I realise this is an old thread, but I ran across it whilst researching torque wrenches. I've got a couple if old CM wrenches -- a 3/8" (44541) and a 1/2" (44476). I have always treated these wrenches fairly gently and always wound them all the way down when not in use.
The company I work for is having a bunch of stuff calibrated right now so a calibration company has their trailer parked in our parking lot. I asked them if they'd be interested in doing some work on a cash ticket and they said, "sure."
I gave them the two CM wrenches. The 1/2" has never been checked and the 3/8" was last calibrated about 20 years ago. (I know, I know....) Both failed. The 3/8" was out about 8% (tolerance is 4%). The 1/2" was out 50% (five zero percent)!

Turns out the jam nuts that hold the handle onto the adjustment screw came loose and the handle shifted, throwing out the calibration. I searched online and found this is a common problem with this wrench -- especially is you wind it to zero "with authority." They want another $40 to repair it but there's not another calibration charge.
I may let them fix it, but in the meantime I wanted another wrench and saw HF had their 1/2" wrench on sale for $24.99. With a 20% coupon, that puts it less than $20. "What the hell," I figured, "let's give it a try." I bought one and gave it to the cal folks to see how far it's out. That way, I'd know how much fudge factor to figure in.
The damn thing passed!
He said the tolerances are a little looser than he would have liked, and he didn't know the manufacturer's spec so he assumed 6% (his generic spec). He said it would not have passed 4%. He also said it will probably go out quicker than a higher-dollar wrench. But he also said that he does a lot of work for the Navy (his co. is located near a base) and they buy SO by the case. He finds that a large number of them are out of spec straight out of the box. So I have more respect for this $20 HF wrench than I expected to have!
EDIT: For the record, the manufacturer is Hsian Dai Co, Ltd., of Taiwan. I found little about them on the web other than that they are a Taiwanese tool manufacturer. There's no identifying info on the wrench itself apart from a serial number -- not even a COO -- but the mfr name is on the blow-molded case.