# Truss rod installation tips



## NKGP (Sep 13, 2012)

Hi,

I'm in the process of building my very first guitar. It's about time to install the truss rod but since it's a neck through construction and I don't have any experience, I'd love to have some light shed on this matter.
(I have read about this stuff but I want to be educated a bit more thoroughly before I go any further, I need details)

I've got this type of rod:






1: When installing this, the flat bar goes on the top? I've read this on more than one site but I want to be 100% sure.

2: How tight does it have to fit the slot? Should I route the slot with a bit of the same width as the rod itself? Or is it okay to have it a hair bigger? How much bigger is still okay? Should it be okay to have it a bit wider, would it be okay to put tape around the end of the rod to make it fit firmly at the end?
Should the slot be exactly as deep as the rod? If not, how much deeper?

3: Should the slot be in the exact center of the neck? Or should I calculate which strings and tuning (tension) I would use to find the location of the resulting stress?

4: _We suggest using a filler strip (mahogany for example) to prevent "rod rattle." This also takes up backlash in the rod._ - Truss Rods - Guitar Parts: Allied Lutherie
What does this mean? How can I prevent the rod from resonating? This guitar being neck through, it would pretty much ruin the project.

5: How do you avoid getting glue in the truss rod channel? I've seen this technique before:




But how does that prevent glue squeeze-out going into the channel?

6: Lastly, is it necessary to do fretboard radiussing and fretting before gluing the board to the neck? And if so why is that?

I'm sorry if this is a lot, but I want to get the best out of what I'm doing and there's a ton of topics out there but it never really goes into the details I'm looking for.

A millistep by millistep explanation of this whole truss rod chapter would help me enormously.

Thanks in advance.


----------



## silent_k (Sep 13, 2012)

This is can be a complex process, particularly on a neck through depending on your construction technique, but here are a few quick answers based on how I've done it:

1. Yes

2. The slot should match the width of the flat part of the rod, which should be essentially the same as the width of the square ends. It needs to be a snug fit -- you don't want the channel to be wider than the rod or the rod won't be able to do its job and will surely rattle inside the neck. In the photo it looks like the weld between the square ends and the flat bar might protrude a bit -- I would try to file that back until it's as close to flush as possible. I use rods from Allied Lutherie that are very well made and are 1/4" in width. I use a 1/4" round nose bit to cut the channel (corresponding with the round rod), then a 1/4" flat bottom bit for the square ends of the rod.

Regarding depth, the rod should sit just below the surface of the neck blank -- we're talking about just a hair's difference here, not much. I always back the adjustable rod against the flat bar and press down on the square ends on either end to ensure they will sit at proper depth. You want just a small amount of material left above the flat bar because you'll need to lightly sand/scrape that material before gluing the fingerboard on to open up the pores for the glue. But, again, you're going for a snug fit on the top side as well. Measure everything, go slowly, measure and test fit as you go, and only take off small amounts at a time and you should be good.

3. Yes, center the rod. If you want extra stability, you can add carbon fiber reinforcing rods on either side of the truss rod. That can get complicated, and usually for medium to light-gauge strings a truss rod is enough (what kind of neck wood are you using?).

4. This really depends on construction. Some people rout concave channels that vary in depth and use a "skunk strip", a la Fender, to fill in (you can find some examples of this technique on the offsetguitars.com forum). I've never done it that way -- I always rout the truss channel from the fingerboard side of the neck, and again if you get the right width and depth you don't need any filler. Rods like the one you have have a plastic sheath around the metal part of the rod, and I've seen some people put a small amount of silicone sealer in the bottom of the channel to help eliminate any rattling, but that shouldn't be necessary.

5. This is a good technique. I use a corresponding strip of tape on the fingerboard, as well. You cannot completely eliminate squeeze-out from seeping into the truss channel, but using the tape trick can minimize it. On my first neck I didn't use tape and it didn't matter -- if you get a bit of wood glue in the channel it shouldn't affect the performance of the truss rod. Filling the channel with glue, or getting a lot of seepage with a different adhesive, like polyurethane glue or epoxy, would be a different story. Try not to over do it on the glue and you should be OK with this method.

6. Again, it depends on your construction method. I leave the fingerboard flat and unfretted for as long as possible because of my particular way of building necks -- it makes it easier to register the board on the neck and rough in the taper in the back of the neck prior to carving, but these things could be accomplished other ways. Other people radius and fret beforehand. Look around for different techniques to find what's going to work best for you.

All of this, by the way, is just the way I have done it. I've had pretty good luck so far, but others surely have different/better ways of doing it. There's certainly more to say about all this. Good luck!


----------



## sibanez29 (Sep 13, 2012)

1. I have used the same style of truss rod. The flat bar goes on top.

2. If using a router, use the same size bit as the rod (most likely 1/4"). The tighter it fits width-wise, the less chance for rattle. Make the slot just as deep as the rod or a hair deeper, making sure that it does not stick out above the channel.

3. The center of the neck is fine.

4. Use either a small bead of silicone or a tiny strip of foam under the middle of the rod (in the slot) to prevent rattle.

5. Just apply the glue around the channel and wipe off any excess. A little may squeeze into the slot when the fretboard is applied, but that will not affect the performance of the rod.

6. Personally, I fret and radius the board before gluing it on when doing a neck-through guitar. It allows more room for tools (for example, you can use a belt sander to trim fret ends) and if you make a mistake you can get a new board instead of having to scrap the entire project. This is preference; however I would recommend doing this especially for a first-timer.

You seem like a very bright individual who is also very careful. I'm sure you will do just fine.

EDIT: silent k beat me to it! Oh well, I guess I offer another perspective.


----------



## canuck brian (Sep 13, 2012)

You can also use saran wrap around the rod once to prevent any glue from getting between the double rods. I usually use caulking under the truss rod to prevent rattle. 

I've been looking at the LMI rods recently, but for the most part i use the Stewmac Hot Rods and their Hot Rod routing bit to create a perfect channel.


----------



## Pikka Bird (Sep 13, 2012)

People have already said what needs to be said. I do think, however, that a filler strip is a good thing for one reason- you can use it to prevent glue seeping into the channel. 
What you'll need to do is route the channel 2-3mm deeper than it needs to be and then make a strip of wood that's exactly as wide as your channel (needs to be a tight fit) and a mm or so too tall. Then you'd insert the rod, apply glue to the sides _of the filler strip_. That way it scrapes excess glue off when you insert it into the channel and push it all the way down as far as it'll go.
Now you'll have the strip jutting out a little, with glue squeeze-out along the sides. Then you just take your plane and get it level again. After some slight sanding* have a perfect surface for gluing and you can spread your glue over the entire top of the neck without having to worry.

*) This gives the glue something to grip on to- this'll also help reduce obvious glue lines, so remember to sand every gluing surface, especially when gluing similar woods that need to be joined subtly, like body blanks or bookmatched tops.


----------



## NKGP (Sep 16, 2012)

Thanks a lot for the replies.
I'm using padauk for both the body and the neck of the guitar.

The rod is 6mm and the smallest bit I have was a 6,35mm (1/4") so I ordered a 6mm one. I already made the template for the router so I hope I can get the channel done after a few test runs.
I'm super excited about how this is coming together. Thanks again guys.


----------



## bob123 (Sep 16, 2012)

You don't want the rod super duper tight. The 1/4 th bit would probably fit real well...


----------

