JPS6389211A - Twist drill - Google Patents

Abstract

PURPOSE:To enable deep hole boring about 4-6 times as deep as diameter by enlarging a groove-width ratio, applying a combination of V-shaped projection and recess to the ridge line of a tip cutting edge and providing an oil hole on a tip flank in the twist drill of super alloy. CONSTITUTION:The ridge lines 4 of a tip cutting edge are so made that primary and secondary straight ridge lines 4a and 4b will form a V-shape projection, a chisel edge 12 and an inner ridge line 4c a V-shape projection and the primary straight ridge line 4a and the inner ridge line 4c a recess shape, respectively. The length (l) of the primary straight ridge line 4a is taken at (0.02-0.06)XD, provided that D is the diameter of the cutting edge, and rake angles theta1 and theta2 in a radial direction are taken as theta1=-15 deg.--25 deg. and theta2=0 deg.--10 deg. respectively for the primary and the secondary straight ridge lines 4a and 4b. Also, a width ratio A/B of a groove part 5 and a land part 8 is taken at 0.8-1.0. Furthermore, a pitch circle diameter D1 for an oil hole 10 of diameter (d) open to a tip flank 9 is so determined as to be D1/D=0.3-0.6, and an oil hole ratio d/D is taken at 0.05-0.20.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) "Kihatsu" relates to a twist drill made of cemented carbide that can drill deep holes suitable for steel machining by effective chip disposal.

(Conventional technology) Conventionally, this type of twist drill made of cemented carbide was
For example, those found in US Pat. No. 4,583,888 are disclosed.

The material shown in this specification has improved shapes such as core thickness and groove width ratio in order to compensate for the brittleness of cemented carbide. That is, in this specification, the core thickness is 25% to 25% of the drill diameter.
In addition to reducing the groove ratio to 0.4 to 0.8:1 with a large drill diameter of 35%, the rake angle of the radius method when viewed directly from the cutting edge outside the drill diameter of 273 is -5° to positive. The distance from the outer edge of the groove wall to the perpendicular line to the reference line, which is opposite to the reference line passing through the 2/3 point of the drill diameter on the outer peripheral edge of the cutting edge and the end face of the cutting edge, is equal to the diameter of the drill. It has been disclosed that the ratio is 47% or less. Furthermore, this specification describes coating the drill body with Tic, T1CN, etc., and forming oil holes.

However, from the practical results of this twist drill, it has been found that reducing the groove width ratio to 0.4 to 0.8:1 to cover brittleness in particular leads to a decrease in groove section cross-section and deterioration of chip disposal, and This was found to be inconvenient for deep hole machining. In other words, the ratio L/D of the machining depth L to the drill diameter is usually used as a judgment criterion for deep hole machining, but in the above-mentioned twist drill, 3541
For drilling holes, L/D = 3 is the limit, and even for those with oil holes, L/D = 3 may be exceeded without being able to take advantage of the cooling effect due to the small groove width ratio mentioned above. I couldn't do it.

(Problems to be Solved by the Invention) The present invention solves the problems of deep hole machining with conventional products, on the premise of adopting a large groove width ratio and oil holes.
By adding improvements to the cutting edge configuration, etc., it is possible to effectively dispose of chips and compensate for the brittleness of cemented carbide. In short, the present invention aims to solve the problem of deep hole drilling by making it possible to drill L/D=4 to 6, which could not be done with conventional carbide twist drills.

(Means for Solving the Problems) The present invention has been made in view of the above-mentioned points, and has a pair of tip cutting edges formed at one end of the tool body, and a groove formed in the axial direction of the tool body. The present invention provides a twist drill made of cemented carbide in which a land portion with a margin and an oil hole are each formed with twist.

That is, the tip cutting edge has a substantially V-shaped convex shape due to the bending of the first linear ridge and the second linear ridge on the outer peripheral side where the margin exists when viewed in the end face direction,
Furthermore, on the chisel edge side, the linear chisel edge and the linear inner edge connected thereto form a substantially V-shaped convex shape, and furthermore, the part connecting the secondary linear edge and the inner edge has a rounded concave shape. It is designed to have a shape. As a specific shape, the radial angle θ1 of the first linear edge and the second linear edge is
, θ2 are respectively θI = -15' to -25', 02
= set within the range of O° to -10°, and the cutting edge length of the outer straight edge is based on the cutting edge diameter D, i: L-1
1=(0.02 to 0.06)D is set within the range.

Further, the land portion and the groove portion have a groove width ratio A/B between them of A/B=0 in a cross section near the beginning of the outer cutting edge edge.
．． The value is set to more than 8 and less than 1.0.

Furthermore, the oil holes are each opened on the tip flank side, and the oil holes (10
) pitch circle diameter D1. The diameter d of the oil hole (10) is D+=
(0,3-0.6)D.

d= (0,05~0.20)D(7)tl surrounding Te3Q
It was designed so that the

(Function) The twist drill of the present invention has a groove width ratio A/B of more than 0.8 and less than 1.0, which increases the groove volume, that is, the chip disposal volume, compared to conventional carbide twist drills. It is something that

Furthermore, regarding the tip cutting edge of the twist drill of the present invention, chips are finely divided by a combination of a convex shape and a concave shape exhibiting a substantially V shape, thereby smoothing the chip disposal action. It is something.

Furthermore, since the twist drill of the present invention can internally supply cooling oil as the oil hole is formed, the cooling action is efficiently performed and the drilling action is performed with high efficiency.

For these reasons, the twist drill of the present invention is capable of stable chip disposal even when drilling deep holes of L/D = 4 to 6, which was not possible with conventional carbide drills when drilling steel materials. It is.

(Example) Hereinafter, an example of the twist drill of the present invention will be described with reference to the drawings.

In Figures 1 to 4, (1) is the tool body (2)
This is a twist drill made of cemented carbide, consisting of a shank (3) and a shank (3), and is usually applied to drills with a cutting edge diameter of φ3 to φ30 mm.

This tool body (2) has a pair of tip cutting edges (
4) is formed, and a groove part (5) is formed in the axial direction.
), a margin (8) and a land portion (8) having a peripheral cutting edge (7) are each formed with twist. In this case, the helix angle α at the outer cutting edge (7) is generally applied to α=200 to 35°, and the back taper is.

It is set at approximately 0.03/Zoo.

The tip angle β of the tip cutting edge (4) is generally:
β=130° to 150°, and in the case of the tip flank (6), the first flank (8a) and the second flank (9b) whose angles are changed stepwise in the case of one illustration configured. And this secondary flank (9b)
An oil hole (10) with a twist is opened at the center of rotation, and a chisel edge (12) is formed by thinning (11) at the center of rotation. This oil hole (10) is formed by, for example, being twisted during extrusion molding of the material in the tool body (2) and shank (3), or by being reheated and twisted after sintering. . The pitch circle diameter D1 of the oil hole (10) and the diameter d of the oil hole (10) are D+=(0.3 to 0.6) when the oil hole (10) is based on the diameter of the cutting edge. D, d= (0,05
~0.20) D. This can be seen from FIGS. 5 and 6, which will be described later.

It was determined from the relationship between the bending strength ratio of the drill and the amount of oil, and the relationship between torsional displacement and bending displacement.

Furthermore, the chisel edge (12) is chamfered to strengthen the cutting edge, as clearly shown in FIG. The amount of chamfering δ is usually about 0.05 to 1 m.

And this tip cutting edge score (4) is the chisel edge (12
) to the outer peripheral cutting edge ridge (7) when viewed in the end face direction.

That is, as clearly shown in FIG. 2, the tip cutting edge (4) forms a primary linear ridge (4a) on the outer peripheral side where the margin (8) exists when viewed in the end face direction. The first linear edge (4a) and the second linear edge (4b) are bent to form a substantially V-shaped convex shape. Also,
On the chisel edge (12) side, a straight chisel edge (
12) and a linear inner edge (4C) connected thereto, it has a substantially V-shaped convex shape. Furthermore, in the portion connecting the first linear edge (4a) and the inner edge (4c),
It has a concave shape with roundness. This is to avoid a decrease in rigidity due to the notch.

The tip cutting edge (0) configured in this way divides the chips into fine pieces due to the presence of the first linear ridge (4a), the second linear ridge (4b), and the inner ridge (4c) described above. Improve processing performance.

Specifically, the first linear ridge (4a) has a length of the cutting edge when the diameter of the cutting edge is based on the diameter of the cutting edge.
, 02 to 0.06) D.

In addition, the first linear edge (4a) and the second linear edge (4b
) for the radial rake angle θ1.02,
01 = -15' to -25°, respectively.

θ2 is set within the range of 00 to -10'.

Furthermore, regarding the groove width ratio A/B between the land portion (8) and the groove portion (5), as shown in FIG. It is set by the width B of . That is, the groove width ratio is set to exceed A/B=0.8 and to be less than i and o in the cross section near the beginning of the outer peripheral cutting edge ridge (7).

In this case, for the heel (13) in the land portion (8), it is preferable to form a chamfered portion in order to avoid stress concentration due to cutting resistance and to widen the groove width for chip evacuation. Chamfering amount γ of the chamfered part
For example, if the diameter of the cutting edge is φ10m, γ=0
．． It is about 25 mm. In addition, regarding the core thickness, from the relationship with torsional rigidity, the diameter of the cutting edge that is usually adopted is
It is set within 5-35%.

Note that the twist drill (, 1) of the present invention has a tool body (
In the part 2), TiC, TEN, T1CN.

By forming a single layer or multiple layers of a coating layer made of A-texture 203 or the like, wear resistance is enhanced and cutting performance is improved.

Figures 5 and 6 show the tip flank (2) of the tool body (2).
8) is a diagram illustrating the reason for limiting the size and size of the oil hole (10) that opens in the oil hole (10).

That is, in FIG. 5, in order to specify the position of the oil hole (10) from the relationship of material strength, the pitch circle diameter D1 of the oil hole (10) and the ratio of the cutting edge diameter D + /D are taken on the horizontal axis. ,
The vertical axis shows bending displacement and torsional displacement. In this case, 1 bending displacement is shown by the 0 curve, and the torsional displacement is shown by the H curve, but the conditions at this time are that the tool body (2) with the cutting edge diameter D = φloms is supported at the 1/2 lead position. Then, a bending load FY = 100 kgf and a torsion load Mz = 100 kgf were applied separately. In addition, Fy=100kgF and M, = 10
0 kgF is a large value that approximates the case of actual cutting. Regarding other tool specifications, the core thickness is 0.3I) (=3+en), the groove width ratio is A/B=0.85, and the diameter of the oil hole (10) is d=φ1.
Regarding the material properties of the tool body (2), the Young's modulus was 54000 kg4/mso2, and the Poisson's ratio was 0.22.

As a result, especially from the relationship of torsional displacement, /D=0.
It has been found that a range of 3 to 0.6 is suitable.

FIG. 6 is an explanatory diagram comparing the amount of cutting oil and the bending strength ratio of the drill by changing the diameter d of the oil hole (10). Then, the bending strength ratio of the drill is calculated by setting the value when no oil hole (10) is present as 1, and calculating the decrease rate thereof, and is shown by the work curve. Moreover, one curve shows the change in oil amount. Regarding the tool specifications, the diameter of the cutting edge is D = φ10am, the pitch circle diameter of the oil hole (10) is
= 0, 50 (=φ5mm), core thickness 0.30 (
= 3 shoes), the groove width ratio was set to A/B = 0.85, and the cutting oil was a water-soluble emulsion 10 times diluted (pressure: 5 kg).
/c layered.

As a result, the oil hole ratio (d/D) requires a lower limit of d/D=0.05 due to the oil amount, and an upper limit of d/D=0.05 due to the drill strength. 20 was the limit.

Figures 7 to 10 show the above-mentioned first-order straight edge (4&).
cutting edge length, radial rake angle ('l + second straight line edge b), radial rake angle θ2. Regarding the groove width ratio A/B, the reason for its limitation, effects, etc. are explained.

That is, FIG. 7 compares the cutting edge length and chip shape with regard to the effectiveness of the primary straight edge (4a).

The tool shape of the twist drill (1) is the cutting edge diameter D = φ1
0 mm, the length of the cutting edge is varied, and other shapes are commonly applied within a numerically limited range. Therefore, the rake angle 01 in the radial direction of the first linear edge (4a) and the second linear edge (4b),
For θ2, θ1=-20°, 02=-5°, groove width ratio A/B, A/B=0.85, oil hole (10)
The pitch circle diameter DI =φ5m+s and the diameter d of the oil hole (10) were kept constant at 1.0 mm. The work material is 5541, and the cutting conditions are: cutting speed v = 60 m/win, 8 c) m/gin, feed f = 0, 3 m/+*in, machining depth L/D = 5.
As a result, water-soluble cutting oil is supplied internally from the oil hole (10).

As a result, the cutting edge length of the first straight edge (4a) is good in the range of (0,02 to 0,06)D from the finely divided chip shape with respect to the cutting edge diameter. Ta. In addition,
In Sentence = O, 015D, some finely divided chips were mixed, but the majority of the chips were long and continuous, showing a tendency for chip clogging, and in the cutting test with machining depth L/D = 6, There was a problem with chipping at the chisel edge (12). In addition, a separate cutting test was conducted.
．． In the case of 07D, cutting was impossible due to chip clogging at a cutting speed of 60 m/sin and chipping of the cutting edge.

Since the evaluation based on the chip shape described above is abstract, Fig. 8 shows 23 m (L/D = 3
) This shows the damage to the cutting edge during cutting.

That is, in the product of the present invention, the cutting edge length of the first linear edge (4a) is i=o, 03D, and the comparison amount is l=o
, o7I). Regarding the tool shape at this time, the cutting edge diameter D = φ10 track layer, the pitch circle diameter DI of the oil hole (10) = φ5IIa, and the diameter d of the oil hole (10) = φ1. Omm, radial rake angle θ, = -20'
, θ2=-5°, twist angle α=306, tip angle β=14
It was common with 0'. Also.

Regarding cutting conditions, cutting speed V=, 100m/win
+Feed f = 0, 2mm/rev, machining depth 1.
/D=5, and water-soluble cutting oil was applied.

As a result 1, the present invention, as clearly shown in FIG.
The flank wear of the tip cutting edge (4) was approximately VB#0.2 mm, indicating normal wear, and it was possible to continue drilling. Also,
Cutting with L/D=6 was also possible. On the other hand, in the comparative sample, chipping was observed at the chisel edge (12), making it impossible to drill holes. Note that the shape of chips showed the same tendency as shown in FIG. 7 described above.

Furthermore, FIG. 9 illustrates the effectiveness of the rake angle θl in the radial direction at the first linear edge (4a).

In other words, the effective deviation amount of the cutting edge length statement described above = (0,02
~0.06) D, the rake angle θI = -15° to -25°, which showed the same chip shape as in Fig. 7, was good. Therefore, the effective range of the first linear edge (4a) was the range surrounded by the frame of FIG. 9 in relation to the overall IAI. When θ was less than −15° (on the left side of the frame), elongated chips as shown in Figure 1 were produced, and there was no chip separation effect. In addition, if θ1 exceeds -25° (on the right side of the frame), there is a tendency for chips to become entangled, and abnormal wear or chipping of the margin (6) will occur. The radial rake angle θ2 in (4b) was compared over the range of +3'' to -14° as shown in Table 1, and it was confirmed that θ2 = 00 to -10° is a suitable range. , As for the first linear edge (4a), those within the effective range were applied based on the above-mentioned FIGS. 7 and 9.

For those with θ2=00 to -10'.

Cutting tests were conducted at a machining depth of L/D = 6, and all results were good, with V B # 0 and 2Il at 25 m cutting.
It showed normal wear of l+.

FIG. 10 below shows a comparison of the increase in motion at the groove width ratio A/B with respect to chip shape and machining depth L/D based on changes in cutting speed.

That is, in the present invention, the groove width ratio A/B is A/B = 0.8.
In the case of more than 1.0 or less, the comparison amount is A/B=0. °
~0.75. And other tool specifications,
Cutting conditions, work material, etc. were applied as common items.

As a result, up to L/D=2, there was almost no difference in chip shape between the inventive product and the comparative product. However, the comparison amount was found to be at its limit as long elongated chips began to be generated as L/D=3 approached, and a tendency for chips to become clogged was observed at L/D=3 or higher. As for the comparison amount, at cutting speed V=80.100+s/sin, L/D
As a result of the =4 test, there were defects such as chipping and chipping of the cutting edge.

On the other hand, the product of the present invention exhibits almost the same chip shape in the range of L/D=1 to 6, and it was confirmed that deep hole drilling with L/D=6 is possible.

Figure 11 is a diagram showing the applicability of machining depth L/D, and the tool specifications, workpiece materials, cutting conditions, etc.
This is the same as Figure 1O.

As a result, the product of the present invention could be processed to a processing depth of L/D=6.

On the other hand, with the comparative amount, chip clogging was observed due to lack of space in the groove (5), and if cutting was continued at the limit of L/D = 3 to 4, cutting edge damage would occur, resulting in a machining depth of L/D = 5. I couldn't do that. Also, under the same conditions, the groove width ratio A/B
The test was conducted in the case where the value exceeds 1.0, but the tool body (
2) The lack of rigidity caused the cutting edge to break, which was a problem.

Furthermore, tests were conducted using the tool specifications found in US Pat. No. 4,583,888, but L/D=3 was the limit.

As a result, the tip cutting edge ratio (4) and groove width ratio A in the present invention
/B and the effect of the oil hole (10) were confirmed.

Note that in this embodiment, the tool body (2) and the shank (
All of 3) have been applied to tools made of cemented carbide, but they can also be applied to tools in which only the tip of the tool body (2) is made of cemented carbide and the rest is high-speed steel and both are brazed. Of course. In this case, the diameter of the cutting edge can be set larger than that of the embodiment described above.

(Effects of the Invention) As explained above, the present invention specifies the shape of the tip cutting edge (4) and the configuration of the oil hole (10) in a cemented carbide twist drill with a large groove width ratio. Since it is specified, it has the following effects.

First, due to improved chip disposal, the limit of machining depth L/D has been increased to L/D=4 to 6. This is due to the increase in the volume of the groove (5) as well as the tip cutting edge (4).
) This is because the chips are finely divided due to the improved shape of the hole (10), and the chip discharge performance is improved due to the internal supply of cutting oil due to the presence of the oil hole (10). Therefore, this is a great concrete effect compared to the conventional product shown in US Pat. No. 4,583,888, which had a machining depth limit of L/D=3. The limit of the conventional product was L/D = 3 because
This is due to the fact that the groove width ratio A/B = 0.4 to 0.8, resulting in insufficient space in the groove portion (5), and the cutting edge shape not being able to finely divide the chips.

Second, machining efficiency is improved and stable work is performed. This means that the tip cutting edge (4) has a first linear edge (4a), a second linear edge (4b), an inner edge ( 4C
) and chisel edge (12), the cutting resistance components interfere with each other to stabilize cutting, and the internal supply of cutting oil makes stable chip disposal effective. In addition, the cutting life was increased by 25% compared to the conventional carbide twist drill that does not have an oil hole (10), and machining efficiency was improved.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of the twist drill of the present invention, FIG. 2 is an enlarged bottom view, FIG. 3 is a partial side view of FIG. I'V-rlr inside
Figure 5 is an enlarged sectional view taken along the line, and Figure 6 is an explanatory diagram comparing the position of the oil hole with bending displacement and torsional displacement.
The figure is an explanatory diagram that compares the diameter of the oil hole with the amount of cutting oil and the bending strength ratio of the drill. Figure 7 is a diagram that compares the effectiveness of the cutting edge length at the primary straight ridge with the chip shape. FIG. 8 is an explanatory diagram comparing cutting edge damage. FIG. 9 is an explanatory diagram similarly showing the effectiveness of the cutting edge length and radial rake angle at the primary straight edge. Fig. 10 is an explanatory diagram comparing the effectiveness of the groove width ratio with the chip shape, and Fig. 11 shows the relationship between machining depth L/D and cutting speed V, which can also be applied to the effectiveness of the groove width ratio. FIG. (2)...Tool body (4)...Tip cutting edge (5)...Groove (8)...Margin (7)...Outer cutting edge ridge (8)...
Land part (10)...Oil hole (12)
... Chisel edge (4a) ... Primary straight edge
(4b)...Second linear ridge (4C)...Inner ridge 2-El Shamotomo 3 Figure

Claims (2)

[Claims] (1) One end of the tool body (2) has a pair of tip cutting edges (
4) is formed, and a groove part (5) is formed in the axial direction.
), a land portion (8) with a margin (6), and an oil hole (10) each formed with a twist, the tip cutting edge ridge (4) being , on the outer peripheral side where the margin (6) exists when viewed in the end face direction, the first linear ridge (4a) and the second linear ridge (4b) are bent to form a substantially V-shaped convex shape, and On the chisel edge (12) side,
The linear chisel edge (12) and the linear inner edge (4c) connected thereto form a substantially V-shaped convex shape, and the second linear edge (4b) and the inner edge (4c)
) has a concave shape with roundness, and the rake angles θ_1 and θ_2 in the radial direction at the first linear edge (4a) and the second linear edge (4b) are respectively θ_1=- 15°~-25°, θ_2=0°~
-10°, and the cutting edge length l of the first linear edge (4a) is l=(
The land portion (8) and the groove portion (5) are set within the range of 0.02 to 0.06)D, and the groove width ratio A/B between the land portion (8) and the groove portion (5) is set at the outer peripheral cutting edge ridge (7). In the nearby cross section, A/B is set to be more than 0.8 and less than 1.0, and the oil holes (10) are opened in pairs on the tip flank (9) side, and are based on the cutting edge diameter D. When the oil hole (1
0) pitch circle diameter D_1, oil hole (10) diameter d is D
_1=(0.3~0.6)D, d=(0.05~0.2
0) A twist drill characterized by being set within the range of D. (2) The tool body (2) contains TiC, TiN, Ti.
The twist drill according to claim 1, wherein the coating layer made of CN, Al_2O_3, etc. is formed in one layer or in multiple layers.