Chosen Solution
How do I replace a broken hinge on my OfficeJet HP-6480? Update (04/05/2016) It is the hinge on the left rear of the printer. See attached photo.
Removed both hinges and replaced with an attractive brass piano hinge across the complete rear of the printer at the separation. Used small brass screws that came with the hinge (Home Depot) and clear silicone for extra adhesion. Been in use for thre years, OK. Easy fix , strong and only drawback is I use a prop-stick to hold cover open at appropriate +/- 45 degree angle for cartridge maintenance as the vertical latch the original hinges offer are now gone..