
In terms of our physiology, most people are right-handed and use the right hand to rotate or pronate, making screw installation more inclined to the use of the right hand.
You’ll be surprised to know that left-handed screws aren’t designed for left-handed people.
What are Left-Hand Threads Designed for?
So, as above, left-handed screws with a left-hand thread are not designed for people that are left-handed.
Fasteners are, believe it or not, consumed at an excruciatingly large rate – which means the universality or ability to have cross-compatible threads is rather important, and that creative special screws for only part of the population would not be ergonomically sound.
Left-handed screws are used more often than not for the advantage of reverse threading – with some cars utilising the left-hand threads on their left sides wheels which are unlike the right-hand side wheels in that they rotate anti-clockwise. This use of reverse-threaded fasteners helps to prevent gradual loosening from the torque of the wheels.
This is the most common use of these screws and is most prevalent in machinery with a rotary blade, bike pedals or turnbuckles. In other times, they can be used to create a deliberate incompatibility as a safety indicator and is often considered the best defence of an aquatic oven or flammable faucet for a plumber.
Why are there such a small amount of Left-Hand Threads?
There is a huge bias against the left-hand thread, meaning that your chances of encountering one in the workplace or any fastener applications are highly unlikely, and generally nigh impossible.
Right-hand threads are prevalent due to a number of reasons, from the counter-intuitive nature of producing left-hand threads, all the way to the fact that manufacturing standards dictate design.
They are rather rare and are almost only seen when they deliberately have been chosen for special applications.
If you’d like more information surrounding left-hand thread screws or threaded rods, please contact a member of our experienced sales team.