Brief Description of the Prior Art A number of taper lock arrangements are known in the art, in which a tapered male part is received in a complementarily tapered female part, the angle of the taper for each part being chosen so that the male part is mechanically locked in the female part. For example, a large number of rotary tools in a machine shop employ a Morse taper system for accommodat- ing a quick change of bits, drill chucks, rotatable clamping jaws, and the like in such machines as lathes, drill presses, and milling machines, as well as in heavy duty road building equipment, tractors, mining tools, etc.

Once a male part is captured in a female part of a taper lock system, forces applied laterally of the axis of the rotating member, and especially thrust forces in the direction of inserting the male part into the female part can be withstood without loss of coupling between the two parts. Even a minor amount of axially directed thrust force on the male part tending to push it out of the female part can be accommodated.

As easy as it is to effect the coupling of the male part to the female part in a taper lock system, it is also easy to release the locking engagement. A gentle impactive force (e. g., a tap) on the male part in a direction away from the

female part will serve to break the taper lock for easy removal of the male part and replacement by another male part, for example to replace worn bits or to change sizes of bits quickly and efficiently.

In the prior art, a number of taper lock systems have been proposed, but all of them are associated with a male part having an exterior conical surface mating with a female part having an interior conical complementary and mating surface.

In order to provide a taper lock feature to a flat plate-like member, for example, in the past it has been required to provide a transition section between the flat plate-like member and a conical male or female part for coupling to the opposite configuration on a piece of rotating machinery.

However, this additional transition section makes the part expensive, heavy, and less useful for operating in tight areas.

Moreover, in drilling operations for example, tremendous torsional forces can be applied to a drill bit or a chuck upon encountering an unexpected hard piece of material. This problem is common using spade drills and, on a more practical basis, when the drill becomes dull. Even though conical taper lock systems can bear some significant torsional forces on a rotating member, there are physical limits involved, and when enough torque is applied to a rotating bit or chuck, not only will the taper lock release, but the surfaces of the conical walls of the male and female parts could be permanently damaged requiring much down time and/or complex and costly repair.

There is therefore a need in the art for a taper lock system which can accommodate mechanical configurations of a male and female part combination which are not conical in shape and which can withstand extreme torsional forces without breaking the taper lock.

SUMMARY OF THE INVENTION The present invention overcomes the aforementioned problems of the prior art by providing a taper lock system which employs the taper lock principles while minimizing, or avoiding altogether, a breaking of the taper lock between the male and female parts upon encountering excessive torsional forces between the male and female parts.

According to one aspect of the invention, there is provided a taper lock arrangement, comprising a female part having a non- conical shaped wedge receptacle formed therein, and a male plug part comprising a non-conical shaped wedge portion, the wedge portion fitting into the wedge receptacle in an insertion direction to effect a taper lock.

In another aspect of the invention, there is provided a taper lock arrangement, comprising: a generally rectangular male part; and a female part having a generally rectangular opening therein for receiving the male part in an insertion direction; wherein the opening has a pair of interior surfaces converging in the insertion direction, the male part has a pair of external surfaces converging in the insertion direction, and the male fits into the opening in the insertion direction to effect a taper lock between the exterior converging surfaces and the interior converging surfaces.

The invention may assume a variety of design configurations using both converging interlocking walls and diverging interlocking walls, may use converging or diverging walls offset from one another on either side of a central insertion axis in order to simultaneously effect a bias of the male part against the female part, or may have symmetrical diverging or converging walls to avoid any bias of the male part against the female part.

BRIEF DESCRIPTION OF THE DRAWING These and other aspects of the invention will be better understood, and additional features of the invention will be described hereinafter having reference to the accompanying drawings in which: FIGURE 1 is a front view representation of a spade drill assembly employing a taper lock arrangement made in accordance with the present invention; FIGURE 2 is a side elevational view of the female body portion of the spade drill arrangement shown in Figure 1; FIGURE 3 is a perspective view of a spade bit insert of the type that may be used the spade drill arrangement shown in Figure 1, with the spade insert being configured in accordance with one embodiment of the present invention; FIGURE 4 is a side elevational view of the spade insert shown in Figure 3; FIGURE 5 is a perspective view of one embodiment of the invention showing the female receptacle part in schematic form, i. e. not associated with any particular tooling function, the dashed lines showing a version of the female part without end walls, this figure also showing a male plug part receivable in the female receptacle part; FIGURE 6 is a top plan view of the male part according to a 5 first embodiment of the invention; FIGURE 7 is a side view of the male part shown in Figure 6; FIGURE 8 is a bottom view of the male part shown in Figure 7; FIGURE 9 is a left end view of the male part shown in Figure 7; 10 FIGURE 10 is a right end view of the male part shown in Figure 7; FIGURE 11 is a bottom end view of a female receptacle part according to the first embodiment of the invention; FIGURE 12 is the same view as in Figure 11, showing an 15 inserted and taper locked male part; FIGURE 13 is a partial cross sectional side view of the first embodiment of the invention showing a male plug part inserted into, and taper locked to, the female receptacle, the latter shown in cross section; 20 FIGURE 14 is a top plan view of the male part according to a second embodiment of the invention; FIGURE 15 is a side view of the male part shown in Figure 14;

FIGURE 16 is a bottom view of the male part shown in Figure 15; FIGURE 17 is a left end view of the male part shown in Figure 15; FIGURE 18 is a right end view of the male part shown in Figure 15 ; FIGURE 19 is a bottom end view of a female receptacle part according to the second embodiment of the invention; FIGURE 20 is the same view as in Figure 19, showing an inserted and taper locked male part; FIGURE 21 is a partial cross sectional side view of the second embodiment of the invention showing a male plug part inserted into, and taper locked to, the female receptacle, the latter shown in cross section ; FIGURE 22 is a top plan view of the male part according to a third embodiment of the invention; FIGURE 23 is a side view of the male part shown in Figure 22; FIGURE 24 is a bottom view of the male part shown in Figure 23; FIGURE 25 is a left end view of the male part shown in Figure 23; FIGURE 26 is a right end view of the male part shown in Figure 23;

FIGURE 27 is a bottom end view of a female receptacle part according to the third embodiment of the invention; FIGURE 28 is the same view as in Figure 27, showing an inserted and taper locked male part; FIGURE 29 is a partial cross sectional side view of the third embodiment of the invention showing a male plug part inserted into, and taper locked to, the female receptacle, the latter shown in cross section; FIGURE 30 is a top plan view of the male part according to a fourth embodiment of the invention; FIGURE 31 is a side view of the male part shown in Figure 30; FIGURE 32 is a bottom view of the male part shown in Figure 31; FIGURE 33 is a left end view of the male part shown in Figure 31; FIGURE 34 is a right end view of the male part shown in Figure 31; FIGURE 35 is a bottom end view of a female receptacle part according to the fourth embodiment of the invention; FIGURE 36 is the same view as in Figure 35, showing an inserted and taper locked male part; and FIGURE 37 is a partial cross sectional side view of the fourth embodiment of the invention showing a male plug part inserted

into, and taper locked to, the female receptacle, the latter shown in cross section.

FIGURE 38 is a top plan view of the male part according to a fifth embodiment of the invention; FIGURE 39 is a side view of the male part shown in Figure 38; FIGURE 40 is a bottom view of the male part shown in Figure 39; FIGURE 41 is a left end view of the male part shown in Figure 39 ; FIGURE 42 is a right end view of the male part shown in Figure 39; FIGURE 43 is a bottom end view of a female receptacle part according to the fifth embodiment of the invention; FIGURE 44 is the same view as in Figure 11, showing an inserted and taper locked male part; and FIGURE 45 is a partial cross sectional side view of the fifth embodiment of the invention showing a male plug part inserted into, and taper locked to, the female receptacle, the latter shown in cross section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 shows a rotary spade drill bit assembly employing the concepts of the present invention, the Figure 1 representation being taken from Applicant's copending application entitled "ROTARY DRILL ARRANGEMENT", filed simultaneously herewith and

bearing U. S. Application Serial No.. In that copending application, a rotary spade drill 1 is-basically comprised of three parts, a spade drill body 3, a spade insert 5, and a rotary cutter 7 mounted on the spade insert 5, the rotary cutter 7 being exposed to the material being drilled through a cutout in the lower right hand corner of the rotary spade drill body 3 as shown in Figure 1.

In assembling the rotary spade drill 1, a spade insert 5, shown in detail in Figure 3, is axially inserted into an opening 15 of spade drill body 3 in an insertion direction 4, as best seen in Figure 2, and, using prior art techniques, would be inserted fully into opening 15 until the top surface 11 of the spade insert 5 abuts the stop surface 13 at the bottom of the opening 15, at which time a rivet 9 would be fixed in place. However, employing the concepts of the present invention, the spade insert 5 may be provided with tapered walls 17 and 19 to effect a taper lock function with the opening 15 as will be described hereinafter. No rivet is required to hold the spade insert 5 in place, and the spade insert length will be sized so as to leave a slight gap 2 between the upper surface 11 of the spade insert 5 and the bottom 13 of the opening 15.

Figure 4 is a side view of the spade insert 5 showing a rotatable cutter 7 in place. It will be appreciated that, as the spade insert is rotated clockwise (as seen from the top of the drill), and the rotary cutter 7 is pushed into the material to be cut or drilled, a rearwardly directed force will be transmitted to the portion of the spade insert 5 upon which the cutter 7 is mounted. It would be desirable, then, to insure that the rear surface of the spade insert 5 behind the rotary cutter 7 would be solidly supported by the female

body portion 3, and this is accomplished by the present invention as will be evident from the discussion of certain embodiments to be described hereinafter.

It will be self-evident that providing a taper lock function between a spade insert 5 and its containing body 3 is only one application of an in-line taper lock system according to the present invention, and many other uses will come to mind to the skilled worker. Accordingly, in the remaining figures to be described, the principles of the embodiments will be apparent from the description of a generic female receptacle part and a generic male plug part.

It is also important to note that, when the invention is used as the coupling means for mounting a spade insert into a rotary spade drill body, the spade insert 5 must extend a small distance at the sides and at the bottom of the female body 3, in order to expose the cutting edges of the spade insert 5 to the material or substance being cut or drilled without interference by the body 3. In other applications of the present invention, it may be desirable to have the openings in the female receptacle to have end walls. This would increase the strength of the female body part, and, in some applications, would offer no disadvantages. The drawings remaining to be discussed will show end walls in all embodiments, but it will be understood that these end walls may be removed, since the operating part of the invention lies in the interaction of the tapered walls within the intermediate portion of the female receptacle and at the intermediate portion of the male plug to be inserted therein.

Figure 5 shows a male plug part 29 and female receptacle 31, the receptacle 31 having an opening 33 designed and configured

to receive the male plug 29 in an insertion direction, i. e. in the direction of the arrowed lead line 40. The dashed lines in Figure 5 indicate that the end walls 32 and 24 may be removed without functionally affecting the operation of the various embodiments of the invention.

The male part 29 in Figure 5 has a top surface 21, a bottom surface 23, a tapered exterior wall 47 on one side, and an opposing exterior tapered wall 49 on the opposite side of the male part 29. It will be noted that the slope of the tapered wall 47 is such that the wedge 36 is wider at the bottom 23 than it is at the top 21. Similarly, although not visible in Figure 5, the wedge 38 formed by the tapered wall 49, is wider at the bottom 23 than it is at the top 21. In the female receptacle 31, the opening 33 also has tapered walls 35 and 37 which have a taper that is complementary to that of tapered walls 47 and 49 of the male part.

A first embodiment of the invention is shown in Figures 6-13.

Figure 6 shows a top view of the male part 29 having a top surface 21 and sloping, or tapered, sidewalls 47 and 49.

Figure 7 is a side view of the first embodiment of the invention best showing the sloped or tapered wall 47 and, in phantom, the sloped or tapered wall 49 on the other side of the male part 29.

Figure 8 is a bottom view of the male part of Figure 7 showing, as in Figures 6 and 7, that the walls 47 and 49 of the male part 29 diverge in the insertion direction 40. The tapered walls 47 and 49 are also planar in shape and are angled generally inwardly forming pointed edges 46 and 48, respectively. These pointed edges overlap corresponding and

complementary pointed edges 35 and 37 on the female part (Figures 5 and 11) in a dovetail-like fashion.

In all of the embodiments of the invention, except the fifth embodiment, to be described herein, pointed edges such as 46 and 48 shown in Figure 8 are formed on the male and female parts, their purpose being to keep the engaged and taper locked surfaces 47 and 49 of the male part and 35 and 37 of the female part from moving laterally of the direction of insertion 40. In view of this common feature to most embodiments, the pointed edges will not be specifically identified or commented upon when describing embodiments 2-4.

Figures 9 and 10 show the left and right end views, respectively, of the male part 29 shown in Figure 7, the tapered surface 47 being visible in Figure 9, and the tapered surface 49 being visible in Figure 10.

Figure 11 is a bottom view of a generic female receptacle 31 having an opening 33 and tapered sidewalls 35 and 37 as described earlier. When the male plug part 29 is inserted into opening 33, as shown in Figure 12, also a bottom view of the male/female part combination, the tapered surfaces 47 and 49 of the male part slide in surface contact with the tapered surfaces 35 and 37, respectively, of the female part 31. The further the male part is inserted into the opening 33, the greater the force applied by the female part to push the tapered surfaces 47 and 49 laterally, i. e. outwardly away from the central insertion axis 59 common to both the male part 29 and female part 31. The force by the tapered wall 35 of the female part 31 against the tapered wall 47 of the male part 29 is in the direction of arrow (a) shown in Figure 12. Since the other end of the male part 29 is likewise being locked to

the female part 31, the force directed in the direction of arrow (a) tends to pivot the male part 29 about the insertion axis 59 as shown by the curved arrow (b) in Figure 12. In similar fashion, wall 37 pushes against wall 49 as the male part 29 is further inserted into female part 31 developing a force against wall 49 in the direction of arrow (c), tending to pivot the male part 29 in the direction of arrow (d) about insertion axis 59.

Accordingly, upon full insertion of the male part 29 in female part 31, the assembled male/female arrangement is ready for use, such as would be the case for a rotary spade drill assembly as shown in Figures 1-4. As mentioned, it is important to have a firm backing for a cutter 7 mounted on a spade insert 5. In Figures 6-13, the equivalent component for a spade insert is male part 29, and the dashed lines indicated by numeral 7 represent the position of a rotary cutter mounted on the male part 29. Due to the forces tending to rotate male part 29 in the direction of arrows (b) and (d), the lower right end and upper left end of male part 29 will be forced, or biased, against the adjacent surfaces of the female part 31, at 51 and 55 as shown in Figure 12, acting as stop surfaces, thereby providing the required backing support for the rotary cutters 7. Of course, biasing the male part 29 in the direction of arrow (b) will also result in slight gaps 53 and 57, dependent upon the fit tolerance between the male and female parts 29 and 31.

Figure 13 shows the female part 31 in cross section and the male part 29 in full side view and also fully inserted into the female part. This view shows the relationship between the tapered walls 35,37,47, and 49 (the dashed line 35 is for understanding only, as the surface it represents is, in fact,

on the portion of female part 31 that was removed for showing the cross section in Figure 13).

A second embodiment of the invention is shown in Figures 14- 21. Figure 14 shows a top view of the male part 69 having a top surface 61 and sloping, or tapered, sidewalls 87,87a, 89 and 89a. Figure 15 is a side view of the second embodiment of the invention best showing the sloped or tapered walls 87, 87a. The sloped or tapered walls 89,89a on the other side of the male part 69 are located directly behind walls 87,87a.

Figure 16 is a bottom view of the male part of Figure 15 showing, as in Figures 14 and 15, that the walls 87,87a, 89, and 89a of the male part 69 converge in the insertion direction 40. The tapered walls 87,87a, 89, and 89a are also planar in shape and are angled generally inwardly forming pointed edges. These pointed edges overlap corresponding and complementary pointed edges on the female part (Figure 19) in a dovetail-like fashion.

Figures 17 and 18 show the left and right end views respectively of the male part 69 shown in Figure 15, the tapered surfaces 87 and 89 being visible in Figure 17, and the tapered surfaces 87a and 89a being visible in Figure 18.

Figure 19 is a bottom view of a generic female receptacle 71 having an opening 73 and tapered sidewalls 75,75a, 77, and 77a. When the male plug part 69 is inserted into-opening 73, as shown in Figure 20, also a bottom view of the male/female part combination, the tapered surfaces 87,87a, 89, and 89a of the male part slide in surface contact with the tapered surfaces 75,75a, 77, and 77a, respectively, of the female part 71. The further the male part 69 is inserted into the opening 73, the greater the force applied by the female part to push the tapered surfaces 87,87a, 89, and 89a laterally, i. e. outwardly away from the central insertion axis 99 common to both the male part 69 and female part 71. The forces by the tapered walls 75 and 77 of the female part 71 against the tapered walls 87a and 89 of the male part 69 are in the direction of arrows (f) and (h), respectively, shown in Figure 20. Since the other cooperating surfaces, 75a against 87 and 77a against 89a, result in equal and opposite forces in the directions of arrows (e) and (g), all twisting forces cancel out vectorially. This symmetrical distribution of forces makes this embodiment useful in applications where precise angular alignment between the male and female parts is essential.

Figure 21 shows the female part 71 in cross section and the male part 69 in full side view and also fully inserted into the female part. This view shows the relationship between the tapered walls 77,77a, 87, and 87a.

A third embodiment of the invention is shown in Figures 22-29.

Figure 22 shows a top view of the male part 109 having a top 5 surface 101 and sloping, or tapered, sidewalls 127,127a, 129, and 129a. Figure 23 is a side view of the third embodiment of the invention best showing the sloped or tapered walls 127 and 127a.

Figure 24 is a bottom view of the male part of Figure 23 10 showing, as in Figures 22 and 23, that the walls 127,127a, 129, and 129a of the male part 109 converge in the insertion direction 40. Walls 127a and 129 are not tapered in the insertion direction. The tapered walls 127 and 129a are also planar in shape and are angled generally inwardly forming 15 pointed edges. These pointed edges overlap corresponding and complementary pointed edges on the female part (Figure 28) in a dovetail-like fashion.

Figures 25 and 26 show the left and right end views, respectively, of the male part 109 shown in Figure 23, the 20 tapered surface 127 and straight (non-tapered) surface 129 being visible in Figure 25, and the tapered surface 129a and

straight (non-tapered) surface 127a being visible in Figure 26.

Figure 27 is a bottom view of a generic female receptacle 111 having an opening 113 and tapered sidewalls 115 and 117a.

When the male plug part 109 is inserted into opening 113, as shown in Figure 28, also a bottom view of the male/female part combination, the tapered surfaces 127 and 129a of the male part slide in surface contact with the tapered surfaces 115 and 117a, respectively, of the female part 111. The further the male part 109 is inserted into the opening 113, the greater the force applied by the female part to push the tapered surfaces 127 and 129a laterally, i. e. outwardly away from the central insertion axis 139 common to both the male part 109 and female part 111. The force by the tapered wall 115 of the female part 111 against the tapered wall 127 of the male part 109 is in the direction of arrow (I) shown in Figure 28. Since the other end of the male part 109 is being likewise locked to the female part 111, the force directed in the direction of arrow (I) tends to pivot the male part 109 about the insertion axis 139 as shown by the curved arrow (n) in Figure 28. In similar fashion, wall 117a pushes against wall 129a as the male part 109 is further inserted into female part 111 developing a force against wall 129a in the direction of arrow (k), tending to pivot the male part 109 in the

direction of arrow (m) about insertion axis 139. Being parallel to the insertion axis 40, no forces are developed at the interfaces of walls 115a against 127a and 117 against 129.

Accordingly, upon full insertion of the male part 109 in female part 111, the assembled male/female arrangement is ready for use, such as would be the case for a rotary spade drill assembly as shown in Figures. As mentioned, it is important to have a firm backing for a cutter 5 mounted on a spade insert 7. In Figures 22-29, the equivalent component for a spade insert is male part 109. Due to the forces tending to rotate male part 109 in the direction of arrows (n) and (m), the lower right end and upper left end of male part 109 will be forced, or biased, against the adjacent surfaces of the female part 111, acting as stop surfaces, thereby providing the required backing support for the rotary cutters 7. Of course, biasing the male part 109 in the direction of arrows (n) and (m) will also result in slight gaps 133 and 187, dependent upon the fit tolerance between the-male and female parts 109 and 111.

Figure 29 shows the female part 111 in cross section and the male part 109 in full side view and also fully inserted into the female part. This view shows the relationship between the tapered walls 117,117a, 127, and 127a.

A fourth embodiment of the invention is shown in Figures 30- 37. Figure 30 shows a top view of the male part 149 having a top surface 141 and a single sloping, or tapered, sidewall 169. Figure 31 is a side view of the fourth embodiment of the 5 invention best showing the sloped or tapered wall 169.

Figure 32 is a bottom view of the male part of Figure 31 showing, as in Figures 30 and 32, that the wall 169 of the male part 149 diverges in the insertion direction 40 relative to end wall 171. The tapered wall 169 is also planar in shape 10 and is angled generally inwardly forming a pointed edge. This pointed edge overlaps a corresponding and complementary pointed edge 157 on the female part (Figure 35) in a dovetail- like fashion.

Figures 33 and 34 show the left and right end views, 15 respectively, of the male part 149 shown in Figure 31, the tapered surface 169 being visible in Figure 33, but not visible in Figure 34.

Figure 35 is a bottom view of a generic female receptacle 151 having an opening 153 and a single tapered sidewall 157. When 20 the male plug part 149 is inserted into opening 153, as shown in Figure 36, also a bottom view of the male/female part combination, the tapered surface 169 of the male part slides in surface contact with the tapered surface 157 of the female part 151. The further the male part is inserted into the opening 153, the greater the force applied by the female part to push the tapered surface 169 laterally, i. e. outwardly away 5 from the central insertion axis 179 common to both the male part 149 and female part 151. The force by the tapered wall 157 of the female part 151 against the tapered wall 169 of the male part 149 is in the direction of arrow (o) shown in Figure 36. Since the other end of the male part 149 is being 10 resisted from rotation by the female part 151, the force directed in the direction of arrow (o) tends to pivot the male part 149 about the insertion axis 179 as shown by the curved arrow (p) in Figure 36.

A taper lock is effected by the wedging action between the 15 tapered surface 157 engaging surface 169 and the non-tapered surface 173 engaging non-tapered surface 171.

Accordingly, upon full insertion of the male part 149 in female part 151, the assembled male/female arrangement is ready for use, such as would be the case for a rotary spade 20 drill assembly as shown in Figures 1-4. As mentioned, it is important to have a firm backing for a cutter mounted on a spade insert. In Figures 30-37, the equivalent component for a spade insert is male part 149. Due to the forces tending to

rotate male part 149 in the direction of arrow (p), the lower right end and upper left end of male part 149 will be forced, or biased, against the adjacent surfaces of the female part 151, at 172 and 174 as shown in Figure 36, acting as stop surfaces, thereby providing the required backing support for the rotary cutters 7. Of course, biasing the male part 149 in the direction of arrow (p) will also result in slight gaps 176 and 178, dependent upon the fit tolerance between the male and female parts 149 and 151.

Figure 37 shows the female part 151 in cross section and the male part 149 in full side view and also fully inserted into the female part. This view shows the relationship between the tapered walls 157 and 169 and the straight walls 171 and 173.

A fifth embodiment of the invention is shown in Figures 38-45.

Figure 38 shows a top view of the male part 229 having a top surface 221 and sloping, or tapered, sidewalls 247 and 249.

Figure 39 is a side view of the fifth embodiment of the invention best showing the sloped or tapered wall 247 and, in phantom, the sloped or tapered wall 249 on the other side of the male part 229.

Figure 40 is a bottom view of the male part of Figure 39 showing, as in Figures 38 and 39, that the walls 247 and 249

of the male part 229 diverge in the insertion direction 40.

The tapered walls 247 and 249 are also planar in shape and are angled generally outwardly.

Figures 41 and 42 show the left and right end views, respectively, of the male part 229 shown in Figure 39, the tapered surface 247 being visible in Figure 41, and the tapered surface 249 being visible in Figure 42.

Figure 43 is a bottom view of a generic female receptacle 231 having an opening 233 and tapered sidewalls 235 and 237. When the male plug part 229 is inserted into opening 233, as shown in Figure 44, also a bottom view of the male/female part combination, the tapered surfaces 247 and 249 of the male part 229 slide in surface contact with the tapered surfaces 235 and 237, respectively, of the female part 231. The further the male part 229 is inserted into the opening 233, the greater the force applied by the female part to push the tapered surfaces 247 and 249 laterally, i. e. outwardly away from the central insertion axis 259 common to both the male part 229 and female part 231. The force by the tapered wall 235 of the female part 231 against the tapered wall 247 of the male part 229 is in the direction of arrow (r) shown in Figure 44.

Since the other end of the male part 229 is likewise being locked to the female part 231, the force directed in the

direction of arrow (r) tends to pivot the male part 229 about the insertion axis 259 as shown by the curved arrow (s) in Figure 44. In similar fashion, wall 237 pushes against wall 249 as the male part 229 is further inserted into female part 231 developing a force against wall 249 in the direction of arrow (t), tending to pivot the male part 229 in the direction of arrow (u) about insertion axis 259.

Accordingly, upon full insertion of the male part 229 in female part 231, the assembled male/female arrangement is ready for use, such as would be the case for a rotary spade drill assembly as shown in Figures 1-4. As mentioned, it is important to have a firm backing for a cutter 7 mounted on a spade insert 5. In Figures 38-45, the equivalent component for a spade insert is male part 229, and the dashed lines indicated by numeral 7 in Figure 10 represent the corresponding position of a rotary cutter mounted on the male part 229 in Figure 42. Due to the forces tending to rotate male part 229 in the direction of arrows (s) and (u), the lower right end and upper left end of male part 229 will be forced, or biased, against the adjacent surfaces of the female part 231, at 251 and 255 as shown in Figure 44, acting as stop surfaces, thereby providing the required backing support for the rotary cutters 7. Of course, biasing the male part 229 in the direction of arrows (s) and (u) will also result in slight

gaps 253 and 257, dependent upon the fit tolerance between the male and female parts 229 and 231.

Figure 45 shows the female part 231 in cross section and the male part 229 in full side view and also fully inserted into the female part. This view shows the relationship between the tapered walls 235,237,247, and 249 (the dashed line 235 is for understanding only, as the surface it represents is, in fact, on the portion of female part 231 that was removed for showing the cross section in Figure 45).

It will be understood that the gaps 53,57,176,178,133, 187,253, and 257 are shown exaggerated in size for illustration purposes only. In practice, depending upon the precision required, such gaps may be proportionally much smaller.

While only certain embodiments have been set forth, alternative embodiments and various modifications will be apparent from the above description to those skilled in the art. These and other alternatives are considered equivalents and within the spirit and scope of the present invention.