Fernando,
Bleach is a chlorine compound (sodium hypochlorite solution) It is
used to clean clothing and floors and it is also as a disinfectant.
It is also corrosive to metals. It will damage nickel white golds and
other metals by what is called stress crack corrosion it creates
inter granular corrosion allowing the metal to crack along the
crystal boundaries. It probably is dissolving the drill bits by
electrolysis. It is a poor choice for this due to its ability to
cause the stress crack corrosion. There is an article about this
phenomenon at
Do Chemicals Effect Your Gold?
James Binnion
@James_Binnion
James Binnion Metal Arts
360-756-6550