Where did right hand threads come from?

A friend posed the question on another board. Just to make it painfully obvious, I'm talking about how most screws tighten when you turn them clockwise as viewed from above. Left hand threads tighten when turned counter-clockwise.

I'd assume that right hand threads are the convention because you can hand tighten better that way when you use your right hand, but is the real reason and when did it happen?

According to Encyclopaedia Brittanica, screws date back to at least the 5th century BC and probably earlier. They probably originated in Egypt but there are no records as for why.

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Jim Petty
An oak tree is just a nut that stood it's ground

I seem to remember, way back in high school, learning something in my physics class about a "right hand rule of rotational momentum" or some variation on that. The gist of it was that if something is rotating clockwise (from the observer's point of view), it will naturally want to move away from said observer. Mr. Lew gave this as the reason that some guy decided to use right hand threads instead of left, as left hand threads don't naturally want to screw into stuff. Of course, this was a while ago, and I really don't rememeber a lot of the stuff in that class.


------------------
Jeremy....

I can think of no more stirring symbol of man's humanity to man than a fire engine - Kurt Vonnegut

"right hand rule of rotational momentum"
if something is rotating clockwise (from the observer's point of view),
it will naturally want to move away from said observer. Sounds like Mr. Lew had a screw loose left hand or right hand I don't know.
There is that thing about elecro magnetism , electrons rotating or something where you make a fist.Seems like this is just a thing that became convention through use.

Right hand rules and all that jazz apply to charged particles moving through magnetic fields... And not to screw threads. Not sure where the convention came from, but its an arbitrary convention. The physics of a screw say that it makes no difference which direction you screw it in.

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Jason R Remy

"Open mindedness is not the same thing as empty mindedness."
-- John Dewey Democracy and Education (1916)

Or it could be a very fuddled memory of gyroscopic precession. But, one way or another, it would have nothing to do with screw threads.

------------------
John W. Kennedy
"Compact is becoming contract; man only earns and pays."
-- Charles Williams

There once was a fellow named Fred,
Whose........... oops sorry

The right hand rule is associated with manny, manny physical phenomena. For an explanation of the right hand rule as it applies to mechanical engineering, see http://www.physics.uoguelph.ca/tutorials/torque/Q.torque.intro.html#RHR

The main point isUsing the right hand rule, we can find the direction of the torque vector. If we put our fingers in the direction of r, and curl them to the direction of F, then the thumb points in the direction of the torque vector. but check the website for an illustration.

To further explain (or confuse) things: Refer to Figure 2 in the above link. Imagine that the pivot point (yellow dot) is a bolt and the the beam of length 'r' is a wrench handle. The right hand rule tells you the direction of bolt torque (and direction of bolt movement - in or out of the screen) based on the direction of the applied load. This would be so much easier to demonstrate physically.

I'm assuming that the fact that a typical screw moves in the direction of applied torque isn't a mere coincidence, but correct me if I'm wrong. If you have any questions, come see me after class.

OWWWWWW ,Strainger, now my brain really hurts. But why clockwise to tighten?
I may have figured it out. No one could come up with a catchy alternative to "Righty tighty, lefty loosey."

Sorry about your brain, mr john. It's tough to describe verbally. The most effective way to demonstrate the right hand rule would be to make an *.avi file of it (complete with narrative and visuals) and put it on a web page. Unfortunately, I don't have the resources for that.

And, yes, I apply the right hand rule at work. One of the few and proud.

Strainger, don't worry bout my brain I try not to use it too much anyway. I apply a right hand rule at work too, the righy tighty one. Well, really I generally switch to forward or reverse on the Makita.
Engineer ,ey? I am the one that has to build the stuff yall come up with. One of the tired and frustrated.

I can't believe no one has yet pounced on Strainger's remark that Mr. John's brain is difficult to describe verbally.
*wink*

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Live a Lush Life
Da Chef

What a screwy thread
(had to be said)

Sorry guys. You walk away from the PC for a couple of days and you miss everything ;-)

I think that the right hand rule in physics is a convention derived from how the two vectors (lever arm and force) multiply; the cross product will be at right angles to both in the specified direction.

The electromagnetic right hand convention (again, if I remember correctly) relates to the direction of magnetic flux with respect to electron flow within a coil and was used for quite a while before it was proven that mankind had been lucky and got things right on this one. It doesn't have anything to do with threaded screws unless there is a subatomic reason why most people are right-handed (and wouldn't this be advanced research ;-) )

All, thanks for the input (bad puns included.) If it could be proven, I'd still lay money that right hand threads are the standard because a right hander can exert more torque (for comparison, note how when using a crescent wrench, the handle leads the motion; too much force in the opposite direction and the wrench will break or round the flats of the bolt or nut.) It looks like the reason for right hand threads will remain lost in the wastelands of conjecture.

It has been my experience that it is usually harder to UNscrew a tight bolt than torque one down. So to make it easier on a righty shouldn't the threads be reverse? You need to avoid crescent wrenches if you can they do rond um over. But to turn the other way you flop the wrench.
Post Newtonian? Well the rule or law that explained a phenomenon that had always been around. If there is a physical reason the reason would have been there before any one knew why. Things fell down before Newton so people propped um up.
Strainger I still don't see how that applies to the direction. Wether you are turning left or right doesn't the same formula apply? It seems to be more about the amount of force applied by a lever of a given length, not direction.
For a while I was thinking it had something to do with the way screw cutting machines work . but actually it works better the other way.Lathe heads are on the left to accomodate righties and it seems it would be easier to move the cutter away from the head. BOING!
Just popped into my brain. Cutting threads to RECIEVE a screw, (making a nut),(no rude comments) you turn the tap clockwise. For a righty it is easier to control the force and precision pulling with the right hand than the left. Isn't it? maybe
I tried to type a verbal description of my brain but it just made it hurt more. I would send a picture but I can't fit my Kodak to the microscope.

[Strainger]

This new BB setup is really messing with my head.

Cornflakes, you bring up some good questions - most of which, unfortunately, I can't answer (although I'll research as much as I can on my end):

1) Do right hand threads follow the right hand rule? Yes (This is the only question I can answer at this time)

2) Were right handed threads refered to as "right handed threads" before the right hand rule was discovered? I don't know

3) Who were the first people (civilization and time period) to use bolts/screws? I dunno

4) Were the earliest bolt/screws right hand threaded, or did they even have a standard? Don't know this either

I think that about sums up what we're looking for. I'll research these questions and let you know what I find out.

[mr john]

This is great i was sending a reply full of clever witticisms when 'scheduled maintenance' hit.Now I can't do a point by point. I mean the other postings aren't even here below this form. happening to any body else?
Any way, I think I know. At first I thought it had something to do with screw cutting lathes.The power head on a lathe is on the left to accomidate us righties. They turn top down toward you .( If somebody starts a thread about woodworking acidents I'll tell you about the exciting whapped in the face by a mesquite log adventure and you'll know why thet turn down) Anyway, I thought that it was a natural movement to move the cutter away from the head. Guess what? That makes a reverse thread. Then I had the BOING!
Hand tapping. They didn't have lathes WAY back then. They cut threads by hand.The tap is a T handled affair. If you are tapping inside threads ( the nut [no comments now])the tap sticks down, if you are making a screw the tap is a hole in the middle of the handle with hard teeth set at an angle. You slip it over the free end of the screw.Now when you are tapping you turn it... clockwise. I don't know about all righties but I have more control over force and precision when I PULL with my right hand rather than push. ( there is a posting about batting somewhere and they go into that in great detail) That makes a screw with a right hand thread. So that is my take on it for now. OH DANG! I just thought, what if the teeth were angle the OTHER way. Shoot! is there an aesthetic reason? Or maybe cutting the teeth in the tap is easier away and to the right?

[NanoByte]

Well, now, if you're going to invoke all those things you learned in school, how about this?:

The Coriolis force affecting the direction of vortices in the Northern Hemisphere -- like where Egypt is, which location is claimed in a post above to be the place where screwings first regularly took place (although I suspect it was really somewhat further south). ;-) You think those sons o' pharoahs saw those vortices going toward the center of the earth (being north of the equator) and figured that perverted nails would only be so similarly groovy?

Well, I think the name of the game around this forum is to make up a reason when you can't find one. Certainly, all those conventions of physicists and engineers came as a *result* of the right-hand screw's predominating. The right-hand screw is probably only the result of ancient Egyptians (or whoever really first became helically biased)'s being mostly right-handed, and I think it's a lot more natural, for a right-handed person to twist clockwise, and no doubt, such persons can more easily produce a large torque in that direction. You would figure that most people never hang around to take the screws out again, and anyway, in the case of no pre-threading, it requires much more torque to put screws in than to take them out.

BTW, if there are any auto mechanics tuned in, I once had the front disc brakes on my MGA fixed by a brake mechanic. The hubs have opposite threads on the two sides. . . You got it. At 55 mph on the freeway, I suddenly had three wheels and one fixed disk and ended up in the center divider. If you insist on having a British car, be sure you check out whether your mechanic's brain hemispheres are properly polarized.

Ray (Right-handed -- and, hey, I'm just an *electronic* engineer; I don't screw around. But in Berkeley, here, you seemed to get screwed to the left.)

[mr john]

TWO PAGES? Goll durn it if I put both hands on a great long wrench (lever) and hang from it, it don't matter if I got it on the left or the right side! Its getting ALL mt torque. And this new deal after "scheduled maintenance" has got me torqued! I hope they remembered to retighten(clockwise) the oil drain plug, I don't even wanta think about the brakes. There is someother stuff i could say but I can't see the postings.

[rjk]

Cornflakes said:

The electromagnetic right hand convention (again, if I remember correctly) relates to the direction of magnetic flux with respect to electron flow within a coil and was used for quite a while before it was proven that mankind had been lucky and got
things right on this one. It doesn't have anything to do with threaded screws unless
there is a subatomic reason why most people are right-handed (and wouldn't this be advanced research ;-) )

Isaac Asimov wrote an article quite a few years ago that he called "The Left Hand of the Electron", later collected in a book of the same name. He cites some research that seemed to show that electron spin is biased, and suggests that this might explain why proteins (and screws and people!) exhibit handedness.


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Bob the Random Expert
"If we don't have the answer, we'll make one up."

[Astroglide]

Whoa!! My bad. I meant that T = r X F. Yes there is a major difference.

F X r != r X F ?
I feel I must have missed something here. Could you please explain the major difference to those of us who still believe in the commutative property of multiplication?

[Strainger]

Astroglide, the 'X' in this case refers to a cross-product of vectors. The answer gives you a magnitude and a direction. r X F and F X r have the same magnitude, but opposite directions.

[mr john]

Ok so now I know why my electric screw driver works so well. except when I am working over my head then it screws up.

------------------
Signitorily yours, Mr John
" Pardon me while I have a strange interlude."-Marx

[Alphagene]

If you take apart a common home tabletop fan to clean it, you'll usually discover that the nut in the center of the fan holding it on is reverse-threaded. Again, to prevent the rotation of the fan from "unscrewing" the nut.

So why not keep the nut threaded normally and have the fan blades go in reverse?

Actually, there are common uses of left hand (counterclockwise = screwing on) threads. Usually, when they're holding on something that's rotating.

For instance, if you have real wire wheels on your car that screw onto a single center hub, the big screw cap that holds the wheel on will be reverse threaded. That way the rotation of the wheel tends to tighten rather than loosen the nut.

If you take apart a common home tabletop fan to clean it, you'll usually discover that the nut in the center of the fan holding it on is reverse-threaded. Again, to prevent the rotation of the fan from "unscrewing" the nut.

So clearly, there's no reason a reverse-thread can't work just as well. I think it's simply a matter of more people being right-handed and it being easier to exert more force to screw on a right-threaded nut with your right hand (and vice-versa for left-threaded. If most people were left-handed I bet "reverse" threading would be the standard).

cornflakes, the right hand threads are related to the right hand rule as used mechanically. There is a right hand rule regarding magnetic flux, but that doesn't play here. (You're right about the right hand rule being used to determine direction of the cross product). If you look at my first post in this thread along with the link. You'll see that T = F X r where

T is the torque
F is the applied load
r is the lever arm distance at which the load is applied

A right hand threaded bolt moves in the direction of torque, i.e. it follows the right hand rule.

Whoa!! My bad. I meant that T = r X F. Yes there is a major difference.

"...the right hand threads are related to the right hand rule as used mechanically"

Are you sure? I assumed that the right hand rule is a post-newtonian concept. Furthermore, I was under the impression that threaded shafts have been around since the Egyptians, Sumerians or Early Greeks and I assume that they had right hand threads. Why?

The ridges on the conch shell in my bathroom form a right hand screw, but you have to rotate the shell in a left hand fashion (counterclockwise as seen from the top) to pour water out of it, so I doubt that they were modeled after nature. The early threaded fasteners were probably used in static applications, so the thread direction didn't matter, as it does in moving assemblies; maybe it was just the natural direction for the workers to turn something after having used earlier mechanisms (windlass, touniquets, etc...)

[mr john]

Have the fan blades go in reverse?
Alpha,I think this has to do with that electromagical stuff they are talking about.

[EnigmaOne]

{{{I can't believe no one has yet pounced on Strainger's remark that Mr. John's brain is difficult to describe verbally. *wink*}}}---Chef Troy

Actually, I was thinking of pouncing on this:

{{{And, yes, I apply the right hand rule at work.}}}---Strainger

But I won't . *G*
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
{{{So why not keep the nut threaded normally and have the fan blades go in reverse?}}}---Alphagene

As an aside: Because that would suck.

So much for lurking!


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--Kalél
(The Original EnigmaOne)

[mr john]

well, corn, you started this thread about threads. Now look how flakey it's become.
The obvious answer is because it's the only right way to do it, as any right wingnut will tell you.

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Signitorily yours, Mr John
" Pardon me while I have a strange interlude."-Marx

[NanoByte]

Well, none of the above explains why drill bits drill clockwise. And what about the corn borer. Does it bore clockwise or counterclockwise? And which way did the Egyptians make their animals turn their water pumps and why?

Maybe all these things depend on which way the earth is spinning. It did change a few times, didn't it?

Ray (wouldn't be this corny if I weren't so bored)

[Strainger]

::Kicking myself in the ass as I type this::

I was at the used book store this weekend (the books, not the store, were used), and decided to find out what I could about screws. To summarize (from memory, so cut me a little slack):

1) Although they did exist some time earlier, the use of screws didn't really take off until the invention of Archimedes' screw.
2) There were no standards regarding pitch, size, etc. until early in this century (or maybe it was late last century).

I wasn't able to find anything about right-handed threads until I pulled out one of my textbooks here at work. The answer was about 2 feet away from me the whole time. From Mechanical Engineering Design by Shigley and Mischke:All threads are made according to the right-hand rule unless otherwise noted.It doesn't require a giant leap in logic to associate the right-hand rule with right-handed threads.

[jayron 32]

A right hand threaded bolt moves in the direction of torque, i.e. it follows the right hand rule.

I'd still have to draw it out to see if it were so (too lazy right now) but if it WERE so, the difference between a righthanded screw and lefthanded screw WRT mechanical advantage due to torque differences is MINISCULE... As r->0, T->0 so for the radius of a screw, torque should be damn close to nil within experimental error for any reasonably small F, such as one that could be exerted by the average human hand. It is doubtful that the ancients, in designing the screw, noticed any difference. Also, I believe, since force is applied equally to points equidistant along a line perpendicular to the axis of the screw, net T=0, but this could be bullshit. So even if the righthanded screw DOES obey the righthanded torque rule (and I have not been convinced that it is necessarily related) it does not make enough of a difference to be measured.

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Jason R Remy

"Open mindedness is not the same thing as empty mindedness."
-- John Dewey Democracy and Education (1916)

[Strainger]

Ignore my response to the first quote, jayron. Upon rereading, I realize that I misinterpreted that statement earlier.

[jayron 32]

OK... Strainger, I think by your second post you may have gotten my point, but I'll restate it for those that don't:

A screw threaded so that a clockwise turn tightens it offers no mechanical advantage over a screw threaded so that a counterclockwise turn tightens it. Thanks to those who have pointed out that the direction of the torque vector is an arbitrary convention and in no way indicates a mechanical advantage of turning something one way or another...

But even if it did, the difference would be so miniscule as to be immeasurable at the level of a screw turning.

Thus, either way it is an arbitrary convention that we have one kind of screw over another. As is the case with most of these things, a convention IS important to have, but WHICH convention is unimportant.

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Jason R Remy

"Open mindedness is not the same thing as empty mindedness."
-- John Dewey Democracy and Education (1916)

[John W. Kennedy]

Sorry, but the direction of the "torque vector" is just a mathematical convention for expressing a torque in vector form. A left-hand rule could have been decided on just as easily. It's like deciding on which way is +i and which way is -i.

If there is any reason at all for right-handed screws (other than convention) it has to do with right-handed humans using tools.

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John W. Kennedy
"Compact is becoming contract; man only earns and pays."
-- Charles Williams

[NanoByte]

John W. Kennedy's last post is exactly right. . .and is basically only common sense. Jayron 32's post says essentially the same thing.

Strainger apparently bases his mystical thinking on the fact that he is a mechanical engineer. As an electronics engineer, I have run into some of the ways mechanical engineers think. . .or not, as the case may be. In fact, every time I work on my car, I find that cars are incompatible with common sense, apparently for that reason.

Ray (pretty torqued down)

[Strainger]

Am I ever going to get through to you people? I presented evidence as to why they're called right-handed threads and why they're threaded that way (SO THAT THEY'LL FOLLOW THE RIGHT-HAND RULE FOR CHRIST SAKE!!!). In doing so, I used a textbook that is a standard among mechanical engineers, and yet y'all still choose to ignore it.

jayron:I'd still have to draw it out to see if it were so (too lazy right now) but if it WERE so, the difference between a righthanded screw and lefthanded screw WRT mechanical advantage due to torque differences is MINISCULE Jayron, if you turn a right-hand threaded bolt clockwise, it tightens. If you turn a left-handed threaded bolt clockwise, it loosens. This is not a minscule difference.So even if the righthanded screw DOES obey the righthanded torque rule...If it's a right-handed screw, then it follows the right-handed rule by definition.

Look, I'm a mechanical engineer. I use the right-hand rule frequently (not to be confused with the right-hand method) to calculate direction of torques (e.g. on bolts), moments in structures, etc. I am quite familiar with theory behind bolts, nuts, etc. I suggest paying attention to the evidence I presented rather than following your own wild-ass guesses and speculations.

[Strainger]

Nanobyte, don't tell me my business. You obviously don't have a clue about any theories behind mechanical engineering.

I will now summarize:

Q: Why are most bolts and screws threaded in the same direction?
A: Because there needs to be a standard.

Q: Why are these standard bolts threaded so that they tighten when turned counterclockwise and loosen when turned clockwise?
A: Because this is the direction of the resultant torque vector as calculated by taking the cross-product T = r X F, where 'r' is the distance vector (location of the applied force) and 'F' is the force vector. The direction of the resultant cross-product (torque, in this case) is determined by applying the right-hand rule.

Q: Why are bolts threaded this way called right-hand threads?
A: Because they follow the right-hand rule[i]. Duh.

Don't believe me? Check the source ([i]Mechanical Engineering Design by Shigley and Mischke) I quoted earlier. It will verify the information I've given here...every time I work on my car, I find that cars are incompatible with common sense...You must own a Grand Am.

[John W. Kennedy]

Do you also believe the UFOlogists who explain that alien ships "pull themselves across magnetic lines of force"?

If so, do you want to buy my new ocean liner that works by pulling itself across lines of latitude and longitude?

Do you agree with Tom Sawyer that you can tell when you've crossed a state line in a hot-air balloon because the color of the countryside changes to the color of the new state on the map?

The "torque vector" is an imaginary notational convenience, with no actual physical phenomenon to which it corresponds. It is used to make rotational equations more tractable, by fitting into the well-established rules of vector mathematics. But things would work just as well if we had a left-hand rule instead.

I am quite, quite certain that right-hand screws were already standard long before the "torque vector" was ever invented. It is remotely possible that I am wrong, however, in that someone may have said, in the late 19th century, "Let's make it a rule to have screws all threaded the same way, and, to simplify matters, let's make them follow the same right-hand rule as the 'torque vector.'" But if you want anyone to believe it, find a clear record stating that this is an historic fact, and when and where it happened.

------------------
John W. Kennedy
"Compact is becoming contract; man only earns and pays."
-- Charles Williams

[Strainger]

John, try offering up some evidence proving that I'm wrong as opposed to your own uninformed assertions and speculations. I think I've summed it up pretty well and am sure that any intelligent people reading this thread will get it. I'm not going to waste any more of my time trying to pound the correct answer into the heads of the clueless. See my post in the BBQ Pit if you're so inclined.

[Nickrz]

Well, I hate to say it, but I read your rant in the pit, and I went and read the site you so helpfully provided including the "example of the right hand rule" and NOWHERE in all this have I seen anything to indicate or explain exactly what this "right hand rule" consists of. You've not explained it, the web site does not explain it, and I've read nothing to indicate anywhere that it has the slightest thing to do with why most threads are right hand threads.

It appears the only thing these two subjects have in common are the words "right hand" and this "rule" somehow relates to torque vectors. However, torque vectors are independant of CW-CCW conventions; what the hell does the direction of travel in relation to a clock face have to do with torque? Nothing at all.

I think you came closest to the real answer when you said "Seems like this is just a thing that became convention through use."

I think you've become so convinced this happenstance of wording is correct, you've been blinded to any argument. But hey, don't feel alone, I do it all the time.

Explain the "right hand rule" and tell us how it applies to early right hand threads.
Maybe then we'll get it.

[jayron 32]

Explain the "right hand rule" and tell us how it applies to early right hand threads.

AH, but his proof is that his little Mech-E text SAYS so. This sounds like a rather "biblical" rather than a tested proof. The right hand rule of torque exists to minimize the negative signs in calculations, not because a force is actually acting in that direction. The force is acting tangentally to the rotation. Torque is a mathematical convenience invented so we don't have to keep moving our force vectors around in a circle. It's magnitude is an average of the force vectors, its direction is along the axis, but since the torque itself is not a force, it has no effect on such things as rotating screws. Torque is not a force.

Here's proof that it doesn't:

If it did, we could theoretically make a "left handed" screw large enough so that as you tightened it the torque exceeds the force pulling the screw into the hole. Thus as you screwed it "in," its come out of the hole. Impossible. Likewise, you could make a "righthanded" screw large enough that the "torque" force you describe could overcome the force of friction, leading to perpetual motion. Also impossible.

------------------
Jason R Remy

"Open mindedness is not the same thing as empty mindedness."
-- John Dewey Democracy and Education (1916)

[mr john]

Thank you nick,took the words right off my keyboard,only you made them make sense.
I been rethinking my 'hand tapping' theory and it seems the most logical from the practical point of view. I misspoke when i said something about cutting the teeth the other way. With the T handle in a horizontal plane i have more control pulling with the right hand. I have some old augers that work the same way,that could explain the direction of a drill bit twist.When the bit is in a brace it is easier for me to turn it clockwise. I have used srewdriving bits in braces so I have had to apply controlled force and precision both ways.

[Strainger]

Nickrz, your response is along the lines of "I don't understand what you're saying. Please explain further" as opposed to "I understand what you're saying, and you're wrong" which is the statement made (or at least implied) by a couple of other posters. I will therefore do my best to present my assertion to you. First off, there are two major challenges to explaining the right-hand rule:

1) Explaining vector cross-products to laymen. No offense, but this is not something you pick up in your basic high school curriculum. I spent at least a year in college (majoring in engineering) before I learned this theory. It was even longer before I learned some of the practical applications involved with it.

2) Regardless of your understanding, it's a bitch trying to explain how the right-hand rule applies to torque without the benefit of illustrations (at least for me). Admitedly, that I referenced earlier fell short of explaining things (IMHO), but it provided the best supporting graphics I could find at the time.

I looked up the right-hand rule in my physics book today, and I think that quoting its explanation (along with providing my own embelishments to further illustrate) is the best way to approach it. The book is at work and I'm at home now, so you'll have to wait until tomorrow. One qualifier: You have to know the configuration of the x,y and z axes regarding the plotting of points in 3-D space. Once I present the theory, I welcome any questions you have about it, Nickrz and mr john, be it in this thread or through email. This whole thing needs to be taken a step at a time to fully understand it. Once you grasp one step, I'll move on to the next.

I admit that my first couple of posts kind of muddied things up by trying to verbalize something that is best represented graphically and by presenting ideas in the opposite order that they should have been. I considered asking Nickrz to delete all but my last two posts in this thread because of this. Feel free to do so if you're so inclined.

I also admit that I've drawn conclusions based on my own experience and the evidence I've found so far. Sometimes, ya just gotta do that. Feel free to ask any questions about how I arrived at my conclusions, but be diplomatic about it. Not to brag, but I know a lot more about bolts than most of you would ever care to. I think a lot of misunderstanding is due to the challenge of communicating this stuff.

I'll repost again tomorrow when I have my Physics textbook in front of me.

[Strainger]

Me:Admitedly, that I referenced earlier..... It should've said "Admitedly, the site that I referenced earlier....." Sorry about that.

[Nickrz]

I'm sorry, but my reply was not "I don't understand what you're saying" it was "you haven't said anything."

You've insisted the right hand rule is the reason why most threads are right-handed, but you have explained neither the rule itself nor the reason why you think this is so. Your argument seems to consist entirely of "you don't understand" so just take my word for it.

I would not argue with you in such wise had I not seen your posts decrying the intelligence of people who were not buying your theory. I've broken enough taps and chased enough threads in my life to know quite a good deal about threads and threading and the forces involved in those types of fasteners.

The truth of the matter is, a left-handed thread is identical in all aspects to a right handed thread, save the orientation.
You're not going to tell me a physics formula or law that applies equally and identically to left-hand threads, by dint of its name and with no correlation to the orientation or direction of a torque vector gives our civilization preference of one condition over the other.

Unless, of course, I'm wrong.

[Strainger]

Nickrz and mr john, I don't like to put people down, but your understanding of this theory will be greatly facilitated if you ignore any posts provided by anyone besides me, Dex, and k0myers (and anyone else that I approve of later on). jayron's last post is so incredibly f@#!!ed up that I don't even know where to begin picking it apart.Torque is not a force.No shit, it's a moment (having units of force x distance). The best way I can come up with to define moment to the layman is turning tendency. To illustrate, close your door (any door) by pushing it at the edge. Now close it by pushing it near the hinges. Easier to close by pushing it at the edge, isn't it? This is because by pushing it at the edge, the force is applied at a greater distance from the hinges. Hence, the resulting moment is greater.

[Strainger]

Nickrz, pay no mind to my flame in the BBQ pit. It was not directed at you and I apologize if it offended you. (BTW, "You have presented nothing" is still a lot more diplomatic than "You are wrong.") I genuinely want you to understand my assertion.The truth of the matter is, a left-handed thread is identical in all aspects to a right handed thread, save the orientation. Exactly. Orientation is the only difference between right-hand and left-hand threads. But, I need to start at the very beginning for all of this stuff to become clear.


Gawd, I've never seen a GQ thread as out of control as this one is!

[pmh]

Strainger, as an engineer I 'get' the RHR. But at this point I have to say I agree more w/ jayron. You have explained why a fastener that already has RH threads tightens as it is turned clockwise, but not why it has RH threads to begin with.

Please, no flames. I'm just saying I don't follow your argument. Are you defining F (in T=rXF) as upward (tension in fastener), or tangent to the fastener head? Either way, the resulting vector lies either through a radius or down the shank (no resulting torque). If I'm missing something, I'll be happy to admit it and apologise, but I'm afraid you'll have to spoon-feed me this one.

DrEvil, I suspect that you will find LH threads on only one side of the car. LH threads are also found on bicycle crank sets, ring gears in RWD automotive applications, and on the driver side of Chrysler cars up to the mid '70 model year (all objects that turn CCW when viewed from the direction the fasteners are inserted).

And finally, Nano, dont blame MechEs for the counterintuitive nature of automobile design. Blame corporate bean counters and government imposed standards.

WOTSB

[Strainger]

pmh, you're close. Imagine that you're turning a bolt with a wrench the way you normally would. Think of the 'r' vector as the wrench handle. Now, apply a load 'F' at the end of the handle in a direction tangential to the bolt head (the way you would normally turn a wrench). The direction of the resulting torque vector (don't even consider magnitude in this instance) indicates which way the bolt will move along its axis. If you have any further questions, please send me an email. I've muddied the water enough here and would like to refrain from doing any further damage!

[E1skeptic]

cornflakes asked:I'd assume that right hand threads are the convention because you can hand tighten better that way when you use your right hand, but is the real reason and when did it happen?and here we have Strainger "witnessing" about the "RIGHT HAND RULE"!

Sorry Strainger, but it looks like you missed the whole point from the very beggining. Let me ask you a few questions to see if this helps:

1. When was the "right hand rule" discovered (invented, devised, developed)?
2. Did right threads exist as a "standard" before the "right hand rule"?
3. Could it be that the aforementioned rule was devised because of the commonality of right hand threads?
4. If most humans were left-handed, and we had "left hand threads" instead of right ones, would we have a "LEFT HAND RULE"?

We are not as ignorant as you might think, Strainger. Some of us would even like to regard ourselves as intelligent people :). But the fact is that you haven't explained anything, and you completely missed the point of the OP.

Me thinks John K. answered the question as close as possible (he's only missing the "when"):If there is any reason at all for right-handed screws (other than convention) it has to do with right-handed humans using tools.
Whether the "right hand rule" has something to do with right hand threads, or not, given the fact that this rule (and I'm not saying that the rule doesn't apply) was discovered thousands of years after the threads were invented and in common use, is utterly irrelevant to the question posted by cornflakes. Ok?

Saludos.

------------------
Men will cease to commit atrocities only when they cease to believe absurdities.
-Voltaire

[NanoByte]

What could be Strainger?:

I've never seen a GQ thread as out of control as this one is!

The whole thread is screwed (righthandedly, of course)! The whole world is wrong; only the Strainger knows. Maybe you would want to pause and wonder about this situation.

I spent at
least a year in college (majoring in engineering) before I learned this
theory.

Now, there must be a theory as to why that year is supposed to prove that you are right. Basically, what you should've learned was *not* a *theory*, but a convention. As I recall, I started studying vectors and cross-products in my *first* year of college (Cornell U.) and used such in numerous applications, not just for torque. I got a 5-year BEE from that school. I used the same *general mathematical conventions* at Stanford, where I got an MSEE. John W. Kennedy and jayron 32 (Jason R. Remy) sound even better qualified (or more recently exposed to this) than I. But there are certainly many who never even went to college who get the basic point discussed here, which you just plain don't seem to get!

I think I've summed it
up pretty well and am sure that any intelligent people reading this thread
will get it. I'm not going to waste any more of my time trying to pound
the correct answer into the heads of the clueless.

;-)))))) Typical ME -- just give him a bigger hammer.

your
understanding of this theory will be greatly facilitated if you ignore any
posts provided by anyone besides me, Dex, and k0myers (and anyone
else that I approve of later on).

Jawohl! Proof by qualification of only those who agree with you? Did they teach you that also at that school where you had to finish, during your first year there, what you should've learned in high school?

I admit that I don't know how one should go about getting the proper 'aha' to occur in your mind. It seems to me that you first of all don't get the basic feel for mathematics in general, or its application to physics -- that it all has to start with conventions, and only then move on to derive consistent theories. It's basically a nonverbal thing to pick up on this.

I don't quite buy Nickrz' comment about nonrelationship between clocks and screws. The only way clocks get into this is from the term 'clockwise'. Clocks also go clockwise only through convention. All we then do is equate, in English, the two terms 'clockwise' and 'righthand rotation'. Either term is appropriate to describe the "righthand rule" *convention*, a convention that may either be used to define a rotational vector or to establish the direction of advance of a "righthand" thread or bit. The righthand rule, however, does not *explain* why the standard thread direction, throughout the world, conforms to this righthand rule. I think most of us agree that the highest probability of why it does, is that it is easier for a righthand person -- of the mighty majority with political clout -- to manually apply greater torque in that direction, and thus more easily force a righthand thread into an untapped hole in any material that gives way to such thread. I next wonder, however, if there are any materials with the odd characteristic that a thread of one handedness will more easily penetrate it than a thread of the opposite handedness. Well, if there be such, we definitely should start a different thread on that. I wouldn't want to needle anyone, but I think we just about have the subject here sewed up.

Ray (If they drive on the left in England, why should they not use lefthanded threads as a standard? No, I really don't want to know.)

[Nickrz]

I've examined all the information Strainger so thoughtfully provided me via email. Unfortunately for his argument, this info has only served to strengthen my inescapable conclusion that the "right hand rule" and "right-handed" threads share only one correlation: their nomenclature.

The right hand "rule" is a rule only in the sense of a "rule of thumb." (In this case, both figuratively and literally). Someone who wishes to calculate radial thrust loads and the direction of a torque vector simply uses his right hand to "grasp" and "pull" on two variables in the formula, and the thumb indicates the direction of the vector.

Understanding the equations the rule describes is completely tangential to the real question and has no bearing on the matter whatsoever.

I submit this "rule" came about for the same reason right-hand threads came to be the norm: the vast majority of people are right-handed. The RHR is no more responsible for the preponderance of RH threads than it is our inclination to use our right hands for performing certain other.. uh.. rituals. (Brushing one's teeth springs immediately to mind, you deves).

Right-hand threads:

If you are using a wrench to tighten a bolt, the natural tendency for right-handers is to hold the wrench at the 3 o'clock position and put the hand over the wrench, curl the fingers downwards and pull toward the body.
(And yes, Strainger, this is an accurate representation of one of the illustrations used in the RHR explanations).

Similarly, when tightening a screw using a screwdriver, the skeletal and muscular construction of the human hand and arm allows more force to be exerted in a clockwise direction when using the right hand.

I think it's as simple as that. (My apologies to any others who have voiced these same examples or arguments, I didn't have time to pull quotes).

This question turned into a sort of "which came first, the chicken or the egg" when, as it turns out, the answer is "chickens are not responsible for turtle eggs."

[TheDude]

Forgive me if this is redundant, but there seems to be some confusion as to what exactly the right-hand rule is and I thought I'd share the simple rule of thumb (no pun intended, as you'll see) that I was taught.

With regards to screws: Curl your four fingers (as if you were making a fist) in the direction the screw is turning. The thumb is now pointing along the axis of the screw in the direction in which the screw will move.

With regards to cross products (including torque): Point your fingers in the direction of the first vector. Now curl them towards the second vector. Your thumb will be pointing along an axis perpendicular to both in the direction of the new vector.

It seems to me that the confusion on this thread so far is in making the classical mistake of confusing correlation with causality. That is, just because both processes involve a right-hand rule and can be described similarly does not mean that one caused the other. Chances are, (and this is a bit of a WAG, so forgive me Strainger) that in both cases we had to choose an arbitrary convention and in both cases we chose the right hand rule rather than the left because we are mostly right handed and have always favored right-handedness (note that the word dexterity comes from the Latin for "right" and sinister comes from the Latin for "left").

I hope this clears things up a bit and that I have not just gotten myself involved in a flame war.

TheDude