Righty Tighty - But Why?

because most humanoids are right-handed?

Dale

(Both above and

Most people are right-handed. More torque from a screwdriver tightening in that direction.

Depends if you hold the screw driver with the blade end away from the pinky finger, that would give more torque un-screwing. If the blade faces away from the thumb, then you have more torque tighting. Give it a try.

Sheesh Jeff, I must have more time on my hands then you actually trying this out.

Bernd

For larger bolts (or nuts), which you would tighten with a wrench, the natural process for a right-handed individual is to approach the hex (or square) with the wrench held horizontal in the right hand, and the head more or less in front of your face. I believe that you can get more torque on it by then hanging your weight from the end of the wrench (thus producing a clockwise torque) than by pushing up on it, unless you do a lot of workouts with weights.

This is probably why it seems more difficult to take something apart than to assemble it. :-)

Even with smaller ones, such as with a 1/4" drive ratchet, I seem to approach it with the wrench in my right hand, with the head sticking out the thumb end. Or for more speed at less torque, I choke up on it, holding the head and near part of the handle, with the remainder sticking out to the right. So with this orientation, clockwise tightening seems a lot easier.

Enjoy, DoN.

And, did you ever realize that you find a long bladed screwdriver is easier to "get more torque from" than a stubby one, even if the handle sizes are the same?

That's because you've got to keep the bit pretty well aligned with the screw axis to prevent its camming out of a slot or Phillips head screw.

So, with a stubby driver, the torque has to come pretty much all from twisting the handle, but with a long bladed screwdriver you tend to unconciously move the handle off axis and create additional torque by also pulling on the handle in a "cranking" fashion. That torque would be applied even if the handle was free to rotate on the shank. (Think of a "speeder" socket handle.)

The longer the blade, the greater crank arm you can get, for the same amount of tolerable bit to slot misalignment.

Jeff

I would say that most people being right handed , that one's thumb and lower part in the palm of the thumb work better at pushing than pulling to put things together.

Try crumpling up a newspaper and twisting it into a ball clockwise and then counterclockwise... Bet lefties like it counterclockwise.

Just part of the standardised thread forms that Whitworth introduced into

19th Century manufacturing. Why he chose right and 55 degrees for the thread form instead of left and 54 degrees - God knows. Maybe something to do with the direction of rotation of the early steam engines and the right hand thread being less prone to coming loose?

Because when God made the world He said proper threads should be right handed. If left handed they would be sinister. Look it up (sinister-coming from the left). Just like political opinions. opinions on the right are what God wants. From the left they are sinister and obviously from the devil. See? Any question posted here can devolve into either a political or religious off topic discussion. Or both. And I sure cussed up a storm when I tried to remove the left side lugnuts on my "67 Dodge Dart the first time. Cheers, Eric R Snow

I think the more interesting question is why are 95+% of people right handed, rather than 50/50. Since right-handed people invented the threading systems for their advtange, this seems like the real question.

-Adam

How about rope ??! Regards. Ken.

"Roger Martin" snipped-for-privacy@bribieisland.net

I don't think right-hand thread use can be attributed to any one individual. Way too basic. Right-hand threading was the standard long before Whitworth. I understand that vee-angle standardization is associated with Whitworth in England and Sellers in the US, but in the US, the same standard right-angle fractional threads that we would use today were common (but with sharper vee top) before the "standardization" to USS in the 1860s. My take from checking threading on some pre-1860s US machinery.

As to why righty, I don't know. But if you think of hand die cutting a thread, say in vertical in a vise, it is "easier" for a right- handed person to start the thread with a clockwise motion, pulling the die stock handle towards your right side. Frank Morrison

"Jeff Wisnia" wrote

The advantage to making most threads in the world have the _same_ handedness is obvious. The reason we _call_ the predominant type "right-handed" is probably because most people are right-handed. I mean, think about it: what is it about the actual geometry of the helix that screams "right" or "left"?

Ben Franklin had a 50/50 chance to designate "positive" and "negative" in such a way that the electron, the thing that usually moves when current flows, would be _called_ "positive" a century later. He guessed "wrong", and we ended up with some extra minus signs in the equations of physics. Likewise, the form of helix we commonly use for screws could have been _called_ either "right" or "left". Since the universe turns out to be weakly "left-handed" by the definition we chose for _screws_, you could say that whoever named screws got it "wrong" too :-)

-- Tony P.

Aw Yess. I had a 42 Plymouth with the same problem. My first car. ...lew...

Almost all nuts have right hand thread in them. Same with glass jars. Making lids for the jars or bolts for the nuts with left hand thread would be stupid, you'll never get the lid on or the bolt started. However when RH thread is used it all fits together nicely. Simple eh? HTH

Think about it - you have just 'invented' the lathe. You have just about exhausted the possibilities inherent in round shapes and you want to go a little further. Threading rears its ugly head. The lathe turns clockwise (as viewed from the head stock end of things - because that is how the 'hand-held' cutting tool works). Your choice is - make the thread right-hand and risk running into the 'chuck' or make it left hand..... or maybe my lathe would have its drive to the right of the operator - keeping my dominant hand away from danger? "If I had a rocket launcher" *left* would be the direction of choice. Regards. Ken (Left hand dislectic machinist)

It is one of those things that likely is lost to history. Probably a relevant question is when were threads invented? I am sure that the first threads were made from wood. I know that some woodworkers prefer wooden threads for work bench vices and clamps. There are guys out there that specialize in wooden threads. The sell the big screws used in woodworker's vices. Were there wooden screws 1000 years ago? 2000 years ago? Was there a preferred direction for Archimedes screw?

Pete.

dalecue wrote: : because most humanoids are right-handed? --Not true; turns out this tendency is the last vestige of conditioning that is no longer practised in (most) schools. Lefty-righty is about 50-50 otherwise..

Our adoption of right-handed threads as the norm comes, I'm guessing, from two things: our natural tendency to right-handedness and the mechanics of the lathe.

By itself, our right-handedness should have no great effect in determining thread direction. But it did determine that lathes - from the earliest woodworking lathes onward - were built with the headstock on the left. I've never seen one with the headstock on the right, but wouldn't rule it out. The mechanics of the lathe dictate that the work generally turn toward the user. So we're now locked into a machine in which the work or the tool, looking toward the headstock, turns counter clockwise.

It all follows logically from that point. Spindle threads? Well, they've got to be right hand or they'll loosen with use. Wooden threads? At one point, they were all chased by hand. No difference between right and left, right? Not quite. It's just as easy to chase a LH thread as a RH one on a lathe, provided it's external. Chasing an internal thread is a different matter. RH gets the nod. Taps and dies in the lathe? Again, the CCW rotation favors RH over LH.

There are a few non-lathe processes that seem to favor RH threads over LH. Twist drills or augers in a bit brace, for example. (Except maybe for the left-handed person). With screwdrivers there may be a small edge. By and large, though, I'm betting that it was the lathe that sewed things up in favor of the RH threads.

John Martin