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  #16 (permalink)  
Old 11-05-2005, 12:47 PM
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http://www.kentool.com/Wrenches_TorquesocketsSUV.htm

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Old 11-05-2005, 01:52 PM
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NXS, As I have already said about the extensions for an impact, That deals with IMPULSE force and has nothing to do with what we are talking about, we are dealing with CUMULATIVE force when using a torque wrench. You have apparently been searching for something to back up your point but I can predict that you are only finding info that deals with wrench type extensions that set the torque wrench off center of the fastener. You will search in vain trying to find credible info to back up what you are saying. you are also wrong about what you said about flex head torque wrenches, while it is true that changing the angle of the handle will affect the leverage by effectively changing the length it will only change the amount of force required to APPLY the desired torque reading but will have NO effect on the reading itself since this is a function of the amount of resistance encountered at the square drive connected to the fastener. Again go back to the link, so thoughtfully provided by Farna, and read what it says about handle length and you should plainly see why this would not affect the reading. An extension will have a profound effect on an impact wrench(impulse force) due to the fact it(the impact) must overcome inertial forces because of the mass of the extension and socket but once the force from the first blow is released this is lost and with each succeeding blow the cycle has to start all over again, this is the principle that those torque limiting impact extensions are based on but it has no effect on a torque wrench using a steady applied force. I trust you did notice that those extensions are for limiting torque only on impact wrenches? I honestly am not trying to be a smart$#% here it is just that this old tale has been bounced around for years, always with the same mistaken reasoning about extension flex but take an honest look at what you are saying and think about it. If a shaft is under tension from a twisting force how on earth could it have more force on one end than on the other? think about it. Any force induced into the extension, socket or any other attachment will be distributed equally over the entire length. Again, not tying to be a smart$#&, but by your reasoning of the spring absorbing applied(steady) force you could put springs on the soles of your shoes and make you bathroom scale read wrong.
Read what some of the other guys on the forum have to say about the subject.

Need a New Torque Wrench

Last edited by oldred; 11-05-2005 at 02:01 PM.
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Old 11-05-2005, 03:59 PM
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Quote:
Originally Posted by oldred
I would like to invite you down here to the mines where this is done all the time on certain mining equipment and you can explain to all these guys that they have been doing it wrong all these years and Caterpillar Tractor company does not know what it is talking about and needs to change it's service manuals!
I worked in an open faced mine (rock quarry) for 4 years on off road haul trucks and loaders. Not to mention heavy equipment dealerships like Komotso and John Deere. We used long extentions daily. You do need two people to do it correctly though. One to pull and one to hold the extension straight.
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Old 11-05-2005, 04:55 PM
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I agree the extention wont change the reading, or if it does its very little, I have used extentions to torque wheels, cylinder heads etc and not had a problem, and never once in school have they told us it changed values. I know my opinion isnt worth much since theres guys here that have been doing this longer than I've been alive but thats my 2 cents
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Old 11-05-2005, 05:08 PM
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I am a diesel tech, and having a flex head torque wrench at times saves some aggravation. So for me, yes it was worth it plus I don't have to look for that extension I just had two seconds ago. Just my two cents!
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Old 11-05-2005, 05:54 PM
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This may seem like making a big deal out of nothing but there has been untold numbers of over-torqued and broken fasteners along with engine and equipment failure because of this very common myth. When a bolt is torqued to it's max and then the mechanic adds an extra 10% or so to make up for the "loss from using an extension" then the bolt is simply over-torqued by that much with predictable results. The odd thing is that using an extension can cause a false reading if allowed to tilt over from center but if that happens it will read LESS than the actual applied torque instead of more since the distance from the fastener center to the torque wrench drive center will provide leverage. Bottom line is using a socket extension PROPERLY will result in ZERO error.
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Old 11-06-2005, 07:40 AM
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I still think on a pivioting Tq wrench it will not read accurate if the handle is brought up to a 45* angle.
========
An extension reduces energy being transfered to the bolt guaranteed. Now wheter or not this actually changes the reading or not...it would seem unlikely but my experience has shown that it does. of course these were not scientific tests..but I can assure you that if an extension {socket extension, not breaker extension} is used more energy will be requred to reach a desired Tq.
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Old 11-06-2005, 08:38 AM
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NXS, -"an extension reduces energy being transfered to the bolt guaranteed"-- TRUE! (This statement says the same as the next)
--"I but I can assure you that if an extension(socket extension, not breaker extension) is used more energy will be required to reach a desired tq"-- TRUE!

Any extra ENERGY required to "twist" a springy extension will be added by simply pulling the wrench farther(tiny amount though it may be) this energy is then stored in the "spring" as static energy and will be released when the "spring" is allowed to relax. The TOTAL amount of ENERGY USED will not be absorbed by the bolt but the FORCE applied will be the same on each end! I think maybe the problem here is confusing APPLIED FORCE with TOTAL ENERGY used. If you want to think of it in terms of TOTAL ENERGY ok then think of it like this--amount of energy applied to fastener plus any energy absorbed by the spring(extension)=total ENERGY applied. But the "spring" cannot absorb more energy than it will take to "twist" it until it reaches equilibrium(resistance=force applied)at which point the balance of the total energy being used will be transferred to the fastener. If you still cannot understand what I am saying then You really need to brush up on elementary physical science and learn about levers and applied force.

The flex head torque wrench should be easy to understand if you will think about it. The torque reading is taken from the amount of resistance encountered at the square drive and has nothing to do with how the force is applied, The length of the handle only determines the amount of force needed to reach this resistance. Simply put if those things were in error when the handle is angled then they would include some sort of compensation method or just not make the dang things in the first place, surely you can understand that.

Last edited by oldred; 11-06-2005 at 08:45 AM.
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  #24 (permalink)  
Old 11-06-2005, 09:04 AM
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If a flex head torque wrench was not accurate I'm sure Snap-on and other companies woun't make them. It costs big amounts of money for the tooling to make these things and if they weren't accurate people woun't buy them and the tool companies would loose money.
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Old 11-06-2005, 10:02 AM
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Big Rat, I am well acquainted with the type of equipment you maintain and I am sure you run into using extensions and flex head type torque wrenches even more so than in auto work simply because of the sheer size of those things. I have worked on that sort of equipment(mostly welding)for over thirty years and I would not want to do anything else. We have maintained a fleet of 240 ton 830 Haul-Pacs along with various loaders, dozers, electric power shovels and other mining equipment. Demanding but interesting work
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Old 11-06-2005, 11:23 AM
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Quote:
Originally Posted by oldred
Big Rat, I am well acquainted with the type of equipment you maintain and I am sure you run into using extensions and flex head type torque wrenches even more so than in auto work simply because of the sheer size of those things. I have worked on that sort of equipment(mostly welding)for over thirty years and I would not want to do anything else. We have maintained a fleet of 240 ton 830 Haul-Pacs along with various loaders, dozers, electric power shovels and other mining equipment. Demanding but interesting work
The biggest trucks we had at the quarry were Cat 777 85 ton trucks, and I thought those were big. Your stuff are monsters. Since your a welder I hope you enjoy hardfacing, LOL!
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Old 11-06-2005, 11:42 AM
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Hardfacing!
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  #28 (permalink)  
Old 11-06-2005, 11:49 AM
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I've been doing a tiny bit of reading on Tq wrenches and have found that they are generally between 3-6% accurate. The 1 ft/lb difference we see at 28 ft/lbs works out to about a 4% difference {quick estimation} so it's actually probably within specs for accuracy.

Now let us move on to the swivel head again.
If you do not think of a click style but rather an older beam style with the pointer....
And you imaging it being a swivel head and then imagine it being tilted up at a 45* angle...
We must now pull twice as hard to acheive the same Tq on the bolt head...which results in twice the amount of main shaft flex and the readings will acutally be twice what the actual bolt has been torqued to. Maybe you need to brush up on your HS physics ... or think outside the box and don't fall for the "they wouldn't make it if it didn't work" mentality.
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Old 11-06-2005, 01:01 PM
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Originally Posted by NXS
or think outside the box and don't fall for the "they wouldn't make it if it didn't work" mentality.
Ohhhhh, your soooooo smart! PHTTTTTTTTTTTTTTTTTTTT.
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Old 11-06-2005, 02:07 PM
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NXS, You are comparing apples and oranges again. Have you used a beam type torque wrench with a flex head? Look man, I am sorry if I sounded a little testy but you have been insisting that you are right and insinuating that I am wrong although you are ignoring simple laws of physics. You have offered nothing credible to back up your point of view just irrelevant data along with some outlandish claims about 4 foot extensions and yet you tell me to brush up on HS physics, ok show me where I am telling you wrong and I will do just that. You came back and said that you are still right about the flex head yet you do not offer any explanation as to why you are right. I really don't know why but I will try once more to explain the flex head. Take the darn handle off the thing and if you could twist the drive part hard enough with your bare hands it would STILL read correctly! The torque reading is a measure of the resistance encountered at the point of connection to the socket, extension, whatever. The handle serves only to allow leverage to apply the force required to reach this desired torque. The shorter the handle the more force required until the handle is completely gone at which point the force required and the force applied would be the same! The reading is a measurement of resistance at the fastener not how much force is applied to the handle.

Think about this, if you take an extension and connect two torque wrenches then apply force to each(holding one stationary and turning the other will do exactly the same thing) now will one read less than the other? If so why and which one?

As for thinking "outside the box" and the "if it did'nt work they would'nt make it mentality" Do you honestly think Snap-On, who makes an excellent flex head, would build a wrench that works wrong? Well do you? Have you seen a warning on a flex torque wrench or read in a manual not to allow the handle to angle while applying torque? What would the purpose of a flex head be if it reads incorrectly with the handle angled? Well?

If you really believe you are right and you can show me where I am telling you wrong then I will have learned something and we will both benefit from this. I am not just being stubborn as you probably believe but I am basing this on what I understand to be common physics and sound engineering and if you will respond likewise and not just argue a black sheep is white then maybe we will get some where with this.

BTW the tolerance numbers you found can be important to accuracy but again they really mean nothing to the principles being discussed here since this is a function of wrench accuracy and has nothing to do with any attachments or how the force is applied.

As I have said a couple of times this old wives tale has been argued for years and however you want to believe how do you explain the lack of info regarding compensating for error while using an extension or a flex head if such error is real? There are easily found formulas for correcting error while using wrench type extensions or other factors that do affect readings but none for socket extensions or flex head wrenches, Why is this?
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