# Righty-loosey, lefty-tighty **URL:** \ **Category:** Factual Questions\ **Created:** [May 22, 2011, 4:46am UTC](https://boards.straightdope.com/t/righty-loosey-lefty-tighty/582756 "2011-05-22T04:46:28Z")\ **Posts on this page:** 12\ **Page:** 4
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [May 29, 2011, 12:59pm UTC](https://boards.straightdope.com/t/righty-loosey-lefty-tighty/582756/61 "2011-05-29T12:59:35Z")
> [@rowrrbazzle](#): > > This had confused me, too. Your explanation is clear and makes perfect sense. But do people who use it really think this, or have they just memorized “right” to describe the movement of the screw? I’ve just memorized “right” to describe the movement. Or, more accurately, I think of this as an alternate meaning for “right” and “left”. Lacking historical insight, I just consider it originally a misuse of “right” and “left” to mean “clockwise” and “counterclockwise”, but accept it as an alternate use of “right” and “left” now. Likewise in reference to helices. The more proper terms I know of are “dextral” and “sinistral”, but since these derive from the Latin for “right” and “left”, they’re really more of the same. BTW, another place lefthanded threads turn up is in the nuts and bolts drawers of machine shops, around April Fool’s Day. ---
**Author:** ![california\_jobcase](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@california\_jobcase](https://boards.straightdope.com/u/california_jobcase)\ **Post date:** [May 29, 2011, 2:33pm UTC](https://boards.straightdope.com/t/righty-loosey-lefty-tighty/582756/62 "2011-05-29T14:33:00Z")
Here’s a friendly warning for anyone who owns a Ford Festiva- One of the rear spindle nuts is threaded left-hand. I destroyed it with an electric impact wrench. Fortunately the nut was a lot softer than the spindle, and only the nut threads were damaged. It’s the kind of nut one stakes with a punch instead of using a cotter pin, so the reverse threads don’t make too much sense there. ---
**Author:** ![Jeff\_Lichtman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jeff_lichtman/32/1531_2.png) [@Jeff\_Lichtman](https://boards.straightdope.com/u/Jeff_Lichtman)\ **Post date:** [May 30, 2011, 5:22pm UTC](https://boards.straightdope.com/t/righty-loosey-lefty-tighty/582756/63 "2011-05-30T17:22:08Z")
> [@Ruby](#): > > Which begs the question, why in hell can’t the reverse threads be marked somehow so that the user KNOWS not to righty-tighty with the potential for major damage. Hex heads on left-handed nuts and bolts often have distinctive notches on their corners. [This page](http://www.myinfo-123.com/hardware/rod-end-&-spherical-bearings/fk-bearings-steel-lock-nuts--unf-and-metric-threads/2182/8070) shows examples of nuts with both right-handed and left-handed threads, with notches on the left-handed nut. ---
**Author:** ![Fourtyfold](https://avatars.discourse-cdn.com/v4/letter/f/f475e1/32.png) [@Fourtyfold](https://boards.straightdope.com/u/Fourtyfold)\ **Post date:** [May 30, 2011, 8:20pm UTC](https://boards.straightdope.com/t/righty-loosey-lefty-tighty/582756/64 "2011-05-30T20:20:29Z")
> [@mlees](#): > > Speculation: The only thing I could think of might be something like the magnetic naval mines, or time delayed bombs, air-dropped into enemy territory. You might make your screws non-standard, just to make it tougher on a bomb disposal specialist. But I don’t know if that (reverse screw) was ever actually ever done. As I recall (can’t remember which book I have that mentioned this) there were reverse threaded fuses fitted to some regular or time delayed bombs to catch out the bomb disposal squads. If the fuse was attempted to be withdrawn in the regular fashion, the tightening of the fuse would break a vial of acid to initiate a detonator. There was a variety of different fuses used, but at least for the larger bombs I believe that eventually the prefered method of disarming them was to cut through the casing and steam out the explosive. I don’t believe the Germans ever used poison gas as a booby trap. ---
**Author:** ![thelabdude](https://avatars.discourse-cdn.com/v4/letter/t/dc4da7/32.png) [@thelabdude](https://boards.straightdope.com/u/thelabdude)\ **Post date:** [May 30, 2011, 8:40pm UTC](https://boards.straightdope.com/t/righty-loosey-lefty-tighty/582756/65 "2011-05-30T20:40:09Z")
Trailer jacks have a left hand thread. I had the nut strip out in one. Try finding a one inch left hand Acme screw nut. Don’t ask how I managed to make one without a lathe or other machine tools. Office chairs may have them too. Maybe I need to check the screw on my radial are saw that controls the height. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [May 30, 2011, 9:00pm UTC](https://boards.straightdope.com/t/righty-loosey-lefty-tighty/582756/66 "2011-05-30T21:00:42Z")
> [@Fourtyfold](#): > > As I recall (can’t remember which book I have that mentioned this) there were reverse threaded fuses fitted to some regular or time delayed bombs to catch out the bomb disposal squads. If the fuse was attempted to be withdrawn in the regular fashion, the tightening of the fuse would break a vial of acid to initiate a detonator. > > There was a variety of different fuses used, but at least for the larger bombs I believe that eventually the prefered method of disarming them was to cut through the casing and steam out the explosive. I don’t believe the Germans ever used poison gas as a booby trap. That was covered in the BBC series Danger UXB That was fictional, but based on facts from WWII. I don’t recall that there were actually reverse-threaded fuses. Rather there were anti-withdrawal devices in later bombs, so that if the fuse was withdrawn from the bomb, a spring-loaded trigger shot across and hit the detonator. I don’t think acid detonators were used in these bombs; they would be too slow for aerial-dropped bombs. Acid detonators are used in time bombs, like those used in resistance sabotage. ---
**Author:** ![Mk\_VII](https://avatars.discourse-cdn.com/v4/letter/m/5f9b8f/32.png) [@Mk\_VII](https://boards.straightdope.com/u/Mk_VII)\ **Post date:** [May 30, 2011, 9:46pm UTC](https://boards.straightdope.com/t/righty-loosey-lefty-tighty/582756/67 "2011-05-30T21:46:12Z")
In the early days of threaded fasteners nut and bolt were individually cut for each other according to the workman’s whim (as anyone who tries to dismantle an old steam engine will soon discover). Many industries developed special-to-industry threadforms, and one or two, like British Cycle Thread, still survive. Joseph Whitworth was the first to develop a standardised [Whitworth] thread system, in 1841. ---
**Author:** ![Fourtyfold](https://avatars.discourse-cdn.com/v4/letter/f/f475e1/32.png) [@Fourtyfold](https://boards.straightdope.com/u/Fourtyfold)\ **Post date:** [May 30, 2011, 11:14pm UTC](https://boards.straightdope.com/t/righty-loosey-lefty-tighty/582756/68 "2011-05-30T23:14:24Z")
> [@t-bonham@scc.net](#): > > That was covered in the BBC series Danger UXB That was fictional, but based on facts from WWII. > > I don’t recall that there were actually reverse-threaded fuses. Rather there were anti-withdrawal devices in later bombs, so that if the fuse was withdrawn from the bomb, a spring-loaded trigger shot across and hit the detonator. I don’t think acid detonators were used in these bombs; they would be too slow for aerial-dropped bombs. Acid detonators are used in time bombs, like those used in resistance sabotage. I can’t find the source book as I think it must have been from a library, but I’m certain the reverse threaded fuse was specificly mentioned by the (ex bomb squad) author. The delayed detonation wouldn’t be a problem I’m sure, bombs with delayed fuses of some type were common enough. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [May 31, 2011, 4:09am UTC](https://boards.straightdope.com/t/righty-loosey-lefty-tighty/582756/69 "2011-05-31T04:09:19Z")
> [@hibernicus](#): > > Because you weren’t looking at it from the object’s point of view, and you were privileging a certain direction as “up”! Actually, that’s what you are doing also. Your examples (planes, running around the block) work because you can’t look at either example from below. Looked at from the bolt end, a nut tightens by turning left. > [@GreasyJack](#): > > I’ve always heard right-handedness is the convention because a right-handed person can put more torque on a right-hand screw than a left-hand one, and something like a wood screw is usually a lot easier going in than coming out. I don’t buy this for two reasons. One, I don’t really think the strength disparity is true. I think I can turn with about the same strength both ways. Two, the same convention applies to all threaded things. Bolts, screws, bottle tops. Most of these things you would want your _weaker_ turning direction to be doing it up, not undoing it. Tightening things sufficiently tight is not usually the problem. It’s loosening things that is the problem. ---
**Author:** ![thelabdude](https://avatars.discourse-cdn.com/v4/letter/t/dc4da7/32.png) [@thelabdude](https://boards.straightdope.com/u/thelabdude)\ **Post date:** [May 31, 2011, 4:22am UTC](https://boards.straightdope.com/t/righty-loosey-lefty-tighty/582756/70 "2011-05-31T04:22:17Z")
Exactly. Many times I have had to get a wrench to loosen something I tightened with my fingers. The coefficient of static friction is higher than the coefficient of dynamic. I think it is an instinctive right hand thing. It got to ‘‘be the way things are always done’’ before much thought went into it. ---
**Author:** ![Projammer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/projammer/32/559_2.png) [@Projammer](https://boards.straightdope.com/u/Projammer)\ **Post date:** [May 31, 2011, 5:02am UTC](https://boards.straightdope.com/t/righty-loosey-lefty-tighty/582756/71 "2011-05-31T05:02:18Z")
Plenty of examples here, but I’ll go ahead and add mine. A couple of months ago I did a complete teardown and rebuild on my old Wards table saw. The anchor nut on the blade tilt lock lever was a left hand thread. ---
**Author:** ![mittu](https://avatars.discourse-cdn.com/v4/letter/m/ecd19e/32.png) [@mittu](https://boards.straightdope.com/u/mittu)\ **Post date:** [May 31, 2011, 12:48pm UTC](https://boards.straightdope.com/t/righty-loosey-lefty-tighty/582756/72 "2011-05-31T12:48:48Z")
According to an episode of QI, British armed forces used to supply POWs being held by the Germans with coats that had small compasses hidden inside the coat buttons. The Germans figured this out so they began to use buttons with a reversed thread so when the Germans tried to unscrew them they only tightened the lid. [Previous page](https://boards.straightdope.com/t/righty-loosey-lefty-tighty/582756.md?page=3)