HONE IN

[hone in] vi [alter. of home in] (1965): to move toward or focus attention on an objective "looking back for the ball honing in --George Plimpton" "a missile honing in on its target --Bob Greene" "hones in on the plights and victories of the common man --Lisa Russell" usage The few commentators who have noticed hone in consider it to be a mistake for home in. It may have arisen from home in by the weakening of the /m/ sound to /n/ or may perhaps simply be due to the influence of hone. Even though it seems to have established itself in American English (and its mention in a British usage book suggests it is used in British English too), your use of it esp. in writing is likely to be called a mistake. Home in or in figurative use zero in is an easy alternative.