CN103485723B - Control the device and method of reaming-while-drillibit bit pressure distribution relation - Google Patents

Abstract

The invention discloses a kind of device controlling reaming-while-drillibit bit pressure distribution relation, belong to drilling equipment field.Described device comprises drill-following reamer (1), stub boring quickly (2) and pilot bit (3), the upper end of described drill-following reamer (1) and described stub boring quickly (2) is connected, the lower end of described stub boring quickly (2) is connected with described pilot bit (3), described drill-following reamer (1) is provided with at least one reaming hole toolbox (11), the diameter of described pilot bit (3) is less than the external diameter of described drill-following reamer (1) under described reaming hole toolbox (11) expansion state.The invention also discloses a kind of method utilizing this device to control reaming-while-drillibit bit pressure distribution relation.Reaming-while-drillibit bit pressure distribution relation controls in the scope of setting by the cutting power often turning cutting depth and reamer of adjustable pilot bit by the present invention, strengthens safety and the stability of reaming hole process.

Description

Control the device and method of reaming-while-drillibit bit pressure distribution relation

Technical field

The present invention relates to drilling equipment field, particularly a kind of device controlling reaming-while-drillibit bit pressure distribution relation and the method controlling reaming-while-drillibit bit pressure distribution relation.Can the pressure of the drill relations of distribution in Reasonable adjustment reaming while drilling process, improve the safety and stability of reaming hole operation.

Background technology

In the reaming while drilling process of drilling technology, the relations of distribution of the pressure of the drill between pilot bit and drill-following reamer are one of parameters needing special concern, if the pressure of the drill relations of distribution are unreasonable, then very easily cause the stick-slip of neck eye drill string or violent oscillation crosswise, drilling tool premature breakdown, rate of penetration decreases.

The ratio of the pressure of the drill that the pressure of the drill relations of distribution are generally born separately with pilot bit and drill-following reamer represents, the pressure of the drill distribution ratio of general agreement pilot bit and drill-following reamer is with alphabetical f _wmark, then

$f_w=\frac{W_r}{W_b}$

Wherein W _bby pilot bit is born the pressure of the drill, Wr is born the pressure of the drill by drill-following reamer.

Normally, f _wsectional area by pilot bit and drill-following reamer institute broken formation affects comparatively large, thus often excises the cross-sectional area on stratum than the ratio as the two suffered the pressure of the drill using drill-following reamer and pilot bit during estimation.It is single that this method relates to factor, and accuracy rate is not high, is difficult to the pilot bit needed for correct matched design reaming while drilling and reamer accordingly.

Prior art has the thick cylinder being considered as the borehole wall to be subject to interior external pressure, analyze pilot bit and drill-following reamer cut the compressive strength difference on stratum, propose the alias index the calculating being introduced into the pressure of the drill distribution ratio that characterize above-mentioned difference, but this method hypothesis drill-following reamer is identical with the power of pilot bit rock cutting, adapts to field narrower.

Realizing in process of the present invention, inventor finds that prior art at least exists following problem: existing drilling tool can not the pressure of the drill relations of distribution in Reasonable adjustment reaming while drilling process, there is larger safety and stability hidden danger in reaming hole operation; And the design of drill-following reamer and pilot bit can be instructed to ensure that the pressure of the drill distribution ratio is in rational scope without effective method.

Summary of the invention

In order to solve the problem of prior art, embodiments provide a kind of device controlling reaming-while-drillibit bit pressure distribution relation and the method controlling reaming-while-drillibit bit pressure distribution relation, can the pressure of the drill relations of distribution in Reasonable adjustment reaming while drilling process, instruct the design process of drill-following reamer and pilot bit, and then improve the safety and stability of reaming hole operation.Described technical scheme is as follows:

On the one hand, provide a kind of device controlling reaming-while-drillibit bit pressure distribution relation, described device comprises: drill-following reamer, stub boring are quickly and pilot bit, described drill-following reamer is connected with described stub boring upper end quickly, described stub boring lower end is quickly connected with described pilot bit, described drill-following reamer is provided with at least one reaming hole toolbox, the diameter of described pilot bit is less than the external diameter of described drill-following reamer under described reaming hole toolbox expansion state.Like this, the footpath, neck eye hole that pilot bit cuts is less, and drill-following reamer continues to cut on the neck eye basis that pilot bit cuts, and the footpath, main borehole hole by drill-following reamer cuts again is expanded, and is conducive to the discharge balancing drilling tool and be cut mudstone.

Further, described reaming hole toolbox comprises reamer wing, wing cutting teeth and wing stable section, and described reamer wing telescopically is arranged on described reaming hole toolbox, and described wing cutting teeth and described wing stable section are covered on described reamer wing; Described wing stable section is arranged on the middle part of described reaming hole toolbox, and the two ends of described wing stable section are provided with described wing cutting teeth.Reaming hole toolbox is integrally along the circumferential direction arranged on the rod member of drill-following reamer, and reaming hole toolbox can operationally enlargement and contraction.Wherein the outline line of reamer wing is comparatively sharp-pointed, can cut the ground of different geology; Wing cutting teeth is PDC cutting teeth, and have the forward leaning angle larger than existing cutting dental transition, thus its cutting power is strengthened greatly; Wing stable section is covered in the middle part of reaming hole toolbox, and it is manufactured by carbide alloy, is mainly used in stablizing reamer wing, wing cutting teeth in cutting reaming hole process, and improve the stability of whole drilling tool, this wing stable section does not have cutting power.

Further, described wing cutting teeth to be top rake the be taper cutting teeth of 25 ° ~ 30 °.

Further, described drill-following reamer is provided with three, four or six described reaming hole toolboxs.Preferably on drill-following reamer, arrange three reaming hole toolboxs, its spreading performance and symmetric stability can be better like this.

Further, described pilot bit is provided with many neck eye wings, for returning bits groove between every two described neck eye wings; The nose of described neck eye wing is provided with wear-resistant pad, and the ipsilateral penumbra of many described neck eye wings is provided with Cutter, and described wear-resistant pad partly covers described Cutter.Be preferably and arrange four neck eye wings at the bizet of pilot bit, four roads forming indent in the spacer portion of four neck eye wings return bits groove, are namely discharged by returning bits groove by the ground that neck eye wing cuts.Be provided with multiple Cutter abreast by the top of neck eye wing and shoulder, those Cutters are PDC cutting teeth, have larger cutting power.At the wear-resistant pad that the nose of every only neck eye wing is arranged, its surfacing, does not possess cutting power, but can be changed the cutting power of Cutter by the thickness of those wear-resistant pads of adjustment.So-called wear-resistant pad partly covers Cutter, but these capped Cutters are not all capped.A wear-resistant pad surfacing, in wing place, is returned bits groove place and is not arranged wear-resistant pad.In addition, for increasing the cutting power ratio of drill-following reamer and pilot bit further, also can adjust the Cutter setting angle of pilot bit and cutter set density.Basic law is: Cutter top rake is larger, and cutting power is stronger; Cutter set density is less, and cutting power is stronger.

Further, each only described neck eye wing is disposed with Cutter described in several to spacing, is namely arranged between each Cutter on neck eye wing and has certain gap.

Further, the hard alloy layer of described wear-resistant pad to be thickness be 2 ~ 3mm.

Further, the tooth footpath of described wing cutting teeth is less than the tooth footpath of described Cutter.

On the other hand, provide a kind of method controlling reaming-while-drillibit bit pressure distribution relation, reaming while drilling the pressure of the drill distribution ratio f _wfactor except neck eye and the geometric area ratio of main borehole, also have the cutting power etc. of formation characteristics, drilling tool self, then described method comprises: according to Teale(name, proposes in 1964) rock that proposes is than merit expression formula:

$E_s=\frac{W}{A}+\frac{120\mathrm{\π}\·\mathrm{\Ω}\·W\·T}{A\·v}---\left(1\right)$

In formula (1), E _sfor rock compares merit; W is the pressure of the drill; A is the sectional area that rock crushing tool cuts that stratum generates well; T is moment of torsion; Ω is rotating speed; V is rate of penetration.

Derive the pressure of the drill distribution ratio f _wfor:

$f_w=\frac{W_r}{W_b}=\frac{{\mathrm{\σ}}_r}{{\mathrm{\σ}}_b}\·\frac{{\mathrm{\η}}_b}{{\mathrm{\η}}_r}\·\frac{k_b}{k_r}\·\frac{A_r}{A_b}---\left(2\right)$

In formula (2), k _rfor reamer acutance, k _bfor drill bit acutance; η _bfor drill bit drilling efficiency, η _rfor reamer drilling efficiency, σ _rrock stratum compressive strength is met, σ for reamer bores _bfor bit drills meets rock stratum compressive strength, A _bfor the neck eye sectional area that bit cutting stratum generates, A _rfor reamer expands the annular cross-sectional area of leading eye to be formed afterwards.

When drill-following reamer and pilot bit are apart from time closer, be considered as described drill-following reamer and described pilot bit is in stratum of the same race, then the pressure of the drill distribution ratio f _wonly relevant to the cutting power of described drill-following reamer and described pilot bit.Normally, evaluation drilling tool cutting power the most intuitively index is rate of penetration, and when the drilling tool of equal nominal dimension creeps into same stratum under same process condition, rate of penetration is faster, then cutting power is stronger.

Drill-following reamer is the consumable accessory in reaming while drilling drilling assembly, therefore pays close attention to the pressure of the drill particular importance that drill-following reamer bears.The expression formula of the pressure of the drill distribution ratio is rewritten as:

$f_r=\frac{W_R}{W_R+W_B}=1-\frac{1}{f_W+1}$

Wherein, f _rfor acting on the pressure of the drill portion in total the pressure of the drill on drill-following reamer, it has been generally acknowledged that f _rbetween 20 ~ 35% time, reaming hole process is comparatively stable, now f _wbe about 30 ~ 50%.Consider that the difference of both drill-following reamer and pilot bit cutting power bears the affecting laws of the pressure of the drill to drill-following reamer below.With f _rfor function, k _r/ k _bfor variable, draw relation curve as shown in Figure 1.

Curve in Fig. 1 shows, when other parameter constants, reaming while drilling wing is the stronger (k of cutting power more _r/ k _blarger), its pressure of the drill got is less; Otherwise reaming while drilling wing is the more weak (k of cutting power more _r/ k _bless), its pressure of the drill got is larger; In the most extreme case, drill-following reamer at all can not cut stratum (k _r/ k _bbe 0), so the pressure of the drill meeting 100% puts on reamer wing.

According to above-mentioned principle, reaming-while-drillibit bit pressure distribution relation can be controlled by the cutting power relation of adjustment pilot bit and drill-following reamer.

Further, described method also comprises:

S1, adjusts the wear-resistant pad thickness of described pilot bit, controls maximum depth of cut that described pilot bit often turns and changes the cutting power of described pilot bit;

S2, changes the reamer wing cloth tooth mode of described drill-following reamer, makes the cutting power of described reamer wing be better than the cutting power of described pilot bit;

By the adjustment in S1 and S2 step, control the pressure of the drill relations of distribution of described drill-following reamer and described pilot bit.

The specific design method of adjustment drilling tool cutting power is as follows:

First, determine neck eye diameter and main borehole diameter, try to achieve geometric area and compare A _r/ A _b; Secondly, the pressure of the drill distribution ratio f is preset _w, in conjunction with A _r/ A _bdrilling tool acutance can be tried to achieve and compare k _r/ k _b; Finally, use the acutance of said method adjustment pilot bit and drill-following reamer, and test, the pressure of the drill distribution ratio can be limited in comparatively rational scope.

The beneficial effect that the technical scheme that the embodiment of the present invention provides is brought also comprises: by open a kind of drilling tool cutting power that adjusts to control the devices and methods therefor of reaming-while-drillibit bit pressure distribution relation,

1, in the design process of drill-following reamer and reaming hole toolbox, namely consider the performance characteristics of pilot bit and drill-following reamer, both Proper Matchs cutting power, reaming-while-drillibit bit pressure distribution relation is controlled by the cutting power of adjustment drill-following reamer and pilot bit, simple to operation;

2, computational methods are easy, and result comparatively traditional approach is more accurate, are convenient to on-the-spot application;

3, the pilot bit proposed and reamer wing structure are easy to adjustment, can set design parameter as required.

Accompanying drawing explanation

In order to be illustrated more clearly in the technical scheme in the embodiment of the present invention, below the accompanying drawing used required in describing embodiment is briefly described, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.

Fig. 1 is the relation curve schematic diagram of reaming hole the pressure of the drill of the present invention ratio and reamer wing cutting power;

Fig. 2 is the structural representation of the device of the control reaming-while-drillibit bit pressure distribution relation that the embodiment of the present invention one provides;

Fig. 3 is the reaming hole toolbox structural representation of the device that the embodiment of the present invention one provides;

Fig. 4 is the pilot bit structural representation of the device that the embodiment of the present invention one provides;

Fig. 5 is the top view of the pilot bit of this Fig. 3.

Detailed description of the invention

For making the object, technical solutions and advantages of the present invention clearly, below in conjunction with accompanying drawing, embodiment of the present invention is described further in detail.

Embodiment one

Present embodiments provide a kind of device controlling reaming-while-drillibit bit pressure distribution relation, see Fig. 2, this device comprises drill-following reamer 1, stub boring quickly 2 and pilot bit 3, drill-following reamer 1 and stub boring quickly 2 upper end be connected, stub boring quickly 2 lower end be connected with pilot bit 3, drill-following reamer 1 is provided with at least one reaming hole toolbox 11, the diameter of pilot bit 3 is less than the external diameter of drill-following reamer 1 under reaming hole toolbox 11 expansion state.Pilot bit 3 is arranged on device bottom, uses pilot bit 3 broken formation to form the less neck eye of diameter; Drill-following reamer 1 is arranged on the drill string upper end of this device, and the cutting diameter after drill-following reamer 1 expansion is greater than the cutting diameter of pilot bit 3, and drill-following reamer 1 high-ranking military officer eye expands as the larger main borehole of diameter.

Reaming hole toolbox 11 is fixed on the outer wall of drill-following reamer 1 along the circumferencial direction of drill-following reamer 1, the periphery wall of drill-following reamer 1 offers the cavity that can hold reaming hole toolbox 11, when reaming hole toolbox 11 to be installed in this cavity and to be in contraction state, its external diameter is a bit larger tham the external diameter of drill-following reamer 1 mobile jib, or both are basically identical.At the lower position of the reaming hole toolbox 11 of drill-following reamer 1, cutter protection part 12 is set; when putting in inside drilling well under whole drilling tool; when work do not opened by reaming hole toolbox 11; the neck eye that diameter is less may collide reaming hole toolbox 11, and the setting of cutter protection part 12 avoids reaming hole toolbox extends through in journey damaged 11 times.

Preferably, drill-following reamer 1 is provided with four reaming hole toolboxs 11, like this, drill-following reamer 1 had both had stronger cutting power, had again good balance quality.As other embodiment, can as required and consider that mechanical characteristic arranges the reaming hole toolbox 11 of three or six or other quantity on this drill-following reamer 1.

In conjunction with see Fig. 3, reaming hole toolbox 11 comprises reamer wing 101, wing cutting teeth 102 and wing stable section 103, reamer wing 101 telescopically is arranged on reaming hole toolbox 11, wing cutting teeth 102 and wing stable section 103 are covered on reamer wing 101, wing stable section 103 is arranged on the middle part of reaming hole toolbox 11, and the two ends of wing stable section 103 are provided with wing cutting teeth 102.This wing cutting teeth 102 elects PDC cutting teeth as, makes the cutting power of wing cutting teeth 102 stronger; This wing stable section 103 forms for Hardmetal materials manufacture, wing stable section 103 covers on reamer wing 101, be positioned at the medium position of reamer wing 101, and be fixedly connected on drill-following reamer 1 mobile jib, strengthen reamer wing and the stability of wing cutting teeth in working angles, thus improve the stability of whole drilling tool.Preferably, wing cutting teeth 102 to be top rakes the be taper cutting teeth of 25 ° ~ 30 °, compared with existing wing cutting teeth, increases the forward leaning angle of wing cutting teeth, thus enhances the cutting power of this wing cutting teeth 102.

Embodiment two

Present embodiments provide a kind of device controlling reaming-while-drillibit bit pressure distribution relation, this device comprises drill-following reamer 1, stub boring quickly 2 and pilot bit 3, the drill-following reamer 1 of this device, stub boring are quickly 2 identical with the annexation in embodiment one with the annexation of pilot bit 3, the parts included by drill-following reamer 1 of this device and the annexation of each parts is identical with embodiment one or have on the basis that can realize embodiment one said function and reasonably improve and optimize.

In conjunction with see Fig. 4 and Fig. 5, the bizet of pilot bit 3 is provided with many neck eye wings 31, for returning bits groove 32 between every only neck eye wing 31, the end of neck eye wing 31 is provided with wear-resistant pad 301, the ipsilateral penumbra of many neck eye wings 31 is provided with Cutter 302, and wear-resistant pad 301 partly covers part Cutter 302.Neck eye wing 31 is spaced apart and arranged in the bizet of pilot bit 3 with returning bits groove 32, greatly can improve the cutting power of Cutter 302 and cut into speed, can be discharged by returning bits groove 32 by the ground be cut in time.Each only neck eye wing 31 are disposed with several Cutters 302 to spacing, and those Cutters 302 are PDC cutting teeth.The hard alloy layer of wear-resistant pad 301 to be thickness be 2mm ~ 3mm, the wear-resistant pad 301 that this carbide alloy is made does not possess cutting power, Cutter 302 can be changed by the thickness changing wear-resistant pad 301 and expose the height leading eye wing 31 and wear-resistant pad 301, Cutter 302 exposes higher, and its cutting power is stronger; Otherwise Cutter 302 exposes lower, its cutting power is more weak.Therefore, the cutting power of pilot bit 3 can be changed by the thickness of change wear-resistant pad 301, thus adjustment reaming-while-drillibit bit pressure distribution relation.

Preferably, the tooth footpath of the wing cutting teeth 102 on drill-following reamer 1 is less than the tooth footpath of the Cutter 302 on pilot bit 3.Wing cutting teeth 102 is made to lead the cutting ability on wall near the eyes better.

Embodiment three

Embodiments provide a kind of method controlling reaming-while-drillibit bit pressure distribution relation, reaming while drilling the pressure of the drill distribution ratio f _wfactor except neck eye and the geometric area ratio of main borehole, also have the cutting power of formation characteristics, drilling tool self.The method comprises, according to Teale rock than merit expression formula:

$E_s=\frac{W}{A}+\frac{120\mathrm{\π}\·\mathrm{\Ω}\·W\·T}{A\·v}---\left(1\right)$

In formula (1), E _sfor rock compares merit; W is the pressure of the drill; A is the sectional area that rock crushing tool cuts that stratum generates well; T is moment of torsion; Ω is rotating speed; V is rate of penetration.

Derive the pressure of the drill distribution ratio f _wfor:

$f_w=\frac{W_r}{W_b}=\frac{{\mathrm{\σ}}_r}{{\mathrm{\σ}}_b}\·\frac{{\mathrm{\η}}_b}{{\mathrm{\η}}_r}\·\frac{k_b}{k_r}\·\frac{A_r}{A_b}---\left(2\right)$

In formula (2), k _rfor reamer acutance, k _bfor drill bit acutance; η _bfor drill bit drilling efficiency, η _rfor reamer drilling efficiency, σ _rrock stratum compressive strength is met, σ for reamer bores _bfor bit drills meets rock stratum compressive strength, A _bfor the neck eye sectional area that bit cutting stratum generates, A _rfor reamer expands the annular cross-sectional area of leading eye to be formed afterwards.

When drill-following reamer 1 and pilot bit 3 are apart from time closer, be considered as drill-following reamer 1 and pilot bit 3 is in stratum of the same race, then the pressure of the drill distribution ratio f _wonly relevant to the cutting power of drill-following reamer 1 and pilot bit 3.Normally, evaluation drilling tool cutting power the most intuitively index is rate of penetration, and when the drilling tool of equal nominal dimension creeps into same stratum under same process condition, rate of penetration is faster, then cutting power is stronger.

Drill-following reamer is the consumable accessory in reaming while drilling drilling assembly, therefore pays close attention to the pressure of the drill particular importance that drill-following reamer bears.The expression formula of the pressure of the drill distribution ratio is rewritten as:

$f_r=\frac{W_R}{W_R+W_B}=1-\frac{1}{f_W+1}$

Wherein, f _rfor acting on the pressure of the drill portion in total the pressure of the drill on drill-following reamer, it has been generally acknowledged that f _rbetween 20 ~ 35% time, reaming hole process is comparatively stable, now f _wbe about 30 ~ 50%.Consider that the difference of both drill-following reamer and pilot bit cutting power bears the affecting laws of the pressure of the drill to drill-following reamer below.With f _rfor function, k _r/ k _bfor variable, draw relation curve as shown in Figure 1.

Curve in Fig. 1 shows, when other parameter constants, reaming while drilling wing is the stronger (k of cutting power more _r/ k _blarger), its pressure of the drill got is less; Otherwise reaming while drilling wing is the more weak (k of cutting power more _r/ k _bless), its pressure of the drill got is larger; In the most extreme case, drill-following reamer at all can not cut stratum (k _r/ k _bbe 0), so the pressure of the drill meeting 100% puts on reamer wing.

According to above-mentioned principle, reaming-while-drillibit bit pressure distribution relation can be controlled by the cutting power relation of adjustment pilot bit and drill-following reamer.

Determining to affect reaming while drilling the pressure of the drill distribution ratio f _wfactor after, the method also comprises:

S1, wear-resistant pad 301 thickness of adjustment pilot bit 3, controls the maximum depth of cut that often turns of pilot bit 3 and changes the cutting power of pilot bit 3;

S2, changes the reamer wing 101 cloth tooth mode of drill-following reamer 1, makes the cutting power of reamer wing 101 be better than the cutting power of pilot bit 3;

By the adjustment in S1 and S2 step, control the pressure of the drill relations of distribution of drill-following reamer 1 and pilot bit 3.

The further method for designing of adjustment drilling tool cutting power has:

First, determine neck eye diameter and main borehole diameter, try to achieve geometric area and compare A _r/ A _b; Secondly, the pressure of the drill distribution ratio f is preset _w, in conjunction with A _r/ A _bdrilling tool acutance can be tried to achieve and compare k _r/ k _b; Finally, use the acutance of said method adjustment pilot bit and drill-following reamer, and test, the pressure of the drill distribution ratio can be limited in comparatively rational scope.

The invention described above embodiment sequence number, just to describing, does not represent the quality of embodiment.

The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (7)

1. one kind controls the device of reaming-while-drillibit bit pressure distribution relation, described device comprises drill-following reamer (1), stub boring quickly (2) and pilot bit (3), the upper end of described drill-following reamer (1) and described stub boring quickly (2) is connected, the lower end of described stub boring quickly (2) is connected with described pilot bit (3), it is characterized in that:

Described drill-following reamer (1) is provided with at least one reaming hole toolbox (11), the diameter of described pilot bit (3) is less than the external diameter of described drill-following reamer (1) under described reaming hole toolbox (11) expansion state;

Described pilot bit (3) is provided with many necks eye wing (31), for returning bits groove (32) between every two described neck eye wings (31);

The nose of described neck eye wing (31) is provided with wear-resistant pad (301), the ipsilateral penumbra of many described neck eye wings (31) is provided with Cutter (302), described wear-resistant pad (301) partly covers described Cutter (302), can be changed the cutting power of described pilot bit (3) by the thickness changing described wear-resistant pad (301).

2. device according to claim 1, it is characterized in that, described reaming hole toolbox (11) comprises reamer wing (101), wing cutting teeth (102) and wing stable section (103), described reamer wing (101) telescopically is arranged on described reaming hole toolbox (11), and described wing cutting teeth (102) and described wing stable section (103) are covered on described reamer wing (101);

Described wing stable section (103) is arranged on the middle part of described reaming hole toolbox (11), and the two ends of described wing stable section (103) are provided with described wing cutting teeth (102).

3. device according to claim 2, is characterized in that, described wing cutting teeth (102) to be top rake the be taper cutting teeth of 25 ° ~ 30 °.

4. device according to claim 1, is characterized in that, described drill-following reamer (1) is provided with three, four or six described reaming hole toolboxs (11).

5. device according to claim 1, is characterized in that, each is only disposed with Cutter described in several (302) to the upper spacing of described neck eye wing (31).

6. device according to claim 1, is characterized in that, the hard alloy layer of described wear-resistant pad (301) to be thickness be 2 ㎜ ~ 3 ㎜.

7. device according to claim 1, is characterized in that, the tooth footpath of described wing cutting teeth (102) is less than the tooth footpath of described Cutter (302).