CA1072373A - Insert-type drill and insert therefor - Google Patents

Abstract

Abstract A single flute drill has a single, replaceable cutting insert which can drill from the solid, as well as being used for other single point machining operatings such as turning, internal and external diameter boring, contouring and facing. The insert is configured and related to the drill body so as to provide a single, radially extending cutting edge which has an effective neutral rake and negative lead. The insert comprises a solid body having parallel upper and lower faces each generally in the shape of an equilateral parallelogram and joined along their peripheral edges by side walls. One cutting edge is formed along the juncture of one side wall and the upper face and is inclined along its length toward the lower face. A second cutting edge is formed along the juncture of the lower face and a second side wall which intersects the first side wall at a corner. The second cutting edge is in-clined along its length from the corner of the intersection toward the upper face.

Description

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This is a division of our co-pendlng Canadian Patent Application No.
280,589 filed 15th June 1977.
Background of Invention The subject is directed toward the art of metal removal cutting tools and, more particularly, to an improved cutting insert for a drill capable of drilling from the solid in steel as well as, performing other single point metal removal operations such as boring, contouring and facing.
The invention is particularly sui~ed for embodiment in a carbide in-sert and will be described with reference thereto; however, the invention can be embodied in other materials.
Carbide has long been recognized as a particularly suitable material for use in cutting tools for metal removal operations. Most current uses of : carbide for cutting involve the use of a tool support body or holder which carries one or more small carbide elements or inserts which deine the cutting edges. These types of cutting tools have achieved widespread acceptance for a variety of operations including boring, milling, facing and contouring. How-ever, attempts at using this general construction for tools capable of drilling steel or ferrous materials from the solid (as distinguished from enlarg;ng a previously drilled hole) have not been particularly successful. Tools allegedly capable of performing this general function are shown in United States Patents 3,422,706 to Lunsford and 3,540,323 to Rishel. The drills sho~l in these patents are for all intents single purpose and cannot perform other machining operations to the extent desirable.
Brief Description of the Invention The present invention provides a cutting insert for use in a drill of the type described comprising a solid unitary body ha~ing opposed, parallel, upper and lower faces each in the shape of a parallelogram having a pair of opposed acute angle corners; peripheral side walls joining said upper and lower "
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faces and generally perpendicular thereto; a irs~ recess extending inwardly of said body from the upper face continuously along the entire length of a peripheral edge of said upper face from a first acute angle corner to a first obtuse angle corner, the bottom of said first recess being defined by a bottom surface which is inclined downwardly from the top face in a direction from the first acute angle corner to the firs~ obtuse angle corner, the bottom surface ofsaid first recess intersecting the respective peripheral side wall to define a first cutting edge which extends generally diagonally of the respective side wall; a second recess extending inwardly of the bottom face continuously along the entire length o~ a peripheral edge of the lower face from said first acute angle corner to the second obtuse angle corner, the bottom of said second re-cess being defined by a bottom surface which is inclined downwardly from the bottom face in a direction from the first acute corner ~o the second obtuse corner.
Preferably, but not necessarily, the insert is positioned to provide a negative lead in the range of 1 to 5 throughout substantially the entire cutting edge. However, for drilling applications, in the area of the edge closely adjacent to the centerline of the drill body, it has been found highly desirable to provide a short section of the edge with a much greater lead of from 30 to 60.
The described drill has been found capable of drilling from the solid in a variety of metals, including hard and soft steel, cast iron, and most non-ferrous metals. The single flute, single indexable insert design results in substantial cost savings. In addition, as will subsequently be explained, the ability of the drill to be used for other machining functions reduces the numberof tool stations required for other machining operations.
A preferred embodiment of the invention is described in relation to - an insert type d~ill which has the ability to drill from the solid in a . .' ' j .

i73 variety of metals, the major being ferrous metals. The drill has the ability to machine ferrous materials at three to four times the speed obtainable with conventional high speed drill cutting bodies, and can be used for many different machining opera*ions including turning, boring, facing and contouring. The drill can p~rform the no~ed operations with only one indexable cutting insert.
The insert can be indexed to provide a plurality of usable cutting edges.
Brief Description of the Drawings The advantages of the invention will become apparent from the follow-ing description when read in conjunction wi~h the accompanying drawings wherein:
Figure 1 is a side elevation view of an insert type drill including an insert embodying the invention;
Figure 2 is a view looking at the left end of ~he drill of Figure l;
Figure 3 is a view taken on line 3-3 of Figure l;
Figure 4 is a diagrammatic view showing the manner in which the drill of Figure 1 can be used for performing machining operations in addition ~o drilling;
Figure 5 is a pictorial view showing a preferred form of insert for use in the drill of Figure l;
Figure 6 is a top plan view of the insert of Figure 5;
Figures 7 and 8 are views taken on lines 7-7 and 8-8, respectively, of Figure 6; and, Figure 9 is a greatly enlarged cross-sectional view taken on line 9-9 of Figure 6 showing the chip breaker edge configuration.
Detailed Description of the Preferred Embodiment Referring more particularly to the drawings wherein the showings are for the purpose of illustrating preferred em~odiments of the invention only and not for the purpose of limiting same, Figures 1 through 3 show the overall arrangement of an insert type drill. In particular, the illustrated drill com-3i~3 prises a main body 10, formed from steel or any suitable ma~erial capable of providing the required strength and rigidity. The body 10 has a generally cylindrical shape and includes a mounting or shank end section 12 and a drill or cutting end section 14.
Extending axially inwardly of the body from the left hand end section 14 (as viewed in Figure 1) is a recess or groove 16 which defines a single, straight flute 17. The groove 16 has, as best shown in Figure 2, a generally V-shaped cross-section in planes perpendicular to the longitudinal axis 18 of the body 10. Additionally, flute 17 extends radially into section 14 a dis-tance at least substantially equal to the radius of sec~ion 14. In order toassure sufficient rigidity, the flute 17 should preferably be no larger than necessary to provide sufficient space for proper chip flow.
Mounted at the left hand end of flute 17 is an indexable type hard insert 20 formed of tungsten carbide or the like. The insert 20 is contoured and/or related to the end of the cutting shank portion 14 such that its cutting edge 21 extends continuously throughout a distance of from at least the center axis 18 to slightly beyond the maximum radial extent of section 14. As best shown in Figure 2, the cutting edge 21 lies exactly on a radius of section 14.
Additionally, the insert 20 is contoured or positioned so as to provide back clearance behind the radial outer corner 21a of the cutting edge 21. This is ; best seen in Figure 2.
Even more important than the location of the cutting edge are the relationships best illustrated in Figures 1 and 3. In particular, the insert - 20 is contoured and/or located such that the cutting edge 21 has or provides the `
drill with a negative lead. That is, the radially outermost corner 21a of the cutting edge is located axially outwardly of the end of the shank portion 14 a greater distance than the radial inner end 21b of the edge. The amount of negative lead could vary somewhat, however, according to the subject embodiment, '' ~ . ' , ..

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~h~ negative lead preferably ls in the range of approximately 1 to 5. In addition to ~he negative lead, the insert is preferably positioned such that the cutting edge 21 has an e~ective neut~al cutting rake.
As mentioned earlier, the maximum radial extent of the cutting edge 21 is slightly greater than the maximum radial extent of the cutting end section 14 of body 10. As shown in Figure 1, the outer corner 21a thus provides clearance for end section 1~. Preferably, a clearance "a" should be kept to a minimum to prevent chips from packing between the end section 14 and the wall of the hole being machined when the ~ool is being used as a drill.
It has been found that the described relationship of a single insert having the noted negative lead and neutral rake permits the drill to drill a hole ~rom the solid in steels, as well as, other ferrous and non-~errous metals and alloys. In addition, the relationship permits the drill to be used for a variety of machining operations in addition to drilling. For example, Figure 4 illustrates how the drill could be used in a static, non-rotating condition in a conventional, numerically controlled or automatic chucking machine. In this figure a cross section of the work piece is shown and identified with the numeral 24. To perform a drilling operating the drill is simply moved axially into the counter clockwise rotating work piece 24 as shown at location 2~. As

2~ the drill moves through the work piece it will, of course, drill a hole at a diameter D which is generally equal to twice the maximum radial extent of the cutting edge 21. As the drill emerges from the left hand side of the work piece 24, a segment having the configuration illustrated typically at 29 immer-ges from the work piece. By positioning the drill transversely to the axis as shown at position 31 and feeding it into the work piece it is possible to counter-bore as illustrated by the lines 30. Similarly, contouring of the inner surfaces can likewise be accomplished. It is important to note that the negative lead provide the capability to single point the bottom wall of the previously machined counterbore perpendicular to the axis of work piece rotation.
By reversing the directlon of the work piece, the outside diameter can be contoured or chamferred as shown by reference lines 32 merely by moving - the drill to the positions illustrated at 34 through 35. Facing can likewise be accomplished by moving the drill to positions 36 or 37 and, based on spindle rotation, causing it to ~eed in a generally perpendicular direction relakive to the axially rotation of the work piece. tNote that positions 34, 35 and 37 require the work piece to rotate in the clockwise direction as viewed from the right end in Figure 4. Positions 28, 31 and 36 require counterclockwise work piece rotation.) The ability of the drill to perform a variety of metal removal operations is particularly desirable since it allows a plurality of stock re-moval machining functions to be carried out at a single work station wi~hout a tooling or machine station change. It is also important to note that all machining cuts are performed with the same single insert.
An adequate supply of coolant to the cutting edge 21 is comparatively important with the subject type of drill. For this reason, the body 10 tsee Figures 1-3) is provided with a longitudinally extending coolant supply passage 37. Passage 37 has a pair of inlet ports 37a and 37b. Fither of the ports can be used for coolant supply depending upon the type of machine on which the drill is mounted. The nonused port is~ of course, merely plugged. Discharge from passage 37 is through two outlet ports 38a and 38b. Outlet port 38a is angled as shown to direct coolant flow at the radially inner end 21b of cutting edge 21. Preferably, the coolant is supplied at a comparatively high pressure to assist in moving the chips away from the part. Coolant flow in this area is important since the cutting edge adjacent to the center axis namely 21b approaches a cutting speed of zero surface feet per minute. Outlet port 38b is positioned to direct coolant at the outer radial end 21a of the cutting edge .
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:l~)'JZ~ 3 21. A good flow of coolant in this area is also important especially when the drill is being used for turning, facing and contouring operations.
While it is apparent that many different insert configurations could be used provided they were capable of assuring the relationships discussed above, the subject invention preferably incorporates an insert having ~he configuration best seen in Figures 5 through 8. This particular insert configuration allows the insert ~o be mounted in the drill in a retaining pocket 40 machined in the end groove 16 and having a bot~om wall and a pair of side walls which join the bottom wall at a 90 angle. This 90 angle relationship permits the insert to be rigidly locked in the pocket through the use of a simple removable connec~ing means such as a screw 42. Additionally, the ~op surface of the insert shown can join the bottom surface of the flute 17 with a smooth transition for proper chip flow.
In the description of the indexable insert which follows, terms such as upper and lower will be used merely for the sake of clarity. These terms are not, however, to be considered as limiting the manner in which the indexable insert is used or related to the drill shank or recess 16.
Referring in particular to figures 5 through 8 the insert 40 is shown as comprising a solid, unitary body 46 of any hard ma~erial suitable for cutting tools such as tungsten carbide or the like. In general, the body 46 includes upper and lower spaced, generally parallel, faces 48 and 50. The faces 48 and 50 are joined about their peripheral edges by vertically extending opposed pairs of side walls 52 and 54, respectively.
As shown in Figures 5 and 6, the body 46 has a configuration which is the shape of an equilateral parallelogram in planes parallel to the upper and lower faces 48 and 50, The angles of the acute corners 49a and 49b must be selected so as to provide the required negative lead discussed with reference to Figure 1, as well as, a clearance "a" shown a~ 58 an Figure 1. Generally ' q7"

the included angles of the acute corners of the parall~logram will or should be in the range of 83 to 88 to produce the required or desired angle ranges for lead and clearance. ~dditionally, as shown the acute angle co~ner 49a is preferably given a slight radius in the range of 1/32" so as to improve the cutting action when used for drilling as well as single point cutting operations.
Extending into the body 46 along the juncture of one side wall 54 and the top face 48 is a groove or recess 60. The groove 60 begins at approximate-ly the top of the acute corner 49a and is inclined downwardly to the opposite end of the respective side wall 52. The groove 60 terminates in a bot~om wall 62. The juncture between the groove's bottom wall 62 and the side wall 54 defines the cutting edge 21.
The end portion of the cutting edge 21 in ~he area adjacent to the obtuse corner 51a is chamferred at an angle in the range of 30 to 60. This provides a better distribution of forces acting on the corner and reduces the possibility of failure of the cutting edge in this area. Additionally, the surface under the cutting edge a~ corner 51a is provided with an incline of approximately 4 to 8~ ~o assure cutting clearance.
The end of the cutting edge at the acute corner 49a preferably has a small radius 63 to improve the cutting action for drilling or when it is functioning as a single point tool as described earlier. Also, the cut~ing edge in this area is a smooth transition from the juncture of surfaces or walls 62, 70, 54 to the juncture of the face 48 and wall 52.
In order to improve the cutting action a chip breaking or control con-figuration is required. However, it should be noted that various configurationscould be used based on material being machined. As shown a short, flat sur-~ace 70 extends back from edge 21 a distance of approximately .02". The sur-face 70 is joined to the bottom wall 62 of groove 60 by a w~ll 72 which is inclined as shown. This typical configuration produces proper chip formation . . .

, and improves the cutting action oX the insert.
In order to control the chip breaking requirements for facing operations~ an additional chip breaXer configuration 73, which shown at the juncture of surface 48 and wall S2, from the acute corner 49a is provided.
The insert shown is designed to provide a second cutting edge which can be indexed into cutting position by inver~ing and rotating the insert.
For this reason, a second cutting edge 21' is formed generally at the junc~ure of one side wall 52 and a groove 60' formed in bottom face 50. The second cut-ting edge is effectively identical to the first and is positioned such that the insert 46 is symmetrical relative to a vertical plane which includes corners 49a and 49b. Consequently, the various surfaces which form the second cutting edge are identified with numerals identical to those which identify the corres-ponding surfaces forming the first cutting edge.
Because o~ the design of the insert it is possible to have a single insert provide two separately usable cutting edges, while retaining the smooth transition from the top surface of the insert to the surface of the flute.

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Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A cutting insert for use in a drill of the type described comprising:
a solid unitary body having opposed, parallel, upper and lower faces each in the shape of a parallelogram having a pair of opposed acute angle corners;
peripheral side walls joining said upper and lower faces and generally per-pendicular thereto; a first recess extending inwardly of said body from the upper face continuously along the entire length of a peripheral edge of said upper face from a first acute angle corner to a first obtuse angle corner, the bottom of said first recess being defined by a bottom surface which is inclined downwardly from the top face in a direction from the first acute angle corner to the first obtuse angle corner, the bottom surface of said first recess inter-secting the respective peripheral side wall to define a first cutting edge which extends generally diagonally of the respective side wall; a second recess ex-tending inwardly of the bottom face continuously along the entire length of a peripheral edge of the lower face from said first acute angle corner to the second obtuse angle corner, the bottom of said second recess being defined by a bottom surface which is inclined downwardly from the bottom face in a dir-ection from the first acute corner to the second obtuse corner.

2. The cutting indexable insert as defined in claim 1 wherein said acute angles are in the range of from approximately 83 to 88° and wherein each of said acute angles are provided with a radius.

3. The indexable insert as defined in claim 1 or 2 wherein the bottom surface of each recess intersects the adjacent peripheral side wall at an angle of substantially 90°.