Torque wrench verification

[To Bear Arms]

Of the 8 dealers I've dealt with over the years, none of them had one on the truck. They usually have somebody they'd send it to. Same goes for the Matco/Mac/Cornwell dealers I've had.

For a calibration it's is sent off. All the dealers I have worked with have a unit that just verifys torque.

[soldier-of-the-apocalypse]

"I have a good quality Craftsman ft lb torque wrench" is this a joke, I'm done with crapsman now that its all Chinese junk if you break your good quality USA made tool and take it in the just give you harbor freight junk that's branded as craftsman. They were always pretty crappy but it was decent and USA made, now I just stick with snap on and mac and they calibrate torque wrenches on the truck

[vossman]

No joke here, the high end Craftsman products used to be good quality IMO. Haven't bought anything in a while from them so quality is probably gone to shit but I'm not looking for a $1000 torque wrench either.

To the member that recommended youtube, thanks. Easy little formula to get an accurate measurement.

[hobowh]

Since Sears started to slide downhill so has craftsmens quality at least fro what I have noticed. Since yours is an older unit it was prob a quality one that was actually made by one of the big 3. To get a true idea if it's true you need to get it to someone with a torque meter, and can calibrate it if needed.

[ben4372]

Harbor Freight has a digital torque extension for something like 40 bucks. Hotrod magazine did a comparison. They checked accuracy against better brands and it was super accurate. Like less than 1 percent off. Was even better than a couple big brands. Likely less than the cost of calibration.

[james_bond_007]

This is actually not a bad article http://www.wikihow.com/Calibrate-a-Torque-Wrench (even though it is Wiki How) to help calibrate a torque wrench for non-government use (aka the home mechanic) vs $25 for calibration (See http://www.anglerepair.com/charges/ )

SUMMARY:

1. Place the wrench drive fitting in a vise, so the handle can move when loaded, and is parallel to the floor.
2. Get a weight (load) of known value (could be a water jug you fill up with sand or lead shot and weigh yourself to a known weight).
3. Place it at a known distance on the handle, from the drive fitting center. (I'd use a piece of wire fashioned into a hook to hook the jug on the handle)
4. Move the weight closer/farther from the head, and see where the wrench "slips".
5. Check the reading against the calculation (see below)
6. Adjust the wrench and repeat, using different loads, until you are comfortable with the "calibration".

CALCULATION
Torque (ft-lbs) = Weight (pounds) * distance (in feet)

EX:
Jug = 10 lbs
Distance = 10 " = 10in * (1 ft /12in) = 0.8333 ft

Torque = 10 lbs * 0.8333ft = 8.333 ft-lbs


NOTE: This is not a substitute for a professional calibration or a 'perfect' way to measure torque.
NOTE: I'd NOT expect a Craftsman (non-precision) wrench to be linear across the full specified range.
NOTE: I'd expect the wrench to be more linear in the middle of the range, than at the extremes
NOTE: You could also take the weight of the hanging wrench handle into account, but unlike the article (it says to weigh the wrench), I don't think you can get away with just weighing it.
Weighing the wrench assumes a lumped model at some distance. The weight of the wrench is actually follows more of a distributed model along the length of the handle.
It will have a lumped equivalent model, but it is likely not equal to the weight of the handle when weighed separately.

Again, this is NOT a precision calibration method, but should
a) tell you if you are in the ballpark (if you have no calibration adjustment)
or
b) allow you to GET in the ballpark (if you have a calibration adjustment).