JP2012056055A - Drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drill which can be suitably used as drill for separating a spot welded portion of a chassis of an automobile, and can increase the number of drilled holes for spot welding separation up to four times that of a conventional one.SOLUTION: The drill has two cutting edges which are formed symmetrically with respect to a rotation axis, and a secondary spiral concave groove formed along the spiral grooves forming the cutting edges. In the secondary spiral groove, a contour line is an arc shape when seen from a drill tip end side or a substantially arc shape, from the projection portion of the drill tip end to a heel portion.

Description

  The present invention relates to a drill suitably used for peeling off spot welds of an automobile body.

Most parts constituting the automobile body are joined by spot welding, except for joining methods such as screws and rivets.
Therefore, when repairing an automobile body, it is necessary to peel off the spot weld when replacing the panel of the car body, and many dedicated drills for peeling off the spot weld are commercially available.

However, in recent years, due to the use of a collision safety body, a hard steel plate called a high-strength steel plate has been used for a part of the vehicle body, and depending on the part of the vehicle body, a conventional drill may not be able to cope with it.
In view of such circumstances, the present applicant has devised a drill disclosed in Patent Document 1 below.
The drill disclosed in the following Patent Document 1 is thinned at the center of the drill, narrowing the width of the center of the drill to reduce cutting resistance as much as possible, and is compatible with extremely hard steel sheets of about HRC45 can do.

  However, in order to cope with extremely hard steel sheets of about HRC45, it is necessary to use powder high-speed steel that is expensive and difficult to process, which is costly, and the center of the drill is made thinner by thinning. There were problems such as the fact that a clear rake portion could not be formed at the center, and that the cutting edge created by thinning was a straight line, and as a result, it was easily worn out and easily chipped.

Patent Documents 2 and 3 listed below also disclose drills used for peeling off spot welds.
The drills disclosed in the following Patent Document 2 and Patent Document 3 both have a structure in which a cemented carbide tip is joined to the tip of the shank member, and correspond to a hard steel plate depending on the hardness of the cemented carbide tip. It is.
However, since the carbide tip has very low toughness, spot welding peeling using a manual drill can easily be chipped if a light impact is applied to the cutting edge due to shaking of the hand or sliding of the cutting edge. There is a drawback.

Moreover, although the following patent document 4 is not the objective of peeling off spot welding, the drill which provided the subgroove (secondary spiral groove) in the center part is disclosed.
However, the drill disclosed in the following Patent Document 4 is intended for metal working or the like, and is intended to perform machining by attaching a drill to a rigid spindle with respect to a fixed workpiece. Therefore, the shape is extremely inappropriate for not only the purpose of peeling off the spot welded portion but also the drilling operation with a hand drill.

JP 2006-88267 A JP 2009-269119 A JP-A-8-118316 JP-A-63-84807

  The present invention has been made to solve the above-described problems of the prior art, and is capable of cutting a hard steel plate such as a high-tensile steel plate without using an expensive material, and is applied to a normal steel plate. In this case, the number of times of use at the time of drilling or spot welding peeling can be dramatically increased, and the cutting force at the center of the drill when using a hand drill is improved by improving the cutting force at the center of the drill and reducing wear. Provided is a drill capable of preventing a significant decrease.

  The invention according to claim 1 has two cutting blades formed symmetrically about the rotation axis, and a secondary spiral groove is recessed along the spiral groove forming the cutting blade, and the secondary spiral The groove relates to a drill characterized in that a contour line viewed from the drill tip side is formed in an arc shape or a substantially arc shape from a protruding portion of the drill tip to a heel portion.

  The invention according to claim 2 relates to the drill according to claim 1, wherein the contour is formed by a combination of two or more arcs having different radii.

  The invention according to claim 3 is characterized in that the chisel width is 0.3 to 0.6 mm, and the radius of the secondary spiral groove as viewed from the drill tip side is 1 to 6 mm. Regarding drills.

  In the invention according to claim 4, the chisel width is 0.3 to 0.6 mm, and the radius of the secondary spiral groove viewed from the drill tip side is 1 to 3 mm in the portion from the center portion of the drill to the heel portion. It is 1-6 mm in the part from the center part of a drill to a cutting blade, It is related with the drill of Claim 2 characterized by the above-mentioned.

  The invention according to claim 5 relates to the drill according to any one of claims 1 to 4, wherein the length of the secondary spiral groove is set within three times the diameter of the drill.

  The invention according to claim 6 relates to the drill according to any one of claims 1 to 5, wherein the cutting edge has a cutting edge tip angle set to 160 to 190 °.

  In the invention according to claim 7, when viewed from the drill tip side, the linear distance parallel to the cutting edge from the drill center to the boundary between the secondary spiral groove and the cutting edge is 20 to 70 of the drill radius. The drill according to any one of claims 1 to 6, wherein the drill is set to%.

According to the first aspect of the present invention, the secondary spiral groove in which the contour line viewed from the drill tip side is formed in an arc shape or a substantially arc shape from the protruding portion of the drill tip to the heel portion is equal to or greater than the thinning. Along with the centripetal force, a secondary cutting edge is newly formed by the secondary spiral groove, and a clear rake angle is obtained at the center like the spiral groove forming the cutting edge. A cutting force can be obtained. Thereby, it becomes possible to cut hard steel plates, such as a high-tensile steel plate, without using an expensive material.
Furthermore, since the secondary spiral groove has an arc shape or a substantially arc shape, the cutting resistance is remarkably reduced as compared with thinning, and the secondary spiral groove discharges heat at the time of cutting. Wear of the cutting edge portion to be formed, that is, wear of the center portion is greatly reduced, and continuous use for a long time is possible. Therefore, when it is applied to a normal steel plate, the number of usable times at the time of drilling or spot welding peeling can be dramatically increased.

  According to the invention which concerns on Claim 2, when the outline seen from the drill front end side of the secondary spiral groove is formed by the combination of two or more arcs having different radii, the cutting resistance can be further reduced. It becomes possible.

  According to the invention according to claim 3, since the chisel width is as narrow as 0.3 to 0.6 mm and the center of the drill is not thinned, the thrust resistance during cutting is small and the force applied by the operator is small. It is possible to reduce the amount, and it is difficult to cause chipping and wear due to cutting resistance, and the spot welding part can be easily peeled off.

  According to the fourth aspect of the present invention, the chisel width is as narrow as 0.3 to 0.6 mm, the center of the drill is not thinned, and the radius viewed from the drill tip side of the secondary spiral groove However, the difference between the part from the center part to the heel part and the part from the center part to the cutting edge means that the thrust resistance during cutting is small, less force is applied by the operator, and chipping and wear due to the cutting resistance are required. Is less likely to occur, and the spot welding part can be easily peeled off.

  According to the invention which concerns on Claim 5, since the length of a secondary spiral groove is set to less than 3 times the diameter of a drill, when big force is added at the time of cutting, it bends in parallel with the longitudinal direction of a drill. Is prevented.

According to the invention which concerns on Claim 6, since the blade edge | tip tip angle is set to 160-190 degrees, a suitable tip angle can be set according to the shape of a spot weld part.
For example, if the spot weld is recessed, set it closer to 160 °, and if the spot weld is flat, set it closer to 180 ° from 190 ° horizontally. I can work.

  According to the invention which concerns on Claim 7, when it sees from a drill front end side, the linear distance parallel to the cutting blade from a drill center part to the boundary part of a secondary spiral groove and a cutting blade is 20-70 of a drill radius. Therefore, the necessary cutting force can be ensured, and the operator can easily perform the peeling work of the spot welded portion.

It is a figure which shows the drill which concerns on this invention, Comprising: (a) is a top view (figure which looked at the drill from the front end side), (b) is a front view. It is an upper surface enlarged view showing a first embodiment of a drill according to the present invention. It is an upper surface enlarged view which shows 2nd embodiment of the drill which concerns on this invention. It is an upper surface enlarged view which shows 3rd embodiment of the drill which concerns on this invention. It is a perspective view which shows the secondary spiral groove of the drill which concerns on this invention. It is a graph which shows the measurement result of the force required at the time of the cutting of the drill of an Example. It is a graph which shows the measurement result of the force required at the time of cutting of the drill of comparative example 1. It is a graph which shows the measurement result of the force required at the time of cutting of the drill of comparative example 3.

Hereinafter, a preferred embodiment of a drill according to the present invention will be described with reference to the drawings.
The drill according to the present invention is particularly suitable for peeling work of spot welded parts of an automobile body using a hand drill.
FIG. 1 is a view common to all the embodiments of the drill according to the present invention, wherein (a) is a top view (view of the drill as viewed from the tip side), and (b) is a front view.
As shown in the drawing, the drill according to the present invention has two cutting blades (1) formed in a rotationally symmetric manner, and a secondary helical groove (3) along the helical groove (3) forming the cutting blade (1). 4) is recessed so as to extend downward from the drill tip.
In the secondary spiral groove (4), the contour line viewed from the drill tip side is formed in an arc shape or a substantially arc shape from the projecting portion (2) of the drill tip to the heel portion (6).
A secondary cutting edge (5) is formed in the protrusion (2) by a secondary spiral groove (4).

In the drill according to the present invention, the secondary spiral groove (4) is provided along the spiral groove (3) that forms the cutting edge (1) from the protruding portion (2) formed at the center of the tip. The width (T) of the chisel portion is set as narrow as 0.3 to 0.6 mm.
The reason for setting the chisel width in this range in the present invention is that, in use with a hand drill that depends on the arm strength of the operator, if the chisel width exceeds 0.6 mm, the force required for cutting increases and the center is Because it is not stable, the center slips when the drill starts to rotate, and there is a disadvantage that there is no hole in the correct place. On the other hand, if it is less than 0.3 mm, the strength of the chisel part is lost, and in some cases the chisel part is This is because there is a possibility of chipping, which is not preferable in either case.

The blade tip angle (α) formed by the two cutting blades (1) is preferably set to 160 to 190 °. This means that when the edge of the blade edge (α) is less than 160 °, the panel that is spot-welded with two or more sheets is peeled, and there will be holes in the panel that will not peel, If the angle exceeds 190 °, the outer peripheral portion of the cutting blade (1) becomes too acute, and the outer peripheral portion of the cutting blade (1) is likely to be chipped, which is not preferable in either case.
By setting the blade tip angle (α) to 160 to 190 °, an appropriate tip angle can be set according to the shape of the spot weld.
For example, when the spot welded portion is recessed, the angle is set near 160 °, and when the spot welded portion is flat, it is set near the horizontal 180 ° to 190 °. Thereby, in any case, it becomes possible to perform the peeling work of the spot welded portion satisfactorily.

FIG. 2 is an enlarged top view showing a first embodiment of the drill according to the present invention.
In the drill of the first embodiment, the contour line viewed from the drill tip side of the secondary spiral groove (4) is formed in an arc shape having a radius (R) from the protruding portion (2) to the heel portion (6). . A chisel is formed at the center of the drill tip.
In this way, the contour line viewed from the drill tip side of the secondary spiral groove (4) is formed into an arc shape from the projecting part (2) to the heel part (6). A blade (5) is formed.
The cutting edge (1) originally has a rake angle formed by the spiral groove (3), but the arcuate secondary spiral groove (3) extends along the spiral groove (3) from the protrusion (2) to the heel part (6). By providing 4), a clear secondary cutting edge (5) is also formed in the protrusion (2).

  According to the drill of the first embodiment, the chisel width (T) is set as narrow as 0.3 to 0.6 mm, and a clear secondary cutting edge (5) is formed in the protrusion (2). As a result, a powerful cutting force can be obtained. For this reason, the operator can easily perform the peeling work of the spot welded portion while relying on the cutting force of the drill itself without applying a strong force when using the hand drill.

  The radius (R) of the secondary spiral groove (4) viewed from the drill tip side is preferably set to 1 to 6 mm. This is because when the radius (R) is less than 1 mm, the width of the secondary cutting edge (5) becomes narrow, and the ability as a secondary cutting edge cannot be exhibited. Since the portion is formed like a wall, the cutting resistance will be increased, and if it exceeds 6 mm, the secondary spiral groove will be increased, so that the length of the cutting edge (1) will be shortened, And since the intensity | strength of a drill falls, it is because in any case, it is unpreferable.

FIG. 3 is an enlarged top view showing a second embodiment of the drill according to the present invention.
Hereinafter, only a difference between the second embodiment and the first embodiment will be described, and the same components as those in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

The drill of the second embodiment is formed by a combination of two arcs having different radii from the projecting portion (2) to the heel portion (6), with the contour line seen from the drill tip side of the secondary spiral groove (4). ing. Specifically, the radius (R1) of the portion from the center portion to the heel portion (6) and the portion from the center portion to the cutting edge (1) as seen from the drill tip side of the secondary spiral groove (4). The radius (R2) is different. A chisel is formed at the center.
In this way, the contour line seen from the drill tip side of the secondary spiral groove (4) is formed by a combination of two arcs having different radii from the protrusion (2) to the heel part (6), and the radius (R2) When the cutting progresses from the secondary cutting edge (5) of the projecting portion (2) to the cutting edge (1), the cutting resistance does not vary greatly. The operator can easily perform the peeling work of the spot welded portion.

In the drill of the second embodiment, it is preferable to set the radius (R1) to a range of 1 to 3 mm and the radius (R2) to a range of 1 to 6 mm. If the radius (R1) is less than 1 mm, the chip discharging effect by the secondary spiral groove will be hindered, and if it is more than 3 mm, the heel part formed by the spiral groove (3) will be greatly scraped. Is also not preferred. When the radius (R2) is less than 1 mm, the width of the secondary cutting edge (5) becomes narrow, and the ability as a secondary cutting edge cannot be exhibited. At the same time, the portion that contacts the cutting edge (1) is a wall because the radius is small. Therefore, the cutting resistance becomes large, and if it exceeds 6 mm, the secondary spiral groove becomes large, so that the length of the cutting edge (1) becomes short, and the drill In any case, it is not preferable.
The radius (R2) is preferably larger than the radius (R1). The reason is that by reducing the radius (R1), the strength of the drill is maintained, and by increasing the radius (R2), the cutting resistance of the drill due to the secondary spiral groove can be reduced.

  As for the drill of the second embodiment, in FIG. 3, the contour line viewed from the drill tip side of the secondary spiral groove (4) has two arcs with different radii from the projecting part (2) to the heel part (6). Although what was formed by the combination was shown, you may form the said outline by the combination of three or more circular arcs from which a radius differs.

FIG. 4 is an enlarged top view showing a third embodiment of the drill according to the present invention.
The drill of the third embodiment specifies the distance (A) from the drill center to the boundary between the secondary spiral groove (4) and the cutting edge (1) in the drill of the first embodiment or the second embodiment. The range is set.
More specifically, when viewed from the drill tip side, the distance from the drill center to the boundary (linear distance parallel to the cutting edge (1)) (A) was set to 20 to 70% of the drill radius. Is.
The reason for setting the distance (A) within this range is that if the width is less than 20%, the width of the secondary cutting edge (5) formed on the protrusion (2) becomes narrow, so the secondary cutting edge (5) This is because it acts like a wall with respect to the direction of rotation of the drill to increase the cutting resistance, making it difficult to peel off the spot welded portion. 1) The width of 1) becomes extremely narrow, the cutting force decreases, the strength of the cutting blade (1) decreases, and the cutting edge from the cutting blade (1) to the secondary spiral groove (4) is likely to be chipped. is there.
In addition, the drill shape at the time of less than 20% becomes like the drill disclosed by the said patent document 4. FIG.

  The outer diameter of the drill according to the present invention is preferably set to about 6.5 to 10.2 mm since the diameter of the spot welded portion of the vehicle body is in the range of about 6 to 10 mm. However, when the diameter of the spot welded portion is out of the above range, the drill diameter can be changed in proportion to the diameter of the spot welded portion, and is not necessarily limited to the above range.

The drill according to the present invention is premised on the use of a hand drill, and has a large secondary spiral groove. Therefore, the chisel width is set to a very narrow range of 0.3 to 0.6 mm. Therefore, it is bent in a way that does not occur with conventional drills. Specifically, when a large force is applied at the time of cutting, the conventional drill bends at a substantially right angle with respect to the longitudinal direction, whereas in the drill of the present invention, when the secondary spiral groove becomes long, it is parallel to the longitudinal direction of the drill. May break (vertically from the center).
In the drill according to the present invention, such a fold can be prevented by setting the length of the secondary spiral groove (4) (the length along the spiral) within three times the drill diameter.
According to the inventor's experiment, in a spot welding peeling operation, when a drill with a secondary spiral groove length of 24 mm and a drill with a diameter of 30 mm is used for a drill diameter of 8.2 mm, Even if the tip slipped and hit the surrounding car body, it did not break, but the 30mm one broke vertically under the same conditions. (After folding vertically, the cracks progressed vertically and broke in a substantially right angle direction from the root of the secondary spiral groove.)

  Hereinafter, the effect of the present invention will be made clearer by showing examples and comparative examples of the drill according to the present invention. However, the present invention is not limited to the following examples.

<Test 1: Drilling test 1 with a hand drill>
(Example drill)
A drill having a diameter of 8.2 mm was formed into the shape shown in FIGS. 1, 2, and 4 having the dimensions shown in Table 1, and this was used as the drill of the example.

(Drill of comparative example)
As Comparative Example 1, a drill made in Germany having the dimensions shown in Table 2 and having the dimensions shown in Table 2 and having the conditions closest to those in Examples was used.

  As Comparative Example 2, a drill having dimensions shown in Table 3 (a product of Patent Document 4, manufactured by Mitsubishi Materials Corporation (former company name: Mitsubishi Materials Kobe Tools Co., Ltd.), miracle drill, model: VCSSSD0820) was used.

(Comparative test)
The drills of Examples and Comparative Examples 1 and 2 were each mounted on a hand drill and a drilling test was conducted.
As the conditions for the hand drill, compressed air (6 to 8 kg / cm ² ) was used as the drive source, and the no-load rotation speed was 1200 rpm.
In Example and Comparative Example 1, a hole having a depth of about 1 mm was made in a center pillar (high-tensile steel plate) of an automobile (manufactured by Toyota Motor Corporation, Prius). In Comparative Example 2, the tip shape was greatly different from that of the example, so a hole was made in a metal plate (SS400 steel plate, thickness 9 mm).
As a result, the drill of the example was still sufficiently cut when 100 holes were made, but was interrupted because the wear of the cutting edge (1) was confirmed.
On the other hand, the drill of Comparative Example 1 was not cut when 27 holes were made. In the drill of Comparative Example 2, the burden on the operator's arm was very large, and drilling had to be stopped within about 1.7 mm from the tip to the outer peripheral blade.
The state of the drill of Example and Comparative Example 1 after use was enlarged with a magnifying glass.

The drill of the example was still fully usable although there was overall wear and a small chip in the cutting edge (1). What should be noted is the state of the secondary cutting edge (5) of the protrusion (2), no chipping was observed, and the wear was a minute one that could not be considered after 100 holes were drilled.
On the other hand, the drill of Comparative Example 1 was in a state where the chisel, the thinning portion, and the cutting edge were clearly chipped and could not be used.
In addition, about the drill of the Example, after that, 20 holes were drilled and the test was completed with a total of 120 holes. In this state, chipping with a width of about 1 mm from the outer peripheral portion of the cutting blade (1) was confirmed in the center direction, but the secondary cutting blade (5) was not worn but was not worn. .

From the above test results, it was confirmed that according to the example, that is, the drill according to the present invention, four or more times more holes can be drilled than the conventional drill (Comparative Example 1).
In addition, the work using the drill according to the present invention was less fatigued than the work using the conventional drill, and the work was easier. In the operation using the drill of Comparative Example 1, the latter half of the 27 holes was very difficult to drill and felt great fatigue, whereas the operation using the drill of the Example was the same as that of Comparative Example 1. Despite making 120 holes more than 4 times, it was easy to the end.
As described above, the drill of Comparative Example 2 was very difficult to drill with a hand drill. This is because the drill of Comparative Example 2 is designed for high-rigidity machining centers and capable of high-speed rotation and high-speed feed, and is not intended for hand drills. This is probably because the use of is not considered at all.

<Test 2: Cutting force comparison test>
(Example drill)
The same drill as in the example of Test 1 (see Table 1) was used.
(Drill of Comparative Example 1)
The same drill as in Comparative Example 1 of Test 1 (see Table 2) was used.

(Drill of Comparative Example 3)
The drill described in Table 4 (the drill described in Table 1 of Patent Document 1) was used.

(Comparative test)
Each of the drills of Examples and Comparative Examples 1 and 3 is attached to an NC milling machine, and a hole is made in the vertical direction for a metal plate (SS400 steel plate, thickness 8 mm, double-sided machine finish), which is required for the drilling operation. The force (cutting force) was measured.
The measurement was performed by placing a plate on a dynamometer, fixing the plate to the table of the NC milling machine, and measuring the force transmitted from the drill during drilling (force required for drilling) with the dynamometer. The output signal from the dynamometer was converted into a graph using a memory high coder (manufactured by Hioki Electric Co., 8860-50) and displayed.
The results (graphs) are shown in FIGS. 6 shows the results of the drill of the example, FIG. 7 shows the results of the drill of Comparative Example 1, and FIG. 8 shows the results of the drill of Comparative Example 3.

As shown in FIGS. 6 to 8, the maximum force value (224N) measured in the example is the maximum force value (468N) measured in Comparative Example 1 and the maximum force value measured in Comparative Example 3. It was less than half of the value (460N). From this, it was found that the drill of the present invention can be cut with a force less than half that of the conventional drill.
Further, it was confirmed from the graph that the drill of the present invention has a very small amplitude when cutting compared to the conventional drill.
This test result shows that when the drill according to the present invention is used with a hand drill, the force required for cutting is very small, so that the work can be easily performed, and a stable and accurate drilling operation is performed because there is little vibration. It shows that you can.

  The drill according to the present invention is particularly preferably used for peeling off a spot welded portion of an automobile body.

DESCRIPTION OF SYMBOLS 1 Cutting blade 2 Protruding part 3 Spiral groove 4 Secondary spiral groove 5 Secondary cutting blade 6 Heel A Straight line distance parallel to the cutting edge from a drill center part to the boundary part of a secondary spiral groove and a cutting edge R Secondary spiral groove Radius as seen from the drill tip side of the R1 Radius of the portion from the center portion to the heel portion seen from the drill tip side of the secondary spiral groove R2 Portion from the center portion to the cutting edge seen from the drill tip side of the secondary spiral groove Radius T Chisel width

Claims (7)

It has two cutting blades formed symmetrically about the rotational axis, and a secondary spiral groove is recessed along the spiral groove forming the cutting blade,
The secondary spiral groove is characterized in that a contour line viewed from the drill tip side is formed in an arc shape or a substantially arc shape from a projecting portion of the drill tip to a heel portion.   The drill according to claim 1, wherein the contour line is formed by a combination of two or more arcs having different radii.   The drill according to claim 1, wherein the chisel width is 0.3 to 0.6 mm, and the radius of the secondary spiral groove viewed from the drill tip side is 1 to 6 mm.   The chisel width is 0.3 to 0.6 mm, and the radius viewed from the drill tip side of the secondary spiral groove is 1 to 3 mm in the portion from the center of the drill to the heel, and from the center of the drill The drill according to claim 2, wherein the diameter is 1 to 6 mm in a portion extending to the cutting edge.   The drill according to any one of claims 1 to 4, wherein the length of the secondary spiral groove is set within three times the diameter of the drill.   The drill according to any one of claims 1 to 5, wherein the cutting edge has a tip angle of 160 to 190 °.   When viewed from the drill tip side, the linear distance parallel to the cutting edge from the drill center to the boundary between the secondary spiral groove and the cutting edge is set to 20 to 70% of the drill radius. The drill according to any one of claims 1 to 6, characterized in that: