CROSS-RECESSED STRUCTURE IN SCREW

摘要

PROBLEM TO BE SOLVED: To provide a cross-recessed structure in which cam-out can be prevented while ensuring an effective length of a blade groove and even when a screwdriver bit is thinned by wearing, a rotational force can be transferred effectively.;SOLUTION: In a screw 11, four fins 22 of a cross-point screwdriver bit 21 are inserted into four blade grooves 3 of a cross hole which is terminated in an inversely conical bottom hole 2 formed in a screw head part 12, lower end portions 22a of the four fins 22 are articulated to lower end portions 3a of the four blade grooves 3, and a rotational force of the screwdriver bit 21 is transferred. When the fin lower end portion 22a is worn, a fin release groove 4 accepts that fin lower end portion 22a and articulates a sound portion continued to above the worn fin lower end portion 22a with the lower end portion 3a of the blade groove 3. Such fin release grooves 4 are formed continuously to the lower end portions 3a of the blade grooves 3, and the inversely conical bottom hole 2 is formed continuously to lower end portions 4a of the fin release grooves 4.;COPYRIGHT: (C)2014,JPO&INPIT