| 摘要 |
An apparatus for forming a slot in a semi-product of a bolt prior to thread formation includes a punch and a die mechanism. The die mechanism includes a tubular member, and an elongated die member formed integrally with a slot-forming plate which is located at a front end portion thereof and which has a uniform-thickness flat middle portion and two side portions that are wider than the middle portion. The semi-product can be compressed between the punch and the slot-forming plate of the die member in a central bore in a high-hardness block, which is fixed in the tubular member, to form the slot. Accordingly, the slot has a uniform-width middle portion and two end portions which are wider than the uniform-width middle portion. When threads are formed on the semi-product by means of a lathe, no projections are created in the uniform-width middle portion of the slot, thereby permitting a wedge-shaped end of a screwdriver to engage fittingly the uniform-width middle portion of the slot.
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