Following are a number of back-translations as well as a sample translation for translators of Proverbs 27:17:

• Kupsabiny: “Friends make one another understand/realize
  as how one iron sharpens another.” (Source: Kupsabiny Back Translation)
• Newari: “Like iron sharpens iron,
  a friend sharpens a friend.” (Source: Newari Back Translation)
• Hiligaynon: “As iron can-be-sharpened by iron also, a man can-learn from his fellowman.” (Source: Hiligaynon Back Translation)
• Kankanaey: “A person is taught by his fellow person, like the way iron is sharpened by its fellow iron.” (Source: Kankanaey Back Translation)
• Shilluk: “A person learns from a person who walks with him like sharpening a spear with another spear.” (“In considering this proverb, the Shilluk translators found that in their culture ‘iron’ has the connotation of raw material, not an implement that could sharpen something. They chose instead to substitute a specific iron implement in order to have a more powerful image.” — Source: Cynthia Miller in The Bible Translator 2005, p. 129ff. )
• English: “We can use one iron tool to sharpen another iron tool;
  similarly , when one person shares what he is thinking, it can help other people to think more clearly.” (Source: Translation for Translators)