Inside diameter machining method

Inside diameter machining method in boring machining for machining inside a workpiece using a turning tool having a main body in the shape of a bar with a top end portion which is bent in the shape of a hook, said top end portion having a cutting portion, comprising:

• at the time of turning machining where the size of a tool insertion hole of the workpiece into which the turning tool is inserted is smaller than the machining diameter of the portion to be machined inside the workpiece,
• in the case where said top end portion cannot pass through said insertion hole by only linearly moving said top end portion through said tool insertion hole, whereby said linear movement causes said workpiece and said tool to interfere with each other;
• moving said top end portion of said turning tool in first and second directions corresponding to first and second orthogonal axes respectively, and in a third direction which is rotational and has a rotational axis orthogonal to both the first and second axes, to move said top end portion relative to said tool insertion hole of a workpiece to be machined along a bent portion of said top end portion so as to insert said top end portion into said tool insertion hole without interference with said tool insertion hole and positioning said cutting portion of said turning tool at the portion to be machined inside the workpiece;
• and
• starting turning machining on the portion to be machined of said workpiece in the above-mentioned state.