Cuando alguien dice lo de a ojo de buen cubero.
I'm unable to translate this exactly: "Cuando alguien dice lo de a ojo de buen cubero........ etc" I believe I understand the meaning of "ojo de buen cubero" - eye of a good cooper. But I'm not confident on why the "lo de a" precedes it in the clause.
2 Answers
The phrase is missing something that will give it sense.
" Lo de " could mean, "give it" (to somebody), e.g:
" Necesito que (usted) me lo dé" - I need you to give "it" to me. And that "it" should be given by an experienced eye (a ojo de buen cubero).
"A ojo de buen cubero" is an idiom that means roughly. Look up cubero in the dictionary here and it tells you this. The whole sentence would translate as something like "When somebody says it roughly."