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Truss Rod routing

Discussion in 'Luthier's Corner' started by MovinTarget, May 14, 2019 at 3:21 PM.


  1. MovinTarget

    MovinTarget

    Jan 30, 2018
    Maryland, USA
    I am in the process of making my first necks and I am *really* nervous about the route depth for the rods...

    I am using home-roasted maple that is ~.68" thick before even shaping and I guess I'm just wondering how thin is too thin, even with a low profile truss rod?

    This is for a 28.5" scale headless with the truss access point at the end of the neck, not the heel, in case that matters.

    Thanks!
     
  2. I try to have about 3/16" of material behind the truss rod. I don't recall off the top of my head how deep a truss rod is.
     
  3. MovinTarget

    MovinTarget

    Jan 30, 2018
    Maryland, USA
    Supposed to be 3/8" deep which translates to .375" which leaves .305"...

    3/16" would be .1875" so I guess would be looking at very little back taper (if thats what its called), but doable...
     
  4. Gilmourisgod

    Gilmourisgod

    Jun 23, 2014
    Cape Cod MA
    Same here, i agonized about it. I use DA trussrods, they average 3/8" deep, i left 3 /16" under the rod rough, probably sanded off another 1 /32" finishing it. What method you using for neck carve? I highly recommend " facet" method, pretty much guarentees a flat spot along the neck centerline, then you just blend in. Very controllable process.

    Edit: Adding a volute on the neck back under the nut is another way to get a lot more strength where the TRC adjustment pocket hogs out wood, most DA rods get wider/deeper at the nut.
     
    Last edited: May 15, 2019 at 6:01 AM
    MattZilla and Beej like this.
  5. MovinTarget

    MovinTarget

    Jan 30, 2018
    Maryland, USA
    If the "facet method" is basically angled cuts/shaves, long-ways, getting progressively smaller to create the neck profile, that's what I plan to do...
     
    Gilmourisgod likes this.
  6. Gilmourisgod

    Gilmourisgod

    Jun 23, 2014
    Cape Cod MA
    Yep, that’s it. I don’t know how people do the method of carving profile at nut and heel and then “connect the dots”. Great Skill, I guess, but easy to eff up. Facet method is pretty much foolproof. What rods you using? I tried the BBG rods, kinda cheap and sloppy hex key fit. The Stewmac low profile rods look identical, who knows. The LMI rods are supposed to be good, may try them next time. Good luck , and post photos!
     
  7. MovinTarget

    MovinTarget

    Jan 30, 2018
    Maryland, USA
    As it's my first time I just got some cheap low profile off Amazon, same dimensions as StewMac...

    I will test your assertion that this method is "foolproof"! :D
     
    Gilmourisgod likes this.
  8. Beej

    Beej

    Feb 10, 2007
    Victoria, BC
    Having been down this path more than once, I highly recommend testing the rod before putting it in. :D Put it in a vise and use the wrench to crank it in both directions. Check the welds at the nut for continuity around it, or at least in a good pattern to prevent it coming apart in use. I also whack the welds a little with a hammer. I've had one where the weld at butt broke when tapped with a hammer, and another one where the nut was only partially welded on, and pulled off when worked with the wrench. More than once I've had to file the edges of the welds around the nut to get it smoothly sit in the slot.
     
    MovinTarget likes this.
  9. MovinTarget

    MovinTarget

    Jan 30, 2018
    Maryland, USA
    Since I have your attention, I tried a neck blank previous that failed (for other reason), but I was left wondering;

    Should the truss rod only be able to slide in via the groove you've routed, in other words once you get to the fat end, should it only fit through the end of the blank, or is it okay if the whole thing can just "drop" in from the top.

    I know some people give it a few calculated squirts of epoxy to hold it in, but I never found a clear answer to the above...
     
  10. Gilmourisgod

    Gilmourisgod

    Jun 23, 2014
    Cape Cod MA
    No epoxy! The typical DA rod needs to move in the slot! I just put a little blob of silicone caulk in the slot each end to keep it from rattling. When you glue the fingerboard on, put a piece of 1/2” tape over the rod and centerline of FB, spread your glue on both surfaces, pull off the tape exposing unglued area, and clamp up. This keeps any glue out of the truss rod slot. @Bruce Johnson has a trussrid design made to be glued in, but the standard DA rods are supposed to move in the slot. That’s why they have the plastic film, I suppose.

    Edit: I drop in from the top. The FB spans over the nut end of the rod. In theory, if you have enough headstock angle and a long TRC pocket, you could pull the rod right out. Just friction and any rod bow holding it in.
     
  11. MovinTarget

    MovinTarget

    Jan 30, 2018
    Maryland, USA
    Ugh I meant Silicone... the clear stuff lol

    I guess my thought was if the nut end wasn't pushing against the FB (depending on the pressue) it would keep it from putting too much pressure on the glue joint.

    This is for a headless short scale so I guess you are saying that I should be able to just pull the rod out if there is no tension and I can get a grip on the nut.
     
  12. Beej

    Beej

    Feb 10, 2007
    Victoria, BC
    I usually rout the channel to fit the rod exactly (as dropped in from the top), and rout a little wider at the TR nut end. Depending on the design of the rod, I also sometimes carve a little relief in the underside of the fretboard (and string nut) in order to ensure the TR nut can move freely. I also use little dabs of silicone under the rod, but I use three dabs: end, middle and nut. :) I can't stand TR rattle...too often it sounds like fret buzz and messes with me during setups... :D
     
  13. ctmullins

    ctmullins fueled by beer and coconut Gold Supporting Member

    Apr 18, 2008
    MS Gulf Coast
    I'm highly opinionated and extremely self-assured
    1. Don’t buy cheap rods. Get good ones from a good supplier. It’s not worth the amount of labor necessary to replace.
    2. Vintage-style compression rods work, but modern-style double-action rods are easier to install, remove less wood, and aren’t as close to the back of the neck.
    3. When the rod is used to counteract string tension, it pushes towards the back of the neck near its ends, and pushes against the fingerboard in the middle. So you want more meat in the neck wood near the ends. This is usually not a problem at the heel, but it’s a great reason to include a volute at the headstock. This is also why it’s not usually a problem to carve the neck profile close to the rod in the center section of the neck, as the rod isn’t trying to push in that direction anyway.
     
    MattZilla, Gilmourisgod, Beej and 2 others like this.
  14. Gilmourisgod

    Gilmourisgod

    Jun 23, 2014
    Cape Cod MA
    ^^^^^What he said. The crappy BBG rod I put in my Ric build is a sloppy fit for a standard 4mm hex wrench, worried it will strip out eventually. A better rod is cheap insurance.
     
  15. MovinTarget

    MovinTarget

    Jan 30, 2018
    Maryland, USA
    ugh, okay... soooo Stewies and what else?
     
  16. Beej

    Beej

    Feb 10, 2007
    Victoria, BC
    I've used all of these suppliers with success:

    Best Bass Gear
    Allparts
    LMII
    Grizzly
    WD Music

    I now use a Canadian supplier pretty local to me who has a wide variety of lengths for just under $20. (sounds high, but they work out to less than exchange and shipping from US).
     
    MovinTarget likes this.
  17. Beej

    Beej

    Feb 10, 2007
    Victoria, BC
    I also used a batch of Amazon sourced rods, and although most worked out, all of the problems I mentioned above were had with their rods. To be fair, they all came from the same seller on Amazon, I forget which, but probably was either Kmise, or Musiclily...
     
    MovinTarget likes this.
  18. ctmullins

    ctmullins fueled by beer and coconut Gold Supporting Member

    Apr 18, 2008
    MS Gulf Coast
    I'm highly opinionated and extremely self-assured
  19. MovinTarget

    MovinTarget

    Jan 30, 2018
    Maryland, USA
    Wow the LMI ones are even pricier than StewMac
     
  20. ctmullins

    ctmullins fueled by beer and coconut Gold Supporting Member

    Apr 18, 2008
    MS Gulf Coast
    I'm highly opinionated and extremely self-assured
    You can shop on price if you want. I’m not.
     

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