Modular reamer

A modular reamer (fig.1, 100) for use in a wellbore comprises an uphole end member 110, a center member 130, and a downhole end member 140, with reamer sleeves 120 removably slidable over a sleeve mounting portion 245, 265 of the center member or one of the end members, and are held between shoulders 240, 250, 260, 270 of the end members and the center member when assembled into a downhole tool. The reamer sleeves may be positioned at any desired rotational angle relative to each other and are prevented from rotational movement relative to the center member by spines or keys formed on the mating surfaces (fig.3, 310) of the reamer sleeves and corresponding members of the modular reamer. The modular reamer may be eccentric.