with references to the attached drawings , please be described of the preferred embodiment as follows . first , with references to fig1 - 4 , this invention proposes a torque screwdriver structure that comprises : a holder 10 , a positioning bar 20 , a sliding tube 30 , a spring 40 , an adjusting tube 50 , and a screwdriver bit bar 60 . the holder 10 has , along the shaft axis , an elongated hole 11 that further has a concave 12 at the bottom set for being fitted by the positioning bar 20 , and has inner threads 13 on the top for threading with the male threads 52 of the adjusting tube 50 . the positioning bar 20 has , in one side , a fitting body 21 that can fit with the concave 12 of the holder 10 when assembled , and has , in the other side , a fixing ring 22 with at least three equally - spaced ball holes 221 on its wall . and further , each ball hole 221 collaborates with one fixing ball 23 . the sliding tube 30 sets a conical hole 31 at bottom to push fixing balls 23 into or release them from the ball holes 221 when the sliding tube 30 slides along the fixing ring 22 . this is so to fix the screwdriver bit bar 60 . the spring 40 is installed and stretches against the washer 53 and the top face of the sliding tube 30 on its both ends . the adjusting tube 50 sets a penetrating hole 51 so that the screwdriver bit bar 60 can penetrate through the adjusting tube 50 . it further has male threads 52 on the surface so as to thread with the inner threads 13 of the holder 10 , and has a washer 53 at the bottom . the screwdriver bit bar 60 can contain screwdriver bit in one side , and is mounted with a thin rod 62 that has multiple tooth 63 at its bottom . the tooth 63 can fit inside the fixing ring 22 in one side and collaborates with the conical hole 31 of the sliding tube 30 in the other side . the toothed grooves 631 are curved shaped so that the fixing balls 23 can well fit with the surfaces of them for firm fixture of the screwdriver bit bar 60 . for collaboration purpose , the positions of multiple tooth 63 and toothed grooves 631 match with the that of ball holes 221 . moreover , as shown in fig3 , the spring 40 can be depressed or loosed by threading adjusting tube 50 into or out of the holder 10 so as to adjust the and set the driving torque . when the exerted driving torque is greater than the set driving torque , the fixing balls 23 would be first pushed out gradually from the toothed grooves 631 to the tooth surface 632 and then they further push the sliding tube 30 outwards by interacting with the conical hole 31 until the bit bar 60 is completely loosed from the positioning bar 20 and sliding tube 30 . furthermore , as shown in fig3 and 4 , because the radius of the spring 40 is slightly smaller than that of the penetrating hole 51 , a washer 53 is set between them so that the spring 40 can be depressed more evenly and stably without bending . in case of an equal radius of the spring 40 to that of the penetrating hole 51 , the washer 53 can be omitted . from the tooth surface 632 to the toothed groove 631 is a curved surface , so the fixing balls 23 can roll easily in both left and right directions , which makes the torque screwdriver able to operate both clock - and counterclockwise as traditional screwdrivers . the fig5 and 6 show another embodiment for the screwdriver bit bar 60 , which makes the torque screwdriver can only perform either clockwise or counterclockwise for certain operational needs . the feature is that , symmetrically for all teeth 63 , one side of them is a 20 concaved surface 6411 , and the other side is a convex surface 6412 . the aforementioned concaved surface 6411 has the same radius and circle - center as the fixing balls 23 when they fit together . besides , the length of the tooth is around the radius size of the fixing balls 23 . this is so set that the concaved surface 6411 can prevent the fixing balls 23 from moving out of the toothed groove 631 for the purpose of locking the screwdriver bit , and on the contrary the convex surface 6412 allows the fixing balls 23 to roll out of the toothed groove 631 to release the screwdriver bit . with the aforementioned structure , therefore , a one - solo - direction torque screwdriver can be formed . with all aforementioned , the invention deserves grant of a patent based on its capability of industrial application and absolute novelty . the example illustrated above is just an exemplary embodiment for the invention , and shall not be utilized to confine the scope of the patent . any equivalent modifications within the scope of claims of the patent shall be covered in the protection for this patent .