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My Truss Rod Repair

Discussion in 'Hardware, Setup & Repair [BG]' started by 72LML, Jan 4, 2012.


  1. 72LML

    72LML

    Dec 25, 2009
    Burnsville, MN
    So, I found a 1998 MIM Fender 5-string Jazz at a pawn shop a few months ago for $125 and the neck was serverly bowed. I was hoping the truss rod would straighten it out but after setting it up it turns out that wasn't going to be the case and it snapped. Long story short I've got a bass with a bad neck. Knowing it's not worth the cost of paying somebody to pull the fret board off to replace the rod I thought that I would give it a shot myself but in a different way.:bag:

    Being that I work for a machine shop I thought, "would it work if I machined out the anchor end and drill 1/4" hole in the heel to pull the broken rod out from?" Well, here is what I did this afternoon. Hopefully this will work. If not, I'll still be stuck with what I already have, a bad neck. Nothing lost but my time.

    Here is the neck at the start. I plunged out the first part of the plug. It was 3/4" in dia and about .100 deep.
    6639058967_5e749f8d08_b.

    Here is a shot about halfway through the .625 dia main plug. You can see how the truss rod is anchored in the end.
    6639060361_59bfc1802e_b.

    Once I got done machining the plug out I drilled a 1/4" hole in the end of the heel to allow the broken truss rod to pass thru.
    6639062989_0b34dfc05e_b.

    Here it is with the broken truss rod out. All that's been modified on the neck so far is a 1/4" hole drilled in the heel that I can fill with a maple dowel rod. 6639064233_c6a708c8cc_b.

    Last, in this pic you can see some remaining glue stuck to the side of the truss rod. Maybe this is what prevented it from working properly? 6639065437_b5fdca8251_b.

    Now I've got to find a new rod the same size, thread one end, and figure out a way to anchor it in place. I've got a few ideas. ;) Stay tuned.
     
    Alan Scharrer and Michael B like this.
  2. Craig_S

    Craig_S Banned

    Oct 15, 2008
    Metro Detroit
    Looks very interesting. Sub'd
     
  3. 96tbird

    96tbird PLEASE STAND BY Supporting Member

    You've peaked my curiosity. I've wondered about this kind of thing. Sub.
     
  4. tjh

    tjh Supporting Member

    Mar 22, 2006
    Minnesota
    Nathan, you are drawing a crowd ... :)
     
  5. Shoot an arrow with the neck before you straighten it. Come on we all want to see it.
     
  6. 72LML

    72LML

    Dec 25, 2009
    Burnsville, MN
    Here is a little more background info on where I came up with the idea of how to do this.
    Lite Ash Truss Rod Replacement - Telecaster Guitar Forum

    My only complaint with the thread from the telecaster forum is that while it was nice that the guy documented what he did he never gave a conclusion to whether or not it fixed the original problem. After all was said and done did he still have a neck that was bowed excessively that the truss rod couldn't straighten out?

    That leads me to a question for those of you who have done truss rod replacements before.

    When you pull the fret board off do you sand or machine the neck flat again before reattaching the fret board? I have this fear that if the neck has a certain amount of bow or stress that is naturally in it will replacing the truss rod be enough to correct the bow and overcome those forces. After all why didn't the original truss rod correct this issue?

    One interesting thing to note is that after I got the truss rod out it has a natural bow to it. So much that if I push down on one end the other end is over 1/4" off the table. I'm not sure if that is the way they are supposed to be but it certainly doesn't seem like it would help the situation much. No reason to fight the tension of the truss rod, wood, and strings.
     
  7. 96tbird

    96tbird PLEASE STAND BY Supporting Member

    The rod channel is curved so the middle of the neck the rod is lower than the ends, looking from the fret side. The rod will, over time, become bowed. So as you tighten the nut, the rod tensions up against the low wood in the middle, removing bow in the neck.

    You should back clamp the neck before installing the rod. Leave it that way for a few days. Check the forum a guy just fixed his neck this way. His thread should.be on the first page of this section. His last post was yesterday.
     
    Scatabrain likes this.
  8. I had to do this same thing to one of my MIM basses (the rod snapped at the anchor)….you are on the right track but you will have to route a channel as wide as the anchor from the anchor hole to the heel (also make sure it’s as deep as the anchor hole).
    The truss rod has to be secured (very well) to the anchor…. some people push the truss rod through the anchor and weld the two together…other people do this (I did it this way) by using a half round file and file a fairly deep divot on the heel side of the anchor and then thread the rod (most rod anchors I’ve seen are 10/32 thread and you may have to thread the end of the truss rod too) into the anchor all the way through with a bit of the end of the rod hanging out and then peen that part of the truss rod until it is flat in the divot….then you have to push the truss rod up through the heel end of the neck, pushing the anchor through the routed channel. If you measured everything correctly, there should be enough threaded truss rod end sticking up in the truss rod nut hole to thread the nut on.
    Finishing things up, I also cut a block of maple that fit in the routed hole and glued it in with yellow carpenter’s glue. The fix worked great!

    The link you have is essentially what I did (I wish I knew that link was there when I did mine...it would've save me lots of aggravation). Mine turned out fine. I didn't have to do any thing other than a normal setup once I replaced the trussrod.
     
  9. 202dy

    202dy Supporting Member

    Sep 26, 2006
    Anchor point thought for debate:

    Bore cross holes through the metal disc. Bore a hole through the diameter of the rod. The disc would have one hole just large enough for a loose press fit (no heat required) and a smaller hole through the face of the disc. Insert the rod through the large hole. Insert a pin through the disc and peen over. Plug the end of the neck and touch up with lacquer.
     
  10. jumbodbassman

    jumbodbassman Supporting Member

    Dec 28, 2009
    Stuck in traffic -NY & CT
    Born Again Tubey
    i'm in...
     
  11. 96tbird

    96tbird PLEASE STAND BY Supporting Member

    Another anchor point idea. Use a half moon piece of steel as the anchor and weld the end once you insert the rod.

    EDIT: sorry Timmus, you said that already! I quit reading when you said route a channel. :eek:
     
  12. To give one an idea of the stress on the anchor, it seems that at least the MIM's are welded but on mine, the weld broke free.
     
  13. 96tbird

    96tbird PLEASE STAND BY Supporting Member

    Possibly, you could tap the semi round anchor, thread the rod ends; both, insert rod, thread rod into anchor from the head side then weld it.
    Our fearless Op said he had ideas, please elaborate. This is interesting.
     
  14. K-Frog

    K-Frog

    Feb 6, 2002
    Camden, AR, USA
    subscribed, since i'm in the early stages of repairing a broken truss rod myself, but from the front.
     
  15. nervous

    nervous Supporting Member

    Jan 5, 2010
    Beautiful Central, NY
    What a great idea. I wish that I had this info before I destroyed my Spector CRFM. As I look at this I could have drilled a hole up through the lower strap pin area and driven the broken rod out through the headstock. The resulting damage and repair would have been virtually nothing compared to what I have to deal with now. Damn. That would have so easily solved my problem. The new truss rod would have simply slid back into place. I am now aggravated that I didn't think of that as an option.

    Nice work and all the best with this project.
     
  16. rojo412

    rojo412 Walnut is fun! Supporting Member

    Feb 26, 2000
    Cleveland, OH.
    AWESOME! Sub'd :ninja:
     
  17. 72LML

    72LML

    Dec 25, 2009
    Burnsville, MN
    Works been crazy busy the last few days so I haven't been able to make much progress on this. I'll see if I can work up some CAD drawings this weekend of a few concepts.

    One issue I'm running into is the size of the replacement rod. The old rod checks .218 which makes it a 7/32 rod. Finding a rod that size is not really an issue, we have a bunch here at work made out of O1 Drill Rod, but finding it in the proper material is the problem. O1 in it's annealed state it's not too hard but as soon as you hit it with a welder it gets very hard and brittle which may make for a weak joint. A few other options out there are A2 and S7 tool steel but they have similar properties to O1 above and the same issues with heat treating. So I may have to do a few test weld samples to determine if welding is even an option. Otherwise I may have to grab a 1/4" dia rod and grind it down. Not exactly want I want to do.

    One concept we have been kicking around here at work (lets see if I can describe this so people can understand) is to make up a .625 dia cylinder with a .219-.220 cross drilled hole thru it for the rod to pass through. The center of the cylinder would be threaded for a fine pitch set screw and there would also be a flat milled near one end of the rod. That way the plug could be put in place, the truss rod passed through it until the flat lines up properly, and then add a set screw (with loctite) to tighten against the flat on rod. Not only would this prevent the rod from twisting, it would also prevent it from being pulled out of the anchor. Like I mentioned above I'll see if I can get some drawings made up so it's easier to understand.

    One interesting thing to note is that the thread for the truss rod nut on this one is not the standard 10-32 that most of them are. Being that the diameter of the rod checks .218 that would put it at the proper size for a 12-28 thread. I may have to do a little hunting this weekend for a proper truss rod nut and measure the threads in it. A 1/4-28 nut threads onto the few threads left on the old truss rod but it's a pretty sloppy fit. We'll see what I can find.
     
    Alan Scharrer likes this.
  18. 96tbird

    96tbird PLEASE STAND BY Supporting Member

    What kind of steel do you think the rod is made of? If its tempered, just go to a large hobby shop and get some, they call it music wire and use it to make model plane landing gear. Since you are a machinist, you will know if welding it will soften it too much, but you could still quench it. Or use it as you say, with a set screw.
     
  19. bolophonic

    bolophonic

    Dec 10, 2009
    Durham, NC
    There was a thread a while back where a guy had found a beautiful 70's bound and blocked Jazz neck with a broken truss rod and everyone kept telling him to plane off the fretboard to fix the rod. I kept wondering why nobody thought to go through the back...

    Now I get to see what really happens when you go through the back!
     
  20. jb63

    jb63

    Jan 3, 2002
    Cleveland, Ohio
    When I was working as a machinist I made some truss rods for a friend who was building guitars. I believe we used 1018 steel.

    Your idea of putting a flat on the truss rod and anchoring it with a set screw should work fine w/loctite etc.

    The thread on the original truss rod might have been metric (an M5.5 perhaps). It's been a long time but if I remember correctly, a 10-32 and an M5.5 are pretty close in pitch and size.

    It's always nice to work at a shop that allows you to do "government work". ;)
     

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