JPS5850801B2 - Cutting tools for continuous metal machining and their manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to the correct geometry of cutting tools for continuous machining of metals and for special machining operations of the type used in lathes, planers, shapers or the like. The invention also relates to a cutting tool having the geometry so defined.

Up until now, the main consideration in determining the shape and dimensions of a cutting tool has been to look at the tool from the perspective of how the shape and dimensions should be.

For example, conventional tools made of carbides, such as tungsten carbide, titanium carbide, tantalum carbide, or the like, have negative rake angles and very small clearance angles, allowing them to machine almost any material. had.

The general reason for this is that carbides have extremely high red-hot hardness and compressive strength.

Negative geometries create cutting pressures that are directed into the body of the carbide tool, thereby taking advantage of the extremely high compressive strength of the carbide.

A small relief angle will support the cutting edge.

This approach overstates the compressive capabilities of carbides, creating poor cutting conditions and generating excessive heat and pressure that only tools with the high red-hot hardness and compressive strength of carbides can withstand.

Furthermore, when a compressive force is applied to the tool, an equal and opposite force is applied to the workpiece.

The minor surface damage thus generated can later lead to vibrational stresses or corrosive stresses.
This can cause major fractures in areas that are subjected to extreme stress conditions such as 5tresses.

The present invention completely breaks away from this conventional way of thinking.

According to the present invention, the appropriate rake angle is determined by the material to be machined and not by the cutting tool.

It is the properties of the workpiece that dictate the appropriate geometry of the tool, which are determined by the physical effects of external loading on the metal workpiece specimen to failure.

Cutting metal with a cutting tool is a form of destruction.

If the cutting tool cannot create such fractures, cutting will not occur.

If excessive work is required to create the fracture, heating and wear of the cutting tool, overheating of chips cut from the workpiece, and damage inflicted on the surface of the workpiece can occur.

If the metal fracture created during the cutting process is achieved with minimal work, the heating and wear of the cutting tool will be minimal, the chip temperature will be low, and the damage caused to the surface of the workpiece will be minimal. It will be limited.

As a result, cutting efficiency is optimized and tool life is extended.

The amount of work required to cut metal with a cutting tool for given cutting conditions varies depending on the geometry of the cutting tool.

In the present invention, the metal specimen to be cut is subjected to a tensile load;
causing destruction of the metal sample.

The dimensional changes resulting from fracture of the sample are measured.

From these measurements the appropriate geometry of the tool is calculated.

Tensile samples are used to determine the appropriate geometry of the cutting tool.

This is because the fracture of the metal during cutting is due to compression in the area that is in direct contact with the cutting edge of the cutting tool.
This is because the cut metal is immediately removed from the cutting area and is therefore not constrained by any metal interference that exists when subjected to normal compressive loads.

Therefore, machining the workpiece produces the same type of granular slip as would be produced by applying a tensile load to a specimen of the workpiece, and in this important respect the type of failure is the same.

According to the invention, therefore, a test bar made of the same material as the workpiece to be machined is subjected to a tensile load and destroyed.

When a tensile load is large enough to fracture the metal, the failure area takes the form of a cup-cone whose outer circumferential surface lies at an angle to the axis of the metal measured in the direction of the applied tensile force. is doing.

This angle is constant for a given metal and is generally considered to be 45 degrees.

Also, since the stress level reaches a maximum at cup-cone fracture, the region of the cup-cone exhibits greater hardness.

These maximum stress levels cause the specimen to be maximum work hardened in its cup-shaped conical region.

A metal test bar undergoes elongation and local shrinkage before its failure.

This elongation and local contraction angle vary depending on the metal and are generally determined by the ductility of the metal.

However, for a given metal, when several samples of the same material fail under a tensile load, the elongation rate and local shrinkage angle are approximately uniform.

The two forces appear to be relevant because there are two physical changes in the geometry of the test specimen: elongation and local contraction.

One is the tensile force that causes elongation, and the other is the internal tensile force within the metal that causes local shrinkage.

These two forces are perpendicular to each other because the metal produces a local contraction perpendicular to its direction of elongation due to internal attraction.

Before a tensile load is applied to the test bar and failure occurs, the material must be deformed by a certain minimum amount as a result of elongation and its local contraction in its localized contraction area.

If it is not deformed, no fracture will occur. Similarly, the metal being cut must be deformed by the same minimum amount before failure occurs in the metal workpiece being machined.

According to the invention, therefore, the cutting angle of the cutting tool required to deform the metal of the workpiece by the minimum amount required to cause failure is determined by is a function of local contraction angle and elongation.

This cutting angle is called the effective rake angle.

In conclusion, since the test specimen is work-hardened to its maximum hardness in the cup-conical region where failure occurs, and metal machining also produces this same type of failure, an appropriate effective rake angle is required. C can also be defined as the minimum angle that produces the maximum hardness of the machining chip.

Another aspect of the invention resides in the proper selection of the clearance angle of the cutting tool.

Just like the rake angle, the clearance angle of conventional tools was chosen as small as possible to maintain maximum support for the cutting edge.

This was especially true for carbide cutting tools.

On the contrary, the cutting tool of the present invention recognizes the abrasive properties of some workpiece materials and is designed to maintain the cutting edge by the abrasive action of the workpiece material during the machining process. Self-grinding is achieved by appropriate selection of the side clearance angle and front clearance angle.

To strengthen the cutting edge of the tool, a thin wear land is formed just below the cutting edge and another at the end of the cutting edge.

These lands have a substantially zero clearance angle.

When cutting a workpiece with a tool, the chips that are formed tend to erode the top surface of the tool at the cutting edge, forming a depression, and the surface of the workpiece tends to erode the wear land. be.

These erosions become larger and larger as processing continues.

The rates of these erosions are not necessarily the same and depend on the tool, the workpiece material, and the feed and speed during machining.

However, for a given material and a given feed and speed, the erosion rate of a given tool face will be constant, and the erosion rate of these wear lands will be constant, although not necessarily the same.

If the width of the wear land becomes smaller due to erosion imbalance during machining, the cutting edge becomes too sharp and unsupported.
It will break.

On the other hand, if the width of the wear land increases, a point is reached where the extra wear land causes rubbing, rattling, and tool failure.

If the width of the wear land remains constant during the machining process, the erosion on the top surface will balance the erosion on the wear land, the tool will effectively self-grind, and the tool life will be increased.

This can be achieved by appropriate selection of the lateral and front clearance angles, which is a feature of the invention.

It is therefore a principal object of the present invention to create a cutting tool with significantly improved life, having a geometry that cuts metal workpieces with minimum work and with maximum efficiency, and to define a procedure for determining the geometry. It is.

The present invention is primarily directed to a method of determining suitable geometries of geometries suitable for continuous machining of metal, and to cutting tools having the geometries so defined.

In a preferred embodiment of the invention, the invention is directed to a cutting tool made of a material with high red-hot hardness.

The implication is that the temperature at which these tools maintain their cutting effectiveness is above about 1200'F.

Such materials range from ceramics such as those based on carbides (including those of tungsten, tantalum, titanium, etc.), alumina, silica, etc., natural diamonds and synthetic diamonds, etc.

Among these materials, all of which are commonly known in the art, carbides are particularly preferred.

Such materials have been covered in many publications, including by Metcut Research A, Cincinnati, Ohio.
s5ociate, Inc.) published in 1972.
Machining Data Handbook
Data Handbook) J Volume 2, No. 789
Pages 793 to 793 may be cited.

Although the principles of the invention are understood to apply generally to tools adapted for continuous machining of metals, such as lathe tools, drills, end mills, reamers, broaches, or the like, as described below, this specification This book describes a tool for a lathe to facilitate understanding of the present invention.

As used herein, "continuous machining" refers to the generally continuous machining of metal, as often occurs with machine tools, and may or may not result in continuous chip formation.

Tools used for such machining include, for example, lathe tools, broaches, drills, end mills, and the like.

The cutting tool of the present invention is suitable for cutting tools such as those used in power-operated machines.
It is suitable for "continuous machining of metals" and therefore usually includes a support, such as a shank or rod, which is gripped by a machine tool holder, such as in a lathe tool holder.

A cutting portion of a cutting tool having a cutting edge and a cutting angle defined as described below is rigidly attached to a support of the tool.

In some cases, the cutting portion is silver-brazed or otherwise attached to the support of the cutting tool.

In other cases, such as the preferred embodiment of the invention, the cutting tool is of one material, one end of which is adapted to be attached to a metal working machine, and the other end of which is adapted to cut a metal workpiece. Contains a blade.

Each of these tool shapes is characterized by including a support for mounting the tool on a metal processing machine and a cutting portion that includes a cutting edge and a cutting angle as defined herein.

1, 2 and 3 show a cutting tool 20 for a lathe.

The tool 20 is also shown in FIG. 4 cutting the workpiece W, which illustrates the selection of the first, second and effective rake angle locations and determination of those angles. For illustrative purposes, no gaps or clearance angles are shown.

The geometry of the lathe cutting tool 20, including various angles, is described relative to the workpiece using a three-dimensional X, Y, Z coordinate system, as is common in the art.

The coordinates XY define a plane that passes through the tip of the cutting tool and the axis a of the workpiece W, and the coordinates XZ define a plane that passes through the tip of the cutting tool and is perpendicular to the XY plane and parallel to the axis a.

The coordinate YZ defines a plane that passes through the tip of the cutting tool and is orthogonal to both the XY plane and the XZ plane.

Tools having geometries defined with respect to other coordinate standards can be easily converted mathematically to the coordinates used herein.

Although the tool of the present invention is described without a chip breaker as is known in the art, it can be provided with one if desired.

The cutting tool 20 has a shank 21 and a nose 22, the nose 22 having a cutting point 23, a face 24, a bottom face 25, a front flank 26, a side face 27 and a side flank 28.

This nose 22 has a cutting edge 30 and an upper front edge 31.

As seen in Figures 1 to 3, the horizontal angle that the cutting edge 30 makes with the vertical plane indicated by the line 32 parallel to the YZ plane with respect to the coordinate system in Figure 4 is expressed as angle g. This is the side clearance angle, and the vertical angle that the side clearance surface 28 makes with the vertical surface 32 is the side clearance angle expressed as an angle.

The horizontal angle indicated by the line 35 that the upper front blade 31 makes with the vertical plane XZ is the front cutting edge angle expressed as the angle i,
The vertical angle that the front clearance surface 26 makes with the vertical surface 35 is the front clearance angle expressed as angle j.

The angle that the upper front blade 31 makes with the horizontal plane indicated by the line 36 parallel to the XY plane before forming the end edge angle i as shown in FIG. 2 is the first cutting angle or rake angle E.

The angle that the cutting edge 30 makes with the same horizontal plane indicated by line 37 before making the crosscut angle g, as best seen in FIG. 3, is the second cutting or rake angle.

This corner is defined by standard tool specifications.
Although the angle is shown as negative and the cutting edge 30 is lowered towards point 23, this angle can also be made positive so that the cutting edge 30 is raised towards point 23. , within the limits described, only the size of the angle is important.

The effective rake angle C is shown in FIG.

This is determined by calculating the combination of the first rake angle E and the second rake angle.

The magnitude of this effective rake angle C is determined by the formula C03C-CO3ECO8D based on the mathematical law of cosines.

Not all tools have a first rake angle and a second rake angle; some tools only have a first (effective) rake angle.

For tools without a second rake angle, the second rake angle is zero, so CO3D is equal to 1, and therefore the effective rake angle C is equal to the first rake angle E, i.e., the same as the first rake angle E. (See Figure 13).

In the direction of the tool in FIGS. 1-4, the workpiece to be machined passes downwardly past the tool, as seen in FIGS. 2-4, while the tool is in the second position during machining.
It is fed to the right as seen in the figure.

The nomenclature previously used to describe the tools of FIGS. 1-4 will also be used below where appropriate to describe other embodiments of the invention.

How to determine the size of the most important angle, the effective rake angle C, will be explained below in accordance with the present invention.

Cutting or machining material from a metal workpiece is accomplished by creating fractures in the metal.

If the cutting tool cannot create that fracture, no cutting will take place.

It has been found that the tool life is directly related to the amount of work required to create its fracture during the machining process.

For a given workpiece and a given machining operation, the more work is required to create a fracture, the shorter the tool life will be; The less work there is, the longer the tool life will be.

Therefore, tool life is maximized when cutting or breaking is performed with the least amount of work and maximum efficiency.

The amount of work required to cut metal with a cutting tool at predetermined set cutting conditions, such as feed and cutting speed, varies depending on the geometry of the tool.

The basic idea of the invention is to determine the geometry of the tool directly from the properties of the metal to be cut, in particular from a metal specimen subjected to tensile loads that lead to fracture.

Some of the changes that occur in a metal sample when subjected to a fracture load are directly related to the changes that occur in the metal workpiece when it is cut or machined.

Because of these relationships, the effective rake angle C is determined by measuring the change in physical properties that results from failure of a specimen subjected to a tensile load.

We will discuss whether these relationships are correct or not, but first we will explain the procedure for determining this angle according to the present invention.

FIG. 5 shows a rod 45, the ends 46 and 47 of which are held in a tensile loading device (not shown) for loading the rod 45 until it breaks.

To determine the initial value li of the bar section before loading, two
56 and 57.

FIG. 6 diagrammatically shows the state of the rod 45 at the time of destruction.

Characteristically, two parts 48 and 4 created by destruction
9 is elongated, and on the opposite side of the failure there are locally contracted sections 50 and 51, the surface angle of each locally contracted section measured from the axis of the applied tensile force being expressed as the angulation.

If actual fracture occurs, an internal frustoconical well 52 is first formed on section 48 and then a complementary external frustoconical section 53 is formed at the end of section 49.

Reference numerals 56 and 57 are located at position 56 on the surface of the local shrinkage region.
' and extended to 5T.

The distance between the symbols, designated 56/ and 5T in FIG. 6, is measured parallel to the axis of rod 45 and is llf.

However, the symbols 56' and 57' within the local shrinkage region
The true elongated distance between is At.

According to the invention, the effective rake angle C of the tool is expressed by the formula C03C
: ! j cosl).

The angularity can be measured directly from the test bar shown in Fig. 6, and li can be measured from the test bar shown in Fig. 5.

However, for Ilf there is no guarantee that codes such as 56 and 57 will be within local shrinkage when stretched; what is needed is a measurement of the local shrinkage or elongation within the rupture region.

Furthermore, a rod of uniform cross-sectional area, such as rod 45, may have several regions of localized contraction or partial localized contraction regions;
Makes elongation measurements unreliable.

To obtain accurate elongation measurements, a rod such as rod 62 shown in FIGS. 7 and 8 is used.

This rod 62 has an annular groove 63 in order to localize the area where failure occurs during tensile loading.

Ends 64 and 65 of rod 62 are gripped by a tensile loading device (not shown) to create fracture 66 shown in FIG.
into two parts 67 and 68.

The distance between the edges 69 and 70 of the annular groove 63 before elongation is Ai
and the stretched distance between these edges 69 and 70 is If as shown in FIG.

Since the rod 62 has a localized region (annular groove 63) where failure occurs, li and lf can be measured accurately.

Therefore, the dimensions li and Iff are determined by loading the rod 62 to break it and measuring the length of the notch before and after the load, and the angle is determined by loading the rod 45 to break it and directly measuring the local shrinkage angle. It is measured by

The effective rake angle is then calculated using the formula C03C=! -j C03D
It can be calculated from

If Figure 9 shows J? regarding the three-dimensional coordinate axes X, Y, and Z? i, 7
The geometric relationship between f, lf is shown vectorially, with the X coordinate parallel to the axis of the test sample.

If a metal specimen of length li is deflected by a force fxy until an angle E, a new length lf is reached.

The difference between lf and 21 is caused by local shrinkage, and since local shrinkage is created by an internal force in the metal with a direction perpendicular to the applied tensile force, the force fXZ applied to the new length lf until the corner is Make the length lt.

The forces fxy and fXZ are at right angles to each other, and fxy is xy
In the diagram, fXZ is parallel to the XZ plane and perpendicular to the XY plane.

The resultant of these forces creates an angle C between the initial length Ai before elongation and the true length 7f after fracture.

Therefore, from FIG. 9, C03C-'-j, C03E
=! j.

C03D −”-t?,, i”wa GcO3c = cos
It can be seen that the temperature is 31lt - cos1).

Since the effective rake angle Cf is determined in this way, the first and second rake angles E and D can be varied within practical limits as long as they are equal to their cosine product force zos C.

These practical limits are related to angles and are
This can best be explained with reference to FIGS. 0 to 12.

FIG. 10 shows a cutting tool 71 with a cutting edge 72 and a second rake angle equal to zero.

This tool 71 is shown cutting a metal workpiece W, and the width of the cutting, that is, the depth of cut is chip d.
epth) is indicated by d.

The direction of rotation of the workpiece W is indicated by the arrow 73, and the tool is viewed as looking into the headstock of the lathe as if it were feeding toward the headstock.

Since the second rake angle is equal to zero, the cutting tool 71 applies one force M to the workpiece W, but it is applied in one direction roughly limited to the area of cutting, i.e., the depth of cut, so that it is extremely Only a small amount of energy is wasted in unnecessarily deforming the workpiece.

A force M' equal in magnitude and opposite in direction to this force M is applied to the tip of the tool in the direction shown.

Zeroing the corner limits the deformation of the workpiece to approximately the area of the chip and at the same time utilizes the compressive strength of the tool to reduce the possibility of chipping or fracture at the tip of the tool. and providing sufficient mass in the cutting area to conduct heat away from the cutting edge is considered one satisfactory solution.

FIG. 11 is generally the same as FIG. 10 except that the cutting tool 74 has a cutting edge 75 and a positive second rake angle.

If the angle is positive, tool 74 is superior to tool 71 because it provides a more reliable confinement of the deformation of workpiece W to the area of the chip illustrated by the direction of force N;
This is disadvantageous because a force N', equal in magnitude and opposite in direction to force N, is applied to the tip of the tool, which is susceptible to chipping or breaking.

Also, as the corners become more positive, there is less and less mass in the cutting area of the tool to conduct heat away from the cutting edge.

Although a small positive angle is desirable to minimize energy dissipation caused by unnecessary workpiece deformation, its size reduces the compression capacity at the tip of the tool, making angle B more positive. In order to reduce the mass conducting heat as the

FIG. 12 is similar to FIGS. 10 and 11 except that the cutting tool 76 has a cutting edge 77 and a negative second rake angle.
It looks very similar to the figure.

If the corner is negative, cutting tool 76 applies a force R to the workpiece as shown, which force R deforms region 78 of the workpiece beyond the depth of cut compared to cutting tools 71 and 74.

This is a consumption of energy and cutting tools 71 and 7
It is more disadvantageous than 4.

However, tool 76 is advantageous because it applies a force R' equal in magnitude and opposite in direction to force R in a direction in which the compressive strength of the tool is utilized to a greater extent than is the case with tool 71.

Tool 76 also provides more mass to the cutting area than tool 74 to conduct heat away from the cutting edge.

As the angle becomes more negative, as indicated by the dashed line, to angle -D', more energy is expended due to this deformation as indicated by the direction of the force S.

Therefore, in some applications, it is desirable to have a small negative radius to take advantage of the compressive strength of the tool, reduce the possibility of tip chipping, and add more mass to conduct heat. However, its size must be limited to avoid excessive deformation of the workpiece.

Even if a positive or negative corner is desired, a small magnitude is generally sufficient.

For example, angles with a size of 10 degrees or less are most common.

13-16 illustrate another embodiment of the invention having a cutting tool 80. FIG.

This cutting tool 80 is shown without the second rake angle and the side edge angle g for clarity.

Cutting tool 80 has a shank 81 , a nose 82 having a cutting point 83 , a surface 84 , a bottom surface 85 , a cutting edge 86 , and an upper front edge 87 .

Since the second rake angle is zero, the first rake angle E is the first
This is the same as the effective rake angle C shown in FIG.

In this orientation of the tool in FIGS. 13-16, the workpiece to be machined moves past the tool in a downward direction, as seen in FIGS. 13, 14, and 16, and the tool During processing, it is sent to the right as seen in Figure 15.

As best shown in FIG.
4, but is offset at its upper end just below the cutting edge 86 to form a narrow lateral land 91.

This lateral land 91 has a width indicated by Xi shown in FIG. 14 and a lateral relief angle of substantially zero.

The remaining part 9 of the side relief 90 directly below the side land 91
2 has a lateral relief angle hi.

Similarly, as best shown in FIGS. 13 and 16, the tool 80 has a point formed in what is called an end land having a width designated by X2 and a front clearance angle of substantially zero. It has a front flank surface 95 with an upper portion 96 near 83 .

The remaining portion 98 of this front clearance surface 95 is formed with a front clearance angle ji.

Note that while lateral land 91 extends substantially all the way across the top of nose 82, front land 96 is only a small, generally triangular surface formed near portion 83.

This is because almost the entire lateral land 91 comes into contact with the workpiece during the machining process, but only a very small portion at the top of the front flank, which is the size of the front land 96, contacts the front cutting edge angle i of the tool 80.
This is because it actually comes into contact with the work piece due to the contact (see FIG. 15).

There are two reasons why the side relief surface 90 and the front relief surface 95 are formed to have a clearance angle with the land surface as shown.

First, forming the cutting tool in this manner strengthens the cutting edge 86 and cutting point 83 to prevent chips from being formed during the machining process under very high loads.

This is distantly related to excellent results with small and hard tool materials such as high-speed steel tools, but it can also be seen when cutting tools are made of very hard and brittle materials such as carbide tools. is particularly important.

A second important reason relates to the processing of relatively highly abrasive materials, such as Al5I4340 steel.

When machining highly abrasive materials, such as the types of materials described above, chips formed from the material during machining wear down the face of the cutting tool near the cutting edge 86.

This erosion continues until it creates a crater in the face 84 of the cutting tool.

The dashed line generally designated 100 in FIG. 16 indicates the cutting tool near its cutting edge during the divine erosion stage.

In cutting tools that have a negative effective cutting angle or a relatively small effective cutting angle, such as less than 10 degrees, chips from the abrasive material create a force in a direction that tends to break the cutting edge.

When this occurs, the tool will fail rapidly, resulting in a severely shortened tool life.

In addition to eroding the surface 84 of the tool, the abrasive chips also attack the cutting edge 8.
The side relief surface 90 near point 6 and the front relief surface 95 near point 83 are eroded because these areas are in contact with the workpiece during the machining operation.

Dashed lines 105 and solid lines 106 in FIG. 13 each illustrate these latter types of erosion at various stages during the processing process.

Erosion of the side and front relief surfaces 90 and 95 occurs regardless of whether the side and front lands and flanks are formed in accordance with this embodiment of the invention.

However, if not formed as such, as these erosions occur, if the clearance angles of the lateral and front flanks are improperly chosen, any erosion 100 on the face of the tool will cause the lateral flank and erosions 105 and 106 on the front flanks 90 and 95 occur at such a rate that they tend to sharpen the cutting edge, so that it eventually becomes unsupported and breaks off. , or the erosions 105 and 106 are too large compared to the erosion 100, so the widths X1 and X2 of the lateral land 91 and the front land 96 are gradually increased.

If these widths become too large, the cutting tool will begin to rub, become stiff, and eventually fail.

According to the invention, therefore, the second lateral clearance angle hi and the front clearance angle Ji are selected such that the widths of the lateral lands 91 and the front lands 96 remain constant during the machining process.

In other words, if the angles hi and ji and the widths X, A blade 86 is made.

The widths X1 and X2 for a given tool material and a given workpiece material are determined by the feed and speed used in the machining operation.

The higher the speed and feed, the higher the land 91 and 96.
As the erosion becomes larger and larger, the width must also become larger.

However, generally for a given feed and speed, the width
1 and X2 must be chosen such that they are not so small that the cutting edge is subjected to heavy loads during machining and cuts, but not so large that they rub and rattle, almost immediately ruining the tool.

Numerical examples for Xl and X2 are given in actual test results as described below.

Once the widths X1 and X2 are determined, it is necessary to correctly determine the lateral clearance angle hi and the front clearance angle ji.

As mentioned above, if the widths X1 and X2 are constant during the machining operation, the side relief angle hi and the front relief angle ji are selected correctly.

Referring to the enlarged view in Figure 16 and remembering that the erosion rate is constant for a given combination of tool material and workpiece material and feed and speed, if the side relief angle hi is too small, continues to increase during the machining operation until it becomes so large that rubbing and rattling occur, ruining the tool.

If the other angle hi is too large, the width X1 will remain in the range during the machining operation until the cutting edge 86 becomes weak and breaks.

Therefore, in order to choose an appropriate angle hi for a given tool material, a given workpiece material, and a given feed and speed, the width
It is only necessary by trial and error to selectively vary the angle hi until 1 remains constant.

The same method is used to select the appropriate front relief angle ji.

Examples giving specific values for hi and ji are set forth in the test results described below.

What has been described above is a description of the cutting tool of the present invention and the method of determining the effective rake angle and clearance angle of the tool in accordance with the present invention.

In order to further appreciate the advancement that this invention represents in the field, the following are proposed as theories or scientific principles that explain how the invention may therefore be practiced as described herein.

FIG. 17 is a composite drawing showing the nose of a lathe tool, such as nose 22 of tool 20 or nose 82 of tool 80.

The workpiece W and chips P are also shown there.

The workpiece W is moved downwardly into the cutting edge of the tool as seen in FIG.

Above it, a portion of a tensile test sample, such as sample 45 of FIG. 5, is superimposed before loading, and a cross-section of the test sample is shown after it has failed under the tensile load.

The cup-like fracture shape 52 previously described with respect to FIG. 6 is aligned with the cut fracture line 110.

The direction of the cut break line 110 and the coincident cup break line is represented by an angle F with respect to a line 111 at the point of the tool where that line is parallel to the axes of the workpiece W and the test sample 45.

This line 111 is the same as the X axis in FIG.

The angle F is considered to be constant for a given material, generally 45 degrees, but as the particle size changes this angle may deviate from its value.

As far as this description is concerned, it is only important that the angle F is constant for a given material.

Points 56 and 57 are also shown on the test sample 45 before loading, the distance between these points being expressed as the initial length Ai, and the local area of the test sample after fracture under tensile load. Points 56' and 57' are located in the contracted region, and the distance between these points is the true length Xt.

These are the same points as shown and described with respect to FIGS. 8-8.

According to the invention, the cosine of the effective rake angle C is li/l! t
It is said to be equal to the ratio of

Referring to the enlarged view of FIG. 18, tensile sample 45 before loading.
The length li of the cup-shaped conical region of is determined from points 56 and 57 to point 56/ after the tensile specimen is loaded and fractured.
and 57', ie, the true length lt.

This new length 21 is the true elongation length, which is the length 11
Failure of the test sample does not occur until the length Xt is extended.

Fracture occurs when the length lt is reached under the influence of both linear elongation and local shrinkage under a tensile load.

If the tensile load is removed just before the length lt is reached, the sample will not fail in tension.

Comparatively, when the tensile force becomes large enough to reach the length Xt, the fracture is unstoppable and complete.

The amount of work required to achieve a length of 21 is a measure of the minimum work expended to break a tensile specimen.

As with test sample 45, in order for a break to occur in the workpiece W as required for machining, the material to be machined must be moved and elongated from the initial length li to the true length 11.

Otherwise, breakage will not occur and the work piece will not be machined.

If the initial width of the chip from the workpiece before failure, which is the same as the tool feed, is transferred to a new length 21 with 7i, the minimum work is done to create the failure condition along line 110. It was done.

Since the initial length 7i has to be transferred to the true length 21 as shown in FIG. 18, the effective rake angle C of the cutting tool is the angle between li and lt or.

. It is automatically determined as 8C=l i. 1 Therefore, the cutting tool has an effective rake angle such that C03C='-i- is the exact effective rake angle required to extend the initial length Ai to length lt, and it is This is the minimum amount that must be done to process the material without causing destruction.

A cutting tool with an effective rake angle thus defined requires minimal work to cause failure, resulting in increased efficiency and tool life.

As a result of this, the metal of the tensile sample 45 in the cup-shaped conical region 52 was found to be much harder than the metal elsewhere in the sample after being subjected to a tensile load and fractured.

In fact, it has been found that the metal in the cup-conical region is work hardened to maximum hardness for the particular metal.

It has also been found that if a suitable angle C is used in the cutting tool, the chips P formed thereby will be work hardened to a maximum hardness for the particular material of the workpiece.

This is clear by analyzing Figures 17 and 18, and the fracture characteristics of the workpiece during machining are the same as the fracture characteristics of the sample in the cup-shaped conical region when it is fractured by applying a tensile load. It is.

Excessive work in causing fracture is believed to generate excess heat and deform the grain structure of the metal, reducing chip hardness.

According to the invention, therefore, the appropriate angle C is the smallest angle that produces the maximum hardness of the chip.

This is determined by gradually increasing the angle C during machining of a specific metal and measuring the hardness of the chips.

If the chips do not become any harder, the value of C is appropriate.

We believe that the foregoing accurately describes the basic theory of why the present invention works as described above to create an excellent cutting tool with greatly increased tool life; Its properties have been proven through actual tests.

In these tests, carbide tools having dimensions defined in accordance with the present invention were compared with conventional carbide tools having conventional dimensions.

Generally, this test is performed on four different materials, namely 303
It included processing of type stainless steel, Al5I4340 steel heat treated to Rockwell C50-31, Al511042 steel and titanium alloy Ti-6AA-4V.

In all of the tests, both the conventional cutting tool and the tool according to the invention were made of tungsten carbide, in particular V.R. Wesson Company.
It was RAMET 1.

All tools were ordered from special lofts, and each individual tool was randomly selected and ground to a specific geometry.

All tests were conducted on the same lathe with a feed of 0.011 cIrL (0.004 inch) and a depth of cut of 0.075 inch (1.91 cm).

Speeds vary depending on the material being processed and are provided by Metcut Research As5, compiled under contract with the U.S. Government.
The speeds were set as recommended in the ``Machining Data Handbook 11972 Edition'' published by Co., Ltd.

All pieces of the same diameter of the same material were rotated at the same speed.

No coolant was used in any of the tests.

The geometries used for conventional tools were specified in the handbook and were the same for all conventional tools, regardless of which of the four materials mentioned above was being processed.

The geometries of each conventional tool used in these tests were as follows.

First rake (side rake) angle E = -5° Second rake (rear rake) angle D = -5° Front relief angle j = 5° Side relief angle h = 5° Side cutting edge angle g = 30' Front cutting Blade Angle 1 = 30° The cutting edge angle was specified in the handbook as 15 degrees, but was changed to accommodate the tool holder used.

This change did not appear to have affected the results of the tests, and the same cutting edge angle was used in each case for the tools of the invention.

For each test, ie for each one of the four materials, all of the workpieces had the same dimensions and were cut from one bar.

In addition, the test specimens used to determine the tool geometry for the tools of the present invention were also cut from the same bar under nine tensile loads to failure.

For each of the four tests, the sample from the bar was tested at test bar 4.
5 and 62, and the fracture tensile load was applied as described above.

The local shrinkage angle, initial length Ai, and final length 7f were measured.

From these measurements, the effective rake angle C was calculated according to the invention and the tool of the invention was ground.

In the manner described above, the lateral clearance angles hi and front clearance angles ji and the widths X1 and X2 of the lateral lands 91 and end lands 96 were selected from previous tests.

According to the invention, the clearance angle and land width are not the same for each of the tests due to the different materials of the workpiece being machined and the different speeds used.

The clearance angle for lateral lands 91 and 96 was essentially zero for all tests.

All results are given in cutting bar length in inches.

Each tool was destroyed unless otherwise stated.

The word "cutting" along with the number means that the tool is still cutting when the test is stopped, such as when the rod is used up.

Exam 1 The material processed was Type 303 stainless steel.

The dimensions of the conventional tool were as described above, and the dimensions of the tool of the present invention were as follows.

Effective rake angle C = 46° First rake angle E = 46° Second rake angle D = 0' Lateral and front land widths X1 and X2 - 0.0127cI
rL (0,005 inches) Lateral and front clearance angles hi and ji = 15° Four types of tools were tested and tabulated as follows:

It seems that the reason why the next tool A8 had a bad result was because that tool had a defect.

Test 2 The processed material is Rockwell
l) Al5I4340 heat treated to C30-31
It was steel.

The dimensions of the conventional tool were as described above, and the dimensions of the tool of the present invention were as follows.

Side and front land width X1 and X2 - 0.0254cr
IL (o, oi inches) Lateral and front relief angles hi and ji = 22° Five conventional tools and four inventive tools were tested.

The results are tabulated as follows. Things to keep in mind are:
When the test was stopped, all the conventional tools were dead and all the inventive tools were cutting.

The average life of the conventional tool is 50.8 cIIL (20 inches) and for the tool of the present invention it is 81.92 cIrL.
(32% inch) and was still cutting.

Exam 3 The processed material was Al511042 steel.

The shape and dimensions of the conventional tool were as described above, and the shape method of the tool of the present invention was as follows.

Effective rake angle C-44° First rake angle E=44° Second rake angle D=O.

Side and front land widths X1 and X2 - 0.0127Cr
rL (0,005 inches) Lateral and front clearance angles h1 and ji = 20° Four tools of each type were tested and the results are tabulated as follows.

Again, it should be noted that when the test was stopped, all the conventional tools had failed, while the inventive tool was still cutting.

Test 4 The processed material was titanium alloy Ti-6A14v.

This material was chosen because it is extremely difficult to process.

The dimensions of the conventional tool were as described above, and the dimensions of the tool of the present invention were as follows.

For tools 4 and 5: Effective rake angle C-33° First rake angle E-33° Second rake angle D=00 Lateral and front land widths X1 and X2 = 0.0127 cr
rL (0,005 inches) Lateral and front clearance angles hi and ji = 20' For tools 6 and 7: Effective rake angle C-33° First rake angle E-32° Second rake angle D = -12V2° Side and front land widths X1 and X2 - 0.0127Cr
rL (0,005 inches) Lateral and Front Relief Angle hi and ji = 20° This test was certified by an independent testing laboratory.

Three conventional tools and four tools of the invention were tested and the results are tabulated as follows.

Several things can be noticed from these test results.

One is a complete departure from the rake and relief angles traditionally taught to use with tungsten carbide tools.

The above handbook covers all these materials.
The effective rake angle for the tool of the present invention for machining these materials ranges from 32 degrees to 46 degrees, with a difference of 39 degrees to 53 degrees.

The clearance angle taught by the handbook for machining these materials is 5 degrees, but the clearance angle of the present tool for these same materials ranges from 15 degrees to 22 degrees.

The use of such large rake and relief angles for carbide tools and tools of high red-hot hardness in general goes directly against the teachings of the prior art.

This means that the effective rake angle C(
By the graph in Figure 19 showing a plot of %) vs. true elongation (%) or 1t-11i x 100,
Further examples will be given.

Curve 120 illustrates this relationship for a tool of the invention, including a carbide tool, where C03C--.

t This curve 120 starts at zero and progresses in the positive direction, representing a zero angle C for a material with no true elongation and zero malleability.

The slope of the curve 120 is relatively small when the true elongation is below 10%, and gradually increases when the true elongation is above 10%.

With the exception of very brittle metals such as brittle cast iron and high carbon steel, many metals have true elongation of greater than 10%.

These include mild and alloyed steels and most non-ferrous metals such as aluminum, stainless steel, copper, titanium, magnesium, etc.

The angle C according to curve 120 is always positive and the true elongation is 10%
At least 24 degrees for all metals listed above.

In comparison, points 121-124 indicate the effective rake angle C for carbide tools recommended by the Machining Data Handbook for cutting the metals used in the tests described above.

These angles are each negative 7 degrees, illustrating the complete offset that the present invention exhibits over the prior art.

We have therefore described a novel cutting tool having a geometry for machining metal workpieces with minimal work, maximum efficiency and greatly improved tool life, and a novel method for determining the correct geometry for this tool. .

It will be readily apparent to those skilled in the art that various modifications and variations may be made to the present invention.

Such variations are within the scope of the invention as defined in the claims.

[Brief explanation of drawings]

1 is a partial plan view of a lathe cutting tool of the present invention having first and second rake angles, FIG. 2 is a front view of the tool shown in FIG. 1, and FIG. 3 is a top view of the tool shown in FIG. 1. 4 is a partial isometric view of the tool of FIG. 1, but without the lateral and front cutting edge angles or relief angles, and shows the geometry of the tool with respect to the coordinate system of the workpiece. , FIG. 5 is a side view of a metal test rod sample of the same material as that to be cut, and FIG. 6 is an enlarged side view of the test rod sample of FIG. Figure 8 is a side view of another test bar specimen with a reduced cross-section area to isolate the plane in which failure occurs; Figure 8 is a side view of the test bar specimen of Figure 7 which subsequently fails under tensile load. FIG. 9 is a three-dimensional geometrical diagram showing the relationship between the first rake angle, the second rake angle, and the effective rake angle, and the relationship between the application of force at the time of metal fracture, and FIGS. 10 and 11. 12 and 12 are side views of a cutting tool for cutting a workpiece for the purpose of illustrating practical limits on the magnitude of the second rake angle, and FIG. 13 is a side view of a lathe tool according to another embodiment of the invention. A front view, FIG. 14 is a fragmentary right side view of the tool shown in FIG. 13, FIG. 15 is a fragmentary plan view of the tool shown in FIG. 13, and FIG. 16 is an enlarged view of the tip of the tool shown in FIG. 13. Fig. 17 is a composite diagram showing the bit, work piece, and chips of a lathe tool together with a tensile test sample before and after fracture to explain the present invention in detail, and Fig. 18 is an enlarged view of the central part of Fig. 17. , and FIG. 19 are graphs showing the relationship between the effective rake angle of the cutting tool and the true percent elongation of the material when the tool of the present invention and the conventional tool are subjected to a destructive tensile load. 20...Cutting tool for lathe, 21...Shank, 22...Nose, 23...Cutting point, 24...Face, 25・・・・・・Bottom surface, 2
6... Relief surface, 27... Side surface, 28.
... Side flank surface, 30 ... Cutting edge, 31 ...
... Upper front blade, 45, 62 ... Rod, 52
, 53... truncated cone portion, 56, 57, 56', 57'... code, 69°70... edge.

Claims (1)

Claims: 1. A cutting edge made of a material that maintains cutting effectiveness at temperatures above about 649°C (1200'F) and having an effective rake angle substantially defined in accordance with EC03C''jf CO3D. Cutting tools for continuous metal machining (however,
In the above equation, C is the effective rake angle of the cutting tool, h is the ratio of the initial length to the final length of the metal specimen to be machined when the destructive tensile load is measured parallel to the applied load, and D is the local shrinkage angle of the test specimen in the fracture area after being fractured by applying a tensile load). 2 The characteristic Il where ′i is measured in a part of the specimen in the fracture region
f. A cutting tool as set forth in claim 1. 3. The cutting tool according to claim 1, which has a carbide cutting edge. 4. The cutting tool according to claim 3, wherein the effective rake angle C is 20 degrees or more. 5 having a lateral wear land surface and a lateral relief surface, wherein the clearance angle of the lateral land surface is substantially zero, and the lateral relief angle is such that when the tool is used to machine a workpiece, the lateral land The cutting tool according to claim 1, wherein the width of the surface is made constant. 6. The tool further comprises a front wear land surface and a front clearance surface, wherein a clearance angle of the front wear land surface is substantially zero, and a clearance angle of the front clearance surface is used for the tool to machine a workpiece. 6. The cutting tool according to claim 5, wherein the width of the front wear land surface is kept constant during cutting.