JPH07290310A - Drill - Google Patents

Abstract

PURPOSE:To prevent a deflection at the time of cutting and bore an accurate hole by providing R-shaped tip blades having a specific rake angle and helical flutes. CONSTITUTION:A drill 21 is provided with four tip blades 23, and the rake angle theta1 of four tip blades 23 is set in the range of 0 deg.-30 deg.. The tip blades 23 are formed into an R-shape. No edge is formed on shoulders 25. Since the tip blades 23 are formed into the R-shape, the spread angle theta2 from a tip section is increased, and the strength of the tip blades 23 is increased. This drill 21 is formed with four helical flutes 26. The helical flutes 26 are set shallow. The cross sectional area of the portion straightly continued in the thrust direction of the drill 21 is large, and the diameter of the inscribed circle N is large. The rigidity of the drill 21 is high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill mounted on a milling machine, NC milling machine, drilling machine, lathe and the like.

[0002]

2. Description of the Related Art A conventional drill 1 shown in FIGS.
Indicates. This drill 1 is provided with two tip blades 3 and a twist groove 5 shown by hatching in FIGS. 5 and 6. Further, the drill 1 is provided with two oil holes 7, and the opening on the tip end side of the oil hole 7 is arranged at a position away from the center T of the flank 9 in the thrust direction. This drill 1 is attached to a milling machine or the like, rotates, and advances straight with respect to a work such as a steel material, thereby making a hole in the work. Further, the cutting chips are discharged through the twist groove 5. Oil is supplied from the oil hole 7 during drilling, and the drill 1 is prevented from breaking due to heat resistance.

[0003]

However, in the drill 1 according to the conventional example, the helical groove 5 is made considerably deep so that the cutting waste can be discharged efficiently.
Therefore, the cross-sectional area of the portion 6 of the drill 1 shown in FIG. 7 which is continuous straight in the thrust direction is small, and therefore the diameter of the inscribed circle N shown by the one-dot chain line in FIG. 5 is small. Therefore, the rigidity of the drill 1 is low. The cross-sectional areas of the portion of the drill 1 which is straight in the thrust direction are 1.47 mm ^{2 for} φ6 and 1.78 mm ² for φ10.

Therefore, due to the cutting resistance applied to the drill 1 at the time of drilling, the drill 1 moves from 0.1 mm to 0.15 m.
There is also a problem in that the size of the hole cannot be controlled with high accuracy because m also swings. Therefore, when it is desired to obtain a precise hole, the pilot 1 must be used to make a prepared hole, and then reaming must be performed. Further, in order to form a more precise hole, it was necessary to perform boring processing.

Further, as shown in FIG. 7, since the protruding amount (distance between the fulcrum and the action point) L of the drill 1 is large, the moment load applied to the blade 3 during cutting becomes large. Further, since the rake angle of the blade 3 of the drill 1 is set to a so-called positive and the spread angle θ2 is also small, the blade 3 is easily damaged and has no durability. The amount of protrusion L of the drill 1 is 2.27 mm for φ6 and 4.
It is 11 mm. Further, since the edge of the drill 11 is formed in the drill 11, the force is concentrated on the drill 11 during cutting and chipping is likely to occur, so that sufficient durability cannot be obtained.

Further, since the opening on the tip end side of the oil hole 7 is arranged at a position distant from the center T of the flank 9 in the thrust direction, there is a possibility that the oil cannot be sufficiently supplied to the chisel edge 13 to which a large cutting resistance is applied. is there. The present invention was made by focusing on the above-mentioned conventional problems,
A drill that can prevent run-out during cutting, can make precision holes, has large strength of the tip blade and the body, has sufficient durability, and can sufficiently supply oil to the chisel edge. The purpose is to provide.

[0007]

According to the invention of claim 1, there is provided a drill having a rake angle of 0 ° to −30 ° and having a rounded tip blade and a spiral groove.

A second aspect of the present invention is the drill according to the first aspect, wherein the depth of the helical groove is set so as to ensure a cross-sectional area of the drill capable of suppressing runout during cutting.

According to a third aspect of the present invention, the opening on the tip end side is close to the center in the thrust direction, and further comprises an oil hole communicating with all the twist grooves provided.
It is the drill described in 2.

[0010]

In the drill according to the invention of claim 1, since the rake angle of the tip blade is from 0 degree to -30 degrees and the tip blade is rounded, the range of contact of the tip blade with the work is increased during cutting. Since the resistance applied to the tip blade is dispersed over a wide area, it is less likely to be damaged. Furthermore, there is no edge on the other side, and the occurrence of chipping can be suppressed.

In the drill according to the second aspect of the present invention, since the depth of the helical groove is set so as to ensure the cross-sectional area of the drill that can suppress the runout during cutting, the runout during cutting can be suppressed. Therefore, it becomes possible to form a precise hole by drilling once.

Further, in the drill according to the invention of claim 3,
Since the opening on the tip side is close to the center in the thrust direction and has an oil hole that communicates with all the twist grooves provided, it is possible to supply sufficient oil to the chisel edge where a large cutting resistance is applied during cutting. Moreover, the cutting dust can be smoothly discharged from the twist groove by the pressure of the oil.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings of FIGS. Reference numeral 21 indicates a drill, and the body 22 of the drill 21 is formed so that its diameter gradually decreases toward the base end, and is so-called back-tapered. The drill 21 is provided with four tip blades 23, and the rake angle θ1 of the four tip blades 23 is set to −25 degrees. Further, since the tip blade 23 is formed in a rounded shape, no edge is formed on the person 25.

Since the tip blade 23 is formed in a rounded shape, as shown in FIG. 3, the spread angle θ2 from the tip of the tip blade 23 is larger than that of the conventional drill, and the strength of the tip blade 23 is increased. growing. The drill 21 has a tip blade 2
No. 3 is formed, and no blade is formed on the base end side of the member 25.

Further, the drill 1 is formed with four twisted grooves 26 shown by diagonal lines in FIGS. The twist groove 26 is set to be shallower than the groove 5 of the conventional drill 1. For this reason, the cross-sectional area of the portion 30 of the drill 21 shown in FIG. 4 which is continuous straight in the thrust direction is large, and therefore the diameter of the inscribed circle N surrounded by the dashed line in FIG. Therefore, the rigidity of the drill 21 is high.

The cross-sectional area of the portion 30 of the drill 21 which is straight in the thrust direction is 3.4 mm for φ6.
² and φ10 are 6.0 mm ² . The cross-sectional area of the portion 30 of the drill 21 that is straight in the thrust direction and the cross-sectional area of the portion 6 of the drill 1 that is straight in the thrust direction (for a φ6 type, 1.47 mm ² , The ratio to 1.78 mm ² ) is 2.
31: 1. Since the rigidity is proportional to the square of the ratio of the cross-sectional areas, it is φ6 and the drill 21 is
2.31 ^2-fold, that is, have a stiffness of about 5.34 times. For a φ10 drill, the cross-sectional area ratio is 3.37:
1, 3.37 ^2-fold, i.e. the drill 21 will have a stiffness of about 11.36 times than conventional drill 1.

Further, since the twist groove 26 is formed shallower than the conventional drill 1, as shown in FIG.
The projecting amount L of is shorter than that of the drill 1. Therefore, the moment load generated on the tip blade 23 during cutting is
It is smaller than the conventional drill 1. The protrusion amount L of the drill 21 is 1.47 mm for φ6 and 1.78 mm for φ10. Drill 21 and drill 1 described above
And the protrusion amount (2.27 mm for φ6, 4.11 mm for φ10) has a ratio of 1: 1.
75.

Since the moment load applied to the blade during cutting is proportional to the cube of the ratio of the protrusion amount L, the moment load applied to the tip of the tip blade 23 of the drill 21 (the portion farthest from the center T) is φ6. Is 1.75 ^1/3 that of the conventional drill 1, or about 5.36. With a φ10 drill, the overhang ratio is 1: 2.0
5, the moment load applied to the cutting edge of the tip blade 23 of the drill 21 is 2.05 / ³ , that is, about 1 / 8.61 that of the conventional drill 1. Since the moment load applied to the tip blade 23 is small in this way, the blade tip is less likely to be damaged and the durability is also improved.

Reference numeral 27 indicates an oil hole, and the opening on the tip end side of the oil hole 27 is the center T in the thrust direction.
The oil hole 27 communicates with all of the four twist grooves 26. The oil hole 27 communicates with the rear end of the handle 29.

Next, the operation and phenomenon when the drill 1 is used to make a hole will be described. The drill 21 is attached to a milling machine or the like, rotates, and is advanced straight to a work such as a steel material, so that a hole is made in the work.
Oil is supplied from the oil hole 27 during cutting.

Further, since the rake angle of the tip blade 23 of the drill 21 is set to -25 degrees, when cutting the work,
The resistance applied to the tip blade 23 is smaller than that of a conventional drill. Further, since the tip blade 23 is formed in a rounded shape, the range S in which the tip blade 23 comes into contact with the work during cutting becomes wider. That is, the area of the tip blade 23 that contributes to cutting is increased. Therefore, the tip blade 23 is less likely to wear than the blade of the conventional drill, and the durability is greatly improved.

As shown in FIG. 3, the spread angle θ2 from the tip of the tip blade 23 is larger than that of a conventional drill. Therefore, the strength of the tip blade 23 increases,
Hard to break. Further, since the tip blade 25 is formed in a rounded shape, no edge is formed on the person 25, and the area that receives resistance is wider than in the conventional drill, and chipping is suppressed.

Furthermore, since the drill 21 has sufficient rigidity as described above, when the work is cut, the drill 21 is
Can be suppressed within a range of several microns. Therefore, without reaming or boring,
It becomes possible to obtain a hole with high dimensional accuracy.

When cutting the work, oil is supplied from the oil hole 27. Since the opening on the tip end side of the oil hole 27 is arranged close to the center T in the thrust direction of the drill 21, oil can be sufficiently supplied to the chisel edge 31 to which a large cutting resistance is applied. Therefore, the cutting resistance of the drill 21 can be reduced, sufficient cooling can be performed, and the drill 21 can be prevented from breaking.

Since the oil hole 27 communicates with the four twist grooves 26, the oil flows smoothly and reliably through all the twist grooves 26. Therefore, the cutting waste in the twist groove 26 is pushed out by the pressure of the oil and is smoothly discharged. Since the opening of the oil hole 27 is arranged close to the center T in the thrust direction, one of the four tip blades 23 is present in the center T.
Therefore, the work is surely cut by the one tip blade 23 even in the portion corresponding to the center T.

By using the drill 21 as described above, a highly accurate hole can be formed by one-time machining, so that the machining time can be shortened and the work efficiency can be improved as compared with the case of performing the reaming and boring. It becomes possible.

Although the embodiment of the present invention has been described in detail above, the specific configuration is not limited to this embodiment, and the present invention is not limited to the change of the design without departing from the scope of the present invention. Included in the invention. For example, the rake angle of the tip blade 23 can be appropriately changed within the range of 0 degree to −30 degrees. In the above embodiment, a drill having four tip blades is shown, but the number of tip blades is not limited to this, and
It may be smaller or larger than the number of sheets.

[0028]

As described above, according to the present invention, it is possible to prevent runout during cutting and to make a precise hole. Further, the strength of the tip blade and the person is large, and it becomes possible to have high durability.

Further, the oil can be sufficiently supplied to the chisel edge which exerts a large cutting resistance, and the drill can be prevented from breaking. Moreover, the cutting pressure can be smoothly discharged from the twist groove by the pressure of the oil.

[Brief description of drawings]

FIG. 1 is a front view of a drill according to an embodiment of the present invention.

FIG. 2 is a plan view of a drill according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view for explaining the spread angle of the tip blade of the drill according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view of a drill according to an embodiment of the present invention.

FIG. 5 is a plan view of a drill according to a conventional example.

FIG. 6 is a partial front view of a drill according to a conventional example.

FIG. 7 is a cross-sectional view of a drill according to a conventional example.

[Explanation of symbols]

 21 drill 22 body 23 tip blade 25 way 26 twist groove 27 oil hole 29 handle 31 chisel edge T center in the thrust direction of the drill S range that contacts the work of the tip blade during cutting

Claims (3)

[Claims] 1. A drill having a rake angle of 0 ° to −30 ° and having a rounded tip blade and a spiral groove. 2. The drill according to claim 1, wherein the depth of the helical groove is set so as to ensure a cross-sectional area of the drill in which runout during drilling is suppressed. 3. The drill according to claim 1, further comprising an oil hole whose opening on the tip end side is close to the center in the thrust direction and which communicates with all the twist grooves provided.