JP4807521B2 - Twist drill - Google Patents

Description

  The present invention relates to a twist drill for metal processing that enables reduction of thrust and improvement of centripetality by reducing the chisel edge while maintaining the strength of the cutting edge at the center of the tip.

Conventionally, twist drills for metal processing have been subjected to a thinning process to reduce thrust and improve biting and centripetalness. 9 to 13 show examples of conventionally used thinning shapes. FIG. 11 shows X-shaped thinning, in which the hatched portion of FIG. 9 is machined to have a clearance angle α (see FIG. 10 ) with respect to the axis CL of the drill, and β is opened between the thinning surfaces 6a and 6b. A groove having a corner (see FIG. 12 ) is generated. One thinning surface 6a continues to the flank 5 and the other thinning surface 6b generates a thinning portion cutting edge 3a (cutting edge generated by thinning) and becomes a rake face of the thinning portion cutting edge.

In the thinning of FIG. 13 , the cutting edge 3 is changed to a blade having a predetermined center rising amount (= 1/2 of the tip core thickness t), and the thinning portion 6 is moved beyond the drill center O to escape the opposite cutting edge. It enters the surface 5 side.

  In addition to these, thinning shapes as disclosed in the following Patent Documents 1 to 3 have also been proposed. Among these patent documents, the drill of Document 1 is used for chip discharge generated by a thinning process by setting an angle formed by a thinning portion cutting edge and a ridge line on the flank side of the thinning portion within a range of 120 ° to 170 °. The space (the groove of the thinning portion referred to in the present invention) is enlarged, thereby improving the discharge performance of chips generated at the center of the tip, and improving the biting stability and straightness.

Further, the drills of Patent Documents 2 and 3 are similar to the thinning of FIG. 13 , in which the thinning portion of the drill having a centering cutting edge is inserted into the flank side of the opposite cutting edge beyond the drill center. The center of the tip is formed by forming a portion where the cutting edge side thinning surface and the flank side thinning surface are continuous (referred to as a groove bottom in this invention) with a concave curved surface. This improves the discharge of chips generated in the process. In addition, the drills of Patent Documents 2 and 3 have an R radius of the concave curved surface of 0.1 mm to 0.5 mm, an overlap amount of the thinning portion is 0 to 0.1 mm, and between the thinning portion cutting edges at the center target position The distance in the direction perpendicular to the cutting edge length is preferably 0 to 0.3 mm, and the width of the chisel edge is preferably in the range of 0 to 0.1 mm.
JP 2005-169572 A JP 2003-266225 A JP 2007-1011 A

The X-shaped thinning of FIG. 11 can reduce the width of the chisel edge by bringing the cutting edge 3 closer to the drill center O, and can improve the biting property and centripetality, but the groove created by the thinning process is small. There is a problem in chip dischargeability at the center of the tip, and clogging occurs, resulting in an increase in thrust (thrust force), resulting in a chip in the center.

In addition, the thinning shape of FIG. 13 has a large groove formed in the thinning portion, which improves chip discharge and reduces thrust, but it is necessary to increase the tip core thickness t in order to ensure the strength of the center portion. And the width w of the chisel edge is increased, the centripetality is lowered, and the hole bending (bending of the processed hole) is likely to occur. Especially in the long drill with low rigidity, the bending of the hole appears remarkably.

  Furthermore, since the drill which patent document 1 discloses is extending the ridgeline by the side of the flank of a thinning part ahead of the rotation direction of a drill, and the groove | channel which arises in a thinning part is enlarged, the cutting edge of a tip center part The amount of the back metal is reduced, and the strength at the center of the tip is lowered. The strength of the center of the tip depends on the thickness of the tip core after the processing of the thinning portion and the R radius of the concave curved surface constituting the groove bottom of the thinning portion, and the two thinning portions are brought closer to the center of the drill. become weak. For this reason, when strength is required at the center of the tip, shortening of the chisel edge must be sacrificed, and it is difficult to achieve both reduction of thrust and securing of strength of the tip center.

  In the drills disclosed in Patent Documents 2 and 3, the groove bottom of the thinning part is formed with a concave curved surface to improve the chip discharging performance at the center part. In the case of a drill, the cutting speed at the center part is zero. Nearly, the thinning part is overlapped at the center of the drill because the chip is generated in a situation where it is crushed rather than cut and tries to enter between the flank face of the opposite cutting edge and the work material. In addition, it is not sufficient to form the groove bottom of the thinning portion with a concave curved surface, and chip clogging is likely to occur at the center of the tip. In particular, as the cutting feed increases, the thickness of the chips increases, and it becomes easy to be caught between the flank of the opposite cutting edge and the work material. When the bite occurs, welding occurs and the thrust increases, which leads to a loss of the center cutting edge.

  In short, with the conventional technology, it is impossible to achieve both the securing of the cutting edge strength including the center portion of the tip and the reduction of the chisel edge for the purpose of reducing thrust and improving centripetality.

  In view of this, an object of the present invention is to improve a metal processing twist drill so that the chisel edge can be made sufficiently small while maintaining the cutting edge strength at the center of the tip of the drill.

In order to solve the above-described problems, in the present invention, the cutting center has a cutting edge on one side and the opposite side with the center of the drill in between, and further, a chip discharge groove corresponding to each cutting edge, and the width of the chisel edge. In the twist drill having a thinning portion to be shrunk, a groove bottom of the thinning portion, that is, a portion where the cutting edge side thinning surface and the flank side thinning surface intersect is formed with a concave curved surface, and the thinning portion of each cutting edge is formed at the center of the drill. The chisel edge is inserted into the flank side of the opposite cutting edge over a predetermined amount so as to overlap by a predetermined amount in the direction in which the thinning part cutting edge extends in the front view of the drill, width further sub thinning portion is provided to reduce the of, constitute the cutting edge as a blade having a predetermined center of the object volume, the sub thinning section, a front view of the drill It was formed so as to enter the drill center side at a predetermined angle with respect to thinning portion cutting edge.

The sub-thinning portion of the twist drill can be provided on the extension of the negative land by forming a negative land for reinforcing the cutting edge on the cutting edge and connecting to the negative land.

  The opening angle between the thinning surfaces in the front view of the drill of the sub-thinning part is preferably 90 ° or more.

  In the drill according to the present invention, the groove bottom of the thinning portion is formed with a concave curved surface, and the strength of the tip center portion can be sufficiently secured by increasing the R radius of the concave curved surface. In addition, if the radius R of the concave curved surface is simply increased, the tip core thickness increases and the width of the chisel edge also increases, causing problems such as increased thrust, bite and centripetal problems. Makes the thinning part of each cutting edge enter the flank side of the opposite cutting edge so that it overlaps beyond the center of the drill, and further, a sub-thinning part is provided in the part located at the drill tip of each thinning part Therefore, the width of the chisel edge is reduced, and in addition to this, the groove of the thinning portion is enlarged, and the chip discharging property is improved, and the thrust is reduced by a synergistic effect thereof. Moreover, since the width | variety of a chisel edge becomes small, favorable biting property and centripetality are also ensured.

Further, since the relative center of the object the cutting edge in the positive plane view was formed sub thinning portion so as to enter the drill center side at a predetermined angle, the negative land for edge reinforcement in setting the size and shape of the sub-thinning portion Without being restricted by size and angle, it is possible to provide a sub-thinning unit having a more excellent function by increasing the degree of freedom of setting.

In addition, if the secondary thinning part is connected to the negative land for reinforcing the cutting edge formed on the cutting edge and provided on the extension of the negative land, the processing of the negative land and the secondary thinning part can be performed continuously. The process can be shortened.

Hereinafter, an embodiment of the twist drill of the present invention with reference to FIGS. 1 to 8 of the accompanying drawings. FIG. 1 shows an entire example of a drill to which the present invention is applied. This drill is a blade-tip-exchangeable drill in which a detachable head piece 2 is provided at the front end of the main body 1 and the cutting edges 3 and 3 are provided on the head piece 2. The cutting edges 3 and 3 are on the opposite side to one side with the drill center O (see FIG. 2) in between, and form a central target shape.

  The head piece 2 and the main body 1 are provided with chip discharge grooves (twist grooves) 4 and 4 corresponding to the respective cutting edges. The headpiece 2 is provided with thinning portions 6 and 6 for reducing the width of the chisel edge 8 and auxiliary thinning portions 7 and 7 corresponding to the respective cutting edges.

The thinning portion 6 is configured to generate a groove between the cutting edge side thinning surface 6a and the flank side thinning surface 6b. The thinning surface 6b of the thinning portion 6 is a surface generated by cutting the heel side of the flank 5 and has a clearance angle α shown in FIG. 10 with respect to the axial center of the drill. A groove bottom 6c at the intersection of the thinning surface 6b and the thinning surface 6a is formed as a concave curved surface having a radius R (see FIG. 3).

  Further, the thinning portion 6 is allowed to enter the flank side of the opposite cutting edge beyond the drill center O, and the thinning portions 6 and 6 of the two cutting edges are in front view of the drill (FIG. 3), A predetermined amount Y overlaps in the extending direction of the thinning portion cutting edge 3a. If the spreading angle θ of the thinning portion 6 in the front view of the drill of the thinning portion 6 is too small, chips are not discharged smoothly, and if it is too large, the amount of back metal decreases and the strength of the opposite side cutting edge is adversely affected. . The range of 75 ° to 120 ° was appropriate for θ when considering the balance between the two. Further, the overlap amount Y of the thinning portions 6 and 6 was appropriate in the range of 0.12 mm to 1.0 mm because the effect of ensuring the core thickness at the tip portion and reducing the thrust was well balanced.

The sub-thinning part 7 is provided in the part located in the drill front-end | tip of each thinning part 6. FIG. The secondary thinning part 7 is a negative land 9 for reinforcing the cutting edge provided along the cutting edge 3 (see FIG. 5).
The width of the chisel edge 8 at the center of the tip is made very small by installing the sub-thinning portion 7.

  The sub-thinning portion 7 preferably has a clearance angle ε shown in FIG. 4 larger than the clearance angle α of the thinning portion 6, so that the machining tool interferes with the flank-side thinning surface 6 b and the groove bottom 6 c. The sub-thinning part 7 can be processed without doing so. Further, by providing the auxiliary thinning portion 7 on the extension of the negative land 9 so as to be connected to the negative land 9, the negative land 9 and the auxiliary thinning portion 7 can be processed continuously in one step.

  If the radius R of the groove bottom 6c is too small, the core thickness becomes thin (compared to the solid line R in FIG. 6, the dash-dot line r with a small radius makes the core thickness thinner). If the value is too large and the value is too large, the core thickness becomes too thick and the effect of reducing the thrust is impaired, so an appropriate value is selected. The value was about the same as the overlap amount Y of the thinning portion 6, specifically, the radius R = 0.15 to 1.0 mm was particularly good. Although it is confirmed that the numerical values in the range are appropriate by adopting a drill having a diameter of φ3 mm to 50 mm that is widely used, this numerical value can also be applied to a drill having a diameter of φ50 mm or more.

  When the spread angle η (FIG. 3) in the front view of the drill of the sub-thinning portion 7 is 90 ° or more, chips generated at the center of the tip are easily discharged, and the connection with the groove bottom 6c becomes smooth. Therefore, it is preferable that the strength of the joint portion is reduced. A more appropriate value of η is about 95 ° to 120 °.

  FIG. 7 shows an example in which the spread angle θ of the thinning portion 6 in the front view of the drill is larger than the spread angle η of the sub-thinning portion 7 in the front view of the drill. With this structure, the groove formed in the thinning portion becomes larger, and the discharge of chips generated at the center of the tip becomes better.

In FIG. 8, the cutting edge 3 is configured as a blade having a predetermined center rise amount (t / 2), and the sub-thinning portion 7 is turned into a center rising edge (thinning portion cutting edge 3a) in a front view of the drill. On the other hand, it is formed so as to enter the drill center O side with a predetermined angle σ. This structure is not restricted by the size and angle of the negative land 9 (γ in FIG. 5) when setting the size and shape of the sub-thinning portion 7, and the degree of freedom of setting is increased and more excellent functions are provided. An auxiliary thinning portion can be provided. The width of the chisel edge 8 is preferably set in the range of 0 to 0.1 mm because excellent biting property and centripetal property are obtained. The structure of FIG. 8 is not subject to installation restrictions due to the negative land 9, so that the width of the chisel edge 8 can be easily reduced to zero. 7 is provided on the extension of the negative land 9, but the sub-thinning portion 7 of FIGS. 3, 6, and 8 is replaced by the sub-thinning portion 7 of FIG. 8 in the present invention. Make it.

  In addition, although the above description gave and demonstrated the blade-tip-exchange-type drill as an example, this invention is applicable also to the solid drill by which the whole is integrally formed.

A more detailed example is shown below.
A blade-replaceable drill (Invention 1) for an outer diameter φ = 14 mm and a processing hole depth 5D (D is a diameter) subjected to the thinning process of the shape of FIG. 3 was manufactured. The dimensions of this drill are as follows: the overlap amount Y of the thinning portion Y = 0.3 mm, the drill front view thinning portion spread angle θ = 105 °, the drill front view auxiliary thinning portion spread angle η = 100 °, and the thinning angle δ = 150. °, negative land inclination angle γ = -25 °, negative land installation width w1 = 0.1 mm, chisel edge width w = 0.05 mm, thinning portion clearance angle α = 35 °, thinning portion groove spreading angle β = 105 °, The sub-thinning portion clearance angle ε = 45 °, and the R radius of the thinning portion groove bottom = 0.5 mm.

For comparison, the conventional product 1 having the same diameter and the same length as shown in FIG. 11 (R radius of the thinning groove bottom = 0.3 mm, thinning overlap Y = 0, chisel edge width) w = 0.05 mm) and the conventional product 2 subjected to the thinning of FIG. 13 (core thickness t = 0.25 mm, overlap amount Y = 0.3 mm of the thinning portion, R radius of the thinning portion groove bottom = 0.3 mm) Chisel edge width w = 0.35 mm) was also prepared.

Next, a hole was machined in the work material of S50C using these drills. As conditions at that time, V = 100 m / min, 80 m / min, and 60 m / min of cutting speeds and f = 0.2 mm / rev, 0.25 mm / rev, and 0.3 mm / rev are combined, and the conditions The thrust at was compared. The results are shown in Figure 14.

Moreover, the centripetal force by each drill was measured by comparing the X component force and the Y component force. The results are shown in Figure 15.

  From this test result, it can be seen that the inventive product has reduced thrust compared to the conventional products 1 and 2. In addition, the centripetality is significantly better than that of the conventional product 2, and a result comparable to that of the conventional product 1 subjected to X-shaped thinning is obtained.

Side view showing an overview of drill of the present invention 1 is an enlarged front view of the drill of FIG. The front view which expands and shows the center part of FIG. Side view showing enlarged sub-thinning installation section Sectional drawing along the II line of FIG. The figure which compared the difference in the core thickness by the difference in R radius of the groove bottom of the thinning part An enlarged front view showing another example of the thinning portion An enlarged front view showing still another example of the thinning portion Front view showing an example of a conventional drill Side view of the head of the drill of FIG. The front view which expands and shows the center part (X-type thinning) of the drill of FIG. Sectional drawing along the II-II line of FIG. Front view showing an enlarged central part of a conventional drill with other thinning The figure which shows the comparison test result of thrust A comparison of measurement results of X and Y component forces showing centripetal force

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main-body part 2 Headpiece 3 Cutting edge 3a Thinning part cutting edge 4 Chip discharge groove 5 Relief surface 6 Thinning part 6a, 6b Thinning surface 6c Groove bottom 7 Sub-thinning part 8 Chisel edge 9 Negative land O for cutting edge reinforcement Drill center CL Axis line α Thinning Clearance angle β Thinning groove expansion angle γ Negative land inclination angle ε Secondary thinning clearance angle η Secondary thinning expansion angle θ Thinning expansion angle σ Secondary thinning entry angle δ Thinning angle t Tip core Thickness w Chisel edge width w1 Negative land installation width R Radius of groove bottom formed by concave curved surface
Y Thinning overlap amount

Claims (3)

Each has a cutting edge (3) on one side and the opposite side with the drill center (O) in between, and further, a chip discharge groove (4) corresponding to each cutting edge, and the width (w) of the chisel edge (8) In a twist drill having a thinning portion (6)
The groove bottom (6c) of the thinning part (6) is formed as a concave curved surface, and the thinning part (6, 6) of each cutting edge extends beyond the drill center (O) and the flank (5) of the opposite cutting edge. The thinning portion cutting edge (3a) is overlapped by a predetermined amount (Y) in a direction in which the thinning portion (3a) extends in a front view of the drill, A secondary thinning part (7) for further reducing the width of the chisel edge (8) is provided ,
The cutting edge (3) is configured as a blade having a predetermined centering amount, and the sub-thinning portion (7) is a predetermined angle (σ) with respect to the thinning portion cutting edge (3a) in a front view of the drill. A twist drill that is formed so as to enter the center of the drill. A negative land (9) for reinforcing the cutting edge is formed on the cutting edge (3), and the sub-thinning part (7) is connected to the negative land (9) and provided on an extension of the negative land (9). Item 2. The twist drill according to Item 1 . The twist drill according to claim 1 or 2 , wherein an opening angle (η) between the thinning surfaces in the front view of the drill of the sub-thinning portion (7) is 90 ° or more.

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