a more complete understanding of the components , processes and apparatuses disclosed herein can be obtained by reference to the accompanying drawings . the figures are merely schematic representations based on convenience and the ease of demonstrating the present disclosure , and is , therefore , not intended to indicate relative size and dimensions of the devices or components thereof and / or to define or limit the scope of the exemplary embodiments . although specific terms are used in the following description for the sake of clarity , these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawing , and are not intended to define or limit the scope of the disclosure . in the drawing and the following description below , it is to be understood that like numeric designations refer to components of like function . the singular forms “ a ,” “ an ,” and “ the ” include plural referents unless the context clearly dictates otherwise . as used in the specification , various devices and parts may be described as “ comprising ” other components . the terms “ comprise ( s ),” “ include ( s ),” “ having ,” “ has ,” “ can ,” “ contain ( s ),” and variants thereof , as used herein , are intended to be open - ended transitional phrases , terms , or words that do not preclude the possibility of additional components . it should be noted that many of the terms used herein are relative terms . for example , the terms “ upper ” and “ lower ” are relative to each other in location , i . e . an upper component is located at a higher elevation than a lower component , and should not be construed as requiring a particular orientation or location of the structure . the terms “ top ” and “ bottom ” are relative to an absolute reference , i . e . the surface of the earth . put another way , a top location is always located at a higher elevation than a bottom location , toward the surface of the earth . turning now to fig1 a , in certain embodiments there is a front housing 10 which includes axially extending member 12 having an internal bore 14 , the axially extending member 12 having external threads 13 for coupling the front housing 10 to a tool body . those skilled in the art will appreciate that other ways of coupling the front housing 10 to the tool body could be used and are within the skill in the art . alternatively , the front housing 10 could be made as an integral piece of the tool body , in which case the external threads 13 would not be required . the front housing 10 also includes an annular disc - shaped portion 15 , and a cylindrical portion 16 that includes a plurality of spaced radial locking tabs 17 a , 17 b . in certain embodiments , there are two spaced radial locking tabs 17 a , 17 b , although in certain embodiments there may be additional tabs . the internal bore 14 communications with another internal bore 18 of smaller inside diameter than the internal diameter of internal bore 14 . the annular region 9 between the disc - shaped portion 15 and the locking tabs 17 may accommodate an o - ring 11 ( fig3 ) or the like . as shown in fig1 b , in certain embodiments the locking tab 17 a extends 60 ° around the circumference of the cylindrical portion 16 , as does the locking tab 17 b . regions each encompassing 120 ° that are devoid of tabs separate the locking tab 17 a from , the tab locking 17 b . those skilled in the art will appreciate that the aforementioned spacing of the locking tabs 17 a and 17 b is exemplary and that other spacings are within the scope of the embodiments disclosed herein . turning now to fig2 a , there is shown an expander head ring 20 in accordance with certain embodiments . the expander head ring 20 is generally cylindrical , and may include annular knurled or textured external regions 21 , 22 to facilitate manual gripping of the head ring 20 . in certain embodiments , the head ring 20 includes at one end an internal bore 23 , configured to receive one or more functional elements such as a plurality of expander dies that extend through the bore and are positioned to receive a movable member such as a conical expander 50 , for example ( fig3 ). other suitable functional elements include those that are capable of changing the configuration of a tube or the like , such as elements for flaring and tube forming , for example . the internal bore 23 extends through the expander head ring 20 , expanding in internal diameter in several steps between the smallest internal diameter at end 20 a to the largest internal diameter at end 20 b . as best seen in fig2 b and 5 , in certain embodiments the expander head ring 20 includes an annular ring 127 positioned axially inwardly of the outer edge or free end 20 ′ at end 20 b of the head ring 20 , and that extends radially inwardly from the inner surface of the head ring 20 . in certain embodiments , at one or more intervals along the annular ring 127 , there are two spaced radially inwardly extending projections 27 a , 27 b . the projections 27 a , 27 b extend radially inwardly a distance further than the annular ring 127 , and extend axially ( in the direction away from the free end or edge 20 ′) a distance further than the annular ring 127 . as best seen in fig5 , the ends 27 e of each projection 27 a , 27 b are ramped to gradually taper towards the annular ring 127 . in certain embodiments , a second annular ring 128 is axially spaced from annular ring 127 , as seen in fig2 a and 5 . the space between the second annular ring 128 and projection 27 a defines a first groove 30 . similarly , the space between the second annular ring 128 and the projection 27 b defines a second groove 300 ( fig2 a ). each groove 30 , 300 ramps to a respective stop 32 a , 32 b ( fig2 b and 5 ). each groove is configured to receive a respective locking tab 17 a , 17 b of the front housing 10 . thus , to assemble the front housing 10 to the expander head ring 20 , the locking tabs 17 a , 17 b of the front housing 10 are inserted into the space between the projections 127 a , 127 b of the expander head ring 20 , and then the expander head ring 20 and the front housing 10 are rotated with respect to each other to cause the locking tabs 17 a , 17 b to be slidingly received by the grooves 30 , 300 until the locking tabs 17 a , 17 b abut against the stops 32 a , 32 b , fixing the expander head ring 20 to the front housing 10 and preventing any axial movement thereof . fig3 illustrates the expander head ring 20 assembled to the front housing 10 , which in turn is coupled to an expander tool 200 including expander 50 . the expander 50 preferably terminates in a portion 50 a that is shaped to engage the interior shape of die elements and expand the elements as the portion 50 a penetrates that interior region . in certain embodiments , the portion 50 a is conically shaped . the expander 50 , as shown in fig3 , is in its normal unexpanded position , housed in chamber 210 of tool 200 . biasing member 212 biases the conical expander 50 to the resting position shown in fig3 . in certain embodiments , the chamber 210 is part of a hydraulic pump and may be pressurized by activation of the hydraulic pump such as by manual actuation of a pumping lever associated with the tool 200 as is known in the art , such as the tool disclosed in u . s . pat . no . 6 , 619 , 099 , the disclosure of which is hereby incorporated by reference . pressurization of the chamber 210 causes the expander 50 to move , against the force of biasing member 212 , to the tube expanding position shown in fig4 . as the expander 50 travels through the internal bore 23 , it engages and radially expands a plurality of die elements of a die set ( not shown ) attached to the expander head ring 20 , thereby expanding deformable tubing positioned on the die set . in accordance with certain embodiments , an expanded tube is formed by clamping or otherwise coupling a tube having a tube end between a plurality of die elements attached to the expander tool 200 that are radially expandable and shaped to form an expanded tube end . the die elements may be held in place in the head ring 20 by a washer 79 and snap ring 80 or the like ( fig5 ). the head ring 20 is attached to the front housing 10 by aligning the spaces between the projections 27 a , 27 b with respective locking tabs 17 a , 17 b , forcing the locking tabs into respective grooves 30 , 300 , and rotating the head ring 20 with respect to the front housing 10 to cause the locking tabs 17 a , 17 b to be captured beneath respective projections 27 a , 27 b and fix the head ring 20 in place . actuation of the tool causes the expander 50 to translate axially in the tool and travel through internal bore 14 , internal bore 23 , and engage the die elements and cause them to expand radially , thereby expanding the tube .