Torque wrench usage


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Old 09-29-08, 02:05 PM
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Torque wrench usage

Ok, I know how to set and use a torque wrench, but here's a question.

Just like a longer screwdriver allows you to get more torque (basically cause its a twisted lever, as I understand, I could be way off base), does an 6" socket extension on a torque wrench change the actual torque applied to the fastener? Or is the setting still accurate?

Any Engineers out there?
 
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Old 09-29-08, 03:30 PM
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As long as you do not increase the length of the torque wrench, such as by adding a crows foot or other linear extension, you will not have a problem. A simple extension, 90 degrees to the wrench, will not affect the accuracy.
 
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Old 09-29-08, 05:06 PM
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Thx TG...
Seemed like it would, but I guess I was over thinking. How else do you torque things longer than the socket, right?
 
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Old 09-29-08, 05:51 PM
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I don't think changing the length of the handle would affect it either. All that would do is make it easier to torque... the actual readout would remain the same, provided you're stopping once you reach a certain ft/lb.

Kind of like the difference of trying to torque something to 75 ft/lbs while holding the wrench in the middle span of the wrench vs holding it on the end like you're supposed to.
 
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Old 09-29-08, 06:12 PM
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Well, X, I think TG had in mind adding things to the front of the wrench,... that I can understand, then you are changing the length of the lever after the fulcrum. (Man, I love Archimedes!)

I think yer right, putting a cheater on the handle prob wouldn't affect anything. It would still click at the same point. Your mechanical advantage is just increased. Guess thats why the higher range torque wrenches have longer handles.
 
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Old 09-29-08, 07:57 PM
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actully the extensions do affect the torque, when a torque wrench is certified for say aircraft it is with the socket on the head and any extension has to be taken into account. however unless the average user will not need that level of certification. for most of us you can just say it doesn't affect it. but if you tried to use a torque wrench with say a 24" extension you would loose at least 10 ft/lbs of torque. i used to have to torque axle nuts on a transit coach at 1100ft lbs. that was fun even with a 6-1 torque multiplier.



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Old 09-29-08, 09:21 PM
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Is the loss of torque due to the length of the extension... or the difficulty you would have in keeping it perfectly perpendicular to the work?
 
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Old 09-29-08, 10:26 PM
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length of the extension, it acts like a small torsion bar (straight spring) longer extension= more torque lost.

Murphy was an optimist
 
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Old 09-30-08, 07:48 AM
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I used to calibrate torque wrenches in another life. Adding a socket extension to the wrench will not affect the applied torque. Adding an extension to the torque handle changes the applied torque proportional to the length of the extension.

T= F (force) X L(length)

A couple of things about torque wrenches. In order to get the correct applied torque you have to grip the wrench where it was designed to be gripped. To get an accurate torque reading your pull must be perpendicular to the wrench axis. Any lubricant on the fastener threads will have a huge impact on the applied torque. The same is true with the type of lubricant present.

If you are going to buy a torque wrench opt for a deflecting beam type over the micrometer (click) style. The latter are notoriously inaccurate. They rely on the compression of an internal spring and the spring changes over time. At least that was the case 30 years ago when the Navy chose to throw away thousands of click type wrenches because they were so unreliable. If you have a micrometer type you can increase it's life by relieving spring tension after each use.
 
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Old 09-30-08, 12:27 PM
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Sorry, I should have specified increasing the length at the business end as Gunguy said.

I was in Naval Aviation Maintenance (Marine Air; OOH-RAH!) from 1972-1999 and never saw a deflecting beam torque wrench; they were all "clickers", BUT they were all calibrated semi-annually religiously. Correction: a lot of them were dial-reading type, which is a refinement (and much more accurate version) of the deflecting beam. Those torque wrenches the Navy disposed of were probably given to the Marine Corps; you know how that goes.

As cw mentions, zeroing a clicker-type between uses is Torque Wrenches 101.

Some reading:

http://www.algeo.com/~joe/KIAT/kiat_3.htm
 
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Old 09-30-08, 12:37 PM
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Hey TG.....must have all been clickers cause it was easier to teach Marines to listen than to read...LOL J/K...OK?

Haven't been able to use any Marine jokes in years and years.
I liked workin with Marines/Army/SEALS better than most of the Navy guys.
 
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Old 09-30-08, 12:44 PM
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Yeah, I was going to say somethng about not being able to read the numbers on one, but figured someone would, probably cw if he's an old swabbie. Going off on a tangent, having worked around the Navy for almost three decades, I have nothing but respect for Sailors.

And anyway, Marines just tighten things until they feel tight enough; if the bolt breaks it needed replacing anyway.
 

Last edited by the_tow_guy; 09-30-08 at 12:46 PM. Reason: Additional thoughts.
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Old 09-30-08, 04:42 PM
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Working in the cal lab was part of my punishment for doing a shore duty tour at a Naval Air Station. It was NAS Key West so that was a plus. Best fishing and diving in the US

The Navy wised up after a year or so. They figured out that the clicker style torque wrench could be made more reliable by relieving the spring compression after use and by exercising the wrench before use. However, by then thousands of wrenchs had hit the dumpsters. Many of those were liberated by those in the know.

22 years in the Navy and my only contact with the USMC was a memorable 3 day liberty in San Francisco with a couple of guys just back from Nam and some Waves (a designator now non PC) we hooked up with at the EM club on TI. I was really impressed with how much the Marines could puke.
 
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Old 09-30-08, 05:00 PM
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...Yes I know...but since I started it...I should get a little leeway. I promise this is the end.

cw...musta been on shooters or birdfarms the whole time? Nothing better than being on amphibs and comshawing some C or K-rats (later MRE's, man those were great! They even had Tabasco!).

The grunts and us squids may have fought at certain times, but when it came down to it, no-one I'd rather be beside.
 
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Old 09-30-08, 09:55 PM
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Hmmm, personally I would be a little reluctant to be on liberty with a squid in San Franscisco..... Partied with plenty of them in other places around the globe, tho.

If any Marines saw you dumping perfectly good torque wrenches in a dumpster you KNOW where they ended up.
 
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Old 10-01-08, 08:14 AM
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well i respect em both as my older brother is a squid, my younger brother a jar head, and my son a squid airdale. by the way that reading was exellent tg.

life begins when the kids leave home and the dog dies
 
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Old 04-04-09, 04:58 AM
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Just to clear this up

HOW TO COMPUTE TORQUE WHEN USlNG ADAPTORS

If an adaptor or extension is attached to the square drive of a click-type torque wrench and this adds to its length, then the applied torque will be greater than the pre-set torque. A formula can be used to find what the preset-set torque should be in order to obtain the correct applied torque.

Here is the formula:
http://www.torqwrench.com/images/Pre...ue_formula.jpg


RS = Torque setting of the torque wrench.

http://www.torqwrench.com/images/ThisBecomesFormula.jpg

A = Distance from the center of the square drive of the torque wrench to the center of the handle grip pull point.
B = Length of the adaptor from the center of the square drive to the center of the nut or bolt. Use only the length which is parallel to the handle. See figure 1
T = Torque desired. This is the actual torque applied to the fastener. Here is a typical problem: What should the setting be when ‘‘A’’ is 12’’, ‘‘B’’ is 6’’ and ‘‘T’’ is 30 Ib. ft.

http://www.torqwrench.com/images/RSFormula.jpg

Therefore 30 pound foot of Torque will be applied at the fastener when ‘‘RS’’ is 20 pound foot.

Note: If the torque wrench reads in pound foot, then ‘‘T’’ should also be in pound foot. ‘‘T’’ and ‘‘RS’’ should be in the same unit of measurement. ‘‘A’’ and ‘‘B’’ should also be the same unit of measurement.

http://www.torqwrench.com/images/Dial_calc.jpg



I can fully attest to the validity of this. Try breaking off the heads of a few bolts because you have 24' extension and 33 ft. lbs. and you'll know too.
 
 

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