Probably the most used tool for pin repair is the hollow shaft, thin wall, nut driver.
Faster than you can find the proper socket for your wrench, this is "the" color coded nut driver set.
The set uses the same colors as the one your grandfather had, so the red is the familiar 1/4", the yellow 5/16"... you get the idea.
The shafts are hollow, so the screw threads enter it without the need for a deep well socket or open ended wrench (you need this for pop bumpers).
Wrap the shaft with a layer of electrical tape if you like to live dangerously and service playfield lights with the power on, lol
Regularly $40 on sale for $20
Lifetime warranty through Sears or B&D