JPH02232111A - Slotted hole machining small diameter drill - Google Patents

Abstract

PURPOSE:To prevent slope in a hole center line and breakage by setting a helical angle formed at a main body part to 25 deg.-35 deg., a point angle to 145 deg.-170 deg., the web thickness to 15-30% of a blade tip diameter in the vicinity of the tip of a cutting blade and the web thickness taper to 0.04-0.06 on the basis of 1mm. CONSTITUTION:A pair of helical gashes 4 are formed in the axial direction of the main body part 3 of a small diameter drill 1 formed of a shank part and the main body part 3, and the helix angle thereof is set to 25 deg.-35 deg. taking machinability and rigidity into consideration, or the point angle alpha is set to 145 deg.-170 deg. taking account of the influence given to the position accuracy of a machined hole in the case of slotted hole machining and chamfer to a base. The web thickness (d) is also formed accompanied by the formation of the helical gashes and is set to 15-30% of the blade tip diameter D in the part close to a tapered cutting blade tip 5, the web thickness taper is set to 0.04-0.06 on the basis of 1mm, and thus the rigidity of the main body part 3 is heightened so as to prevent its breakage at the escaping time of the drill during machining.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a small diameter drill for machining long and large printed circuit boards such as glass-epoxy steel laminates, and in particular improves machining efficiency by improving its shape. This is what I did. (Conventional technology) Conventionally, long holes in printed circuit boards are machined using a small-diameter drill for normal drilling, and the holes are drilled sequentially from the start point to the end point of the long hole at a pitch smaller than the diameter of the drill being used. There is. Another method is to set the board in a router machine and process it with an end mill. (Problems to be Solved by the Present Invention) However, in the method using a small-diameter drill, the drill may break or the machining accuracy may be low. For this reason, the machining speed had to be extremely slow compared to normal drilling, and this resulted in extremely low machining efficiency.

In addition, the method using a router end mill has the problem of reduced work efficiency due to chip clogging or changeover to a router machine.

For this reason, the present invention prevents hole bending and breakage.
The purpose of this invention is to provide a small diameter drill with an optimal shape that allows the drill to be drilled.

(Means for Solving the Problems) The present invention has been made in view of the above-mentioned points. Tip angle a. Core thickness d
The shapes are optimized.

That is, the twist angle θ is set to 25° to 35°,
The tip angle a is set to 145° to 1701°.

In addition, the core thickness d is set to 15 to 30% of the cutting edge diameter D at the axial cross section near the cutting edge ridge, and the core thickness taper is
It is set within the range of 0.04 to 0.06 based on the lIII1 standard.

(Function) The small diameter drill of the present invention has a tip angle a of ]45°~! 70
Since the cutting edge is set within a range of 100° to 100°, it ensures bite to the substrate during long machining and reduces the force applied to the cutting edge in the direction perpendicular to the axis.

In addition, the small diameter drill of the present invention has a core thickness taper of 1IIIm.
Since the diameter is increased to 0.04 to 0.06 in Jlt+ standard, the machining accuracy of the hole is good and the quality of the hole is also improved.

(Example) An example of the small diameter drill of the present invention will be described below with reference to the drawings. In Figures 1 to 3, (1) indicates the shank portion (
2) and a main body portion {3}, a pair of helical grooves (4) having a helix angle θ are formed in the axial direction of the main body portion (3), and a tip portion thereof A tip cutting edge ridge (5) is formed by the tip angle α. In this case, the helix angle θ is set to 25° to 35°, and the tip angle a is set to 145° to 170°. If the helix angle θ is less than 25°, chip disposal and machinability will be poor, resulting in chips remaining in the helical groove (4) or
Fuzz on the edge of the board. Occurs in Paris, etc. Furthermore, when the helix angle θ exceeds 35@, machinability improves, but rigidity decreases and hole machining accuracy deteriorates.

On the other hand, the reason why the range of the tip angle α is limited is to take into consideration the influence on the positional accuracy of the machined hole when machining a long hole and the tendency to bite into the substrate. That is,
When the tip angle α exceeds 145°, the force that bends the drill in the lateral direction becomes smaller, and this has a good effect on the positional accuracy of the hole. However, if the tip angle a exceeds 170°, For example, when drilling the first hole in which no U2W is received from the hole, the adhesion to the substrate becomes poor, resulting in poor hole position accuracy.

Further, the main body portion (3) has a core thickness d due to the formation of the twisted groove (4). The core thickness d is set to 15 to 30% of the cutting edge diameter D in the axial cross-sectional area near the cutting edge ridge (5). Furthermore, the core thickness taper is 1m.
m standard is set at 0.04 to 0.06. these are,
This is to increase the rigidity of the main body part (3) and prevent breakage when the drill escapes during machining. In particular, the core thickness taper is 0.
The value of 0.04/1 to 0.06/I was determined based on the evaluation of hole misalignment on the bottom surface of the substrate, as shown in FIG. In this case, the specifications of the small diameter drill tested in Fig. 4 are drill diameter D=φ0.81'llll. Core thickness d=0, 16. Tip angle Q = 150', groove length = 71. The workpiece is
I. This is a stack of three 6m thick FR-4 boards. At this time, the small diameter drill JL, (11) has a rotation speed of 70.0 (10 rpl1.
&v, a long hole of 51I1M length was machined. As a result, the core thickness taper is 0. It can be seen that when the diameter is smaller than 04, the accuracy of hole machining deteriorates. Also, the core thickness taper is 0. [Even if it exceeds +6, there is little hole misalignment.

However, as the helical groove (4) becomes smaller, chip evacuation becomes difficult and the quality of the hole deteriorates, so this method was excluded. In this example, a punch type small diameter drill (1) having a margin length Lr along the outer cutting edge ridge (6) is used.
Although it was applied to the straight type that is commonly seen, it can also be applied to the straight type that is commonly seen.

(Effects of the Invention) As explained above, the present invention specifies the tool specifications of the small diameter drill (1) and makes it suitable for long and large machining, so the following hardening is performed.

First, when machining long holes, it is possible to increase feed and reduce hole bending. This is the following notation and the fifth
It is clear from the figure.

In other words. This is because the results shown in Table 1 were obtained when the products of the present invention and comparative products with diameters of 0.8 and 3.0 mm were subjected to long-length machining. The evaluation in this case is O:
Good. Δ: Poor hole bending. ×: Broken. Specifications of the comparative product are tip angle = l30°. Core thickness taper = 0. 02/! In other respects, the specifications are the same as those of the product of the present invention.

Furthermore, although Fig. 5 shows a machined hole with a long hole, the state of the machined hole is determined by the feed rate (μm/rev
) is 90, it is more accurate than the comparative product of 30. Therefore, the product of the present invention has improved machining efficiency and machining accuracy.

Second, compared to conventional router end mills, there is less decrease in work efficiency due to setup changes from the router machine. This is because the same drilling machine is used. This is because NG control can be performed.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of the small diameter drill of the present invention;
Figure 2 is a partially enlarged front view showing the tip, Figure 3 is:
4 is an enlarged side view, and FIG. 4 is an explanatory diagram showing the relationship between hole slippage and core thickness taper. FIG. +11 ・One small diameter drill (2) ...Shank part (3)・One body part +4) -・
・Twisted groove t5) - Tip cutting edge ridge 16>
−...Peripheral cutting edge ridge patent applicant Toshiba Tungaloy Corporation

Claims (1)

[Claims] A shank portion (2) and a body portion with a smaller diameter than this (
3), and the main body portion (3) has a core thickness d formed by forming a pair of helical grooves (4) having a helix angle θ, and has a tip cutting edge ridge (
5), in which the main body portion (3) has a helix angle θ of 25° to 35°.
°, the tip angle α is set to 145° to 170°, and the core thickness d is set to 15 to 30% of the cutting edge diameter D at the axial cross section near the tip cutting edge ridge (5), A small diameter drill for machining long holes, characterized in that the core thickness taper is set within the range of 0.04 to 0.06 based on 1 mm.