Tighten and loosen nuts and bolts.I have never understood a left-right handedness on a circle i.e., tighten or loosen a nut. There is really only clockwise and counter clockwise directions.

Me, I use the old finger curl method to loosen or tighten nuts and bolts since there are lefand right handed threaded items around.

Point the appropriate thumb(left for left threaded, right for right threaded) in the direction to move the nut, culr ones fingers into to palm and twist the nut in that direction. Know that there are left and right handed threaded items on cars.


There are indeed left handed bolts and nuts and they are usually used in applications where the combination of rotation and vibration tends to loosen the nut / bolt. Chrysler used to use left handed lug nuts for their wheels. (Not sure when they stopped.)

They are usually marked in some way. The ones I have seen have a dot or a slash on a visible location.

BTW, the inlet / oulet of my propane tank for my grill is left handed.


Chrysler stopped so long ago I don’t even remember. Too many studs got busted off. The theory is sound, but it was a case of trying to solve a problem that didn’t really exist. Properly torqued lug nuts don’t come off.

The only other left handed threads I can think of are on bicycle bottom brackets.


The nut on the flush handle of some toilets threads onto a left handed thread. I spent half an hour trying to remove a broken handle when I realized that it had the left handed thread. My 1948 Dodge had the left handed threads on the driver’s side of the car. Apparently, Chrysler believed that the bolts would work loose on this side with right handed threads. I guess someone at Chrysler observed that cars with right hand threads on the left side weren’t losing their wheels, so they went with the rest of the world.


One more classic about left handed threads from the folklore: Apparently, theft of light bulbs from the subways in New York City was a real problem. The answer was to have special bulbs with left handed threads. Thieves couldn’t easily unscrew them and even if they did figure it out, where could they use the bulbs?


Any other lefty knuckle busters other than old VW left rear wheels torqued to 220 ft-lbs? I just wish that the lefty-righty axiom would go away.Those toilet parts, being plastic, will make one swear after the time being spent screwing around. And ,yes, rotational and vibrational qualities made left handed threads necessary.


The “right hand rule” where your curled fingers indicate the direction of turning and your thumb indicates the direction of movement is standard practice in physics when treating angular displacement and velocity as a vector.
Also, when using conventional current flow, that is electricity goes from the positive termanal to the negative terminal of a battery, the curled fingers of the right hand indicate the flow of current in a coil and the thumb is the north pole of the resulting magnetic field.

Home built airplanes that used Volkwagon engines needed special props pitched for left hand rotation since they used the bell housing for the firewall engine mount and placed the prop on the harmonic balancer end of the engine. Most all the Russian planes of WWII had left hand props.

The acetylene hose of a oxy-acetylene torch has a left handed thread and the oxygen hose has a right handed thread so you won’t mix them up.


It’s been a long time since I’vde changed one, but I seem to recall that propane tanks also have left hand threads.


Also, one’s thumb, index and middle fingers will physically describe a right or left-handed coordinate system (i,j,k unit vectors).


Tighten and loosen nuts and bolts.I have never understood a left-right handedness on a circle i.e., tighten or loosen a nut. There is really only clockwise and counter clockwise directions.

It’s just a matter of perspective. Right/Left handedness can refer to the direction the wrench handle is moved to tighten the fastener when the handle is at the 12 o’clock position.


MGBs and other British sports cars that had a center spline and a single nut (traditionally a knock-off) had different handing depending on the side of the car (similar to Chrysler). I had my MGB servived by an uninformed mechanic, and he replaced a worn-out hub with a wrong handed one. I drove about 3 miles and noticed my wheel rolling off into the distance when I came to a stop. Very diturbing.