A key destroyer preferably deploys an angle grinder fitted with a grinding chamber, cover, and insertion tube through which a key can be inserted to be destroyed. The key is gripped in a holder that can slide key foremost through the support tube so that the coded portion of the key can pass through a safety wall at the inner end of the support tube and engage a rotating abrasive disk that grinds away the coded portion of the key. The head of the destroyed key can then be retained as evidence that a particular copy of a key no longer exists.