Rotary ultrasonic machining (RUM) is considered as an effective machining method, which has been utilized to machine hard and brittle materials such as advanced ceramics. In order to improve the hole wall surface quality during RUM, it is important to wash away swarf in the gap between the tool and the workpiece as fast as possible. In this paper, a new machine process – intermittent rotary ultrasonic machining (IRUM) – is introduced for the first time. The cutting force, surface roughness and coolant flow rate in conventional rotary ultrasonic machining (CRUM) process and IRUM process are compared. It is found that compared with CRUM, the output coolant flow rate could be increased significantly by using the IRUM method. It is also found that the surface roughness of workpiece can be improved significantly in IRUM.