Drilling tool

Abstract

The invention provides a drilling tool, which is capable of preventing chip winding and capable of stably drilling holes by using a small-diameter drill bit with a diameter smaller than 0.7 mm, in particular smaller than 0.4 mm, and achieves long breakage-resistant lifetime and excellent practicability. The tail end of a tool body (1) is equipped with one or more cutting blades. Multiple helical chip-evacuating grooves are formed in the outer circumference of the tool body (1) from the tail end of the tool body to the base end, wherein the multiple chip-evacuating grooves at least comprise one main groove (2a) and one auxiliary groove (2b). The one or more auxiliary grooves (2b) are joined with the main groove (2a) at the halfway portion of the main grove (2a). In addition, the join portion (6) where the main groove (2a) and the auxiliary groove (2b) are joined has class difference (7).

Description

technical field [0001] The invention relates to a drilling tool. Background technique [0002] Used in the drilling of printed circuit boards (PCB) such as figure 1 A drill as shown is composed of a drill body A having a cutting edge C and a shank B. As shown in FIG. Depending on the application, the size of the drill varies, but generally speaking, drills with a diameter of 0.7 mm or less are used. [0003] Specifically, on the blade C, such as figure 2 As shown, a helical chip flute 22 is formed on the outer periphery of the main body 20 from the drill tip to the base end side. The cutting edge 21 is formed at the intersecting ridgeline portion (for example, refer to Patent Documents 1 and 2). In addition, in the figure, reference numeral 25 is a second relief surface, and the second relief surface 25 is continuously provided on the rear side of the first relief surface 24 in the tool rotation direction, d' is a tool diameter, and l' is a flute The groove length, α' ...

AI Technical Summary

Problems solved by technology

[0013] In addition, although, for example, Patent Document 4 discloses a technique in which, on a PCB drill having two cutting edges and two chip flutes, the chip flutes are merged at a position retreated by a predetermined amount from the tip, A groove is formed behind the meeting point, thereby improving the rigidity of the drill, but Patent Document 4 does not mention the winding of chips, and the above-mentioned requirements cannot be met.

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