How to solve the Hanayama Cast Quartet metal puzzle

Check out this video tutorial on how to solve the Hanayama Cast Quartet metal puzzle. These cast iron Hanayama puzzles are a great way to kill time and sharpen your mind, and this Cast Quartet puzzle will do that with a level 6 out of 6 in difficulty.

From Hanayama himself: True bonds has always been hard to form, but once formed such bonds are eternal and hard to break. My original version was created with this image in mind, but the puzzle was completed into a cast puzzle with a bond that is truly difficult to unravel. How would you go about breaking and forming this bond? There are two approaches to this puzzle and I challenge you to both! The key word is "Bond."