I was once told don't lend your mower, your missus or your tools, they'll come back f***ed.
I only have one 'brother' that I lend tools to.
I recently 'hired' an old mower to an old friend, and was having to do a few repairs when I got it back.
The guy I left my cement mixer with when my house burnt down and I had to leave town, don't wan't to give it back!
My advice on lending tools, is don't do it unless you have a new one and didn't really want the old one anymore.