Where did right hand threads come from?

Factual Questions
41

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

42

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.

43

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.

44

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)

45

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.

46

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.

47

Me:

It should’ve said “Admitedly, the site that I referenced earlier…” Sorry about that.

48

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.

49

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.

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.

50

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.

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!

51

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

52

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!

53

cornflakes asked:

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”):

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

54

What could be Strainger?:

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.

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!

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

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.)

55

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.”

56

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