At what point are a contactors contacts worn out? This is from a Square D Nema 3 contactor.
Technically when the contactor metal is eroded/worn away, ie. down to the copper substrate.
The other unasked question is,
when should they be replaced??
That of course depends on the application. In a high load ( run at or near the rated capacity of the contactor), high cycle environment ( hundred to thousands of contacts per day), and/or a critical application ( device down causes loss of $$ or even life), and given that you tore it down already you would be remiss if you didn't replace them. Conversely if your running this on your compressor, or your going to use it in your phase convertor, as Aceman said " keep running it" as it will probably out last you!
William.....