As those of you with the Hewlett-Packard desktop printing calculators know, the center (idler) gear in the printers are prone to failure due to their age and the fact they are made of relatively soft plastic.  There are excellent instructions, published on the HP Calculator Museum Website, for manufacturing aluminum replacements for these gears.  I have used these instructions more than once; if you have never done this you have to buy parts from two different manufacturers, plus specialized tooling, and there is a bit of physical labor to modify the gear you buy before you can install it in your machine's printer.  Deciding to go one better I have in my possession, locally manufactured using actual gears as the model, aluminum replacement gears for the HP-91/92/97 calculator printers.  These gears are "like for like", exact copies of the original gears, and require ZERO MODIFICATION to install in your calculator.  I have installed these on several 97s and I guarantee these will fit in your machine.   If you would like more information or photographs of one of these gears installed in a 97 please email us. Note: Free shipping worldwide!