bsvitale:
Torque wrenches are not a buy it, and use forever wrench.
They must be calibrated periodically.
There is no hard rule for how often this is necessary, but it IS necessary if you want accurately torqued fasteners.
Some say every 6 months, but that seems excessive, and probably applies only if you are using the tool every day, for 6 months.
Some say to re-calibrate after 2500 uses. For most of us that too would be never occur.
The real story here is that the settings for a new wrench, when compared to a wrench that has been used, or sitting in an unheated building, or has been dropped, may be very different.
Good information! I will also add some more pointers that I learned in a torque class at work taught by an instructor from a tech college in Tennessee. He was affiliated with Snap-On and of course, all the equipment he brought to class was Snap-On brand.
1) Torque wrenches should always be stored with it set to its lowest setting. Typically, that is "0", but some wrenches don't go down to "0".
2) Torque wrenches have a tolerance, some of the better ones (more $$$) are pretty low, down to about the +/- 3% range. The lower priced units can have a tolerance range as much as +/- 10%. So, keep that in mind.
3) A wrench should be sized appropriately. For example, if you have a nut that should be torqued to 148 ft lbs, don't use a wrench that only goes up to 150 ft lbs. You can do that, but it's not going to you accurate pulls on a consistent basis. You need to use a wrench that has an upper working upper limit that is at least 10% above the highest setting you will use it for. Example, for a 150 ft lb wrench, don't use it for pulls above 135 ft lbs. Likewise, the same holds true on the lower end of a wrenches working range.
4) As bsvitale stated above, if you drop a torque wrench, all bets are off and it should be recalibrated before being used again.
5) For a good pull, use a slow, steady, and firm action to get the wrench to click. Don't jerk it! Never check a nut that has been torqued!!! In other words, don't click the same nut again AFTER YOU JUST TORQUED IT. I know the urge to do that is irresistible, but that WILL result in an over-torqued condition! You must have faith in your tools to do it right the first time.
6) Nuts that have been torqued once should NOT be used again. I know this one gets ignored 99% of the time, but that's what we were told. There is a reason for that and it has to do with the nut and or bolt being stretched after it has been torqued once.
So there you go, my company paid a lot of money for that information (which is just some of the high points), but you are getting it for free and you are welcome to use all or none of it. :thumbsup:
