Abstract: A method, machine tool and boring bar for machining bores in a series of concentric journals for a camshaft in a cylinder head or block of an engine. The boring bar has an elongate and cylindrical body with a single cutting insert at one end for machining all of the journals one at a time and a plurality of circumferentially spaced and longitudinally extending bearing pads on the body which, when the insert is machining one journal, are received in the previously machined journals to radially constrain and support the boring bar. The other end of the bar is received in a chuck or drive spindle of the machine tool which rotates and advances the boring bar through the journals to machine them. Each workpiece is located and clamped in the machine tool with its series of journals to be machined substantially concentric with the axis of rotation of the insert of the boring bar.