| 摘要 |
PROBLEM TO BE SOLVED: To machine an inside surface at a high speed by providing a vertical reciprocating mechanism and a horizontal reciprocating mechanism. SOLUTION: A horizontal reciprocating mechanism 30 is provided with four driving bodies 32, of which upper ends are fixed to a shaft, and the four driving bodies 32 are arranged corresponding to four blades 20. A lower end of each driving body 32 is formed with a tapered surface 34 so that the outer surface thereof is gradually enlarged in the radial direction as it comes lower. The taper surface 34 supports a base end of the blade 20 freely to be relatively moved in the vertical direction in the taper-to-taper condition. A clearance is formed between the inner peripheral surface of a lower end of the driving body 32 and the shaft, and when the shaft is raised by the predetermined distance by an elevating mechanism 40, the taper surface 34 of the driving body 32 pushes the blade 20 outward in the radial direction. A blade surface 22 formed at a tip of the blade 20 is engaged with an inside surface 94 of a bore 92. A base substance 12 vertically moves the horizontal reciprocating mechanism 30 and the blades 20 accompanied with the vertical movement of the vertical reciprocating mechanism 50.
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