JPH02122712U

JPH02122712U -

Info

Publication number: JPH02122712U
Application number: JP2999789U
Authority: JP
Priority date: 1989-03-15
Filing date: 1989-03-15
Publication date: 1990-10-09

Description

[Brief explanation of the drawing]

第１図はこの考案の一実施例の要部を示す側面
図、第２図は芯厚部の断面図、第３図は正面図、
第４図は従来ドリルを示す図で、同図ａは側面、
ｂは先端の拡大側面、ｃは正面を各々表している
。１……切刃、２……チゼル刃、３……マージン
部、４……刃溝、５……シヤンク、α……ねじれ
角、θ……先端角、Ｄ……ドリル径、ｌ……刃長
、Ｗ_１……先端芯厚、Ｗ_２……溝切上り部芯厚、
ｍ……マージン長、Ｐ_１〜Ｐ_４……ねじれ角の変
化領域。 Fig. 1 is a side view showing the main parts of an embodiment of this invention, Fig. 2 is a sectional view of the thick core part, Fig. 3 is a front view,
Figure 4 shows a conventional drill, where a is the side view;
b represents an enlarged side view of the tip, and c represents a front view. 1... Cutting edge, 2... Chisel blade, 3... Margin, 4... Blade groove, 5... Shank, α... Helix angle, θ... Point angle, D... Drill diameter, l... Blade length, W ₁ ... Tip core thickness, W ₂ ... Grooving upward core thickness,
m...margin length, _P1 to _P4 ...change area of twist angle.

Claims

[Scope of utility model registration request]

The drill diameter is 0.5 mm or less, the hole depth ratio (aspect ratio) is 10 or more, the flute helix angle at the tip of the drill is 25° or more, and the core thickness ratio (core thickness / drill diameter) is 2.
0-30%, core thickness ratio at the cutting edge of the blade groove is 60-8
0%, and the groove width ratio is set to 1.5 to 2.5:1 in a printed circuit board drill with a core thickness taper. A small-diameter drill for printed circuit boards, characterized in that the drill is gradually or continuously loosened by 3 to 7 degrees per double length.