JPH0112903Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a broach including either an external broach or an internal broach, and particularly relates to a broach in which the rough cutting edge region is shaped like a multi-stage skipping edge.

Prior Art The arrangement of the blades in the rough cutting blade area of a conventional broach is as shown in FIG.

In other words, the blades Ti arranged sequentially from front to back,
The depth of cut for Ti+1, Ti+2, etc. increases sequentially by a constant distance h.

By the way, when the surface of the workpiece exhibits a so-called black crust (altered layer) such as forged skin or cast skin, the above-mentioned normal type broach is inappropriate.
This is because if a plurality of front and rear blades are used to cut such black scales, chipping or severe wear may occur on the blades.

Therefore, a type of broach called a multi-stepped broach has been conventionally provided for cutting the black scale of a workpiece. An outline of this multi-stepped broach is shown in Figures 2 and 3. As shown in the figure, this broach has a set of multiple (usually two, but in some special cases three) adjacent blades in its rough cutting edge area, and the cutting edges are sequentially removed for each group. I am trying to increase the depth of cut. In Figure 2, two blades Ti and Ti
+1 forms one set, followed by the blade Ti +
2 and Ti+3 form a pair. In each group,
The cutting depth of the cutting blade is the same. However, between the set of blades Ti, Ti+1 in the front position and the set of blades Ti+2, Ti+3 in the subsequent position, the cutting depth of the cutting blades is set to 2×h. That is, the first
As is clear from the comparison with the figure, the amount of increase in the depth of cut is twice that of the case shown in FIG. By increasing the amount of change in the cutting depth in this way, the surface layer of the workpiece containing the black skin is scraped off all at once or in a very small number of times, and the blade acts on the fabric underneath the black skin. This reduces pitching and wear of the blade.

In the above-mentioned multi-stage skipping-blade broach, the cutting load is shared between the front blade Ti and the rear blade Ti+1 or the front blade Ti+2 and the rear blade Ti+3, avoiding a large cutting load on each set of front blades Ti and Ti+2. , 3rd
As shown in the figure, the front blades Ti and Ti+2 are
are formed at equal intervals. In other words, the front blade Ti,
Ti + 2 cuts the workpiece only with the part without the mark N, and the rear blade Ti + 1,
Ti+3 cuts only the portion left uncut by the front blades Ti and Ti+2. This cutting situation is shown in Figure 4. Figure 4 shows the front blade Ti,
This shows a state in which a portion _W1 of a workpiece W is partially cut by a portion of Ti+2 that is not coated with a nick N. On the other hand, Fig. 4 shows the front blade Ti, Ti
The part W ₂ left uncut by +2 is replaced by the rear blade Ti +1,
It shows the state of cutting with Ti+3.

However, in the above blade configuration, as is clear by comparing Fig. 4, the front blades Ti, Ti
+2 is still subject to a large cutting load or has poor cutting conditions, which causes the problem that chipping is likely to occur on the front blade and the wear of the front blade is much greater than that of the rear blade. That is, the front blade Ti,
When cutting the workpiece W with Ti+2 (Fig. 4), the side surfaces a, a of the partial blade divided by the adjacent cuts N and N start to bite into the workpiece W, but this side surface The tip of a is not formed as a cutting edge, and the side surface a is not configured as a clearance surface.
Therefore, the cutting resistance to this portion becomes very large, and chipping is likely to occur at the tip of the side surface a. On the other hand, the rear blade Ti+1,
When cutting the uncut portion W ₂ of the workpiece with Ti+3, only the original cutting edge t of the blade is involved in cutting, and only the uncut portion of the front blade, that is, about half of the whole, is cut. Compared to the front blade, the cutting resistance is very small and the cutting conditions are good.

In order to reduce the cutting load on the front blades Ti and Ti+2 as described above, it is possible to increase the amount of Nikku N, but even if that is done,
Since the tip of the side surface a (the side surface that is not the cutting edge) of the partial blade defined by the cut must be involved in cutting, the situation remains that chipping is likely to occur and wear is severe.

Purpose of the Present Invention Accordingly, the purpose of the present invention is to alleviate chipping and severe wear of each set of front blades in a multi-stage flying-blade broach, thereby extending tool life.

Summary of the present invention The basic idea of this invention is to create a difference in rigidity between the front and rear blades in each set in response to their ease of damage, that is, the degree of chipping and wear. There is.

In addition, with this invention, when regrinding the blade, the tool life is determined by the amount of regrinding of the front blade, which is prone to chipping and wear, and even if the rear blade has an axial land width sufficient to withstand use. , focusing on the fact that the tool life ends when the land width of the front blade reaches its usable limit, attempts to make the rigidity of the front blade sufficiently greater than that of the rear blade.

That is, in the multi-stage skipping-blade broach according to the present invention, the axial land width of the front blade in each set is made larger than the axial land width of the rear blade, thereby making the rigidity of the front blade larger than that of the rear blade, It is characterized by reducing chipping and severe wear on the front blade.

In addition, in the above configuration, since the amount of wear on the cutting edge side of the side surface a of the partial blade divided by Nik N is approximately twice the amount of wear on the rear blade, the amount of re-grinding of the front blade is It is preferable to have a configuration in which the land width can be approximately twice as large as that of the front blade, and specifically, the ratio of the land widths of the front blade and the rear blade is preferably 5 to 6:3.

According to the above configuration, since the front blade, which is subjected to large cutting resistance, has high rigidity, chipping is less likely to occur at the cutting edge. Furthermore, although the front blade wears more than the rear blade due to cutting, the number of times the front blade is re-ground can be increased due to the difference in land width. In particular, considering that the front blade wears about twice as much as the rear blade, the land width ratio of the front blade and rear blade should be set at 5 to 6:3.
By setting the amount of re-grinding of the front blade to twice that of the rear blade, the land width ratio of the front blade and rear blade will hardly change even after re-grinding, and the land width will not be increased unnecessarily. This is very advantageous in extending tool life. For example, if the land width of the front blade is made three times that of the rear blade, the pitch of the blade will increase, the amount of cutting will decrease, and the life of the rear blade will be shorter than that of the front blade.
If it is about 1.3 times, the effect of extending the life of the front blade will not be noticeable.

Embodiment The embodiment of the present invention shown in FIG. 5 will be described in detail below.

The broach shown in FIG. 5 has two blades in each set of blades in its rough cutting edge area. Although not clearly shown in FIG. 5, the general structure of the front blades Ti, Ti+2 with nicks and the rear blades Ti+1, Ti+3 in the rough cutting edge area of the broach according to this embodiment is the same as that in FIG. A detailed explanation thereof will be omitted.

As shown in the figure, in this example, the front blade
The pitch P ₁ of Ti and Ti+2 is made sufficiently larger than the pitch P ₂ of the rear blades Ti+1 and Ti+3. That is, the axial land width L of the front blades Ti, Ti+2 is set to be sufficiently larger than the axial land width L of the rear blades Ti+1, Ti+3, preferably at a size ratio of 5 to 6:3. Incidentally, the axial length l' of the tip plume B formed between the respective blades does not need to be particularly changed for each blade, and is set to the same dimension in this embodiment.

As mentioned above, the front blade Ti, Ti+2 is replaced by the rear blade Ti+1,
By making the land width dimension significantly larger than that of Ti+3, the rigidity of the front blade becomes sufficiently greater than that of the rear blade, so the front blade Ti and Ti+2 are
Even though its cutting conditions are more severe than that of Ti+1 and Ti+3, it can relatively withstand chipping and severe wear, thereby extending tool life.

Then, the front blade Ti, Ti+2 is the rear blade Ti+1, Ti+
Compared to No. 3, even if it wears out, the axial land width is sufficiently larger than before, so the number of times it can be re-grinded increases, and the tool life is greatly extended. .

In particular, the ratio of the land width of the front blade and the rear blade is 5 to 6:3.
In the case of 2
If set to double, the ratio of the land widths of the front and rear blades will hardly change even if re-grinding is performed, and the number of re-grinding can be increased without unnecessarily increasing the land width of the front blade. This is very effective in extending tool life.

As described above, according to the embodiment described above, the intended purpose of the present invention is achieved.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional explanatory view of main parts showing the arrangement of blades in the rough finishing blade area of a normal type broach, and Fig. 2 is a cross-sectional view of main parts showing the arrangement of blades of a conventional multi-stepped broach. 3 is a perspective view of the reduced main part of FIG. 2, FIG. 4 is a cross-sectional explanatory diagram illustrating the situation in which a workpiece is cut with the broach shown in FIGS. 2 and 3, and FIG. 5 is an implementation of the present invention. FIG. 2 is a cross-sectional explanatory diagram of a multi-stage flying edge broach according to an example. h...Increase in depth of cut, T...Blade, Ti, Ti+
2...Front blade, Ti+1, Ti+3...Rear blade, N...
Nick, W... Workpiece, W ₁ ... Cutting part,
W ₂ ... Uncut cutting part, t ... Cutting edge, a ... Side surface, P ₁ , P ₂ ... Pitch, L ... Land width of front blade,
l... Runt width of rear blade, B... tip plume,
l′...width of chip plume.

Claims (1)

[Claims for Utility Model Registration] (1) In the rough-cutting blade area, multiple adjacent blades are set as one set, and the depth of cut of the cutting blades is increased sequentially for each set, while the depth of cut of the cutting blades within each set is In a multi-stage flying-blade broach with the same depth and a groove formed on the front blade of each set, the axial land width of the front blade that performs main cutting is the same as that of the rear blade that performs auxiliary cutting. A multi-stage skipping-blade broach characterized by having a larger axial land width than the axial land width. (2) The multi-stage skipping-blade broach according to item 1, wherein the ratio of the axial land width of the front blade to the axial land width of the rear blade is (5 to 6:3).