Many have read where I recommend using a torque wrench to set the torque value of propeller bolts. There are reasons for this.

Attached is a picture of a brand new propeller that ran for about 30 minutes. The hub had been drilled incorrectly, permitting a pre-load to be applid to the prop bolts when inserted becasue the holes were just fractionally tight. The bolts had been attached using an adjustable torque, battery powered, electric drill. Absolutely no accurate torque value was established prior to setting the limit stop on the drill motor. One of those "feels about right" situations. Same as what is often used by modelers and a hand held hex key. The end result is frightening, especially if you were the one on the business end of the propeller.

In this case, just about everything was done wrong. Something I fear may be much too common an occurance in the RC world. There will be a lot of comments from people about how this or worse could never happen to them because they have been doing RC for many years, have a calibrated wrist or elbow, or some other point of denial. This propeller was installed by an individual that is highly experienced and knew better, but in the interest of saving time and effort....