This might sound silly and I am sure I know but how many inch/pounds equal a foot/pound?

 

Not a dumb question. The only dumb question is the one not asked.

12. Hanging a 1 lb. weight on an arm 1 foot distance from the pivot point will equal 1 lb/ft. Just have to remember a few things, like the weight of the arm and hanger come into the equation, and the weight needs to be applied at a right angle to the arm, hanging straight down. Otherwise, the law of sines/cosines must be applied. Many other factors as well, but these are the primary.

 

I am clear on all that, I think. What I am getting at is this, if a fastener requires 24 inch/lbs can I set my torque wrench to two foot/lbs?

 

You could, but the uncertainty (accuracy) of your torque wrench is most likey a percentage of full scale. To illustrate this, if your wrench has a range of say 50 lb./ft. and the uncertainty is +/-5%, that means if in calibration, set at 50 lb./ft., it could torque at anywhere from 47.5 to 52.5 lb./ft.

Now, since this is a full scale uncertainty of +/- 2.5 lb./ft., it applies to all settings. Setting your wrench at 2 lb./ft. it could torque anywhere from 0 to 4.5 lb./ft., and still be considered in tolerance. This 0lb./ft. is an extreme example of course.

If you are looking for a torque of 24lb./in, and want the same 5%uncertainty, your target would be 22.8 to 25.2 lb./in. in lb./ft. that equates to 1.9 to 2.1 lb./ft. Quite a difference!

This is why manufacturers recommend using your torque wrench in the upper 1/3 to upper 1/2 of it's range. Some do give you an uncertainty of +/- X% of setting, but those are few and far between.

Does this help? To qualify myself, I worked in the calibration field for over 20 years, working on physical, dimentional, and electronic equipment, as well as developing and writing cal procedures. Training was provided courtesy of Uncle (Navy) Sam.

 

I won't answer this question as it has already been thoroughly answered, but in the front of every haynes manual that I've ever seen, there is a thorough conversion table in the beginning.

 

I was going to mention the Haynes manuals also
But riffish is very correct on his answer, best answer ive seen to a question of that nature

 

Isn't it true then, that there are 12 inch pounds in 1 foot pound? And that if the specification is in inches, then use a torque wrench that is meant to be used in that range (inches) and not in "foot". Thus, one needs at least two or three torque wenches for ordinary, use.

 

Very true, and a good point.

I suggest doing a search on torque, as there were some very good posts some time back on this topic. Went into a lot of other details, such as use of extensions, applications, etc. Tons of valuable information!

 

I have three torque wrenches just to cover a good range. I have a 1/2" beam style that I use to check the calibration of my 1/2" and 3/8" click-style wrenches against. If I need very small torque settings I can borrow my neighbors 1/4" torque wrench.

 

I appreciate all of your replies , they were very informative. Just wondering so maybe I could buy fewer tools. WAit a minute-what is wrong with me???????!!!!!!!

 

This is a common practice, but you need to understand you have the uncertainty of BOTH wrenches playing here.

 

All I am looking for is gross error that may have come from improper use or storage of the click-style units. This shoudn't be required if you are the only one that uses them tho. I check them for obvious problems when I buy them also.

 

Is there a way to check them by themselves or do you have to use another unit that you know is calibrated properly?

 

There really is no method besides verifying one wrench's torque accuracy by checking the torque with a known calibrated torque wrench, unless you are in a PMEL (Precision Measurement Equipment Lab) environment that has the necessary equipment to verify the wrench's accuracy.

Like Rikfish, I received my "torque-wrench" training from Uncle Sam...(retired Air Force),however, we sent our torque-wrenches to guys like him for calibration - who sounds like he certainly knows his stuff!

While in the Air Force, I gained my torque wrench knowledge by wrenching fasteners on Minuteman II/Minuteman III ICBMs. As you might imagine, that's a pretty touchy piece of hardware (nuclear missiles), so our superiors wanted to make sure we received the best training for our maintenance practices.

Anyway, a few things I learned about torque wrenches (Rikfish - please correct me if I'm wrong):

1. Alway "exercise" the torque wrench at its lowest setting prior to use - This only applies to "break-away" aka "clicker style" wrenches - i.e. If it's a 25-150 ft/lb wrench, leave it at the lowest setting (25 ft/lbs) and place the socket on the fastener to be torqued, and turn the wrench in a smooth manner until the "click" is heard (no farther) that signifies the torque has been met. Do this at least four times (preferably in both directions, if a bidirectional wrench). Then set the wrench to the desired torque and re-torque the fastener (nut/bolt). Always move the torque wrench in a deliberate, but slow and smooth method - this prevents over-torquing.

2. Always store the torque wrench at its lowest setting. Again, if you're using a 25-150 ft/lb wrench, store it at the 25 ft/lb setting.

3. Never drop your torque wrenches - if done, they may require recalibration.

4. Store torque wrenches (prior to use) in moderate temperatures prior to and during use...storing them in very cold temps may affect their accuracy. let them warm up prior to use.

5. This one may be questionable - we (in the AF) were taught that the lowest 20% of a torque wrench's range is not as accurate as the remainder of the range. That may or may not be an accurate statement...Rikfish can probably verify that as true or not.

Anyway...those are some Torque Wrench usage tips courtesy of the US Air Force.

Regards,
Scott

 

78 Explorer,

The A.F. taught you well! Only a few things I would add right now. First is to excercise your wrench a couple of times at each setting you use, prior to actually applying the torque to a fastener. This applies to click or break action wrenches for the most part, but is still good practice with beam or dial types.

Another consideration is how fast or slow you apply the force to the wrench. This can change the applied torque significantly. Slow and steady is the rule of thumb.

I guess they taught us to be rather **** about the use and care of torque wrenches as a PMEL tech..... One drop and it should be checked.

Last for now, most torque wrenches are calibrated for clockwise operation only, unless otherwise marked.

There should be good calibration labs in most major cities, and the cost is normally reasonable, providing the wrench has not been abused or significantly out of calibration. For the most of us, a good quality torque wrench should last a lifetime with good care as outlined by 78 Explorer, although I have seen them wear out too.