embodiments of the invention relate to improvements to prior art shear coupling assemblies to permit use with both reciprocating and rotary pump applications . a description of a conventional shear coupling assembly and method of assembly is provided to assist in understanding embodiments of the invention and the advantages therein . having reference to fig1 and 2 , a conventional prior art shear coupling assembly 1 , applicable to reciprocating pump applications only , comprises two members , a pin coupling member 10 and a box coupling member 12 . either of the pin or box coupling member 10 , 12 can be connected to either of a pump or a rod string ( not shown ) for permitting connection therebetween . the pin coupling member 10 comprises a cylindrical body 14 having an insert member 16 with external threads extending axially outwardly therefrom and connected to the body 14 by a shear neck 18 typically having a relatively reduced section . the insert member 16 is cylindrical and smaller in diameter than the cylindrical body 14 . the reduced section of the shear neck 18 has a known cross - sectional area and acts as a preferential point of parting in the connection between the rod string and the pump under design loading . a top 20 of the insert member 16 is bored with an internally threaded axial counterbore 22 adapted for use for pretensioning the shear neck 18 during assembly , as described below . the pretension in the shear neck 18 is maintained through a seating interface between the pin and box coupling members 10 , 12 along a radial contact shoulder 24 formed at a top of the cylindrical body 14 . the body 14 further comprises a threaded connection 26 at an end opposite the insert member 16 for threaded connection to either the rod string or the pump and can be either a female connection ( fig1 ) or a male connection ( fig2 ) as shown . the box coupling member 12 comprises a tubular body 28 having an internal , threaded , axial bore 30 that co - operates with a thread profile of the externally threaded insert member 16 and which extends substantially a full length of the axial bore 30 . a first end 32 of the tubular body 28 is connected to the pin coupling member 10 at the externally threaded insert member 16 . a second end 34 of the body tubular body 28 is threadedly connected to either the rod string or the pump . in an embodiment of a prior art method of assembly , prior to assembling the pin and box coupling members 10 , 12 , a thread - locking epoxy or adhesive is typically applied to the externally threaded insert 16 and the radial contact shoulder 24 of the pin coupling member 10 . the externally threaded insert 16 is inserted into either the first or second end 32 , 34 of the box coupling member 12 and is advanced along the internally threaded , axial bore 30 until the radial contact shoulder 24 of the pin coupling member 10 approaches , but does not yet fully contact , the first or second end 32 , 34 of the box coupling &# 39 ; s tubular body 28 . a tension rod , commonly called a ready rod or bolt ( not shown ) having an external thread at one end matching the profile of the internally threaded counterbore 22 , is inserted through the axial bore 30 of the box coupling member 12 and is threaded into the internally threaded counterbore 22 . the shear neck 18 is placed into tension by pulling upwardly on the tension rod . with the tension rod and shear neck 18 under tension , the box coupling member body 12 is further advanced along the externally threaded insert 16 until the tubular body 28 firmly contacts the radial contact shoulder 24 of the pin coupling member 10 . contact between the tubular body 28 of the box coupling member 12 and the radial contact shoulder 24 of the pin coupling member 10 acts to maintain the pretension in the shear neck 18 . the tensile load on the tension rod is then released and the tension rod is unthreaded and removed from the assembly 1 . the assembled shear coupling 1 is unused for sufficient time to permit the thread - locking epoxy to dry and harden . as shown in fig3 - 5 , a shear coupling assembly 100 according to embodiments of the invention , for use in both reciprocating and rotary pumping applications , driveably connects a first coupling member 102 and a second coupling member 104 . the first and second coupling members 102 , 104 are driveably connected both axially and rotationally as is described herein . the rotational connection is by means other than at a shear neck 116 to prevent rotational loads from affecting the design purpose of the shear neck 116 . a locking member 130 connects axially between the first and second coupling members 102 , 104 . having reference to fig4 and 5 , and as one of skill in the art would appreciate , the second coupling member 104 can have either pin or box coupling ends for connection between the pump and the rod string , resulting conventionally in a box / box ( fig4 ) or a box / pin ( fig5 ) combination . thread sizes for the box and pin couplings within a shear coupling assembly 100 can be the same or can be different , resulting in a crossover arrangement suitable in some applications , as is understood in the art . having reference again to fig3 and 4 , the first coupling member 102 comprises a tubular body 106 having an internal , axial bore 108 formed therethrough for receiving at least a portion of the second coupling member 104 therein . the internal axial bore 108 comprises a lower portion 110 having a substantially irregular female profile p f formed therein . the second coupling member 104 , as in the prior art , comprises a cylindrical body 112 having an externally threaded insert member 114 extending axially outwardly therefrom and connected to the body 112 by a shear neck 116 designed to part under design loads . in the embodiment shown herein , the shear neck 116 has a reduced section . while referred to in the industry as a shear neck , it is believed the parting is a tensile failure . the insert member 114 is bored with an internally threaded axial counterbore 118 used to pretension the shear neck 116 during assembly , as described for the prior art shear coupling assembly 1 . unlike the prior art , the cylindrical body 112 , below the shear neck 116 , further comprises a substantially irregular male profile portion p m which acts to engage the substantially irregular female profile p f formed in the axial bore 108 of the first coupling member 102 , when inserted therein . thus , when the male and female substantially irregular profiles p m , p f are mated , the first and second coupling members 102 , 104 are rotationally , driveably connected , permitting the transfer of torque therebetween for co - rotation of the first coupling member 102 with the second coupling member 104 during rotary pumping operations . as in the prior art shear coupling shown in fig1 , the cylindrical body 112 of the second coupling member 104 further comprises a radial contact shoulder 120 . the radial contact shoulder 120 extends radially outwardly below the shear neck 116 and the substantially irregular male profile p m . as shown in fig6 - 12 , the substantially irregular male profile p m and substantially irregular female profile p f are radially variable about the circumference of the profile p f , p m so that the profile p f , p m of one of the coupling members 102 , 104 interferes with the profile p f , p m of the other of the coupling members 102 , 104 . having reference to fig6 , and in an embodiment of the invention , the substantially irregular male and female profiles p m , p f are substantially circular , serrated or splined profiles . one suitable spline profile is a 30 ° pressure angle , fillet root side fit , 32 / 64 pitch with 48 teeth , according to ansi standard ansi 92 . 1 . as one of skill would understand , other serrated or splined profiles applied to the torque transmitting profiles p m , p f of the shear coupling assembly 100 would also be suitable . in embodiments of the invention , shown in fig7 , the substantially irregular male profile p m and the substantially irregular female profile p f have cross - sectional areas enclosed by curves having three sides ; in other words , substantially spherical triangles . as shown in fig8 - 12 , the substantially irregular male profile p m and substantially irregular female profile p f are polygons having four or more sides . having reference again to fig4 , the substantially irregular female profile p f is greater in axial length than that of the substantially irregular male profile p m to ensure that a lower end 122 of the first coupling member &# 39 ; s body 106 fully engages the radial contact shoulder 120 of the second coupling member 104 when assembled . the axial bore 108 of the first coupling member 102 further comprises a restricted portion 124 above the substantially irregular female profile p f . the restricted portion 124 is sized to permit passage of the insert member 114 of the second coupling member 104 therethrough , but is smaller in diameter than the substantially irregular male profile p m of the second coupling member 104 . the axial bore 128 above the restricted portion 124 is substantially circular , the restricted portion 124 forming a radially inwardly extending , upper shoulder 126 between the substantially circular portion 128 and the substantially irregular female profile p f . as a result of the greater relative length of the substantially irregular female profile p f over the substantially irregular male profile p m does not contact the restricted portion 124 . having reference to fig3 and 4 , in order to ensure the first and second coupling members 102 , 104 remain axially engaged when assembled , the locking member 130 is used . the locking member 130 engages between the first coupling member 102 and the second coupling member 104 for preventing axial separation of the second coupling member 104 from the first coupling member 102 , when assembled . in an embodiment of the invention , as shown in fig3 , 4 and 13 , the locking member 130 comprises a cylindrical body 132 having a threaded axial bore 134 formed therein . the cylindrical body 132 has a diameter sized so as to be insertable downward into the circular portion 128 of the axial bore 108 of the first coupling member 102 for threading onto the externally threaded insert member 114 of the second coupling member 104 which extends above the upper shoulder 126 when inserted therein . the locking member 130 is threaded onto the externally threaded insert member 114 until a lower end 136 of the locking member 130 engages the upper shoulder 126 in the bore 108 . thus , the second coupling member 104 cannot separate from the first coupling member 102 under normal axial loading . advantageously , when assembled , the torque transferring profiles p m , p f and the shear neck 116 are protected within the assembled shear coupling assembly 100 from exposure to potentially corrosive wellbore fluids for improving fatigue resistance . as shown in fig4 , the cylindrical body 132 of the locking member 130 is longer than the insert member 114 on the second coupling member 104 to ensure that the lower end 136 of the locking member 130 engages the upper shoulder 126 in the first coupling &# 39 ; s axial bore 108 before a top 138 of the locking member &# 39 ; s bore 132 engages the insert member 114 . having reference to fig1 , as an aid for assembly , the locking member 130 further comprises engagement means 140 formed in an upper surface 142 of the cylindrical body 132 for engaging a tool end for threading the locking member 130 onto the insert member 114 . in an embodiment , the engagement means 140 is a profile , such as a diametral slot , which is compatible with the tool end . having reference to fig1 - 15 , to set design tensile loading limits and to increase fatigue resistance , it is generally desirable to apply a pretension to the shear neck 116 during assembly . best seen in fig1 , and in an embodiment , the upper surface 142 of the locking member &# 39 ; s cylindrical body 132 further comprises an opening 144 through which a tension rod 208 can extend for applying pretension to the shear neck 116 . after insertion of the locking member 130 downwardly into the axial bore 108 and prior to threading the locking member 130 onto the insert member 114 , the tension rod 208 is inserted through the opening 144 for engagement with the counterbore 118 in the insert member 114 . an upward pulling force is applied to the tension rod 208 and while maintaining the upward pulling force , the locking member 130 is rotated for fully engaging with the insert member 114 for axially driveably connecting the first and second coupling members 102 , 104 and for maintaining the pretension in the shear neck 116 . as one of skill in the art will appreciate there are a number of ways in which embodiments of the invention may be assembled . applicant has described herein one such method of assembly . having reference to fig1 - 16b and in an embodiment of the invention , the second coupling member 104 is affixed to a base 200 , such as by an anvil 202 configured for either a pin coupling ( fig1 a ) or a box coupling ( fig1 b ), connected to the base 200 . typically , the base 200 forms part of a frame 204 to which a hydraulic cylinder 206 is connected for applying pretension to the shear neck 116 during assembly . the first coupling member 102 is lowered onto the second coupling member 104 , inserting the insert member 114 into the lower end 110 of the axial bore 108 of the first coupling member 102 . the insert member 114 passes through the restricted portion 124 of the axial bore 108 . the first coupling member 102 is lowered until the lower end 122 of the first coupling member 102 contacts the radial contact shoulder 120 of the second coupling member 104 . the substantially irregular male and female profiles p m , p f of the first and second coupling members 102 , 104 are mated so as to permit transfer of torque therebetween . the locking member 130 is inserted downwardly into the upper portion 128 of the axial bore 108 of the first coupling member 102 for threaded connection to the insert member 114 of the second coupling member 104 . as shown in fig1 and 15 , where a pretension is to be applied to the shear neck 116 , a tension rod 208 is inserted into the axial bore 108 of the first coupling member 102 after insertion of the locking member 130 . the tension rod 208 passes through the opening 144 in the upper surface 142 of the locking member 130 and engages with the threaded counterbore 118 in the insert member 114 . as in the prior art , an upward pulling force is applied to the tension rod 208 at a predetermined force , such as by the hydraulic cylinder 206 . in this embodiment , while the upward pulling force is maintained , the locking member 130 is threaded onto the insert member 114 until the lower end 136 of the locking member 130 engages the upper shoulder 126 in the first coupling member &# 39 ; s axial bore 108 . thereafter , the tension rod 208 is released from the counterbore 118 and the tension rod 208 is removed from the axial bore 108 of the first coupling member 102 . as shown in fig1 , prior to connecting the tension rod 208 to the hydraulic cylinder 206 , an engagement tool 210 having a tool end 212 is inserted into the axial bore 108 of the first coupling member 102 for engaging the engagement means 140 on the upper surface 142 of the locking member 130 for threading the locking member 130 therein . in the embodiment shown , the engagement tool 210 is integral with the tension rod 208 and is independently rotatable thereabout . alternatively , the engagement tool 210 can be positioned for rotation about the tension rod 208 after the tension rod 208 is engaged with the counterbore 118 of the insert member 114 . the engagement tool 210 is thereafter rotated with the tool end 212 engaged in the diametral slot 140 to thread the locking member 130 onto the insert member 114 . the locking member 130 is threaded until the lower end 136 of the locking member 130 engages the upper shoulder 126 in the first coupling member &# 39 ; s axial bore 108 . the engagement tool 210 is thereafter released from the locking member 30 for retraction from the axial bore 108 . as with the prior art shear coupling assembly , a thread - locking epoxy or adhesive is typically applied to the radial contact shoulder 120 of the second coupling member 104 and to the threads of the insert member 114 and locking member 130 , prior to assembly .