Repair broken plastic parts by pressing metal pieces into the material with a soldering iron. The technique can also be used for fabrication or reinforcement.
The photos show the repair of the arm which holds paper on an adding machine.
I consider smaller, more compact instructions to be preferable, but Instructables
has been refusing to publish this one, presumably because it consists of only
one picture, the intro.
I'll add a step to test this theory.
Step 1: A Broken Piece, or One Needing Reinforcement
It seems to me the intro covers it, please comment if it is unclear,
and you prefer clicking through a breakdown of the process.
You bridge the broken parts with metal ... wire works well, and press the
metal into the plastic with something hot enough to melt plastic, a soldering
iron is well suited.
Once the wire (metal) is melted in, smoosh some plastic over it.
Here's one of the arms which holds the paper roll for an adding machine.
It is broken.