the invention will now be described in more detail by way of example with reference to the embodiment ( s ) shown in the accompanying figures . it should be kept in mind that the following described embodiments are only presented by way of example and should not be construed as limiting the inventive concept to any particular physical configuration . fig1 illustrates a screw - locking wrench working end assembly according to an embodiment of the invention . in particular , fig1 a illustrates a section a — a , and fig1 b illustrates a section b — b . an exemplary illustration of the working end assembly portion is depicted in fig1 c with reference to the cross section of fig1 a , the working end assembly 100 comprises a locking clutch drive 102 , which is centrally disposed . the locking clutch drive 102 has an upper and a lower clutch , as will be explained later with respect to fig6 . surrounding the central cylindrical portion of the locking clutch drive 102 are upper 104 and lower 106 screw locks . the screw locks 104 and 106 have high friction / low wear surfaces which contact corresponding surfaces of the locking clutch drive 102 . a lubed spline washer 108 is disposed between the upper and lower screw locks 104 and 106 . end portions of the upper 110 and lower 112 screw - locking wrench handles are shown at the left side of fig1 a . the upper and lower screw locks 104 and 106 are threaded with locking / unlocking screw thread , and these thread into threaded portions of the upper and lower handles 110 and 112 , respectively , as is shown . an assembly screw 114 is also shown in cross section extending through the top of the locking clutch drive 102 ( the upper clutch ) and into a threaded portion thereof ( the lower clutch ), thereby holding the assembly 100 together . as can be seen in fig1 a and 1 b , the working end assembly 100 is generally circular when viewed from the top , and the components , assembly screw 114 , locking clutch drive 102 , lubed spline washer 108 , and the upper 104 and lower 106 screw locks , are disposed about a common central axis 116 . a drive member 118 ( shown in fig1 c ), for driving a fastener , is disposed along this central axis 116 , as well . fig2 illustrate a screw - locking wrench handle assembly according to an embodiment of the invention . in particular , fig2 a illustrates a left side view , fig2 b illustrates a top view , and fig2 c illustrates three sections taken along the handle in fig2 b at a — a , b — b , and c — c . fig2 show how the upper 110 and lower 112 handles are positioned with respect to each other , and the working end assembly 100 . around the middle of the handles 110 and 112 , between a gripping end 201 and the working end 100 , there is a preload spring pocket or recess 202 for holding a preload spring ( not shown ). the arrows in the vicinity of the preload spring pocket 202 represent the direction of force to lock the wrench , which is also the direction that the preload spring urges the upper 110 and lower 112 handles . the gripping end 201 of the handles 110 , 112 is shown in cross section taken along c — c , in fig2 c at the bottom . each handle gripping end 201 has the cross section of a circle with a triangular extension . the handles 110 , 112 are disposed so that the triangular extension of the upper handle 110 and the triangular extension of the lower handle 112 are disposed to have corresponding sides which extend in opposite directions , such that when the upper handle 110 and the lower handle 112 are rotated in opposite directions with respect to the common axis 116 of their working end portions 100 , e . g ., in the direction of the arrows , respective opposing surfaces of the respective triangular extensions move in close proximity in opposite parallel circular directions , as can be seen . fig3 illustrate an upper handle assembly according to an embodiment of the invention . in particular , fig3 a illustrates a left side view , fig3 b illustrates a top view , fig3 c illustrates three sections taken along the handle in fig3 b at a — a , b — b , and c — c , and fig3 d illustrates a right side view . fig3 shows upper handle 110 in detail . as shown in fig3 b and 3 d , screw threads 302 , preferably engage the upper handle 110 with the upper screw lock 104 is labeled . an upper locking force reaction bushing 303 will be explained in more detail below . fig4 illustrate a lower handle assembly according to an embodiment of the invention . in particular , fig4 a illustrates a left side view , fig4 b illustrates a top view , fig4 c illustrates three sections taken along the handle in fig4 b at a — a , b — b , and c — c , and fig4 d illustrates a right side view . fig4 shows lower handle 112 in detail . as shown in fig4 b and 4 d , screw threads 402 preferably engage the lower handle 112 with the lower screw lock 106 . lower locking force reaction bushing 403 will now be explained along with the locking force reaction bushing 303 of fig3 . a force load path preferably goes through the upper handle threads , through upper handle bushing 303 , through the spline washer 108 , through the lower handle bushing 403 , through the lower handle threads , through the screw locks , through the drive , and back to the upper handle threads . if the handle locking bushings 303 and 403 were allowed to contact each other directly , turning one handle to tighten could turn the other handle to loosen . therefore , a separating spline washer 108 preferably is inserted between them . the washer 108 preferably is splined to the locking clutch drive 102 . fig5 illustrate views of screw locks and spline washer according to an embodiment of the invention . in particular , fig5 a illustrates a top view of an upper screw lock , fig5 b illustrates a top view of a lower screw lock , fig5 c illustrates a section taken along the upper screw lock in fig5 a at a — a , fig5 d illustrates a section taken along the lower screw lock in fig5 b at b — b , fig5 e illustrates a top view of a lubed spline washer , and fig5 f illustrates an edge view of the spline washer of fig5 e . fig5 shows the upper 104 and lower 106 screw locks and the lubed spline washer 108 in closer detail . in particular , the splines 502 of the lower screw lock 106 are illustrated in fig5 b and 5 d , and the spline passages 504 of the upper screw lock 104 are shown in fig5 a . fig5 c and fig5 d show the locking / unlocking screw threads 506 of the screw locks , which engage the corresponding threads of the handles 110 and 112 . high friction , low wear surfaces 508 and 510 of the upper and lower screw locks 104 and 106 , respectively , as also illustrated . these surfaces contact the locking clutch drive 102 as mentioned above with respect to fig1 a . several surfaces of the screw locks 104 and 106 are dry lubricated , as indicated in fig5 a – 5 d . further , all the surfaces of the spline washer 108 are dry lubricated , as indicated . fig6 illustrate views of a locking clutch according to an embodiment of the invention . in particular , fig6 a illustrates a top view of an upper clutch , fig6 b illustrates a top view of a lower clutch , fig6 c illustrates a bottom view of the upper clutch of fig6 a , fig6 d illustrates a bottom view of the lower clutch in fig6 b , fig6 e illustrates a section of the upper clutch of fig6 c taken along b — b , and fig6 f illustrates a section of the lower clutch of fig6 b taken along a — a . as mentioned above , the locking clutch drive 102 is divided into two parts , an upper clutch 602 and a lower clutch 604 , as shown . the lower clutch 604 has threaded splines 606 which extend into spline passageways in the upper clutch 602 . the upper clutch 602 has a screw passageway 608 for receiving the assembly screw 114 , including a screw head seat 610 against which the head of the screw 114 rests when engaged in threaded splines 606 . the clutch wear surfaces 612 on the upper 602 and lower 604 clutch are illustrated in the sectional views fig6 e and fig6 f . the operation of an exemplary embodiment of a screw locking wrench according to the invention will now be described . first , the case in which the operator is tightening a fastener , i . e ., clockwise rotation , is considered . as shown in fig2 , for example , the preload spring forces the upper handle 110 in the clockwise direction and the lower 112 handle in the opposite direction , counter - clockwise , thereby keeping the upper 104 and lower 106 screw locks in intimate contact with the locking clutch drive 102 . the arrows in fig2 b and 2 c show the direction of locking caused by the geometry of the system and by the preload spring . therefore , to initiate clockwise rotation of the locking clutch drive 102 , the operator applies a clockwise torque to the upper handle 110 , as seen in fig2 c . this force in the clockwise direction drives the upper 104 and lower 106 screw locks against the locking clutch drive 102 , instantaneously locking the upper handle 110 , the upper 104 and lower 106 screw locks , and the locking clutch drive 102 into a single unit which rotates the fastener clockwise . the operator experiences negligible backlash / elastic deformation and the fastener is tightened . the system is self - locking , that is , the greater the applied torque , the harder the system locks up . after some arbitrary angle of rotation , the operator can unlock the device ( as will be explained below ), rotate it back to the original starting position , relock it , and drive it again . this can be repeated over and over until the cumulative rotation of the fastener and / or its preload is sufficient . referring back to fig2 c , for a clockwise drive , unlocking occurs when the operator applies force on the upper 110 and lower 112 handles opposite to the arrows . advantageously , this can be accomplished when holding the handles 110 and 112 in one hand by a simple , one - handed rotation of the wrist . this unlocking action compresses the preload spring , drives the upper 104 and lower 106 screw locks away from intimate contact with the locking clutch drive 102 , and the upper 110 and lower 112 handles are free to rotate counter clockwise . relaxing the wrist action allows the preload spring to bias the upper 104 and lower 106 screw locks against the locking clutch drive 102 , and the operator is ready for another tightening increment . if screw locking shows signs of slipping , the operator may squeeze the upper 110 and lower 112 handles together while applying torque , thereby assisting the locking process . the case in which the operator is attempting to loosen a fastener by rotating it counter clockwise will now be described . in this instance , the operator applies counter clockwise torque to the lower handle 112 , shown in fig2 c . thus , the system locks up against counter clockwise rotation , and the fastener is loosened . ( this of course assumes a normally threaded fastener — alternately , a reverse threaded fastener would be tightened in a counter clockwise direction ). unlocking is done by a simple turn of the wrist just as it was done for the clockwise case , and the operator is ready for the next incremental counter clockwise rotation . some additional operational details will now be discussed , and some details on the internal workings of the system will now be described . the upper 104 and lower 106 screw locks preferably are threaded into the upper 110 and lower 112 handles , respectively . the upper 104 and lower 106 screw locks preferably are splined together so that they cannot rotate with respect to each other . a lubed spline washer 108 may be positioned between them , so it and the upper 104 and lower 106 screw locks rotate together as a unit . however , the screw locks 104 and 106 are able to translate axially , and to lock or unlock as the case may be . the preload spring urges the upper 110 and lower 112 handles with equal and opposite force with respect to the upper 104 and lower 106 screw locks and these , accordingly , translate apart until they contact the surfaces of the locking clutch drive 102 and come to rest . when the operator drives the system in either a clockwise or a counter clockwise direction , the mechanical advantage of the screw threads provides the self - locking performance of the device . the lubed spline washer 108 preferably provides a low contact stress , lubed reaction platform for the reactive forces of both the upper 110 and lower 112 handles . splining the washer 108 ensures that , for example , a clockwise motion of the upper handle 110 cannot rotate the lower handle 112 with it and , thereby unlock the lower 112 while the upper 110 is being locked . an analogous case holds for counter clockwise motion . the locking clutch drive 102 preferably is split into two splined halves 602 and 604 ( see fig6 ), and the entire system can be assembled with a single , simple common machine assembly screw 114 , as has been illustrated . locking analysis will now be presented . that is , screw locking will now be discussed from an analytical point of view to provide some measure of insight as to how and why it works . fig7 a and 7 b illustrate ramp locking and wedge drive , respectively . in particular , fig7 a illustrates the wedge action that may be obtained by rotating a threaded handle against its corresponding threaded screw lock . f d =( drive force ) torque applied to the handle divided by the thread radius of its screw lock μ s2 = static coefficient of friction for locking clutch drive / screw lock interface f d = f n1 ⁢ ⁢ μ s1 ⁢ r 1 r 2 + f n1 ⁢ μ s1 ⁢ cos ⁢ ⁢ ϕ + f n1 ⁢ μ s1 ⁢ sin ⁢ ⁢ ϕ ( 2 ) f n = f n1 cos θ − f n1 μ s1 sin φ ( 4 ) or ⁢ ⁢ f n1 = f n ( cos ⁢ ⁢ ϕ - sin ⁢ ⁢ ϕ ) ( 5 ) f d = f n ⁢ μ s1 ⁡ ( r 1 r 2 ) + f n1 ⁢ μ s1 ⁡ ( cos ⁢ ⁢ ϕ + sin ⁢ ⁢ ϕ ) ( 6 ) by construction : ⁢ ⁢ r 1 r 2 ≤ 1 , [ cos ⁢ ⁢ ϕ - sin ⁢ ⁢ ϕ ] ≥ 1 ( 8 ) so : 2 f n μ s2 & gt ; f d ( 9 ) resulting in : ⁢ ⁢ μ s2 ≥ 0 . 5 ⁢ μ s1 ⁢ { r 1 r 2 + [ cos ⁢ ⁢ ϕ + sin ⁢ ⁢ ϕ ] [ cos ⁢ ⁢ ϕ - μ s1 ⁢ sin ⁢ ⁢ ϕ ] } ( 10 ) we will now perform some calculations required for screw - locking ( μ s2 ) using representative screw angles ( pitch / diameter / angle ) and dry lube coefficients of friction ( μ s1 ). for these exemplary embodiments , we conclude that screw locking will occur as long as μ s2 & gt ; μ s1 by ( in the worst case shown for 1 . 25 in . dia / 4 pitch screw lock and μ s1 = 0 . 15 ) of as little as 0 . 0055436 / 0 . 15 = 0 . 03695733 or 3 . 7 % above the lube coefficient of friction . with a slight amount of hand squeezing , the system will lock and work even if μ s2 & lt ; μ s1 . the amount of wrist action needed to open / unlock the wrench will now be examined . from the immediately preceding discussion , we are confident that an exemplary screw lock wrench with φ = 3 . 642647 deg ., pitch of 4 , will work ( lock ). and , with its relatively large pitch , it will open further with less wrist action than finer threads ( higher pitches ). tan φ = 6 . 366198 ( e − 2 )≦ μ s1 ≦ μ s2 ( which is satisfactory ) ( 3 ) we wish a 0 . 005 in . clearance to make certain the screw locks completely release , so : for a 7 in . long handle , the motion to unlock is wedge drive analysis will now be examined , considering the merits of using a wedge drive interface between the screw locks and the locking clutch drive ( fig7 b ). we examine various exemplary wedge angles ( θ in fig7 b ), and calculate the improvement in normal force the wedge provides over no wedge by the ratio we do this for various representative wedge angles , and various coefficients of friction . as the table , shown below , indicates , a wedge angle will improve things , but not dramatically . one of skill will recognize that a wedge angle is not necessary to make the system work and it does complicate construction a bit . ∑ f y = 0 ( 1 ) f n = f nd sin θ + μ s2 f nd cos θ ( 2 ) some advantages of the above described invention over known tools will now be mentioned . one - way ratchet wrenches have a backlash / dead zone region and are limited regarding operation in small spaces . also , they require a separate switching system for changing direction . a screw locking wrench according to an embodiment of the invention has negligible backlash / dead zone region and a totally one - handed operation including wrist switching of direction . the one - way sprag ratchetless wrenches reduce the backlash / dead zone region , however they have load bearing limitations , are relatively complicated in their sprag preload / switching schemes and construction , and require reorienting the wrench to change direction . a screw locking wrench according to an embodiment of the invention has negligible backlash / dead zone region , an essentially negligible load bearing limitation , a preload scheme that is much simpler than sprag wrenches , a totally one - handed operation , including wrist switching , which is much simpler than those of sprag wrenches , and much simpler construction ( fewer parts ) overall . a screw locking wrench according to an embodiment of the invention should be less expensive than either one - way ratchet wrenches or one - way sprag wrenches . also , it should be more rugged and reliable for space operations . although a number of equivalent components may have been mentioned herein which could be used in place of the components illustrated and described with reference to the preferred embodiment ( s ), this is not meant to be an exhaustive treatment of all the possible equivalents , nor to limit the invention defined by the claims to any particular equivalent or combination thereof . a person skilled in the art would realize that there may be other equivalent components presently known , or to be developed , which could be used within the spirit and scope of the invention defined by the claims . yet another embodiment of the invention will now be considered relating to a wedge interface between screw locks and locking clutch drive . the screw locking arrangement shown in fig2 can be reversed . fig2 c can be flipped about its neutral axis ( the c — c section line in fig2 b ) so counterclockwise drive occurs off the upper handle ( as opposed to clockwise drive now ) and clockwise drive occurs off the lower handle ( as opposed to counterclockwise drive now ). it should be clear to a person skilled in the art that , as with the two element embodiment , micro stepping , either active or passive , can be accomplished with the three element embodiment in a similar manner , by controlling the frictional force of the elements during movements , and therefore , further explanation is not deemed necessary . it will be understood that the above described embodiments of the present invention are susceptible to various modifications , changes , and adaptations , and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims . it will be apparent to one skilled in the art that the manner of making and using the claimed invention has been adequately disclosed in the above - written description of the preferred embodiment taken together with the drawings .