JP2010125592A - Drill for cast iron processing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drill for cast iron processing capable of having a long life by considerably reducing thermal stress generated in the drill, processing with high efficiency at high cutting velocity, and further performing dry machining or semi-dry machining with less damages for the environment in the drilling of cast iron. <P>SOLUTION: In the drill for cast iron processing having a chamfering tooth at the peripheral corner, as to the shape of the chamfering viewed from a rake face side, the width of the chamfering tooth is &ge;0.06 and &le;0.15 times of the drill diameter, and the angle of the chamfering tooth to a rotary shaft center of the drill is &ge;35&deg; and &le;55&deg;. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a cast iron machining drill suitable for drilling of cast iron.

  Structural materials such as automobile parts that use cast iron are thinned for weight reduction to reduce the amount of fuel used, such as vermicular graphite cast iron (GGV), austempered malleable cast iron, and spheroidal graphite cast iron (FCD). In addition, in order to increase the strength of structural materials, they are moving toward higher strength and greater wear resistance. Carbide drills that process cast iron are rarely used for cast iron. Generally, cemented carbide drills for steel processing are used, but the following proposals have been proposed for drills for cast iron or cast material cutting.

  Patent Document 1 relates to a cemented carbide drill for cast iron, and compensates for insufficient cutting edge strength by using a cemented carbide material having higher wear resistance than a cemented carbide material used for general steel processing. The shape of the cutting edge to prevent chipping of the outer corner is proposed.

  Further, Patent Document 2 is a hard material drill, in which the cutting edge starts from the cutting corner and is continuously convex to the chisel edge in the axial direction, and the tip of the cutting corner is an auxiliary cutting blade. Since the main cutting blade is lengthened and the cutting corner portion is obtuse, the load on the cutting blade is reduced particularly in the outer peripheral region.

In Patent Document 3, the tip cutting edge is convex, and the tip cutting edge is 1 to 10% of the blade diameter rearward with respect to a virtual line connecting the most convex portion of the convex portion and the thinning blade. There has been proposed a drill with high hardness material drilling, characterized in that the connecting portion between the tip blade and the outer periphery is a chamfered surface.
JP 2005-103738 A Special table 2006-525127 JP 2001-341022 A

Since recent cast iron tends to have higher strength and wear resistance, measures for cutting tools are mainly means for dealing with these characteristics. For example, in Patent Document 1 described above, the edge strength is improved by providing a minimum chamfering blade at the boundary between the cutting edge flank and the margin surface of the carbide drill and providing honing at the leading edge of the cutting edge. It is going to be planned. Moreover, in patent document 2, as the shape which divided the cutting edge into the main cutting edge which draws a curve in a convex shape, and the auxiliary cutting edge on the tool outer peripheral side, the main cutting edge is made with a cutting angle part which is the joint as a sufficient obtuse angle. It has been proposed to lengthen and reduce cutting in the outer peripheral region. The proposals in Patent Documents 1 and 2 are mainly to reduce the chipping or mechanical wear of the cutting edge by reducing a large load at the cutting edge or the cutting corner portion of the outer periphery.
Patent Document 3 proposes that a chamfered surface of 20 degrees to 60 degrees is provided at the connecting portion between the tip blade and the outer periphery to suppress minute chipping and burrs of the workpiece when cutting through holes. This improves the breakage resistance of the cutting edge in the through hole.
However, according to the results of the study by the present inventor, cast iron contains a lot of hard phases (pearlite, martensite, carbides, etc.), and in these drilling operations, a large amount of cutting heat is generated due to abrasion between the hard phase and the cutting edge. It has become clear that there is a problem of tool deterioration due to heat generation that occurs and the tool life is deteriorated.
The background of this heat generation problem is the recent increase in cutting speed in order to reduce the processing cost of products, and the dry processing that can reduce the amount of cutting fluid used to reduce the burden on the environment. There is also a situation that semi-dry processing for supplying air and mist-like oil or low-temperature air is becoming widespread. From the viewpoint of generation of cutting heat, it can be said that reduction in the amount of high-speed cutting and the amount of cutting fluid used has shifted to a direction in which a large amount of cutting heat is generated in the cutting edge of the tool. Due to these changes in the environment surrounding the cutting of cast iron, the cutting edge of the tool will be processed in a harsh environment, but especially in the case of a drill, the outer peripheral corner of the cutting edge with the fastest cutting speed will be hot. As a result, the wear of the tool due to heat progressed remarkably, and the maximum flank wear width of the chamfered blade was greatly generated on the outer peripheral side.

In the case of conventional drills, although proposals have been made to improve the cutting edge strength with chamfering blades and honing, and to reduce the mechanical stress load on the cutting edge by devising the shape of the cutting edge, as in the present invention, There is no example examining the tool shape of the flank wear mode of the chamfering blade mainly focusing on the heat generation phenomenon at the outer peripheral corner of the drill cutting edge. In view of recent usage of new cast iron and the trend of high-speed cutting with a drill, the present invention can reduce the cutting heat generated at the outer peripheral corner of the drill in the drilling of high-strength cast iron. This is a result of studying a tool shape in which the flank wear generated on the outer peripheral side of the chamfering blade is uniformly generated in the entire chamfering blade to reduce the maximum flank wear width of the chamfering blade.
The present invention greatly reduces the thermal stress generated in the drill, thereby extending the life of the drill, enabling high-efficiency machining at a high cutting speed, and further reducing the environmental impact of dry machining and semi-drying. It aims at providing the drill for cast iron processing which can be processed.

  The present invention is an invention specializing in cutting of cast iron, and a first invention thereof is a drill having a chamfering blade at an outer peripheral corner, and the shape of the chamfering blade viewed from the rake face side is the chamfering blade. The cast iron drill is characterized in that the width of the drill is 0.06 to 0.15 times the diameter of the drill, and the angle of the chamfering blade with respect to the rotation axis of the drill is 35 ° to 55 °. .

  2nd invention of this invention is a drill which has a chamfering blade in an outer periphery corner, Comprising: The length of the said chamfering blade is 0.07 times or more and 0.26 times or less of the said drill diameter, The drill for cast iron processing is characterized in that an angle with respect to a rotation axis of the drill is not less than 35 ° and not more than 55 °.

  3rd invention of this invention is a drill which has a chamfering blade in the outer periphery corner of a cutting blade, Comprising: As for the shape of the said chamfering blade, the width | variety of the said chamfering blade is 0.06 times or more and 0.15 times or less of a drill diameter. The cast iron machining drill is characterized in that an angle of the chamfering blade with respect to a rotation axis of the drill is 35 ° or more and 55 ° or less, and a relief angle of the chamfering blade is 8 ° or more and 12 ° or less.

  By using the drill of the new shape of the present invention, the cutting heat generated near the outer peripheral corner of the drill can be dispersed and reduced in drilling with a cast iron drill having high strength and hardness. The drill for cast iron machining according to the present invention makes it possible to extend the life of the drill or perform highly efficient machining at a high cutting speed by suppressing the flank wear of the chamfering blade of a drill having a chamfering blade at the outer corner. To do. Furthermore, since the drilling can be easily performed by dry cutting that does not use cutting oil or the like and semi-dry cutting that supplies mist-like oil and air, an environment-friendly cutting tool can be provided.

  As described above, the present invention was born from the result of studying the problem of how to disperse and release the cutting heat generated at the outer peripheral corner of a drill, particularly for cast iron. The present inventor repeatedly measured various drill shapes and cutting edge wear, and provided a chamfering blade at the outer peripheral corner of the drill, so that the cutting speed was increased and the cutting edge length at a portion where the generation of cutting heat was severe. It has been found that increasing the length is effective for dispersion of cutting heat. The optimum size and shape of the chamfering blade were determined from the cutting test and observation of the flank wear situation of the chamfering blade.

  An example of the present invention will be described with reference to FIGS. 1 is a front view of the present invention, FIG. 2 is a side view of the tip cutting edge of the present invention, FIG. 3 is a front view of the tip cutting edge viewed from the margin 17 direction of the present invention, and FIG. 4 is a rake face 19 of the present invention. The front view of the front-end | tip cutting blade seen from the direction is shown. As shown in FIG. 1, the present invention has a cutting edge 18, a body 16, and a shank 15, and the body 15 is provided with two grooves 6 for discharging chips. The number of grooves 6 may be one or more than two, or may be linear. FIG. 5 shows a side view of the case where there are three tip cutting edges as another example of the present invention. As illustrated in FIG. 5, the features of the chamfering blade of the present invention may include three or more cutting blades of the drill of the present invention. Further, the cutting edge 18 is not limited to a straight line as shown in FIG. 2, but may be a convex curve or a concave curve in the drill rotation direction.

  As shown in FIGS. 1 to 5, a chamfering blade 11 is provided at the outer peripheral corner 10. As shown in FIG. 2, the shape of the chamfering blade 11 is such that the width 12 of the chamfering blade is 0.06 to 0.15 times the drill diameter. The width 12 of the chamfering blade is defined as follows. A straight line 25 passing through the rotation axis 28 and the outer corner 10 is drawn with the side view of the drill shown in FIGS. A straight line 26 perpendicular to the straight line 25 and passing through the boundary (intersection) between the cutting edge 22 of the chamfering blade and the cutting edge 18 is drawn. A straight line 27 that is parallel to the straight line 26 and passes through the outer corner 10 is drawn. The width of the straight line 26 and the straight line 27 is the width 12 of the chamfered blade. With an appropriate chamfering blade width 12, the cutting edge 22 of the chamfering blade near the outer corner where the cutting speed is high and the generation of cutting heat is long becomes long, so that the cutting heat is dispersed and the progress of rapid wear can be suppressed. . If the width 12 of the chamfering blade is less than 0.06 times the diameter, the cutting heat in the cutting edge region where the cutting speed is high cannot be sufficiently dispersed. Therefore, the smaller the width 12 of the chamfering blade, the more rapidly the wear proceeds. Life is shortened. When the width 12 of the chamfering blade exceeds 0.15 times the diameter of the tool, the cutting edge 22 of the chamfering blade becomes too long, so that the cutting resistance increases, so that vibration is generated during machining and stable due to chipping of the cutting edge. Can not be processed.

The angle 13 (hereinafter also referred to as the angle of the chamfering blade) of the chamfering blade with respect to the rotation axis of the drill shown in FIG. 4 is preferably 35 ° to 55 °, and more preferably 40 ° to 50 °.
The angle 13 with respect to the rotational axis of the chamfering blade of the present invention is defined as follows. FIG. 4 shows a state in which the drill 1 is rotated 90 ° in the direction opposite to the cutting rotation direction in the front view of the cutting edge viewed from the margin direction of the present invention shown in FIG. That is, the front view of the tip cutting edge seen from the rake face 19 direction is shown. With the front view of the drill shown in FIG. 4 projected on a plane, a boundary between the cutting edge 22 and the cutting edge 18 of the chamfering edge and a straight line 29 passing through the outer peripheral corner 10 are drawn. The angle formed by the straight line 29 and the rotation axis 28 is the angle 13 of the chamfering blade.
When the angle 13 of the chamfering blade is less than 35 °, the angle formed between the flank 20 of the cutting edge 18 and the chamfering blade 11 becomes small, so that the progress of wear on the tip side of the chamfering blade 11 is accelerated and the tool life is shortened. descend. In addition, when the angle 13 of the chamfering blade exceeds 55 °, a sufficient chamfering blade length 23 cannot be provided and the cutting heat cannot be dispersed. The tool life decreases with progress.

  As shown in FIG. 4, the length from the boundary between the cutting edge 18 and the cutting edge 22 of the chamfering blade to the outer peripheral corner 10 is defined as a chamfering blade length 23. The length 23 of the chamfering blade is desirably in the range of 0.07 times to 0.27 times the drill diameter 3. When the chamfering blade length 23 is less than 0.07 times the drill diameter 23, the cutting heat of the chamfering blade 22 having a high cutting speed cannot be sufficiently dispersed. Life is shortened. Further, when the length 23 of the chamfering blade exceeds 0.27 times the diameter of the drill 3, the cutting edge 22 of the chamfering blade becomes too long, so that the cutting resistance increases and vibration is generated during the machining. Chipping is likely to occur, and stable processing cannot be performed.

The clearance angle 14 of the chamfering blade shown in FIG. 3 is preferably 8 ° or more and 12 ° or less. As a result, the area of contact between the work material and the flank surface during cutting is reduced, so that a large amount of heat can be suppressed, and the heat generated at the outer peripheral corner 10 is sufficiently applied to the cutting edge of the chamfering blade 11. Can be dispersed.
When the clearance angle 14 of the chamfering blade is less than 8 °, the contact area between the work material and the clearance surface cannot be made sufficiently small, and even if the chamfering blade 11 is provided, the cutting heat cannot be dispersed and the tool life is reduced. It causes a decline. When the clearance angle 14 of the chamfering blade exceeds 15 °, the contact area between the work material being cut and the clearance surface is reduced, and generation of cutting heat can be suppressed. However, heat tends to concentrate and wear progresses. In addition, the cutting edge is not strong enough to cause chipping and the cutting life is shortened. Hereinafter, the present invention will be specifically described based on examples.

Example 1
As an example of the present invention and a comparative example, it has an oil hole for supplying coolant through the tool body, the drill diameter is 6.0 mm, the total length is 100 mm, the groove length is 50 mm, the groove twist angle is 30 °, and the core thickness is Table 1 shows the width of the chamfering blade, the angle of the chamfering blade, and the clearance angle of the chamfering blade provided at the outer peripheral corner of the drill in a drill having a 1.5 mm shank diameter of 6.0 mm and a tip angle of 140 °. Various things were made. Comparative Example 17 is a drill having no chamfering blade, that is, a general-purpose drill used for cutting general steel. The base materials of the drills were all ultra-fine cemented carbides with an average particle diameter of WC of 0.8 μm or less and a Co amount of 12 w%, and were coated with an AlCrN film. As test conditions, a rectangular block material of FCD700 was prepared as a work material, and drilling was performed. And at a horizontal machining center, the cutting conditions are a blind hole with a rotation speed of 6400 min ⁻¹ (cutting speed of about 120 m / min), a feed amount per rotation of 0.24 mm / rotation, and a drilling depth of 24 mm (4 times the drill diameter). Was processed. As the coolant, mist oil was supplied through the oil hole.
As an evaluation method, the flank maximum wear width (hereinafter referred to as the maximum wear width) of the chamfered blade after processing 1000 holes and 1500 holes was measured with an optical microscope to be magnified 100 times and evaluated. It was. When chipping occurred during cutting, the processing was stopped at that point and the number of holes was entered. The results are shown in Table 1.

  As a result, Examples 1 to 12 of the present invention were all capable of processing up to 1500 holes, and the maximum wear width was also good at 0.2 mm or less. In the case of the drill of the present invention, in the semi-dry machining using mist-like oil that generates a large amount of heat at the outer corner, the drill of the present invention has a good tool life because the cutting heat is sufficiently dispersed by the effect of the chamfering blade. there were. In particular, Invention Example 2 and Invention Examples 6 and 7 in which the angle of the chamfering blade was set to 40 ° to 50 ° were good, with the maximum wear width in 1500 hole processing being 0.12 mm or less.

Invention Examples 11 and 12 in Table 1 show that the width of the chamfering blade and the angle of the chamfering blade are within the scope of the present invention, but the cutting result is compared with Examples 9 and 10 of the present invention toward the outer peripheral side of the chamfering blade. Maximum wear width increased. Therefore, the range of the clearance angle of the chamfering blade is desirably 8 to 12 °.
The comparative example 13 evaluated the value equivalent to the meaning of the width | variety of the minimum chamfering blade provided in the drill described in the said patent document 1, ie, the chamfering blade which is this invention.
In Comparative Example 13 in which the width of the chamfering blade was set to 0.05 times the drill diameter, that is, 0.3 mm, in order to confirm the influence of the width of the chamfering blade, when the 1427 hole was processed, Chipping occurred. The reason is considered that the width of the chamfering blade was narrow in Comparative Example 13 and the cutting heat was not sufficiently dispersed. In Comparative Example 14, the maximum wear width was increased as compared with Invention Examples 1 to 4. This is presumably because the width of the chamfering blade was too wide, the cutting edge of the chamfering blade became longer, and the cutting resistance increased. Therefore, the range of the width of the chamfering blade is preferably 0.06 to 0.15 times the drill diameter 3 when other examples of the present invention are evaluated.
In Comparative Examples 15 and 16, which were performed in order to confirm the influence of the angle of the chamfering blade, the maximum wear width exceeded 0.2 mm. In Comparative Example 15, since the angle formed between the flank face of the cutting edge and the chamfering blade was small, the maximum wear width on the tip side of the chamfering blade was larger than 0.32 mm and 0.2 mm. Since the comparative example 16 cannot provide sufficient chamfering blade length and cannot disperse cutting heat, the maximum wear width on the outer peripheral side of the chamfering blade exceeds 0.34 mm and 0.2 mm. It became bigger. This is probably because the angle of the chamfering blade is inappropriate. Further, in the conventional example 17, which is a general-purpose drill for general steel that is not provided with a chamfering blade, chipping occurred in the outer peripheral corner when machining 862 holes.

(Example 2)
Next, as examples of the present invention and comparative examples, various types of drills having the same specifications as in Example 1 and having a drill groove length of 140 mm and chamfering blade lengths and chamfering blade angles shown in Table 2 were prepared.
As test conditions, a rectangular block material of FCD700 was prepared as a work material, and drilling was performed. Then, in a horizontal machining center, a blind hole with a cutting speed of 4200 min ⁻¹ (cutting speed of about 80 m / min), a feed amount per rotation of 0.24 mm / rotation, and a drilling depth of 120 mm (20 times the drill diameter). Was processed. As the coolant, mist oil was supplied through the oil hole.
The evaluation method was the same as in Example 1, and the maximum wear width after 200-hole processing was measured with an optical microscope enlarged 100 times and evaluated. The results are shown in Table 2.

As a result, all of Examples 18 to 29 of the present invention could be processed up to 200 holes, and the maximum wear width was as good as 0.2 mm or less. This is a semi-dry process using mist-like oil that generates a large amount of heat at the outer corners, and further, the longer the continuous cutting time is, the deeper the cutting edge is exposed to high temperature for a longer time. Also in machining, the cutting heat is sufficiently dispersed due to the effect of the chamfering blade, so it is considered that the tool life was good. In particular, the present invention example 19 and the present invention example 20 in which the length of the chamfering blade is set to 0.15 times and 0.2 times the diameter of the drill have a maximum wear width of 0.15 mm or less in the 200 hole machining. It was good.

In Comparative Example 30, chipping occurred in the outer peripheral corner when the 181 hole was processed. This is presumably because the cutting heat was not sufficiently dispersed because the length of the chamfering blade was too short.
In Comparative Example 31, the maximum wear width exceeded 0.2 mm, and the practical performance was insufficient. This is presumed that the maximum wear width occurred on the tip side of the chamfering blade because the cutting edge of the chamfering blade became too long, the cutting resistance increased, and vibration occurred.
In Comparative Example 32, the maximum wear width occurred over 0.2 mm on the outer peripheral side of the chamfered blade. This is because the angle formed between the flank face of the cutting edge and the chamfering blade is small, so that the maximum wear width on the tip side of the chamfering blade is larger than 0.29 mm and 0.2 mm. When the above processing was performed, chipping occurred in the vicinity of the outer corner. This is probably because the angle of the chamfering blade with respect to the rotation axis is small and the length of the outer peripheral side of the chamfering blade is short, so that the cutting heat on the outer peripheral side of the chamfering blade cannot be sufficiently dispersed.

FIG. 1 shows a front view of the present invention. FIG. 2 shows a side view of the tip cutting edge of the present invention. FIG. 3 shows a front view of the cutting edge viewed from the margin direction of the present invention. FIG. 4: shows the front view of the front-end | tip cutting edge seen from the rake face 19 direction of this invention. FIG. 5 shows a side view in the case of three tip cutting edges as another example of the present invention.

Explanation of symbols

1 Drill 2 Oil hole 3 Drill diameter 4 Overall length 5 Groove length 6 Groove 7 Torsion angle 8 Center thickness 9 Shank diameter 10 Peripheral corner 11 Chamfering blade 12 Chamfering blade width 13 Chamfering blade angle 14 Chamfering blade clearance angle 15 Shank 16 Body 17 Margin 18 Cutting edge 19 Rake face 20 Relief face 21 Thinning cutting edge 22 Cutting edge of chamfering edge 23 Length of chamfering edge 24 Tip angle 25 Straight line passing through rotation axis and outer corner 26 Straight line passing through rotation axis and outer corner A straight line that passes through the boundary between the chamfering blade and the cutting edge, is perpendicular to the straight line that passes through the boundary between the rotation axis and the outer peripheral corner, is parallel to the straight line that passes through the boundary between the chamfering blade and the cutting edge, and rotates through a straight line that passes through the outer corner. Axis 29 Straight line passing the boundary between the chamfering edge and the cutting edge and the outer corner

Claims (3)

A drill having a chamfering blade at an outer peripheral corner, wherein the chamfering shape viewed from the rake face side has a width of the chamfering blade of 0.06 to 0.15 times the drill diameter, A cast iron drill for drilling, characterized in that an angle with respect to the rotation axis of the drill is not less than 35 ° and not more than 55 °. A drill having a chamfering blade at an outer corner, wherein the chamfering blade has a length of 0.07 to 0.26 times the drill diameter, and the angle of the chamfering blade with respect to the rotation axis of the drill is A cast iron machining drill characterized by being in the range of 35 ° to 55 °. The drill for machining a cast iron according to claim 1, wherein a relief angle of the chamfering blade is 8 ° or more and 12 ° or less.

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