CN117680774A - Screw thread turning blade - Google Patents

Abstract

The invention discloses a thread turning blade, which comprises a body and an angle cutting edge, wherein the angle cutting edge is formed on the outer edge of the body and is matched with a thread groove, and the angle cutting edge is provided with an edge center line; the two edge parts of the angle cutting edge are inwards offset along the edge center line on the upper surface of the body, and a front edge surface, a chip pocket and a first protruding part are sequentially formed; the front cutting surface and the chip flute incline inwards along the cutting center line and towards the lower surface of the body by a certain angle; the first protruding part extends upwards in an inclined mode from the lowest position of the chip flute, and at least one straight surface section is formed at a position higher than the front cutting edge surface so that chips move along the straight surface section; the invention provides a thread turning blade which is simple in structure, simple and convenient to manufacture, easy to realize and low in cost, and solves the problems that the existing thread cutting blade is difficult to roll up scraps, break scraps and large in cutting force and is easy to vibrate and collapse in the machining process.

Description

Screw thread turning blade

Technical Field

The invention relates to the technical field of cutter production, in particular to a thread turning blade.

Background

The thread turning machining is a thread groove machining mode widely used at present, and various industries have popularized automatic production lines successively, so that the thread turning cutter is required to meet the conditions of light and rapid chip breaking, smooth chip removal, stable service life and the like in order to ensure high-quality and efficient machining; because the thread processing relates to various industries, the material types and the machine tools are numerous, the chip breaking and chip removal of the thread turning processing become a big problem; on the other hand, as the overall metal removal amount and feeding of the thread processing are larger, the processing of multi-step feed forming is generally adopted, the cutting depth of each cutter is larger at the position of the front half section of the processing actually participating in cutting, the thickness of processed chips is larger, the effects of chip breaking and chip removal are relatively easy to achieve through the curling of the front cutter surface, and the position of the rear half section actually participating in cutting is longer (namely the area participating in cutting is larger) along with the continuous increase of the total cutting depth, so that the cutting force is larger; in order to reduce the cutting force, the cutting depth of each tool is generally gradually reduced, so that the cutting chips are thinned, the bending strength is reduced, the smaller the curvature radius of the fracture is, the cutting chips are not easy to form through the front tool surface, and the cutting chips are easy to wind a workpiece or a tool bar; as the workpiece rotates at a high speed, a tool nose is easy to strike or the tool nose is processed until the processed chip forms unstable processing, the chipping or the service life is unstable, the surface of the workpiece is scraped by the chip, and the dimensional accuracy is reduced;

moreover, as the cutting depth of the second half section is smaller, extrusion processing is easy to occur, especially for the condition that some softer or sticky materials are easy to generate built-up bits, the generation and periodical falling of the built-up bits are known to most easily cause the breakage of a cutting edge of a cutter, thereby influencing the service life of the cutter and the finish of a workpiece;

in order to reduce the risk, chip breakers are designed on screw thread cutting inserts by commercial manufacturers, which include the following modes, such as through slot design, boss design or groove design, which can reduce the risk in a certain aspect but still cannot meet the processing requirements, and are as follows: although the through groove design can well achieve smooth chip removal, the problem of chip breaking and chip accumulation at the latter half of thread turning cannot be solved; while the boss design can solve the chip breaking problem, the limitation is larger, and the design has the defect that the corresponding cutting force is larger, the vibration is easy to occur, the vibration in the processing process directly affects the surface smoothness, and the risk of cutter breakage is easy to cause; the third is that the recess design can effectual improvement sharpness, is applicable to the processing of soft material, but again can't solve the disconnected bits problem of latter half.

In view of the above, there is a need for further improvements in existing screw cutting inserts.

Disclosure of Invention

The invention aims to overcome the defects or problems in the background art and provide the thread turning blade which has the advantages of simple structure, simple and convenient manufacture, easy realization and low cost, and solves the problems that the existing thread cutting blade is difficult to roll scraps, break scraps and have large cutting force and easy vibration and tipping in the processing process.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

a screw thread turning insert comprising a body, an angle cutting edge formed at an outer edge of the body and adapted to a thread groove, the angle cutting edge having an edge centerline; the two edge parts of the angle cutting edge are inwards offset along the edge center line on the upper surface of the body, and a front edge surface, a chip pocket and a first protruding part are sequentially formed; the front cutting surface and the chip flute incline inwards along the cutting center line and towards the lower surface of the body by a certain angle; the first projection extends obliquely upward from the lowest position of the chip flute and forms at least one straight section at a position higher than the rake surface to move chips along the straight section.

Preferably, the two edge portions of the corner cutting edge are respectively in cambered surface transition with the connecting position of the outer edge of the body, and the distance from the cambered surface to the first protruding portion is smaller than the distance from the intersecting position of the two edge portions to the first protruding portion.

Preferably, the chip flute is formed in a trapezoid shape in cross section along the blade center line, and the flute bottom of the chip flute is arranged obliquely downwards from a position close to the intersection of the two blade parts to the first protruding part.

Preferably, the surface of the flute that meets the rake surface is configured as an abutment surface, and the abutment surface is disposed obliquely.

Preferably, the transverse section of the chip flute is triangular or trapezoidal; the flute depth of the chip flute is 0.02-0.2mm, and the distance from the edge of the adjacent surface to the intersection position of the two cutting edges is 0.1-0.5mm.

Preferably, the chip guiding surface of the first protruding part extends obliquely along the edge center line to the inner streamline of the body, and forms a transitional cambered surface section, a straight surface section, a leading-in section and a tail extending section which are sequentially connected; the transition cambered surface section is smoothly connected with the chip flute, and the straight surface section is positioned between the transition cambered surface section and the leading-in section; the lead-in section has an arc and borders the last extension section.

Preferably, the body is further provided with at least two second protruding parts, and the two second protruding parts are symmetrically arranged at two sides of the first protruding part by the center line of the blade; convex surfaces of the two second protruding parts for rolling scraps incline towards the intersection positions of the two edge parts respectively and form an acute angle with the center line of the edge, so that the rolling scraps are gathered towards the intersection positions of the two edge parts.

Preferably, the highest position of the second protrusion is lower than the highest position of the last extension and higher than the lowest position of the last extension.

Preferably, the body is further provided with a chip guiding protruding portion, which is disposed on a side surface of the second protruding portion, and the height of the chip guiding protruding portion is greater than that of the second protruding portion.

Preferably, the included angle between the straight section and the upper surface of the body ranges from 10 degrees to 35 degrees.

From the above description of the present invention, compared with the prior art, the present invention has the following advantages:

(1) The invention provides a thread turning blade which has the advantages of simple structure, simple and convenient manufacture, easy realization and low cost, and solves the problems of difficult chip rolling, chip breaking, large cutting force and easy vibration and tipping of the existing thread cutting blade in the processing process; the chip collecting and removing device has the advantages that the front cutting edge face, the chip containing groove and the first protruding part are formed on the upper surface of the body in an inward offset mode along the central line of the cutting edge, chip collecting, chip rolling, chip removing and the like of chips are controlled in the cutting process, and the contact area between the chips and the front cutting edge face generated in the machining process is reduced through the design of the chip containing groove, so that the cutting force is reduced, and the machining vibration can be effectively reduced; in addition, after falling in the chip flute, the chips move upwards from the flute body to the first protruding part, so that the flow direction and curling of the chips are controlled, and the chips are effectively prevented from scraping the machined surface due to random movement or moving to carry out secondary cutting on the machined surface; moreover, the chip moving upwards from the chip flute moves upwards in an inclined mode along the first protruding part, the chip is guided to extend to the rear side further through the action of the straight surface section, the cutting force is greatly reduced, especially in the second half section of the machined thread (namely, the stage with the large area of the corner cutting edge involved in cutting), the cutting force in the stage is large, the machining difficulty is high, vibration and tipping occur due to the large cutting force when feeding is performed at a slightly large point, the feeding amount is small, rolling is difficult, and extrusion and chip accumulation are generated.

(2) According to the invention, the two edge parts of the corner cutting edge are respectively in cambered surface transition with the connecting position of the outer edge of the body, and the distance from the cambered surface to the first protruding part is smaller than the distance from the intersecting position of the two edge parts to the first protruding part, so that during the second half processing, the cutting chips at the two edge parts of the corner cutting edge and the cambered surface transition position connected with the trimming edge can flow to the first protruding part faster, the curling of the rear part of the cutting chips is ensured, and the cutting chips at the intersecting position of the two edge parts pass through the chip pocket and then reach the first protruding part, so that the cutting force can be effectively reduced.

(3) The chip pocket is formed into a trapezoid along the cross section of the central line of the blade, and the bottom of the chip pocket is obliquely arranged downwards from the intersection position of two blade parts to the first protruding part; in addition, the transverse section of the chip flute is triangular or trapezoidal; the depth of the chip flute is 0.02-0.2mm, the distance from the edge of the adjacent surface to the intersection position of the two cutting edges is 0.1-0.5mm, the chip flute is arranged in a trapezoid shape, the cross section of the chip flute is triangular, chips can be controlled to enter the chip flute, sharpness of a cutting edge can be guaranteed, cutting force is reduced, machining vibration is reduced, friction between the chips and a rake face is reduced, crater wear is reduced, the chips can be effectively transmitted to the rear part in the latter half of thread machining, and more importantly, the integral strength and stability can be guaranteed; on the other hand, the storage and the flowing of the cooling liquid are facilitated, more heat is taken away, and the cooling effect is better.

(4) The first protruding part is provided with a transitional cambered surface section, a straight surface section, a leading-in section and a tail extension section which are sequentially connected; the first protrusions are symmetrically distributed along the center line of the cutting edge, so that the chip rolling and chip removal effects can be achieved in different feeding modes, the transitional cambered surface degree is connected with the chip pocket, chips flowing from the chip pocket can be effectively received, the chip rolling effect is achieved in the first half processing and the chip guiding effect is achieved in the second half processing through smooth circular arc transition; in addition, the problem of scrap rolling of the latter half section is solved, and the problem of scrap rolling and scrap removal of the latter half section of the thread processing is better solved through the cooperation of the planar straight section and the leading-in section.

(5) According to the invention, two second protruding parts are arranged on two sides of the first protruding part, the convex surfaces of the second protruding part rolling scraps incline towards the intersection position of the two cutting edges, namely, the two second protruding parts are respectively designed at an acute angle relative to the blade center line along the intersection position direction of the two cutting edges, so that good approaching and gathering of the cutting scraps to the middle first protruding part can be met in an alternating cutting mode of radial cutting feed or axial cutting feed, good rolling scraps and cutting scraps effects are achieved while the chip removal direction is effectively controlled, and the cutting scraps are not easy to contact with the processed surface.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the description of the embodiments below are briefly introduced, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic perspective view of a cutting insert according to the present invention;

FIG. 2 is a top view of a cutting insert according to the present invention;

FIG. 3 is a side view of a cutting insert according to the present invention;

FIG. 4 is an enlarged view of portion A of FIG. 2 according to the present invention;

fig. 5 is a cross-sectional view taken along line B-B of fig. 4 in accordance with the present invention.

Reference numerals:

1. a body; 10. a polishing blade; 11. an outer edge; 12. 13, 14, sidewalls; 2. an angle cutting edge; 20. the intersection position of the two edge parts; 21. 22 two edge parts; 3. a front facet; 4. chip-containing grooves; 41. a groove bottom; 42. an abutment surface; 5. a first protrusion; 51. a lowest position; 52. a transitional cambered surface section; 53. a straight section; 54. an introduction section; 55. an end extension; 6. a second protruding portion; 61. a convex surface; 7. a chip guide boss; C. a blade center line; and gamma, an included angle between the straight section and the upper surface of the body.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the described embodiments are preferred embodiments of the invention and should not be taken as excluding other embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without creative efforts, are within the protection scope of the present invention.

In the claims, specification and drawings hereof, unless explicitly defined otherwise, the terms "first," "second," or "third," etc., are used for distinguishing between different objects and not for describing a particular sequential order.

In the claims, specification and drawings of the present invention, unless explicitly defined otherwise, for directional words such as "center", "transverse", "longitudinal", "horizontal", "vertical", "top", "bottom", "inner", "outer", "upper", "lower", "front", "rear", "left", "right", "clockwise", "counterclockwise", etc., the directional or positional relationship is based on the directional and positional relationship shown in the drawings and is merely for convenience of describing the invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, nor should it be construed as limiting the specific scope of the invention.

In the claims, specification and drawings of the present invention, unless explicitly defined otherwise, the term "fixedly connected" or "fixedly connected" should be construed broadly, i.e. any connection between them without a displacement relationship or a relative rotation relationship, that is to say includes non-detachably fixedly connected, integrally connected and fixedly connected by other means or elements.

In the claims, specification and drawings of the present invention, the terms "comprising," "having," and variations thereof as used herein, are intended to be inclusive and not limited to.

Referring to fig. 1, 2 and 4, a screw turning insert comprises a body 1 having a triangular shape, and an angle cutting edge 2 formed at an outer edge 11 of the body 1 and adapted to a screw groove; the corner cutting edge has an edge centerline C; the thread turning blade is generally arranged on the turning tool bar and is fixed by a screw; the thread turning insert is generally triangular, and at least one corner cutting edge 2 is convexly arranged on the outer edge 11 (namely, the joint of the thread turning insert and the outer edges 11 of the side walls on the other two sides) (three corner cutting edges 2 are generally arranged, or 6 thread turning inserts can be also arranged); the cutting is performed by the corner cutting edge 2 during the machining, and the first half referred to in the present invention means: the end part of the angle cutting edge 2 (namely the intersection position of the two edge parts 21 and 22) is continuously fed along the direction of the central line C, and the part from the intersection position of the two edge parts 20 to the middle position of the edge parts participates in processing; the second half refers to: since the two edge portions 21 and 22 of the corner cutting edge 2 are large in area or the entire edge portions 21 and 22 participate in the machining, the cutting surface and cutting resistance are large in the latter half of the machining.

In this embodiment, the insert body 1 covers 3 corner cutting edges 2 for participating in cutting machining, normally 1-6 corner cutting edges 2, in which machining is performed by locking a center hole screw (not shown in the figure), and then machining is performed by rotating the center to the other corner cutting edge 2 after one corner cutting edge 2 fails;

the corner cutting edge 2 is connected to the side walls 12, 13, 14 of the three bodies 1 by the wiper edge 10 (it should be noted here that, in the present invention, the outer edge 11 of the body 1 includes the side walls 12, 13, 14 of the body 1 and the wiper edge 10); the side walls 12, 13, 14 of the body 1 are generally provided for cooperating with a cutter bar; the lower surface of the body 1 and the side walls 12, 13 and 14 are chamfered, so that the boundary between the bottom and the side walls is prevented from preferentially contacting the positioning surface during positioning, and the whole positioning surface cannot be contacted, thereby influencing the positioning stability.

The corner cutting edge 2 comprises two edge portions 21 and 22 (i.e. cutting edges) which participate in machining, the two edge portions 21 and 22 are arranged at an acute angle (the angle of the two edge portions is 30 DEG, 55 DEG or 60 DEG in general, and the intersecting positions 20 of the two edge portions can be connected in a mode of circular arc, straight line plus circular arc or straight line plus chamfer, and are selected and matched according to different tooth type standards), the two edge portions 21 and 22 are connected with the outer edge 11 of the body 1 through cambered surface transition, and the outer edge 11 of the body 1 is configured as a trimming edge 10 for trimming the surface of a thread groove, improving the surface quality of a workpiece, reducing burrs and achieving accurate thread major diameter.

Defining an edge center line C in the middle of the corner cutting edge 2, which is disposed parallel to the body outer edge 11 (here, the body 1 outer edge 11 refers to the edges of the side walls 12, 13, 14 of the body 1, not the position of the wiper edge 10); it should be noted that, in general, the edge center line C is parallel to the outer edge 11 of the body, but some of the edge center lines C of the nonstandard blades are not parallel to the outer edge 11 of the body;

referring to fig. 4 and 5, the front cutting surface 3, the chip flute 4 and the first protrusion 5 are formed on the upper surface of the main body 1 and are offset inward along the center line C by the two edge portions 21 and 22 of the corner cutting edge 2; the front cutting face 3, the chip flute 4 and the first protruding part 5 are respectively and symmetrically arranged with the cutting center line C;

wherein the front cutting edge surface 3 and the chip flute 4 incline inwards along the edge center line C and towards the lower surface of the body 1 by a certain angle, and the inclination is such that the chips smoothly flow (move) to the chip flute 4 and the first protruding part 5;

the chip flute 4 is trapezoidal in cross section along the blade center line C, and the flute bottom 41 of the chip flute 4 is obliquely arranged downwards from the intersection 20 near the two blade parts 21 and 22 to the first protruding part 5; the surface of the chip flute 4 that is in contact with the rake surface 3 is configured as an abutment surface 42, and the abutment surface 42 is disposed obliquely; so that during machining, chips can smoothly enter the chip flute 4 along the abutting surface 42 to guide so as to control the movement track of the chips;

the chip flute 4 of the present invention has a substantially triangular or trapezoidal cross section, which is a cross section parallel to the lower surface of the insert body 1, and may be understood as the chip flute 4 when viewed from the top (i.e., the angle of fig. 2), and the chip flute 4 has a triangular shape; the structural design ensures that the thread can smoothly flow into the chip pocket 4 along with the increase of the cutting area when the thread is processed from the front half section to the rear half section; in addition, the flute depth of the chip flute 4 is generally designed to be 0.02-0.2mm, and the distance h from the edge of the abutting surface 42 to the intersection position 20 of the two cutting edges is generally designed to be 0.1-0.5mm, so that not only is the shrinkage of chips controlled, but also the sharpness of cutting edges ensured, the cutting force reduced, the processing vibration reduced, the friction between the chips and the front cutter surface reduced, the crater wear reduced, the chips can be effectively transferred to the rear part in the latter half of the thread processing ensured, on the other hand, the storage and the flow of cooling liquid are facilitated, more heat is taken away, and the cooling effect is better;

referring to fig. 4 and 5, the first protrusion 5 extends obliquely upward at the lowest position 51 of the chip flute 4, and forms at least one straight surface section 53 at a position higher than the front edge surface 3 so as to move the chip along the straight surface section 53;

in the present invention, the chip guiding surface of the first protruding portion 5 extends obliquely along the blade center line C toward the inside of the main body 1, like the slope of a ridge, and forms a transitional cambered surface section 52, the straight surface section 53, the leading-in section 54 and the tail extending section 55, which are sequentially connected; the streamline here refers to: the transitional cambered surface section 52, the straight surface section 53, the leading-in section 54 and the tail extension section 55 are sequentially connected, and the connecting lines of the surfaces of the sections 52, 53, 54 and 55 are smoothly transitionally extended from low to high in the section state, as shown in fig. 5;

the transition cambered surface section 52 is smoothly connected with the chip flute 4 (the transition cambered surface section 52 is a concave cambered surface, so that smooth flow of chips is ensured); the straight surface section 53 is located between the transition cambered surface section 52 and the leading-in section 54 (in this embodiment, the included angle gamma between the straight surface section 53 and the upper surface of the body 1 ranges from 10 degrees to 35 degrees), which is favorable for the chip flute transition cambered surface section 52 to flow to the straight surface section 53 and further plays a role in chip rolling; the lead-in section 54 has an arc and borders the end extension section 55 (where the arc of the lead-in section 54 is an outwardly convex arc, short distance for bordering the end extension section 55).

Moreover, the two edge parts 21, 22 of the corner cutting edge 2 are respectively in cambered surface transition with the connecting position of the trimming edge 10, the distance from the cambered surface to the first protruding part 5 is smaller than the distance from the intersecting position 20 of the two edge parts to the first protruding part 5, and during the latter half processing, the chips at the two edge parts 21, 22 of the corner cutting edge and the cambered surface transition position connected with the trimming edge 10 can flow to the first protruding part 5 faster, so that the curling of the rear part of the chips is ensured, and the chips at the intersecting position 20 of the two edge parts are conveyed to the first protruding part 5 through the chip pocket 4, so that the cutting force can be effectively reduced.

In addition, the body 1 is further provided with at least two second protruding parts 6 which are symmetrically arranged at two sides of the first protruding part 5 by the blade center line C; the convex surfaces 61 of the two second protruding portions 6 for the chips are inclined toward the intersection position 20 of the two cutting edges (in this embodiment, the included angle between the two second protruding portions 6 and the center line C of the cutting edge ranges from 70 ° to 85 °), so that the chips gather toward the intersection position 20 of the two cutting edges; further, the highest position of the second projection 6 is lower than the highest position of the last extension 55 and higher than the lowest position 51 of the last extension 55, so that the chip direction is brought closer toward the edge center line C.

In the present invention, the main body 1 is further provided with a chip guiding protrusion 7, which is disposed on a side surface of the second protrusion 6 and has a height greater than that of the second protrusion 6, and the chip guiding protrusion 7 plays a secondary protection role, that is, ensures that chips flowing out from the second protrusion 6 without control are limited at the position of the chip guiding protrusion 7, and plays a role in chip control.

In the actual thread processing process:

(1) The body 1 of the screw blade is fixed on a cutter bar (not shown in the figure) through a screw, and one corner cutting edge 2 faces outwards and corresponds to a workpiece to be processed;

(2) The workpiece to be processed rotates and moves relative to the screw thread blade to contact with the angle cutting edge 2;

(3) In the cutting process, the front half part (front half section) is firstly processed, namely, the intersection position 20 of two edge parts of the corner cutting edge 2 is firstly added and cut, the cut chip moves inwards along the inclined direction by the front edge surface 3, then enters the chip flute 4 with the cross section similar to a triangle, moves upwards from the other side of the chip flute 4 after passing through the abutting surface 42 and the groove bottom 41 of the chip flute 4, moves upwards and is curled by the chip guiding surface of the first protruding part 5, and in this way, after passing through the transition cambered surface section 52 of the chip guiding surface in the moving process, the chip flows upwards from the straight surface section 53 to the position of the leading-in section 54 to curl and curl to the chip breaking;

along with the continuous increase of the processing depth of the thread groove, the blade parts 21 and 22 on the two sides also participate in cutting, so that the cutting area is gradually increased, the cutting resistance is increased, and at the moment, the cutting, chip rolling and chip breaking modes are still in the above states until the thread groove is processed to the second half section;

during the latter half machining, the chips at the intersection position 20 of the two cutting edges are curled up as well due to the increase of the cutting area, and the chips generated when the cutting edges 21 and 22 near the position of the wiper 10 cut are quickly moved from the front cutting edge face 3 to the transitional cambered surface section 52 of the first protruding part 5 due to the short distance from the first protruding part 5 and are displaced through the straight surface section 53, and at the same time, the curled chips are gathered towards the edge center line C by the limitation of the second protruding parts 6 arranged at both sides of the first protruding part 5; it should be noted that, during the second half machining, the cutting chips at the transition positions of the arc surfaces, which are connected with the wiper blade 10, and the two edge portions 21 and 22 of the corner cutting edge can flow to the first protruding portion 5 relatively quickly, so that the rear part of the cutting chips is curled, and the cutting chips at the intersection positions 20 of the two edge portions pass through the chip flute 4 and then reach the first protruding portion 5, so that the cutting force can be effectively reduced, and the design can effectively solve the problems of large cutting force and difficult chip breaking and chip removal in the second half machining of the thread machining; moreover, the curling position of the chip is delayed, so that the curling position of the chip is postponed, that is, the chip has enough positions to move backwards and smoothly flow or move, thereby reducing the cutting force, effectively controlling the curling direction of the chip, and greatly improving the chip curling and chip removing effects;

furthermore, the flow of chips to the machined surface is prevented by the secondary guidance of the chip guiding protrusions 7.

The foregoing description of the embodiments and description is presented to illustrate the scope of the invention, but is not to be construed as limiting the scope of the invention.

Claims (10)

1. A screw thread turning insert comprising a body, an angle cutting edge formed at an outer edge of the body and adapted to a thread groove, the angle cutting edge having an edge centerline; the method is characterized in that: the two edge parts of the angle cutting edge are inwards offset along the edge center line on the upper surface of the body, and a front edge surface, a chip pocket and a first protruding part are sequentially formed; the front cutting surface and the chip flute incline inwards along the cutting center line and towards the lower surface of the body by a certain angle; the first projection extends obliquely upward from the lowest position of the chip flute and forms at least one straight section at a position higher than the rake surface to move chips along the straight section.

2. A threading insert as claimed in claim 1 wherein: the two edge parts of the angle cutting edge are respectively in cambered surface transition with the connecting position of the outer edge of the body, and the distance from the cambered surface to the first protruding part is smaller than the distance from the intersecting position of the two edge parts to the first protruding part.

3. A screw-turning insert according to claim 1 or 2, characterized in that: the chip flute is trapezoidal along the cross section of the blade center line, and the bottom of the chip flute is downwards inclined from the intersection position near the two blade parts to the first protruding part.

4. A screw-turning insert according to claim 3, characterized in that: the surface in the chip flute, which is in contact with the rake surface, is configured as an abutment surface, and the abutment surface is disposed obliquely.

5. A threading insert as claimed in claim 4 wherein: the transverse section of the chip flute is triangular or trapezoidal; the flute depth of the chip flute is 0.02-0.2mm, and the distance from the edge of the adjacent surface to the intersection position of the two cutting edges is 0.1-0.5mm.

6. A threading insert as claimed in claim 4 wherein: the chip guiding surface of the first protruding part extends obliquely along the edge central line to the inner streamline of the body, and forms a transitional cambered surface section, a straight surface section, a leading-in section and a tail extending section which are sequentially connected; the transition cambered surface section is smoothly connected with the chip flute, and the straight surface section is positioned between the transition cambered surface section and the leading-in section; the lead-in section has an arc and borders the last extension section.

7. A threading insert as claimed in claim 6 wherein: at least two second protruding parts are also arranged on the body and symmetrically arranged at two sides of the first protruding part by the central line of the blade; convex surfaces of the two second protruding parts for rolling scraps incline towards the intersection positions of the two edge parts respectively and form an acute angle with the center line of the edge, so that the rolling scraps are gathered towards the intersection positions of the two edge parts.

8. A threading insert as claimed in claim 7 wherein: the highest position of the second protrusion is lower than the highest position of the last extension and higher than the lowest position of the last extension.

9. A threading insert as claimed in claim 8 wherein: the body is also provided with a chip guiding protruding part which is arranged on the side surface of the second protruding part and the height of the chip guiding protruding part is larger than that of the second protruding part.

10. A threading insert as claimed in claim 1 wherein: the included angle between the straight surface section and the upper surface of the body ranges from 10 degrees to 35 degrees.