JPS63306811A - Miniature drill - Google Patents

Abstract

PURPOSE:To improve rigidity by setting the axial length of cutting chip discharging groove made from the tip of drill formed with a cutter toward the base portion of drill shorter than 80% of neck length. CONSTITUTION:A cutting chip discharging groove 10 is formed from the tip portion 2 of drill body 1 formed with a cutter 3 toward the base portion 4 thereof, and the axial length l thereof is set shorter than 80% of the neck length L of the drill body 1. Since the groove 10 is not formed upto the base portion 4, rigidity of tool can be improved. Since web thickness and web thickness taper can be reduced at groove portion and the groove width ratio can be increased, chisel can be reduced and thrust force can be reduced while accuracy at biting position can be improved and breaking frequency can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a miniature drill used for drilling a small hole with an inner diameter of 1 mm or less in a workpiece.

[Prior Art] As shown in FIGS. 3 and 4, when drilling holes for through-hole plating with an inner diameter of several hundred μl in a printed wiring board W, the tip of the drill body L has conventionally been used. 2 is formed with a cutting edge 3, and a spiral groove 5 for discharging chips whose length g is longer than the machined hole depth H from the tip end 2 toward the base end 4.
A miniature drill is used in which the drill is formed over substantially the entire length of the drill body l below the neck.

In the conventional miniature drill mentioned above, the NC
It is mounted on a drilling machine or the like and moved up and down once with a predetermined stroke to drill and process holes for through-hole plating in the printed wiring board W.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional miniature drill, the ratio between the axial length Q of the groove and its nominal diameter (IJ/D)
Since the diameter of the tool is approximately 30 or less, which is extremely large compared to a normal drill, the tool has poor rigidity, and therefore has the disadvantage that expensive materials with high toughness such as cemented carbide must be used to prevent breakage.

In addition, since the core thickness cannot be reduced in order to maintain tool rigidity as much as possible, the chisel inevitably becomes larger, resulting in decreased cutting performance and deterioration of centripetal properties, resulting in an increase in thrust force. At the same time, there is also the drawback that the hole position may be defective. Moreover, it is not possible to increase the groove width ratio, and in addition, it is necessary to increase the core thickness at the base end 4 under the neck of the drill body l, where the largest torsional torque acts, so the core thickness taper can be reduced. Therefore, there was a drawback that the chip evacuation performance was poor.

As a result of the above, when drilling a hole like the one shown in Figure 4 with the miniature drill mentioned above, ■ it tends to cause poor biting and bending of the hole, ■ it tends to break the drill body due to buckling, etc., and ■ it causes poor chip evacuation. There was a problem in that the surface roughness of the inner wall of the hole deteriorated.

This invention aims to solve these problems.

[Means for Solving the Problems] In the miniature drill of the present invention, the length of the chip discharge groove in the axial direction is 80% or less of the length under the neck of the drill body.

[Operation] According to the grooved miniature drill of the above configuration, the groove for discharging chips is not formed all the way to the base end of the drill body;
The tool rigidity is significantly higher than that of conventional miniature drills of this type. Furthermore, since the length of the groove is shorter than that of the conventional groove, it is possible to reduce both the core thickness and the core thickness taper in the relevant portion, and to increase the groove width ratio. As a result, it is possible to reduce the size of the chisel, thereby reducing thrust force and improving bite position accuracy.

[Example] Fig. 1 shows an embodiment of the miniature drill of the present invention, and parts common to those shown in Figs. 3 and 4 are given the same reference numerals and explanations thereof are given. In FIG. 1, which is omitted, in this miniature drill, the length Q in the axial direction from the tip 2 to the base end 4 side of the drill body L is 80% of the length under the neck of the drill body L. A groove 10 for discharging chips having a diameter of 1/2 or less (in the figure, approximately 1/2) is formed.

To drill a hole in the printed wiring board W using this miniature drill, as shown in Figure 2, set a stroke smaller than the hole depth H on the drilling machine in advance, and use this stroke to perform multiple step feeds. By repeating the steps above, holes are formed in the printed wiring board W. At this time, chips generated at each step are stored in the groove 10 and sequentially discharged to the outside.

Therefore, according to such a miniature drill, since the groove 10 is not formed as far as the base end 4 under the neck of the drill body l, high tool rigidity can be obtained, and therefore high toughness can be achieved unlike in the conventional drill. It is economical as it does not require the use of materials.

In addition, since the length g of the groove 10 is shorter than that of the conventional one,
Reduce both the core thickness and core thickness taper in the relevant part,
Moreover, the groove width ratio can be increased. Therefore, by making the chisel smaller, it is possible to reduce the thrust force and improve the biting position accuracy, and furthermore, it is possible to improve the chip evacuation performance, and the finished surface accuracy and bending accuracy of the hole can be greatly improved. Moreover, the frequency of breakage can also be reduced.

Here, it is important that the length Q of the groove lO in the axial direction be 80% or less of the length under the neck of the drill body l. In other words, if the length e of the groove lO exceeds 80% of the length under the neck, the tool rigidity will decrease, especially at the base end 4 under the neck, and the core thickness will decrease over the entire length of the groove lO. Also, since it is not possible to reduce the core thickness taper and increase the groove width ratio, it becomes impossible to obtain sufficient chip evacuation performance.

[Effects of the Invention] As explained above, the miniature drill of the present invention has a nominal diameter of 1φ or less and a diameter of 12/D of 30 or less, by adjusting the axial length of the chip discharge groove to the drill body. Since the length under the head is 80% or less, it is possible to obtain high tool rigidity and excellent chip evacuation performance, as well as reduce thrust force, improving the finished surface accuracy and bending accuracy of the hole. can be significantly improved.

[Brief explanation of drawings]

Figures 1 and 2 show an embodiment of the miniature drill of the present invention, with Figure 1 being a side view of the whole, Figure 2 being a diagram showing a hole drilling method using the miniature drill, and Figure 3 being a diagram showing an embodiment of the miniature drill of the present invention. 4 shows a conventional miniature drill, FIG. 3 is an overall side view, and FIG. 4 is a diagram showing a hole drilling method using the miniature drill. l... Drill body, 2... Tip, 3... Cutting edge, 4... Base end, 10... Groove, B...Bottom length of the drill body, D...Nominal diameter, g...
...The length of the groove.

Claims (1)

[Claims] A cutting edge is formed at the tip of the drill body, and a groove for discharging chips is formed from the tip to the base, the nominal diameter is 1.0φ or less, and the length of the groove in the axial direction is l. In a miniature drill where the ratio (l/D) of the diameter and the nominal diameter D is 30 or less, the length l of the groove in the axial direction is 80% or less of the length L below the neck of the drill body. Features a miniature drill.