Patent Publication Number: US-10770039-B1

Title: Drop tuner

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     There are no patent applications filed by me which are related to this patent application. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a drop tuner structure for a fine tuning bridge of an electric guitar. 
     2. Description of Related Art 
     Generally, a drop tuner for a stringed musical instruments has a pitch changing apparatus which produces two distinct pitches for selected strings. By this apparatus, players can change their instruments tuning immediately to the selected tuning between songs. The most popular tuning shift for guitar is to change 6th string tuning from E to D. When a player mounts a drop tuner on the general double locking bridge which has fine tuners as shown by U.S. Pat. No. 4,497,236, the bridge must be fixed against body part by counter spring force so that the bridge does not move by shift motion of a drop tuner. If the counter spring force is not strong enough, the bridge moves around the pivot by shift motion, and the tuning goes out of tune. 
     The drop tuner of U.S. Pat. No. 5,359,144 is specially designed drop tuner for the general double locking bridge which has fine tuners as shown by U.S. Pat. No. 4,497,236. But there are some difficulties in operation. The biggest problem is, when a player operates the drop tuner of U.S. Pat. No. 5,359,144, it is necessary to pinch it between thumb and index finger because of the drop tuner&#39;s shape is like a kind of cylinder. When a player plays the guitar, he usually pinches a pick between thumb and index finger on his right hand, so he must change the pick hold fingers when he operates the drop tuner of U.S. Pat. No. 5,359,144. And this might be a kind of stress for players in some scenes. 
     Other problem of the drop tuner of U.S. Pat. No. 5,359,144 is that it is difficult to adjust the shift amount precisely because of the structure. The order of physical adjustment points location is, shift action point, adjust point, pivot point. So, the shift action amount is larger than adjust amount, and thus it is difficult to set the shift amount precisely. 
     Other problem of the drop tuner of U.S. Pat. No. 5,359,144 is that extension line of shift amount adjust screw&#39;s axis and the axis of string lock screw which is the axis of shift slide motion don&#39;t cross, so rotational moment will be generated on shift amount adjust screw&#39;s tip by shift motion. By this way, the shift amount adjust screw tends to rotate easily and the shift amount will be unstable. 
     And the location of the shift amount adjust screw is not on the centerline of base body. So, the shift amount adjust screw location is better to be changed to the opposite side for left handed guitar players. By this thought, it is better to prepare for right handed model and left handed model, but it might be inventory risk. 
     This invention improves these problems in the field of a drop tuner for the general double locking bridge which has fine tuners as shown by U.S. Pat. No. 4,497,236. 
     BRIEF SUMMARY OF THE INVENTION 
     A drop tuner of the present invention includes a base body movable on a string lock screw and a shift amount adjust screw for adjusting a shift amount of the pitch. A fin is provided on the base body so that the fin can be easily pushed and pulled only by one finger even when a player holds a pick. 
     For adjusting the shift amount, since a pivot point, a shift action point and the shift amount adjust screw are arranged in this order, the shift action amount is smaller than the adjust amount of the shift amount adjust screw. Thus, the shift amount can be finely adjusted. 
     In addition, since an extension line of the axis line of the shift amount adjust screw crosses the axis line of the sliding direction, the rotational moment generated at the shift amount adjust screw is theoretically zero when performing the sliding movement. Thus, the shift amount adjust screw is hardly loosened. 
     The shift amount adjust screw is located at a center surface of the base body. Thus, same type of drop tuner can be used for a right-handed guitar and a left-handed guitar. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective view of an electric guitar. 
         FIG. 2  shows an enlarged perspective view of a headstock part. 
         FIG. 3  shows an enlarged perspective view of a body part. 
         FIG. 4A  shows a perspective view of a saddle unit. 
         FIG. 4B  shows a plan view of the saddle unit. 
         FIG. 4C  shows a side view of the saddle unit. 
         FIG. 4D  shows a cross-sectional view of the saddle unit. 
         FIG. 5  shows a perspective view of an electric guitar in which a drop tuner of U.S. Pat. No. 5,359,144 is installed and it is set at lower pitch side. 
         FIG. 6  shows a perspective view of an electric guitar in which a drop tuner of U.S. Pat. No. 5,359,144 is installed and it is set at higher pitch side. 
         FIG. 7  shows a cross-sectional view of an electric guitar in which a drop tuner of U.S. Pat. No. 5,359,144 is installed. 
         FIG. 8A  shows a perspective view of a guitar bridge in which a drop tuner of U.S. Pat. No. 5,359,144 is installed and it is set at lower pitch side. 
         FIG. 8B  shows a cross-sectional view of a guitar bridge in which a drop tuner of U.S. Pat. No. 5,359,144 is installed and it is set at lower pitch side. 
         FIG. 8C  shows a perspective view of a guitar bridge in which a drop tuner of U.S. Pat. No. 5,359,144 is installed and it is set at higher pitch side. 
         FIG. 8D  shows a cross-sectional view of a guitar bridge in which a drop tuner of U.S. Pat. No. 5,359,144 is installed and it is set at higher pitch side. 
         FIG. 9A  shows a perspective view of a drop tuner of U.S. Pat. No. 5,359,144. 
         FIG. 9B  shows a side view of a drop tuner of U.S. Pat. No. 5,359,144. 
         FIG. 9C  shows a plan view of a drop tuner of U.S. Pat. No. 5,359,144. 
         FIG. 9D  shows a cross-sectional view of a drop tuner of U.S. Pat. No. 5,359,144. 
         FIG. 9E  shows a front view of a drop tuner of U.S. Pat. No. 5,359,144. 
         FIG. 10  shows a perspective view of an electric guitar in which a drop tuner of the present invention is installed and it is set at lower pitch side. 
         FIG. 11  shows a perspective view of an electric guitar in which a drop tuner of the present invention is installed and it is set at higher pitch side. 
         FIG. 12  shows a cross-sectional view of an electric guitar in which a drop tuner of the present invention is installed. 
         FIG. 13A  shows a perspective view of a guitar bridge in which a drop tuner of the present invention is installed and it is set at lower pitch side. 
         FIG. 13B  shows a cross-sectional view of a guitar bridge in which a drop tuner of the present invention is installed and it is set at lower pitch side. 
         FIG. 13C  shows a perspective view of a guitar bridge in which a drop tuner of the present invention is installed and it is set at higher pitch side. 
         FIG. 13D  shows a cross-sectional view of a guitar bridge in which a drop tuner of the present invention is installed and it is set at higher pitch side. 
         FIG. 14A  shows a perspective view of a drop tuner of the present invention. 
         FIG. 14B  shows a side view of a drop tuner of the present invention. 
         FIG. 14C  shows a plan view of a drop tuner of the present invention. 
         FIG. 14D  shows a cross-sectional view of a drop tuner of the present invention. 
         FIG. 14E  shows a front view of a drop tuner of the present invention. 
         FIG. 15  is a modified example of a drop tuner of the present invention. 
         FIG. 16  is a modified example of a drop tuner of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an overall view of an electric guitar which has a general structure of double locking system of U.S. Pat. No. 4,171,661 and fine tuning system of U.S. Pat. No. 4,497,236. This is a type of guitar generally called “Double locking guitar”, in which strings are locked at bridge end and nut end. By this way, the tuning stability after bridge  108  tremolo motion by tremolo arm  109  is maximized. 
     At headstock  103  of the neck  102  which is connected to a body  101 , machineheads  104  are mounted and string tension can be tuned by them. One string end  106  are hooked at machinehead  104 , and another string end is locked on a main saddle  302  of bridge  108 , the sounds are generated by strings  106  vibrating between saddles  302  and nut  105 , and the sounds are converted from physical signal to electric signal by magnetic pickups  107 . 
     The bridge  108  are connected to springs at body back and the springs are connected to the body  101 . The bridge  108  has a tremolo arm to rock the bridge backward and forward. By rocking tremolo arm  109 , the bridge moves pivotally up and down around stud bolt  310  as fulcrum point. By this motion, the string pitch varies higher and lower from original pitch. To minimize going out of tune after bridge tremolo motion, the strings  106  are locked with metal nut  202  and metal pad  203  by tightening lock screw  204  after tuned by machineheads  104 . 
     When the both sides of strings are locked, naturally, there is a problem that it is impossible to tune strings any more. If strings go out of tune even slightly, players must loosen lock screw  204  again, and tune and tighten again. It is very frustrating players. To solve this, general double locking bridge has a structure called fine tuners which is disclosed by U.S. Pat. No. 4,497,236. ( FIG. 3 ) 
     A main saddle  302  is connected to a sub saddle  304  by a pin  303 , so main saddle  302  can rotate around the pin  303 . And the rotation angle is adjusted by fine tuning screw  307  which is screwed on the part which is elongated from baseplate, so even after locking both sides of strings  106 , string tension can be tuned by rotating fine tuning screw  307 , even though the tuning range is comparatively small. This structure is called “fine tuners” and to adjust by rotating fine tuning screw  307  is called “fine tuning”. 
     Generally, the critical contact point curve  314  of main saddle  302  is designed to have the same center point as a pin  303 , so the practical string length does not change by fine tuning. The strings  106  are inserted into the main saddle  302  and then locked with lock pad  305  by tightening lock screw  306 . 
     A drop tuner for a stringed musical instruments has a pitch changing apparatus which produces two distinct pitches (lower pitch, higher pitch) for a selected string. The drop tuner of U.S. Pat. No. 5,359,144 is specially designed drop tuner for the general double locking bridge which has fine tuners as shown by U.S. Pat. No. 4,497,236. 
       FIG. 5  shows a perspective view of an electric guitar in which a drop tuner of U.S. Pat. No. 5,359,144 is installed and it is set at lower pitch side. The drop tuner of U.S. Pat. No. 5,359,144 is composed by a base body  501 , a shift amount adjust screw  502 , a special string lock screw  503 . 
       FIG. 6  shows a perspective view of an electric guitar in which a drop tuner of U.S. Pat. No. 5,359,144 is installed and it is set at higher pitch side. 
       FIG. 7  shows a cross-sectional view of an electric guitar in which a drop tuner of U.S. Pat. No. 5,359,144 is installed. A tremolo block  701  is pulled toward the guitar body  101  by counter springs  702  and stopped at stop block  701 A. The bridge doesn&#39;t move as far as the rotational moment which strings and arm down motion generate does not exceed the rotational moment which these counter springs  702  generate. By this way, even if the strings tension changes by shift motion of the drop tuner of U.S. Pat. No. 5,359,144, the bridge doesn&#39;t move, so the tunings of the other strings except the selected string don&#39;t change. 
       FIG. 8A  shows a perspective view of a guitar bridge in which a drop tuner of U.S. Pat. No. 5,359,144 is installed and it is set at lower pitch side.  FIG. 8B  shows a cross-sectional view of  FIG. 8A .  FIG. 8C  shows a perspective view of a guitar bridge in which a drop tuner of U.S. Pat. No. 5,359,144 is installed and it is set at higher pitch side.  FIG. 8D  shows a cross-sectional view of  FIG. 8C . 
     When the drop tuner of U.S. Pat. No. 5,359,144 is set at lower pitch side ( FIG. 8A ,  FIG. 8B ), the fine tuning screw  307  and the special string lock screw  503  come in contact with each other. The base body  501  is pushed toward the bridge baseplate  301  by spring  801 , and they touch each other by slight force. From this lower pitch state, by holding and pushing the base body  501  by thumb and index finger toward the baseplate  301 , the base body  501  is inserted between fine tuning screw  307  and the special string lock screw  503 . By this motion, the main saddle  302  rotates some amount clockwise around the pin  303  and the string  106  pitch is shifted from lower pitch to higher pitch. The shift amount adjust screw  502  adjusts the insert amount of base body  501  between fine tuning screw  307  and the special string lock screw  503 . For shifting from higher pitch to lower pitch, player pinch the base body  501  between thumb and index finger and pull back like the direction of  FIG. 8D &#39;s arrow. Thus, player can change tuning immediately between two distinct pitches for selected strings. 
       FIG. 9A to 9E  shows multi views of a drop tuner of U.S. Pat. No. 5,359,144. This drop tuner composed by a base body  501 , a shift amount adjust screw  502 , a special string lock screw  503 , and a spring  801 . The spring  801  is for keeping contact between base body  501  and bridge baseplate  503 . Player pushes forward and pulls back this drop tuner by pinching the grip part  501 A between thumb and index finger. But generally, player pinches a pick between thumb and index finger on his right hand for playing the guitar, so he has to pass the pick to other fingers to operate this drop tuner of U.S. Pat. No. 5,359,144. This passing operation will be a kind of stress when the interval between songs is too short. 
     Other problem of the drop tuner of U.S. Pat. No. 5,359,144 is that it is difficult to adjust the shift amount precisely because of the structure. The order of physical adjustment points location is, shift action point, adjust point, pivot point as  FIG. 9D . And direction L which is the motion direction of shift amount adjust screw  502 , and direction M which is the motion direction of base body  501  which occurs by shift amount adjust screw  502  are not the same. By these two reasons, the shift action amount is larger than adjust amount, thus it is difficult to set the shift amount precisely. 
     Other problem of the drop tuner of U.S. Pat. No. 5,359,144 is that extension line of shift amount adjust screw&#39;s axis and the axis of string lock screw which is the axis of shift slide motion don&#39;t cross as  FIG. 9E , so rotational moment will be generated on the shift amount adjust screw  502  tip by shift motion. By this way, the shift amount adjust screw  502  tends to rotate easily and the shift amount will be unstable. 
     And the location of the shift amount adjust screw  502  is not on the centerline Y of base body. So, the shift amount adjust screw  502  location is better to be changed to the opposite side for left handed guitar players. By this thought, it is better to prepare for right handed model and left handed model, but it might be inventory risk. 
       FIG. 10  shows a state that the drop tuner of the present invention is installed on an electric guitar and set to the lower pitch side. The drop tuner of the present invention is formed by a base body  1001 , a shift amount adjust screw  1002 , a special string lock screw  1003  and a spring  1004 . 
       FIG. 11  shows a state that the drop tuner of the present invention is installed on an electric guitar and set to the higher pitch side. 
       FIG. 12  is a cross-sectional view of an electric guitar in which the drop tuner of the present invention is installed. 
       FIG. 13A  shows a state that the drop tuner of the present invention is installed on the double locking bridge which has fine tuners as shown by U.S. Pat. No. 4,497,236 and set to the lower pitch side.  FIG. 13B  is a cross-sectional view of  FIG. 13A .  FIG. 13C  shows a state that the drop tuner of the present invention is installed on the double locking bridge which has fine tuners as shown by U.S. Pat. No. 4,497,236 and set to the higher pitch side.  FIG. 13D  is a cross-sectional view of  FIG. 13C . 
     The base body  1001  extends in a longitudinal direction of the special string lock screw  1003 . The base body  1001  has an approximately U-shape in cross-section. The base body  1001  is installed so as to surround an axis of the special string lock screw  1003 . An opening side of the U-shaped base body  1001  is directed to an opposite side of the fine tuning screw  307 . Namely, the base body  1001  has an approximately U-shape in cross-section, and the base body  1001  is arranged so that the fine tuning screw  307  side of the special string lock screw  1003  is surrounded by the base body  1001  and an opposite side is open. 
     The base body  1001  has a body part  1001   a  which is directed in a longitudinal direction of the special string lock screw  1003  and substantially penetrated by the special string lock screw  1003  and supported by the special string lock screw  1003  at an end portion farther from the main saddle  302  and another end portion nearer to the main saddle  302 . A front end portion  1001   a   1  of the body part  1001   a  is penetrated by the special string lock screw  1003  at the end portion nearer to the main saddle  302  and loosely fixed to the special string lock screw  1003  so that the body part  1001   a  can be inclined against the special string lock screw  1003 . Although the front end portion  1001   a   1  is loosely fixed to the special string lock screw  1003 , the front end portion  1001   a   1  is not detached from the special string lock screw  1003  when the special string lock screw  1003  is inclined. On the other hand, a rear end portion  1001   a   2  is penetrated by the special string lock screw  1003  at the end portion farther from the main saddle  302  and formed into a long hole shape. Because of the long hole shape, the special string lock screw  1003  can be moved within the range of the long hole. Consequently, the body part  1001   a  can be inclined and can be approached to the special string lock screw  1003  and separated from the special string lock screw  1003 . 
     Furthermore, a shift amount adjust screw  1002  is provided on the body part  1001   a  near the portion on which the long hole is formed to penetrate the body part  1001   a . The shift amount adjust screw  1002  is screwed to the body part  1001   a  to project toward an axis of the special string lock screw  1003 . The shift amount adjust screw  1002  is directed to abut an axis line of the special string lock screw  1003  approximately at right angles. A tip of the shift amount adjust screw  1002  is in contact with a side surface of the special string lock screw  1003 . The angle between the body part  1001   a  and the special string lock screw  1003  can be adjusted by rotating the shift amount adjust screw  1002 . 
     As explained above, the axis line of the shift amount adjust screw  1002  is arranged on a center surface of the body part  1001   a  of the base body  1001  and the axis line of the shift amount adjust screw  1002  is arranged to cross the axis line of the special string lock screw  1003 . 
     When the angle between the body part  1001   a  and the special string lock screw  1003  is small, the degree of separating the special string lock screw  1003  from the fine tuning screw  307  is small. When the angle between the body part  1001   a  and the special string lock screw  1003  is large, the degree of separating the special string lock screw  1003  from the fine tuning screw  307  is large. According to the degree of separating the special string lock screw  1003  from the fine tuning screw  307 , the degree of separating the pitch varies when the pitch is shifted to the higher pitch. 
     Here, when the special string lock screw  1003  is inclined by the base body  1001 , a contact point between the front end portion  1001   a   1  of the body part  1001   a  and the special string lock screw  1003  functions as a pivot point, a contact point between the body part  1001   a  and the fine tuning screw  307  functions as an action point, and a contact point between the shift amount adjust screw  1002  and the special string lock screw  1003  functions as an adjust point. Since the action point is located between the adjust point and the pivot point, the displacement of the action point is small with respect to the displacement of the adjust point. Thus, the shift amount can be finely adjusted. As explained above, the pivot point is located at the front side (main saddle side) with respect to the action point of the shift amount adjust screw  1002 . 
     The fine tuning screw  307  is screwed to a bridge baseplate  301  which extends in a longitudinal direction of the special string lock screw  1003  to penetrate the bridge baseplate  301 . The fine tuning screw  307  is supported by the bridge baseplate  301  to abut an axis of the special string lock screw  1003 . The bridge baseplate  301  includes an edge part  301   a  having a straight line perpendicular to the special string lock screw  1003  at the end portion opposite to the main saddle  302 . 
     The end portion of the main saddle  302  side of the base body  1001  has an inclined surface  1001   b  which abuts the edge part  301   a  of the bridge baseplate  301 . Since the inclined surface  1001   b  is in contact with the edge part  301   a , a part of the base body  1001  can be moved toward the special string lock screw  1003  at the main saddle  302  side. 
     When the base body  1001  is pushed toward the main saddle  302  side, the base body  1001  is inserted between the bridge baseplate  301  and the special string lock screw  1003  and contacted with the fine tuning screw  307 . Furthermore, the base body  1001  has a positioning protrusion  1001   c  which abuts an end portion of the bridge baseplate  301  when the base body  1001  is inserted at a predetermined distance. Since the positioning protrusion  1001   c  is formed, the base body  1001  is prevented from moving further toward the main saddle  302  side. According to the protruded length of the shift amount adjust screw  1002  which penetrates thorough the body part  1001   a  and protruded toward the special string lock screw  1003  at this position, the angle of the special string lock screw  1003  inclined by the base body  1001  is determined. Namely, the rotation angle of the main saddle  302  rotated around a pin  303  is determined. 
     Note that the shift amount adjust screw  1002  is screwed to a further side of the main saddle  302  with respect to the positioning protrusion  1001   c . More specially, the positioning protrusion  1001   c  has a shape on which a female screw hole can be formed so that the shift amount adjust screw  1002  can be screwed into the female screw hole. The shift amount adjust screw  1002  is screwed to an opposite side of the main saddle  302  with respect to a contact position contacted with the bridge baseplate  301 . 
     A fin member  1001   d  is formed on the end portion of the base body  1001  at the position farthest from the main saddle  302 . The fin member  1001   d  is projected toward a surface of a guitar on which the drop tuner is installed. As shown in  FIG. 15 , a fin member  2001   d  is also operable by being projected upward of the guitar on which the drop tuner is installed. As shown in  FIG. 16 , a fin member  3001   d  can be also formed on the conventional base body  501 . In the conventional base body  501 , since the fin member is projected to be orthogonal to the radial direction of the lock screw  1003  from the end portion opposite to the main saddle  302 , the fin member  3001   d  can be operated to shift the base body  501  while holding a pick. 
     The fin member  1001   d  has a front surface  1001   d   1  located at the main saddle  302  side and a rear surface  1001   d   2  located at an opposite side of the main saddle  302 . The front surface  1001   d   1  is formed to be approximately perpendicular to the special string lock screw  1003 . The rear surface  1001   d   2  is formed to be an inclined surface approaching the special string lock screw  1003  as separated from the main saddle  302 . 
     The front surface  1001   d   1  is approximately perpendicular to the special string lock screw  1003  so that the fingers can be easily hooked when the base body  1001  is pushed toward the direction of separating from the main saddle  302  along the axis line direction of the special string lock screw  1003 . The rear surface  1001   d   2  is a surface to be hooked by the finger when the base body  1001  is pushed toward the direction of approaching to the main saddle  302  along the axis line direction of the special string lock screw  1003 . At that time, the inclined surface  1001   b  located at the front end of the base body  1001  should be moved under the edge part  301   a . Therefore, in order to act a part of the force of pushing in the axis line direction to also in the direction perpendicular to the axis line (i.e., direction of pushing the inclined surface  1001   b  of the base body  1001  downward), the rear surface  1001   d   2  has the inclined surface approaching the special string lock screw  1003  as separated from the main saddle  302 . 
     As explained above, a drop tuner of the present invention has: a lock screw  1003  projected from a main saddle  302  which is rotatably supported by the drop tuner; and a base body  1001  supported by the lock screw  1003  so as to be capable of being inserted between the lock screw  1003  and a fine tuning screw  307  and separated from the fine tuning screw  307 , wherein a rotation angle of the main saddle  302  varies when the base body  1001  is switched between an inserted state and a separated state, and a fin member  1001   d  projected toward a radial direction of the lock screw  1003  is provided on the base body  1001  near an end portion farther from the main saddle  302 . In addition, a coil spring  1004  is installed to prevent the base body  1001  from being rattled against the special string lock screw  1003 . 
     In a state of being shifted to the lower pitch side, the fine tuning screw  307  and the special string lock screw  1003  are engaged with each other and the base body  1001  is in light contact with the bridge baseplate  301  by the spring  1004 . From the state of being shifted to the lower pitch side, a part  1001 A of the base body  1001  is pushed in the arrow direction shown in  FIG. 13B  by using a middle finger or a ring finger while holding a pick. As a result, the base body  1001  enters between the fine tuning screw  307  and the special string lock screw  1003 . 
     Consequently, the main saddle  302  which locks a string  106  is rotated clockwise around a pin  308  by a predetermined amount. Thus, the tuning of the string  106  is shifted from the lower pitch side to the higher pitch side. 
     The shift amount adjust screw  1002  adjust the amount (length) of entering the base body  1001  between the fine tuning screw  307  and the special string lock screw  1003 . 
     When the tuning is shifted from the higher pitch side to the lower pitch side, a part  1001 B is pushed rearward (in the arrow direction shown in  FIG. 13D ) by using a middle finger or a ring finger while holding a pick. Consequently, the tuning is set to the lower pitch side. Namely, the pitch is lowered. 
     As explained above, the tuning of the specific string can be shifted immediately between two pitches without changing the fingers holding the pick. 
       FIGS. 14A to 14E  are schematic diagrams of the drop tuner of the present invention. The drop tuner is formed by the special string lock screw  1003  penetrating the base body  1001 , the spring  1004  installed between the base body  1001  and the special string lock screw  1003 , and the shift amount adjust screw  1002 . The spring  1004  is provided to always push the base body  1001  forward with a small force to prevent the base body  1001  from being rattled when shifted to the lower pitch side. 
     As shown in  FIG. 14D , the pivot point, the action point and the adjust point are arranged in this order and the motion direction P of the shift amount adjust screw  1002  is same as the motion direction O of the base body, the displacement of the action point is small with respect to the displacement of the adjust point. Thus, the shift amount can be finely adjusted. 
     Furthermore, as shown in  FIG. 14E , the axis line of the shift amount adjust screw  1002  and the axis line of the special string lock screw  1003  intersect with each other. Thus, the rotational moment generated at the shift amount adjust screw  1002  is theoretically zero when performing the shifting movement. Thus, the shift amount adjust screw  1002  is hardly loosened. 
     In addition, since the position of the shift amount adjust screw  1002  is located on a center line Z, the same drop tuner can be used also for a left-handed guitar.