When it comes to any automotive measuring tool, it pays to take good care of them and in my opinion, it pays to have two of of them or at least take the time to compare them to another one on a regular basis if you can't get them calibrated.
Snapon can check your torque wrench and military bases have tools to do as well. A friend once lost the motor on a race bike (and the race) because of a bad torque wrench and only uses Snapon after that experience. I'm not willing to pony up that much cash and I don't have a exotic race bike so I just double check my tools against others.
Timing lights and meters can cause similar havoc. I once pulled a perfectly good F motor out of my Cruiser because of a WAAAAAY out of calibration timing light and recently a bad meter lead me to believe that I had 120 volts on a 220 line. I found after I pulled and tossed that F motor that I just had a bad timing light. I put another back and it after setting the timing, it too ran badly so I borrowed and cross check the tool and it was off.
I've also seen bad vacuum gauges, hand held tach's, dwell meters, compression testers, etc. Once my friend Will was about to pull the motor out of a truck for having low compression, he was doing the test incorrectly and had a gauge that read low - in fact it had perfect compression and just needed a tune up. Do your diagnostics first with tested tools before you start tearing things apart! At first do no harm as they say.
I have some older craftsman torque wrenches and a Utica one. The latter has been calibrated. For what I do, that have served me well.
Last point, when you do torque something, don't bounce against the measurement because each time you hit that click it goes up a bit. Does not matter on a wheel but on something with threads in aluminum or a gasket that will be distorted, it does matter.
I asked one of the engineers at work and they send their equipment over to the Calibration and Testing Branch for re-calibration. I couldn't get him to volunteer to send my wrench. 
