| 摘要 |
PURPOSE:To improve tapping precision, by a method wherein a thread cutting tool is movable in a limit range, and is relatively non-rotatably mounted on a rotary shaft, a bush, threadedly joined with the thread cutting tool is securely placed in front of a main shaft coaxially with the main shaft, and a tool axis is specified. CONSTITUTION:A pair of guide slits 12 are axially bored in the rear part of a thread cutting tool 6, and a pin 13, mounted in a mounting hole 5 of a rotary main shaft 1 and secured to the tip of the main shaft 1, is inserted in the slits 12. A spring 15 is disposed between a support member 14, making contact with the rear end of the tool 6, and the closed end of the mounting hole 5, the tool is relatively movable therebetween, and its relative movement is blocked by means of a pin 1. A cylindrical holder 16 is concentrically secured to the front end surface of a support member 3 of the main shaft 1, and a bush 19, threadedly joined with the cutting thread of a tool 2 is removably secured coaxially with the main shaft 1 to the front end of the holder 16. Thus, the axis of the tool 6 is normally coincided with that of the main shaft 1, and tapping in a low precision hole is effected with high precision.
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