JPS63216619A - Broach - Google Patents

Abstract

PURPOSE:To improve a property of being ground without reducing the life of a broach by reducing the heights of the tooth ends of finishing teeth by stages from the finishing teeth on the frontmost row to the finishing teeth on the rearmost row in a finishing teeth zone in order. CONSTITUTION:A finishing teeth zone 7 consists of a first finishing teeth group 8 consisting of two rows of finishing teeth 1, 2 and a second finishing teeth group 9 consisting of finishing teeth 3, 4. Although the tooth ends of the finishing teeth 1, 2 are of equal height while the tooth ends of the finishing teeth 3, 4 are also of equal height, the height of tooth ends of the finishing teeth 1, 2 is made higher than that of the finishing teeth 3, 4. A land A having a 0 deg. of clearance angle phi which is continuous with the rear of a cutting edge and a flank continuous with the rear of the clearance angle are provided on each of the finishing teeth 1-4. Although all the lands A are of equal width, the clearance angle phi is approx. 1 deg. for the finishing teeth 1, 2 and approx. 0 deg.30' for the finishing teeth 3, 4. Accordingly, regrinding because of wear can be repeated until the height of the tooth ends of the first finishing teeth group 8 become equal to that of the second finishing teeth group 9, improving a property of being ground without reducing a life.

Description

TECHNICAL FIELD The present invention relates to broaches such as inner broaches and outer broaches, and particularly to the structure of their finishing edges.

Prior Art Conventionally, the cutting edge of a broach generally has a rough cutting edge region 31, a semi-finishing cutting edge region 32, and a finishing cutting edge region 33, as shown in FIG.
It consists of The finishing blade area 33 is generally 4 to 4.
Equipped with 8 rows of finishing blades. Each row of finishing blades has a plane called a land 35 that continues behind the cutting blade and has a clearance angle C of 0 degrees. This is because when the cutting edge wears out, the rake face 37
This is the grinding allowance when the broach is ground and reused, and is closely related to the lifespan of the broach.

From the viewpoint of the life of the broach, it is desirable that the land be wide, but it cannot be made very wide because of friction with the finished surface. In other words, if the land is too wide, scratches are likely to occur on the machined surface of the workpiece. Conventionally, a so-called gradual straight land has been provided, which minimizes the negative effects of the land and extends the life of the broach by re-grinding.

This gradually increasing straight land will be explained according to FIG. 4.5.

Each of the finishing blades N+5 to N+8 of the finishing blade area 33 includes a land 35 having the following relationship.

a+<82<83<84 where, a,; in the land of the first finishing blade N+5 a9. a3 in the land of the second finishing blade N+6: a4 in the land of the third finishing blade N+7: a4 in the land of the fourth finishing blade N+8 As is well known, re-grinding of the cutting edge reduces the dimension of the cutting edge height H2O. FIG. 5 is an enlarged view of the first finishing blade N+5 and the second finishing blade N+6. Now, if the rake face 37 reaches the flank surface on the outer periphery in the i-th re-grinding, the rake face 37 retreats to the illustrated i-th grinding line 55.

That is, since the rake face 37 of the first finishing blade N+5 retreats to the area of the flank face 36, the cutting edge height H4 of the finishing blade
o decreases and becomes a new cutting edge height Hso. In other words, a dimensional change in the height of the cutting edge occurs. However,
The width of the land 35 of the second finishing blade N+6 is the width of the first finishing blade N+
Since it is wider than 5 (a+<az), the i-th rake face 37
Even after grinding, the rake face 37 is still provided in the land area.

That is, even before and after the i-th grinding of the rake face 37,
There is no dimensional change in the height of the cutting edge. In this way, rake face 3
The retreat of the core due to grinding No. 7 causes a dimensional change in the height of the cutting edge, and eventually, starting from the finishing blade N+5 in the front row, the cutting edge height exceeds the machining tolerance range of the workpiece. A finishing blade whose cutting edge height exceeds the machining tolerance range of the workpiece no longer functions as a finishing blade. For example, if all the lands have the same width, the i-th grinding of the rake face 37 causes the same amount of change in the height of the cutting edge, and if the height of the cutting edge exceeds the machining tolerance range of the workpiece, then At that point, the brooch's lifespan ends. However, as explained above, since the lands are set wider toward the rear, all the finishing blades do not undergo the same dimensional change at the same time. In other words, it is possible to increase the number of times the finishing blade is ground.

However, on the other hand, since there is no escape on the land surface,
Friction occurs between the land surface and the workpiece. In order to avoid this friction, it is preferable that the width of the land be as small as possible; however, if the width is reduced, the life of the finishing blade will be shortened.

As mentioned above, the gradual increase straight land is provided for the purpose of minimizing the friction between the land surface and the workpiece and increasing the number of grinding times, that is, improving the broach life. Even in the land, the total land width of the finishing blade requires a fairly wide width due to the long life of the broach. Therefore, it cannot be said that the problem of cutting friction has been effectively solved.

Therefore, there is a long-awaited need for a finishing blade that improves machinability by reducing cutting friction without reducing broach life.

41 Technical Problems of the Present Invention Therefore, the technical problems to be solved by the present invention are to improve machinability and minimize scratches and abrasion without impairing the life of the finishing blade area of the broach. It is an object of the present invention to provide a broach with a finishing edge area that can be finished.

Summary of the Invention The present invention was completed by focusing on the processing tolerance range of a workpiece.

(Structure) The broach according to the present invention for achieving the above-mentioned technical problem reduces the height of the cutting edge of each finishing blade in steps from the finishing blade in the front row to the finishing blade in the last row. A finishing blade area formed of a plurality of finishing blade rows is provided.

(Function) In the above configuration, at the beginning of cutting use of the broach, the front row of the finishing blade area, that is, the first finishing blade, participates in cutting the workpiece, and the finishing blades in the other rear rows use the cutting edges that they have. Due to the height difference, it does not participate in cutting. The rake face of the cutting edge is re-ground due to the wear of the cutting edge that occurs during cutting the workpiece. For example, after the i-th rake face grinding, the height of the cutting edge changes to the finishing edge of the second row, that is, the second finishing edge. ,
When the height of the cutting edge becomes equal to or smaller than the height of the cutting edge, the second finishing blade begins to participate in finishing cutting of the workpiece. In this way, the blades involved in finishing cutting sequentially shift from the first finishing blade to the finishing blades in the rear row. Then, the blades involved in finishing cutting shift, and the finishing blade in the last row begins to participate in finishing cutting, and then re-grinding is repeated until the cutting edge height of the finishing blade exceeds the machining tolerance range of the workpiece. If the height of the cutting edge exceeds the above range, the finishing blade region will no longer participate in finishing cutting, and its life as a finishing blade will come to an end.

(Effect) Therefore, according to the above configuration, one row of finishing blades in the finishing blade area is usually involved in cutting, so the friction between the land surface and the workpiece caused by the land surface is reduced, thereby preventing scratches and scrapes. This effectively reduces wear and maintains long-term machining accuracy by ensuring that the difference between the height of the cutting edge in the front row and the height of the cutting edge in the last row is well within the machining tolerance range of the workpiece. can do.

EXAMPLES The present invention will be specifically explained below with reference to the examples shown in FIGS. 1 and 2.

A first embodiment is shown in FIG. In FIG. 1, the finishing blade area 7 consists of a first finishing blade group 8 consisting of two rows of finishing blades 1.2 and a second finishing blade group 9 consisting of two rows of finishing blades 3.4. The height of the cutting edge of each finishing blade 1.2 of the first finishing blade group 8 is formed to be the same, and the height of the cutting edge of each finishing blade 3, 4 of the second finishing blade group 9 is also formed to be the same. However, the first
The cutting edge height of each finishing blade 1.2 of the finishing blade group 8 is formed to be higher than the cutting edge height of each finishing blade 3.4 of the second finishing blade group 9. Further, each of the finishing blades 1 to 4 includes a land A that continues behind the cutting edge and has a relief angle φ of 0 degrees, and a relief surface that continues behind the land. The widths of the lands A of the first and fourth finishing blades 1 to 4 are all the same, but the clearance angle φ is different from that of the first and second finishing blades.
Finishing blades 1 and 2 are 1°, third and fourth finishing blades 3 and 4 are 0°
It is 30°.

In the above configuration, at the start of cutting the workpiece, only the first finishing blade group 8 is involved in finishing cutting.

Because No. 1. This is because a step ΔL in height of the cutting edge is set between the second finishing blade groups 8 and 9.

In cutting in this state, the friction with the workpiece due to the effect of the land surface is effectively reduced compared to the conventional example because the total land width is sufficiently narrow.

When the cutting edge wear progresses to a certain extent due to cutting, the rake face of the first finishing blade group 8 is reground, but the finishing blade to be reground is actually the first finishing blade l and the second finishing blade that were involved in cutting. The third finishing blade 3 and the fourth finishing blade 4 are not necessary. In this way, the first and second finishing blades 1 by re-grinding
．． The height of the cutting edge of No. 2 is the height of the cutting edge of No. 2. Re-grinding is carried out repeatedly until it is identical to the fourth finishing edge 3.4.

Next, the first. The height of the cutting edge of the second finishing blade 1.2 is the third.
If the cutting edge height is the same as or smaller than the height of the fourth finishing blades 3 and 4, the cutting edge involved in finishing cutting will be the third. Move on to the fourth finishing blade 3.4.

The effect of the finishing blade with the above configuration has been explained above, and next, the effect will be explained in detail.

First, a conventional example (FIG. 4) will be described in order to make a comparative study regarding the life of the finishing blade.

In FIG. 4, the numerical values of each cutting edge are set to the following values. still,
The units not entered in the numerical values below are [mm].

Land width of each finishing blade: a+=0.2. a2=0.46
,=Q,13. a, = 0.8 Total rake face grinding allowance related to the life of the finishing blade = b-2 Relief angle of each finishing blade: c = 1' Perform re-grinding under the above conditions and repeat until grinding line 45 shown in the figure. Assuming that it is ground, the dimensional change in height of the cutting edge of the finished blade: Δh is Δh=(2-0,8)Xtanl''=0.021.

In other words, the machining tolerance of the workpiece is the reference value - 0,
021], re-grinding of the rake face can be repeated up to a total grinding stock of 2 mm.

On the other hand, the cutting edge height dimensional change amount Δ of the finishing blade in this example
H is calculated by setting each numerical value in FIG. 1 as follows.

During the land of each finishing blade・A + −A t = A. -A
4-〇, 2 Total re-grinding allowance -B, = 2 Relief angle of each finishing blade; φ, -1°, φ, -0°ao' 1st
Difference in height of cutting edge between finishing blade group 8 and second finishing blade group 9: ΔL=0.01ΔH−Δt,
+(B, -At-ΔLXcotφ, -A,)Xtanφ
2 =0.01+(2-0,2-0,01cot 1″-0
, 2) XtanO'30' = 0.019 In other words, the amount of dimensional change ΔI in the height of the cutting edge of the finished blade due to the total re-grinding allowance is smaller in this embodiment than in the conventional example.

This means that if the machining tolerance of the workpiece is the same, the total regrinding allowance, that is, the total number of regrindings, will be the same.
The fact that the dimensional change ΔH in the height of the cutting edge is small means that there remains an allowance for re-grinding several times.

Therefore, by setting the height of the finishing blade edge in the finishing blade area in two stages according to this embodiment, machinability can be improved without impairing the life of the broach, and the rubbing wear of the finishing blade can be effectively reduced. can be reduced to

Next, a second embodiment will be described with reference to FIG.

The finishing blade area 7a consists of four rows of finishing blades 1a to 4a that do not have a land A surface, and the cutting edge heights of the nominal upper blades range from the first finishing blade 1a in the front row to the fourth finishing blade in the last row. It is formed so that it gradually decreases to 4a. Each of the finishing blades 1a to 4a is provided with a direct relief surface on its cutting edge toward the rear of the cutting edge, and has a relief angle of φ2. ~φ, 4 are all set to be the same.

-11= In the above configuration, the finishing blade involved in cutting is first
There is only the finishing blade 1a. If the cutting edge of the first finishing blade 1a wears out during cutting of the workpiece, the rake face is ground again. If you repeat this re-grinding, the re-grinding will
The height of the cutting edge of the first finishing blade 1a is smaller than the height of the cutting edge of the second finishing blade 2a. Therefore, the first finishing blade 1a loses its function as a finishing blade, and the second finishing blade 2a starts participating in finishing cutting in its place. In this way, the finishing blades 3a, 4a in the rear row gradually participate in finishing cutting.

Regarding the life of the broach, as explained in the first embodiment, if the dimensional change ΔH' in the height of the cutting edge of the fourth finishing blade 4a with respect to the total regrinding allowance is within the machining tolerance range of the workpiece, The lifespan of the brooch is not compromised.

Therefore, in this embodiment, if the initial height of the cutting edge of each of the finishing blades 1a to 4a is appropriately set, the intended purpose is achieved.

That is, the difference in height of the cutting edge of each finishing blade 1a to 4a; ΔL
21 to ΔL 23, clearance angle φ and total grinding allowance B2 of the fourth finishing blade 4a. It suffices if we have the following relationship.

ΔH'=ΔL21+ΔL2. +ΔL2.3+Bt+ta
nφ24≦(Workpiece processing tolerance range) If this relationship is established, it becomes possible to improve the machinability of the workpiece and reduce rubbing wear without impairing the life of the broach.

Next, a third example will be described. The third example is
This is a modification of the second embodiment.

That is, in FIG. 2, each of the finishing blades 1a to 4a has a clearance angle φ2. ~φ, 4, and the height of the cutting edge of each finishing blade 1a to 4a is also gradually decreased.

In this embodiment, by gradually decreasing the clearance angle φ of the clearance surface toward the rear row, the height difference ΔL21 to ΔL2 in the height of the cutting edge of each adjacent finishing blade in the first to fourth finishing blades 1a to 4a is achieved.
The default value of 3 is an example that can have a wider latitude.

Furthermore, the cutting involvement time per finishing blade becomes longer as the relief angle φ is reduced, which is very convenient when determining the shape of the cutting edge of each finishing blade 1a to 4a. It goes without saying that this embodiment has the same effects as the second embodiment.

[Brief explanation of the drawing]

1.2 is an explanatory cross-sectional view of the finishing blade area of broaches according to the first and second embodiments of the present invention, FIG. 3 is an explanatory cross-sectional view of the main part of a conventional broach, and FIG. 3 is an enlarged cross-sectional explanatory view of the finishing blade region according to FIG. 3, and FIG. 5 is an enlarged cross-sectional explanatory view of the finishing blade according to FIG. 4. 1, Ia-first finishing blade, 2, 2a-second finishing blade
Two blades, 3゜3a...Third finishing blade, 4,4a...Fourth
Finishing blade, 5, 5a...Final grinding line, A, A +
, A2, A3. A4...Straight land, B,, B2. B, ... twisting grinding allowance, ΔH, Δ
H. ...Dimension change in height of cutting edge, φ, φ1. φ2. ．． φ22
．． φ23゜φ24... Relief angle, ΔL28. ΔL, 2.
ΔL13...Difference in blade edge height, 7,7a...Finishing blade area, 8...First finishing blade group, 9...Second finishing blade group

Claims (1)

[Claims] 1. In a broach equipped with a finishing blade area (7) consisting of a plurality of rows of finishing blades, the finishing blade area (7) includes finishing blades (1) in the foremost row to finishing blades (4 in the last row). ), the broach is characterized in that the height of the cutting edge of each finishing blade is gradually reduced in order. 2. The finishing blades in each row above have a clearance angle (φ
2.) The broach according to item 1, comprising a land (A) of 0 degrees and a flank continuing behind the land. 3. The broach according to item 1, wherein a relief surface is provided directly rearward from the cutting edge of the finishing blade in each row. 4. Among the finishing blades in each row above, the finishing blade in the front row (1)
The clearance angle of the clearance surface (
The third method is characterized in that φ) gradually decreases in sequence.
The brooch described in section.