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Truss Rod - Headstock or Heel on Single Cut bolt on

Discussion in 'Luthier's Corner' started by chinjazz, Aug 27, 2017.

  1. Headstock

    14 vote(s)
  2. Heel

    6 vote(s)
  1. Hey Folks,

    Subject line pretty much says it, and I've created a poll if you so please.

    I've been designing a single cut bolt on, and wanted opinions on putting the truss rod adjustment at the heel or neck. Here's a pic I took:


    It'll be a 34.5" scale 5, and is in the neighborhood of a jazz style bass (minus my take on fusing other influences) :)

    I'll most likely bolt the neck down like this Ray Roger example:


    It seems like it would a very solid pocket!

    Or I may bolt down a bit more like the new Sadowsky single cut bolt ons..

    What do you think? Headstock, or Heel?

  2. Gilmourisgod


    Jun 23, 2014
    Cape Cod MA
    The heel models with a spoked wheel adjuster are certainly more solid mechanically, but I don't like seeing them exposed , all seem to be higher than the pickguard, requiring an access slot. Maybe there is a crafty way to cover them I haven't seen. I'll vote headstock access just for the aesthetics, easy to cover one with a TRC. Nice looking design, BTW.
    reverendrally and chinjazz like this.
  3. Thanks for your input and compliment Gilmoreisgod!

    I also like the clean look at the heel and am leaning toward the headstock at the moment...
  4. rwkeating


    Oct 1, 2014
    The usual bass truss rods available from LMI and StewMac aren't long enough to cover and entire 34" scale length 24 fret fingerboard. Therefore, I just figured it was better to have the adjustment at the nut. What area of the neck/fingerboard do you want to leave without truss rod "influence". I decided to have the truss rod under frets 1,2, 3... and not under the frets at the body joint since the neck was body support down their.

    I have no idea if any of this matters, but it is the way I tried to work it out on my own.
  5. Gilmourisgod


    Jun 23, 2014
    Cape Cod MA
    I used a BBG double action TR in my Ric build. It was almost too long for the 33.25" scale. I can't recommend them to anyone else though, the 4mm hex key head is a really sloppy fit. I may just use an LMI or Stewmac "low profile" DA rod next time, overpriced, but known high quality. No sense cheaping out on a trussrod. Any thought of using carbon fiber rods? Most builders seem to use either a single trussrod and two CF bars, or two trussrods for a 6 string.
  6. I've been looking at the low profile Stew Mac for various reasons. They're 24" long and wound fit nicely in this neck. I kinda like the blue coated ones On Ebay. Given it'll be a one piece neck (minus the fretboard), think carbon fiber rods will be good insurance? I noticed a few of the big guys use them. Hadn't entertained them, but will look into it.
  7. Gilmourisgod


    Jun 23, 2014
    Cape Cod MA
    I think all the blue taped rods come from the same supplier, sold under various brands, probably Chinese or Indonesian. Quality is a little spotty I think. Ive read various theories on CF rods, I have a Warmouth neck with one DA trussrod and 2 CF rods, its very stable , so I copied that for my build. I was worried it would be too stiff, but so far so good. I've never built a 6 string though, curious to hear other opinions. I think at worst its a bit of insurance that does no harm. From all I've read, you are better off with at least a two piece neck with opposing grain, so movement tends to get canceled out, plus I like the "stripey" look of laminations matching the body wood. Its hard to find one piece that's really stable as-is.
  8. Yeah, the Stew Mac ones aren't that much more, so I may just go with SM.

    I'm with you completely on neck lams, they look cool with stripes, and inherent stability seems to be a given.

    The good news is I'm making 2 necks for this bass as education/experience gain, one as one piece and the other a 3 piece lam. You may have seen my stumblings on making the square strip lams... Still working that into my bag of tricks :)
    Gilmourisgod likes this.
  9. I've built a bass with a heal adjusted truss rod. Like @Gilmourisgod has mentioned, a heal setup is stronger. However, beyond access, there's actually another thing worth considering. The truss rod is designed to provide the most relief between fret 1 and 12. Beyond that the trussrod does very little. So on longer scale basses, a heal end trussrod leaves you with more of the truss rod nearer the heal than the nut. As I understand it, that was the other reason that Fender swapped ends.
    Gilmourisgod likes this.
  10. Interesting insights!

    Actually, why I started this thread was because of the way this bass will be physically touching more of the neck than just the heel pocket (single cut).

    Guys like Martin Keith do go for a headstock truss rod access, as well as Fodera on some models. It varies because I noticed that the Tom Kennedy Standard has a single cut, but has a heel truss rod.

    I wonder how much will the truss rod be able to move the neck if it's braced down all the way up to the 12th fret?
  11. Gilmourisgod


    Jun 23, 2014
    Cape Cod MA
    I used to think (pre TB) the trussrods were strong enough to really bend the neck, but the consensus I'm hearing on LC is that you should always hand bend a little and use the trussrods only to lock in relief. If you want a standard neck depth to resist six strings, I don't think one trussrod alone will do it. @Bruce Johnson builds his own proprietary rods for his Ampeg basses, very different design that's glued in place. The greatest bending force is typically at the heel, but you have extra support with a single cut, not sure how that affects the use of CF rods or 1 vs 2 TR. I'll shut up now and hope somebody versed in singlecuts weighs in.
    chinjazz likes this.
  12. Yes, that makes perfect sense :).
    Thanks again!

    I would think with a 5 string that a low profile Stew Mac TR would be fine, and if recommend, I'll install 2 CF rods. But as you mentioned. having someone with single cut expertise would definitely help.
  13. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    You can use either headstock access or heel access for the truss rod. Either will work well, with a few tradeoffs and guidelines. As several of you have you have mentioned, the truss rod is there to adjust and control the bending of the neck in the zone from the 1st to 12th frets.

    If you use a heel access rod, it has to be long enough that the end is somewhere between the nut and the 1st fret. That's important. If you are buying one of the commercial DADR (double-acting, double rod) truss rods, they are only available in standard lengths. Mostly made for Fender-size, 34" scale, 20 frets.

    With a headstock access rod, the length isn't as fussy. The end should be somewhere in the heel area. The hole or trough for accessing the rod does take away some additional wood from the zone where the neck transitions to the headstock. That makes it weaker, so you have take that into consideration when you shape it.

    A spoke wheel style truss rod isn't any stronger than a similar socket head truss rod. It has the same threads and internal geometry. The spoke wheel nut is just harder for a careless user to mess up the nut. The tradeoff is that it's easier to strip the threads or snap the rod, because of all the torque you can apply.

    For this particular project, I'd recommend a 3-piece laminate maple neck with a single headstock access truss rod. You don't need carbon fiber bars or anything fancier than that. Pay attention to the how you cut and laminate the neck, the orientation of the rings and grain lines, etc., and you'll be fine.
  14. Thank you Bruce!

    I appreciate your advice.

    I'm glad I have bought enough maple to make several necks. I planned on making 2 necks for this bass for multiple reasons. Once I get my chops and tooling/fixtures in order for making laminates I'll make the 3 piece lam neck. If I'm judicious, I might have them done in parallel :)
  15. Keith Guitars

    Keith Guitars

    Aug 25, 2004
    Woodstock, NY
    Builder: Martin Keith Guitars, Veillette Guitars
    @chinjazz PMed me a question on this, but I figured I'd reply publicly in case anyone else in interested.

    I prefer headstock-end adjusters primarily for ease of use - with an allen recess adjuster and a long enough wrench, they are the
    quickest and most immediately adjustable, and you don't have to slack any strings. I've also seen my share of dings and dents on bodies
    from folks trying to wrestle the wrenches in.

    I've never felt that the heel-end adjuster worked as well for me. The double-acting rods I use (the blue-coated Korean rods that are very popular, and IMO very good) are welded at one end, and all the adjustment happens at the other end. In my experience, the rigidity of the welded (non-adjuster) end shifts the active part of the rod up towards the adjuster end a bit, which puts it closer to where I want if I place the adjuster at the head.
    The welded aspect also means that you can cut those rods shorter at the fixed end and reweld them (or have it done by a body shop or machine shop) to customize them to a shorter length. I've done this lots of times. Also, the length becomes less critical since you can have a rod that's a bit short or a bit long and the adjuster will still end up in the right spot. Because my neck pockets are pretty long/deep, I can use rods anywhere from 22" to 25" in length without modification.

    I don't care for the StewMac rods much - I don't like designs which require the whole length of one side to rotate in place. They require more clearance to work well and therefore have more possibility to vibrate. I've used rods like that successfully and still do on occasion as some of them are lighter than the blue rods, but I still prefer the blue ones when weight is not an issue. In many hundreds of instruments built with those rods we've had very, very few failures.
    I also don't particularly care for spokewheel adjusters, but that's probably just because they're pretty much only practical at the body/heel end.

    The strength difference of the headpiece area is negligible IMO - if the neck is properly designed and built , the truss rod access will not appreciably weaken it.
    reverendrally and Beej like this.
  16. Thanks so much for your input Martin! The choice for headstock access is definitely going to be the way I go on this.
    With you're input, and Bruce, and others really helps me going down the right road :)

    In the 90's the heel access with a slot routed in the body kind of grew on me as looking good, but I now I'm feeling that it throws a "wrench" into the design of the face of a body (slight pun there).

    Pretty cool that you can get the double-acting rods machined down also.. I do believe that the blue-coated ones are the same as some that Stew Mac now sells:


    I could be wrong though :) Like others have said, most likely made in the same place somewhere in Asia.

    Thanks for pointing out the physical point where the rigidity of the truss rod shifts to. That really explains a lot to me.
    And the icing of the cake of convenience, lack of needing to slack the strings (forgot about that one).. I'm going to get an allen access adjuster, and long enough wrench for sure, and of course put the Truss Rod access in the Headstock :)

    Again, Thanks for sharing your insights with me, and to the TalkBass LC community!

    reverendrally likes this.
  17. Keith Guitars

    Keith Guitars

    Aug 25, 2004
    Woodstock, NY
    Builder: Martin Keith Guitars, Veillette Guitars
    Yes, that StewMac link looks like the same rod. They are variously wrapped in blue or black plastic.
    They're made in Korea. I know a number of well-known builders that use them.
    I bought 200 of them about 10 years ago and I'm still working through the supply.
    chinjazz likes this.
  18. Gilmourisgod


    Jun 23, 2014
    Cape Cod MA
    Did you have any trouble with sloppy hex key fit? Bought a blue taped one off BBG, the 4mm hex key is really sloppy in the adjuster, worried if will strip out eventually.
  19. I'm definitely going to check for potential sloppiness on the two I'll buy. Would be a big time bummer after gluing it in.
  20. Keith Guitars

    Keith Guitars

    Aug 25, 2004
    Woodstock, NY
    Builder: Martin Keith Guitars, Veillette Guitars
    My experience was that it was the supplied wrench that was crappy.
    A better US-made wrench should be fine. Note that a US 5/32" is close enough to work, though 4mm is better.

    I particularly like the Wera "Hex Plus" wrenches which are available from McMaster-Carr. They work great and present much lower risk of stripping.

    Gilmourisgod and chinjazz like this.

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