Provided is a two part drilling and running tool, a well system, and a method for forming a well system. The two part drilling and running tool, in one aspect, includes a conveyance, and a smaller assembly coupled to an end of the conveyance. The two part drilling and running tool, in accordance with this aspect, further includes a larger bit assembly slidably coupled to the conveyance, the smaller assembly and larger bit assembly configured to slidingly engage one another downhole to form a combined bit assembly.

Provided is a two part drilling and running tool, a well system, and a method for forming a well system. The two part drilling and running tool, in one aspect, includes a conveyance, and a smaller assembly coupled to an end of the conveyance. The two part drilling and running tool, in accordance with this aspect, further includes a larger bit assembly slidably coupled to the conveyance, the smaller assembly and larger bit assembly configured to slidingly engage one another downhole to form a combined bit assembly.

Provided is a two part drilling and running tool, a downhole tool, a well system, and a method for forming a well system. The two part drilling and running tool, in at least one aspect, includes a smaller assembly coupled to an end of a conveyance, the smaller assembly having a spline or slot located along an entire length (L.sub.S) thereof. The two part drilling and running tool, in accordance with this aspect, further includes a larger bit assembly slidably coupled to the conveyance, the larger bit assembly including an other of the slot or spline, wherein the spline or slot in the smaller assembly and the other of the slot or spline in the larger bit assembly are configured to engage one another to rotationally fix the smaller assembly relative to the larger bit assembly as the smaller assembly and the larger bit assembly slidingly engage one another.

Provided is a two part drilling and running tool, a downhole tool, a well system, and a method for forming a well system. The two part drilling and running tool, in at least one aspect, includes a smaller assembly coupled to an end of a conveyance, the smaller assembly having a spline or slot located along an entire length (L.sub.S) thereof. The two part drilling and running tool, in accordance with this aspect, further includes a larger bit assembly slidably coupled to the conveyance, the larger bit assembly including an other of the slot or spline, wherein the spline or slot in the smaller assembly and the other of the slot or spline in the larger bit assembly are configured to engage one another to rotationally fix the smaller assembly relative to the larger bit assembly as the smaller assembly and the larger bit assembly slidingly engage one another.