• Machining
  • Broching a Truss Rod Nut

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    Here’s an interesting situation that came up the other day. A Kramer guitar came into Robot Monster with a truss rod nut with the hex wrench hole stripped out. It is easy to find replacement nuts for Gibson or Fender guitars but it is often difficult to find them for imports with metric threads. In […]

  • Truss Rods
  • Gretsch Super Chet – Burns Truss Rod Repair

    gretsch-burns-truss-rod-repair-01 gretsch-burns-truss-rod-repair-04 gretsch-burns-truss-rod-repair-12

    gretsch-burns-truss-rod-repair-21   gretsch-burns-truss-rod-repair-25 gretsch-burns-truss-rod-repair-37 gretsch-burns-truss-rod-repair-52

     

     

     

    This turned out to be a very interesting repair.  This Gretsch Super Chet has a Burns geared truss rod and the adjustment shaft had broken completely off.   I hadn’t encountered a Burns truss rod before and had difficulty finding information online about how they are constructed.  Removing and opening the gear box revealed that it works much like a tuning key on a guitar with a 16:1 gear ratio.  Each revolution of the adjustment rod turns the nut 1/16 of a turn.

    Fabricating a new worm gear and shaft turned out to be the most challenging part of the job.  It required a 10tpi acme thread which is rather large for my tiny Sherline lathe but going very slowly I managed to turned the required threads. Originally I had planned to leave a long, robust adjustment rod but later figured out that the clearance hole in the body was not lined up exactly so had to cut is close to the neck tenon.  I made a simple slot for a flat head screwdriver to make adjustments.

    Reassembling everything was pretty straight forward. I adjusted the neck angle and tightened the neck joint with shims before reinstalling the large wood screw.  Unfortunately I caused some cracks in the finish on the back of the neck along the center line where it was very thin with the truss rod removed.  I drop filled the missing lacquer chips and it is just barely noticeable.

    All in all I’d say it went very well for a complicated repair.

  • Truss Rods
  • Gretsch Super Chet – Burns truss rod repair

    gretsch-burns-truss-rod-repair-01 gretsch-burns-truss-rod-repair-04 gretsch-burns-truss-rod-repair-12

    gretsch-burns-truss-rod-repair-21 gretsch-burns-truss-rod-repair-25 gretsch-burns-truss-rod-repair-37 gretsch-burns-truss-rod-repair-52

    This turned out to be a very interesting repair. This Gretsch Super Chet has a Burns geared truss rod and the adjustment shaft had broken completely off. I hadn’t encountered a Burns truss rod before and had difficulty finding information online about how they are constructed. Removing and opening the gear box revealed that it works much like a tuning key on a guitar with a 16:1 gear ratio. Each revolution of the adjustment rod turns the nut 1/16 of a turn.

    Fabricating a new worm gear and shaft turned out to be the most challenging part of the job. It required a 10tpi acme thread which is rather large for my tiny Sherline lathe but going very slowly I managed to turned the required threads. Originally I had planned to leave a long, robust adjustment rod but later figured out that the clearance hole in the body was not lined up exactly so had to cut is close to the neck tenon. I made a simple slot for a flat head screwdriver to make adjustments.

    Reassembling everything was pretty straight forward. I adjusted the neck angle and tightened the neck joint with shims before reinstalling the large wood screw. Unfortunately I caused some cracks in the finish on the back of the neck along the center line where it was very thin with the truss rod removed. I drop filled the missing lacquer chips and it is just barely noticeable.

    All in all I’d say it went very well for a complicated repair.

  • Truss Rods
  • Fender P-bass Truss Rod Repair

    fender-jazz-bass-truss-rod-repair-03 fender-jazz-bass-truss-rod-repair-13 fender-jazz-bass-truss-rod-repair-14

    The nut had been cross threaded on this P-Bass neck with such force that the anchor came loose causing the entire truss rod to spin inside the neck. My friend Paul managed to loosen the nut allowing the truss rod to be pushed out the headstock end of the neck. After cleaning the crushed threads with a die I attempted to reinstall the rod but the sleeve inside the neck bunched up causing the skunk stripe to pop up near the base. With a little gentle coaxing I go the entire stripe out. I wrapped the rod in wax paper, epoxied the anchor back in place, and reglued the skunk stripe and headstock plug. Except for a small ridge at the base of the neck you would never know.