A dosing device for a lubricating mechanism is constructed for discharging a measured volume of lubricant into a component to be lubricated, such as a rotary gear box in an aircraft. For this purpose the dosing device has a housing with a defined volume in which a piston is movable in an axial direction to define two chambers. The end walls of the housing are connected through quick coupling connectors to a lubricant supply and to the component to be lubricated. The device operates in such a way that the filling of one chamber with lubricant under pressure pushes the piston, and thus the lubricant in the other chamber, out into the component to be lubricated. Thus, always a precisely measured volume of lubricant is discharged from one chamber while the same volume is being filled into the other chamber and vice versa. A coupling adapter may be used for a quick reversal.