Adjustable boring bar

A cutting tool of the type having an axis of rotation and a peripheral surface area spaced from the axis of rotation with at least one radially displaceable cutting bit mounted thereto comprising:

• mean for biasing said cutting bit in a first radial direction with respect to said axis of rotation,
• means for adjustably moving said cutting bit to a predetermined desired position, said adjustable moving means including a fluid pressure source for an incompressible electrorheological fluid, means communicating with said fluid pressure source and said cutting bit for the flow of electrorheological fluid and for adjustably moving said cutting bit in a direction opposing said first radial direction in proportion to pressure being generated by said fluid pressure source,
• a valve means operably associated with said communicating means for effecting changes in the dynamic stiffness of said electrorheological fluid in response to an electric field,
• electric field producing means for transmitting a sufficient electric field to said valve means to substantially block the flow of electrorheological fluid to said cutting bit from said fluid pressure source and maintain a predetermined radial position of said cutting tool.