This Instructable is for removal and replacement of the small plastic joint holding Barbie's arms on.
Step 1: Parts & Stuff
Thread lock or solder + iron
Step 2: Arm & Body Prep
There are two plastic nibs inside Barbie's chest cavity. Push them in until they fall out, and shake her around until you get them out. If you don't do this, they will rattle around inside her.
Step 3: Replacement Joint Fabrication
After you have the screw the right length, get to work on the nut.
Place the nut in a vice and grind it until it is more or less shaped like the head of the screw.
Step 4: Joint Assembly
Be mindful that you don't want lead contamination and wash Barbie thoroughly after you are done to remove any foreign matter that you may have introduced.
In the second picture above, the shoulder joint assembly is pushed out so you can see the nut. When in the proper position, each end only protrudes about 1/8".
Step 5: Barbie Arm Re-attachement
Don't forget to thoroughly clean Barbie before she goes back into circulation!
This took me about an hour to complete, but this Barbie had been around for 25+ years and so I think it was worth the time to have a pass-down hopefully last another 25.