Righty Tighty - But Why?

John That is the most convincing argument I've heard to date. Makes sense to me.

There is a book titled One Good Turn: A Natural History of the Screwdriver and the Screw. It probably has the answer, but I'll let someone else buy it to find out.

Lane

In my kid's school they are very careful about which hand is to be used. Come to find out she's ambidextrous and base ball teams are now fighting over her cause she's a switch hitter. I had to ask what that meant cause I never did like sports.

I was, up until about third grade (which was a very long time ago) able to write with either hand, without any difference in quality... of course a 3rd grader really doesn't write that well anyway, but at that point in life, my teacher insisted that I choose ONE. I chose the left (although I still can write with either, better with the left). People ask me why did I choose the left - response "because I can see where I'm going when I'm writing as my hand isn't in the way". For what it's worth, I can also write backwards. Also upside down- forwards. Also upside down-backwards. The talent (if it can be called that) really hasn't been all that useful unless I'm lettering the inside of a door glass or the underside of a translucent plastic lid on a storage box, etc. I don't have any problem doing it, but sometimes people have a terrible time reading backwards handwriting. Ken (maybe with a few wires crossed somewhere)

If you tested your theory you would find out that right handedness is the more common version of human. There has been lots of speculation why this should be. It is not cultural. Most people are born right handed. Often though, the left eye and/or foot may be the dominant one on a right handed person. ERS

Would that be right or the left hand ??

It was brought up somewhere in here why threads have any particular handedness in the first place. The answer is: point your thumb in the direction you want the screw to go. Curl your fingers around and they will point in the direction of rotation! Use right or left hand as applicable.

:)

Tim

-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @

And vice-versa on a left handed person, which is why I shoot right handed now.

Pete Keillor

all of these answers assume that the threaded thing will never need to be *un*screwed. after sitting for a while, a thread will likely take more torque to remove than it took to screw it in in the first place. if the predominance of right handed persons and the greater hand strength available to turn clockwise were the reason wouldn't left hand threads be better?

It would be interesting to find out what percentage of all installed threaded fasteners are ever again deliberately loosened.

I'd but my money on it being less than 1% of them. And, considering that probably more that 95% of fasteners are currently being tightened by machines and not hands, in our mass production world, your argument is reasonable, but probably moot.

Jeff

In today's world, sure, but the thread started out asking the origin of the rotational bias. a better question would be what percentage of threaded fasteners at the time (whenever that was... ; ^>....) were removed. I bet it was pretty high. there would have been little reason to use an expensive threaded fastener otherwise, when nails and rivets were were cheap and easy.

Which is, of course, wrong. More torque *available* to untighten than to tighten. I allways use a bigger wrench to loosen pipes than tighten them.

Wires aren't crossed. You are running on AC instead of DC.

Dan

It would depend on which shore of the river the screw was built on.

Why do we skate counterclockwise around the rink?

Dan

Aw man, my silicon rectifier stack musta blew.... Ken.

We skate CCW around the rink because we "keep right" Why do we "keep right?" Who knows.

[ ... ]

Hmm ... in normal maintenance of my computers, perhaps 1/4 of the screws present ever get removed. (Actually, it would be less, if it were not for my recent replacement of a CPU fan in an ULTRASparc 1/140. There were all of five screws just to remove the fan. The normal access to the top of the CPU box involves two or three screws (depending on whether the security cable bracket is still with the computer or not). Two more remove the entire CPU board. When I replace disk drives, I usually don't have spares already mounted in the "spud" (slide-in mounting bracket), so that is four or six screws per drive, with two drives.

However -- once a disk dies, *lots* of screws come out, to gain access to the super magnets, and to the tiny ball bearing assemblies. (Lots of exercise for the tiny torx screwdriver bits). (I also use the platters for decoration, sometimes.)

In contrast, when someone is doing a full restoration on an old lathe, I'm willing to bet that at least 90% of those screws are at least loosened, if not totally removed.

Now for something a bit closer in time to when industrial production of screws started.

When working on an English system concertina, (let's assume a six-sided one for starters), there are twelve screws (six on a side) which secure the endboxes to the bellows frames. At least six of those come out for almost any job on the instrument. Two more (on each end) hold the endbox together, and they have to come out for work on the action or the valves. Four more (on each end) hold the little finger rest and the thumbstrap in place, and while the little finger rest seldom needs replacing, the thumbstrap is usually the first thing to wear out. O.K. -- so far we have 24 screw here, of which all but four will come out during the life of the instrument.

But -- inside the bellows are two reedpans, each containing 48 reed carriers. Each reed carrier has two screws securing the reed (via a clamping bar) to the carrier. Only a *fool* takes any of those screws out, unless the reed is rusted away and needs replacement -- and by preference, unless you are a glutton for punishment, you replace the reed and carrier as a unit. This makes 192 screws which you might as well consider to be rivets. And this design has been pretty much unchanged since about 1829 or so. (At one period, near the beginning of the 1900s, the reeds were actually riveted to the carrier, but that did not last (though some of the instruments did. I own one of those.)

Oh yes -- there are also two wood screws securing each rectangular brass plate into which the endbox screws thread -- 24 more for the normally untouched -- even in an extremely old instrument. That makes 220 which normally are never touched once installed, compared to

20 which will be regularly removed. So -- about 91% of the screws should be expected to be permanent.

Enjoy, DoN.

Enough opinion. Try it on a torque meter and let us know what you find.

I'm probably on your side of the river when it come to taking failed stuff apart to see what could be scrounged for the "hell box" and possibly reused somedday.

But I'm sure even you'd admit that we're a minute minority and more likely the average consumer appliance, car, piece of furniture, or even a house's deck which was built using threaded fasteners (like mine) probably ends its life with very small percentage, if any, of its threaded fasteners ever loosened.

Jeff

[ ... ]

Most appliances would never be taken apart, as the philosophy appears to be "replace, don't repair".

But for an automobile, we can at least expect:

1) Hub nuts -- at least for checking brakes at the annual safety inspection. 2) Rocker cover nuts -- for access to allow scheduled maintenance. 3) Head nuts -- normally loosened and re-torqued after some specified number of miles of operation. 4) Whatever screws (if any) are needed for access to air filter to replace it. 5) On 4WD vehicles, the bolds holding the skid plates on the bottom of the engine compartment, to allow draining and changing of oil and access to oil filter. 6) The bolts securing the battery and its cable clamp bolts. 7) With electronic ignition, we can now eliminate the screws securing the points in the distributor. :-)

The rest of them probably are untouched in most vehicles -- at least through the original owner's possession.

And for the furniture -- I have taken apart used computer furniture, to transport it home and reassemble it. But I would guess that I am the exception there, as well.

For the concertinas which I used as an example of things designed in the 1830s and later, I have worked on a relatively large number of those over the past thirty years.

Enjoy, DoN.