bit / bitt are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
bit: (noun) a small fragment of something broken off from the whole. (noun) piece of metal held in horse's mouth by reins and used to control the horse while riding. (noun) a unit of measurement of information (from binary + digit); the amount of information in a system having two equiprobable states. (noun) the part of a key that enters a lock and lifts the tumblers. (noun) the cutting part of a drill; usually pointed and threaded and is replaceable in a brace or bitstock or drill press.
bitt: (verb) secure with a bitt.
bit: b·IH·t
bitt: NA
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)