Rotational vibration absorber with tangential dampers cap

A vibration damping device for use with a downhole tool having a tool axis may comprise a body coupled to a drill string component. The body may include a longitudinal bore therethrough and at least one lateral bore, the lateral bore having a bore opening and an end wall; an inertial mass slidably disposed in the lateral bore; and a cap mechanically coupled to the lateral bore. The lateral bore may be orthogonal to a radius of the body and may lie in a plane normal to the tool axis. The body may include a plurality of lateral bores, which may be in a co-planar arrangement. Each lateral bore may be blind hole positioned in the body so that it does not intersect the longitudinal bore or another lateral bore. A cap may enclose a lateral bore and fluid may be contained in the bore by the cap.