Is It "Home In" or "Hone In"?
Both are used, but home in does a better job of hitting the mark.
Some animals possess the uncanny ability to return to their home or to the location of their birth from just about anywhere. They're able to "home" without the help of a GPS—which is more than most modern humans can say.
And yes: you can use the word home that way.
In fact, it's this use of home that gave rise to the phrase home in, which is used both literally and figuratively to mean "to find and move directly toward (someone or something)":
… salmon, for example, can home in on dissolved amino acids in river water … — Joseph Dussault, The Christian Science Monitor, 7 Jan. 2016
They effortlessly pin down characteristics of the worst of L.A. types and home in on them … — Rebecca Bulnes, The A.V. Club, 11 Jan. 2016
But sometimes people use hone instead of home:
… the ads are starting to turn aggressive, as candidates and super PACs hone in on their opponents. — Steven Perlberg, The Wall Street Journal, 8 Jan. 2016
Asking the right questions allowed me to hone in on their specific needs. — Linda Harding-Bond, The Huffington Post, 7 Jan. 2016
And who can blame them, really? The use of home that gave us the phrase home in is unfamiliar to the great majority of us for whom the word home is exclusively a noun.
The verb home is relatively young, as words go. The noun dates to Old English, but our earliest evidence of the verb in use is from 1765, when it was used to mean "to go or return home." Within the next hundred years the verb had developed an animal-specific sense: an animal returning to its home or birthplace was said to be "homing." Usually the animal in question was a pigeon—in particular, a homing pigeon.
By the 1920s, pilots were homing toward their destinations; in the decades following, vehicles and projectiles were said to be "homing" as they moved closer to their destinations or targets. By the 1950s home was being used figuratively to describe the action of anyone or anything proceeding toward or directing attention toward an objective.
The verb hone also dates to the late 1700s. Its original meaning is "to sharpen or smooth with a whetstone." By the early 20th century another meaning had developed: "to make more acute, intense, or effective." Instead of just honing blades, people were now honing skills.
It's the narrowing or sharpening of focus implied in the figurative meaning of hone that seems to have made hone in seem like the right phrase to some, rather than home in with its unfamiliar verb home.
This use of hone in dates to around 1965, which makes it only about 10 years newer than the figurative use of home in. We have enough evidence of hone in in use that we enter it in our dictionaries. As the note at that entry makes clear, however, home in remains significantly more common, and is the version to use if you want to avoid criticism. Zero in is also an option if you want to avoid the very similar h-words altogether.