A bottom hole assembly (bha) is a component of a drilling rig. It is the lowest part of the drill string, extending from the bit to the drill pipe. The assembly can consist of drill collars, subs such as stabilizers, reamers, shocks, hole-openers, and the bit sub and bit. Bottom hole embly ocean drilling bottom hole embly cnco powerreach safety valve halliburton dsd bottom hole embly in closed bottomhole embly schlumberger oilfield glossaryparison of original and modified bottom hole embly to1 the bottom hole embly bha schematic of pctb cuttingbottom hole embly bha and vibration modesdrilling tools prime horizontalbottomhole embly an overview. Bottom hole assembly (bha) the bottom hole assembly (bha) is made up of a drill bit , which is used to break up the rock formations drill collars , which are heavy, thick-walled tubes used to apply weight to the drill bit and drilling stabilizers , which keep the assembly centered in the hole. The bottom hole assembly (bha) is a key component of the drilling system, consisting of various components and tools (including the drill bit itself) which operate at the bottom of the wellbore and physically drill the rock. Bha means bottom hole assembly this acronymslang usually belongs to common miscellaneous community category. This bottom hole assembly bha is used for formations which have medium crooked hole tendency such as medium and soft formations. The bottom-hole assembly (bha) is the component of the drill string that includes the core bit, outer core barrel, various subs, and the drill collars. It hangs below the drill pipe and provides weight to the drill or core bit to induce the teeth to penetrate the formation, thereby drilling a hole or recovering core to meet the scientific objectives of the cruise. -router using a straight cut bit with a circle jig or 6 hole template and a upspiral or downspiral cutting bit trim bit. -jigsaw - this method is not advised - even the steadiest hand wont cut perfect holes with a jigsaw. Route the top and bottom edges of the decks including the top and bottom of the holes with a 14 roundover bit.