Go to Fastenall or Brafasco (nut and bolt retailers) and buy a bolt which has a nylon insert in it ( this is called a "Nylock"). The nylon insert extends out a bit beyond the thread plane of the bolt. When you tighten it the bolt in place, the nylon will deform enough to keep the bolt from coming loose. If you ever do want to remove the bolt, a wrench will still remove it.