JP2002172509A - Drill for dry cutting and drilling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a twist drill performing dry cutting and aiming at the shape of a chip pocket from a tip end cutting edge to a part curled to stably generate cutting chips of transitional cutoff type to be excellent in durability, in the case of drilling a work of general structural steel and die steel or the like. SOLUTION: In this drill for dry cutting, constituted by using a cemented carbide alloy or TiCN cermet in a base body to cover a base body surface with a hard coat and/or a lubricating coat, an inflection point is provided in the halfway of a ridge line formed in recessed circular arc shape toward a land heel part from the vicinity of a web thickness of a chip pocket with the axial end view of the drill, the drill for dry cutting is characterized by retracting in the direction opposite to the rotational direction of the drill and retracting in the direction opposite to the rotational direction of the drill toward the land heel part from the vicinity of the web thickness of the chip pocket even in an axial right angle sectional view of this drill.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cemented carbide or TiCN
The present invention relates to a drill and a method for performing a dry or semi-dry drilling process on a twist drill in which a hard alloy containing a base cermet is coated on a base with a hard coating and / or a lubricating hard coating without using a water-soluble cutting oil.

[0002]

2. Description of the Related Art In recent years, dry machining without using a water-soluble cutting oil has been performed for drilling. For example, Japanese Patent Application Laid-Open No. 2000-198011 proposes a drill that increases the strength of the leading edge of a twist drill and prevents chipping of the leading edge that occurs during dry processing. As an example of examining the lubricity from the viewpoint of a film, Japanese Patent Application Laid-Open No. 2000-233324 also proposes a MO (metal oxide) film having a lubricity in the film. Further, when cutting structural steel to high hardness steel as a dry drilling tool, there is a problem of chip discharge. The discharge of chips is achieved when water-soluble cutting oil is used.
Since the chips are discharged in such a manner as to ride on the flow of the cutting oil, it was only necessary to form divided chips called transition cutting type. On the other hand, in dry cutting, there is no flow of the cutting oil, and there is no cooling effect of the cutting oil and no lubricity. It has not been.

[0003] Also, from the aspect of the chip form, Japanese Patent No.
No. 124 describes that the shape of the chip discharge groove is such that when a perpendicular line perpendicular to a straight line connecting this edge and the axis of the drill body is drawn on the outer peripheral edge of the cutting edge, The chip is forcibly curled by defining a concave shape, that is, a radius of curvature at the bottom of the blade groove.

[0004]

The chips generated at the cutting edge of the twist drill, while rubbing the chip discharge groove,
It is curled at the curvature of the bottom of the blade groove, rises along the chip discharge groove, and is discharged outside the drill. At that time, in dry machining, heat generation due to cutting due to continuous cutting called hole drilling and temperature rise due to friction with blade grooves etc. further increased the temperature, the form of chips changed, and the cut Trash
Turns into continuous chips. Further, when a water-soluble cutting oil or the like is used, rapid cooling is performed, so that the temperature of the chip itself does not matter, and stable chip processing is performed. However, in dry cutting, since a morphological change occurs due to an increase in chip temperature, there is a problem that divided chips cannot be generated for a long period of time.

In order to solve the above problems, in the present invention, drilling of a work material such as general structural steel or die steel is performed by dry cutting, and the groove from the tip cutting edge to the curl. It is an object of the present invention to provide a twist drill excellent in durability by stably generating transition cutting chips by focusing on the shape of the drill.

[0006]

Therefore, in the present invention, a cemented carbide or TiCN-based cermet is used for the substrate,
In a drill for dry cutting in which a hard film and / or a lubricating film is coated on a substrate surface, the drill is formed in a concave arc shape from near the core thickness of the blade groove toward the land heel portion when viewed from the axial end of the drill. An inflection point is provided in the middle of the ridgeline, and the drill is retracted in the direction opposite to the rotation direction of the drill. Is a drill for dry cutting characterized by being retracted in the opposite direction.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to reduce the temperature of chips themselves, the distance from the cutting edge to the concave portion at the bottom of the blade groove where the chips are curled, and the length of the concave portion are made as short as possible. This distance only scrapes the chips, but it is sufficient if the curled chips are long enough. Also, as the length increases, the temperature of the chip itself increases, and the thermal effect appears as a change in the form of the chip. Therefore, an inflection point is provided in the middle of the concave portion at the bottom of the blade groove, and the inflection point is retracted in the direction opposite to the rotation direction of the drill so as not to come into contact with the chips.

By providing this inflection point, the direction in which the chips move is already determined, and the chips are pushed and bent by the rotation of the machined inner wall and the drill, and move upward of the drill.
It is discharged outside the drill. Naturally, in the cross section perpendicular to the axis of the drill, similarly, the same action and effect can be obtained by retreating from the vicinity of the thickness of the blade groove toward the land heel in the direction opposite to the rotation direction of the drill. Further, the position of the inflection point of the concave portion is set to 50 to 90% of the drill diameter D.
If the diameter is less than D, a sufficient curl diameter cannot be given by subtracting the core thickness and the like, and the outflow direction of the chips cannot be determined. If the diameter exceeds 90% D, it is the same as a conventional drill. Therefore, it was set in the range of 50 to 90% D. More preferably, it is in the range of 60 to 75% D.

Next, the radius of curvature of the concave portion may be a radius that can virtually draw one circle in the blade groove. Although there is a balance with the core thickness, D is preferably 10 to 20% of the drill diameter. Furthermore, it is preferably 12 to 17% D. Also,
In order to further reduce the temperature of the chip itself, the distance from the cutting edge to the concave portion at the bottom of the blade groove for curling the chip is made as short as possible. Although this distance only scratches the chips, the distance is set in the range of 35 to 45% of the drill diameter in consideration of the space for discharging the curled chips, that is, the groove width ratio. If it is less than 35%, the width of the blade groove becomes relatively narrow, and a space for chip discharge cannot be secured. If it exceeds 45%, the groove width ratio becomes relatively too wide, so that 35 to 45% of the drill diameter. Range. Also, the distance between the perpendicular passing through the cutting edge and the perpendicular passing through the concave innermost part is 45 to 45 mm of the drill diameter.
The reason why the ratio is set to 60% has a balance with the radius of curvature of the concave portion. However, if the ratio is less than 45%, the radius of curvature of the concave portion must be relatively reduced. This is because the radius is too small to be too forcible.
Conversely, if it exceeds 60%, the radius of curvature of the concave portion must be relatively large, and the larger the radius of curvature is,
Since the curl radius of the chips becomes large and the chips are extended and curled so that they are not divided, the content is set to 60% or less. Hereinafter, the present invention will be specifically described based on examples.

[0010]

(Example 1) A commercially available powder metallurgy method using a commercially available WC powder having an average particle diameter of 0.5 micron and a Co powder having the same micron diameter of 0.5 micron, and having a composition of 10% Co and a residual WC powder having a diameter of 8 m.
m of the present invention was manufactured. The physical properties of the cemented carbide after sintering were HRA92, a lattice constant of Co of 3.570 °, and a crack resistance of 90 kg / mm. Using this cemented carbide, 2 blades, outer diameter 8
The distance between a perpendicular passing through the cutting edge on an imaginary line connecting the cutting edge and a perpendicular passing through the point where the core groove and the core thickness are in contact with each other is 37.5% of the drill diameter in a cross-section perpendicular to the axis when the twist drill is 37.5% of the drill diameter. The distance between the perpendicular passing through the hole and the perpendicular passing through the concave innermost part is 50% of the drill diameter, and the radius of curvature of the blade groove bottom is 12.5%.
Drilling was performed. The coating was performed with TiAlN.
Cutting specifications are as follows: Carbon steel S50C, cutting speed 60m / mi
n, feed rate 0.20mm / rev, hole depth 24mm
Hole processing (three times the diameter of the drill) was performed by dry cutting.
The life was determined while observing the shape of chips and the like, and checking the damage state of the cutting edge for each fixed number of processing holes.

As a result, in the example of the present invention, divided chips (transition cut type) were generated in the initial stage of cutting, the chip discharge property was good, and smooth drilling was performed. In addition, a steady state of wear occurred after the number of drilled holes. This chip form continued up to 2,000 hole machining and the amount of wear increased, but the change in chip form was small and the discharge was good. If the machining is further continued, the chips will be continuous in the 3000 hole processing, and the wear at the intersection of the drill tip and the outer periphery will increase. Since the chips became tangled and became entangled, it was judged that the life was over.

(Embodiment 2) Next, using the same drill as in Embodiment 1, the position of the inflection point was set to 40% of the drill diameter, 50%.
%, 60%, 65%, 70%, 75%, 80%, 95%
Were manufactured with a constant curvature radius of 12.5% at the bottom of the blade groove. Using SCM440 (annealed material) for work material,
The morphology of the chips was observed. Cutting specifications are 60m cutting speed
/ Min, feed rate 0.2mm / rev, hole depth 24
mm (three times the diameter of the drill) was drilled by dry cutting. The determination of the swarf form was made based on the presence or absence of a trouble in drilling up to about 500 holes. The presence / absence of a trouble was defined as the case where chips were entangled with the drill body or chips were clogged.

As a result, in the initial processing of up to about 50 holes, the test was stopped because the chip form was not stable in 40% of the samples of the comparative example and the chips were entangled. For the 95% sample of the prior art, the first 100
Chips began to extend from too much holes, and it was judged impossible. Other 50%, 60%, 65%, 70%, 75%, 8
At 0%, the shape of the chips did not change up to 500 holes, and good chip discharge was possible. Further, the test was continued and processing was performed up to 1000 holes. However, the morphology of the chips did not change and good chip discharge was performed at 60%, 65%, 70%, and 75%.
4 samples, and 80% of the samples have slightly extended chips,
It became unstable.

(Embodiment 3) Next, a die steel SK is used as a work material.
Using D61 (heat treatment material, HRC45) and a drill with an oil hole, a comparison was made between completely dry cutting, semi-dry cutting, and wet cutting. The specifications of the drill used were 65% of the present invention used in Example 2 and 95% of the conventional example. Cutting specifications are: cutting speed 30m / min,
Hole processing was performed at a feed rate of 0.15 mm / rev and a hole depth of 24 mm (three times the drill diameter). The reason why the tempered steel is used as the work material is that heat generation during cutting is higher. In semi-dry cutting, air, mist, etc. were supplied from an oil hole, and in wet cutting, water-soluble cutting oil was used and cooled so as not to affect the heat generated during cutting. The state of the cutting edge was observed at every 50-hole machining, and a change in the chip shape was confirmed.
As for the chip morphology, changes in morphology such as divided chips and continuous chips were observed, and when the chips were entangled with the drill body, the test was stopped. In complete dry cutting, the swarf form is cut off in the initial processing up to 50 holes, and the discharge is good, and the state continues up to 500 holes, but the wear increases, and the swarf continues after 600 holes As a result, the wear at the intersection of the drill tip and the outer periphery increased, and if it continued, the chips were not divided at around 800 holes, and the chips became continuous and became entangled. . Semi-dry cutting showed almost the same progress as completely dry cutting. In particular, the forced cooling by air does not have a remarkable effect as compared with the case of using a water-soluble cutting oil, and the discharge of chips is accelerated. In wet cutting, stable chips were obtained, chips cut up to 800 holes were formed, and chips were extended at 950 holes due to abrasion of the shoulder, and became entangled with the drill body. Ceased. In this way, even in dry cutting, by devising the drill blade shape, a life of about 80% can be obtained without reducing cutting data in wet cutting.

(Embodiment 4) Next, carbon steel S50 was used as the work material.
Using C (tempering material, HRC20) and the same drill as in Example 1, a concave curvature radius of 10%, 12.5%,
15%, 17.5%, and 20% samples were prepared, and the influence of the radius of curvature at the bottom of the blade groove was tested. Cutting specifications are: cutting speed 6
A hole with a hole depth of 24 mm (three times the drill diameter) was dry-cut at 0 m / min and a feed rate of 0.20 mm / rev. The chip form was determined based on the presence or absence of troubles in drilling up to about 100 holes, and the test was continued only for those having no troubles. If there is any trouble,
There were cases where chips were entangled with the drill body or chips were clogged. As a result, good chips were obtained in the initial processing up to about 500 holes. When the test was further continued, chips from the sample having a large radius of curvature became continuous, and it was determined that the sample was not acceptable. Good chip discharge was achieved with the other samples.

[0016]

By applying the present invention, divided chips, which are problems in dry cutting, can be obtained for a long period of time, and the life can be improved while maintaining chipping resistance. . In particular, in dry cutting, a chip having a stable and long life can be obtained because chips are easily entrained by chipping and chipping.

[Brief description of the drawings]

FIG. 1 shows a front view of a drill according to an embodiment of the present invention.

FIG. 2 is a front view in the axial direction of the drill of the example of the present invention.

FIG. 3 shows a cross-section perpendicular to the axis of FIG. 1;

FIG. 4 is a sectional view taken along a line perpendicular to the axis of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drill main body 2 Perimeter blade 3 Tip blade 4 Chip discharge groove 5 Land part 6 S-shape D diameter W Core thickness O Shaft center

Claims (4)

[Claims] 1. A dry cutting drill in which a hard metal and / or a lubricating coating is coated on the surface of a substrate using a cemented carbide or a TiCN-based cermet as a substrate. An inflection point is provided in the middle of a ridge line formed in a concave arc shape from the vicinity of the core thickness toward the land heel portion, and the inflection point is retracted in the direction opposite to the rotation direction of the drill, and the cutting edge is also seen in a cross section perpendicular to the axis of the drill. A drill for dry cutting, wherein the drill is retracted in a direction opposite to a rotation direction of the drill from a vicinity of a groove thickness toward a land heel portion. 2. The twist drill according to claim 1, wherein the position of the inflection point is set to 50 to 90% D of the drill diameter. 3. The dry cutting drill according to claim 1, wherein the radius of curvature of the concave portion is 10 to 2 times the drill diameter.
Drill for dry cutting, characterized in that it is 0%. 4. A hole drilling method, comprising: performing drilling by dry and / or semi-dry using the dry cutting drill according to claim 1.