The torque wrench is an often misunderstood tool.
The EAA video's have a good video explaining the click-type torque wrench. I strongly recommend watching it.
Click here for the video link.
Some additional information on using torque wrenches:
A torque wrench exists in different types: there is the one in inch/pounds which you need for the regular kit and there is also a version in foot/lbs which is used for heavier application like torqueing the propellor bolts.
It's also one of the more expensive tools and and is a high precision instrument.
They come calibrated with a certificate.
In Belgium you need this in order to be allowed to use it.
Some often used torque values will be 20-25 inch/lbs for an3 bolts in combination with AN365-1032 nuts and 50-70 inch/lbs for AN4 with AN365-428 nuts. (the values can be looked up in the standard aircraft handbook or "the bible" (being the AC43.13 1B chapter 7 from page 6 which you can find here)
- A torque wrench is a calibrated device. In principle it has to be regularily re-calibrated.
- Whenever you are finished working with it, make sure to re-adjust it to the zero position so the pressure is off the spring.
- When attaching a nut, first use a regular wrench to fasten the nut, then switch to the torque wrench to do the last part.
- Always torque the Nut, not the bolt head.
- First thighten the nut on the bolt with a regular key. Only use the torque wrench to do the final adjustment to the correct torque setting.
- Apply seal immediatly on nut and a fixed struture once you torqued a nut. If you don't you will question yourself if you already torqued it or not at a later date, which means you will apply some pressure to check with the torque wrench and inadvertibly torque it a bit more before the click kicks in. Then later, an inspector might do the same and before you know, you will end up with 40 inch/lbs instead of the intended 25 inch/lbs prescribed.
You might also be interested on this video about applying torque seal laquer once to torqued to the correct value.
