Truss rod installation - headstock adjust

[TRexF16]

Just a word of warning. There are several references above to "round over" bits. This is not the kind of bit we are using to get the effect referenced here. A round over bit is what we use to round over the 90 degree edges of our guitar bodies and it is usually specified in radius. The bit that makes a round bottomed slot for the adjusting nut of the truss rod to lie in is a "core box" bit. I use a 5/32" radius to install Bitterroot rods (5/16" diameter, and I must apologize for incorrectly introducing 5/16" into the conversation as core box bits are usually referenced in radius as well). I must emphasize that other rods may need larger or smaller radii to fit well, but my experience is the 5/16" diameter slot is about the minimum width that allows one to get a complete 1/6 turn of the truss rod nut with the hex key, and this is a real consideration in the whole setup's effectiveness. I use this Amana 45903 bit for my technique with Bitterroot rods.

For StewMac's Martin style one-way rods I needed a 3/16" radius (3/8" diameter) core box bit. And this bit ends up being smaller than the truss rod slot. Each rod must be carefully measured and matched to its corresponding bits.

Hope this helps. Best to all,
Rex

 

[guitarbuilder]

I'm guilty of typing roundover instead of round nose when I meant round nose / corebox. I edited that a few days ago. Your truss rod nut shall determine what bit you need. You need to get your wrench of choice in there. Either way, I've always done it when the wood is a rectangle and after the truss rod slot was made.

A half inch corebox is usually available for cheap. My local store used to carry Vermont American or similar bit for 5-6 dollars.

This type of bit provides a half round slot and removes less wood than a straight bit. In terms of structural integrity, I believe a half round slot would be stronger than a straight flat bottomed slot in the same material. It is in the metals world anyway....

https://www.whitesiderouterbits.com/collections/round-nose-core-box

What's even more important is making sure the wrench you use can actually turn the rod enough to do some work. Being conservative on your slot can end up being a problem down the road if the wrench can't move. You learn that the hard way and then have to get creative.

 

[R. Stratenstein]

Somewhere I have a “template” —sample, actually- neck for using Bitterroot 2-way rods with headstock adjust, with many notations, scribed lines, etc, looking like Rex’s examples in the post he linked to. It was the result of about half a frustrating day trying to figure out why I couldn’t get the rod, at the adjustment end, to lay flat in the route. As I recall, it takes 3 different diameter bits, each adjusted to a slightly different depth to account for the different diameters, to get a tight, clean fit, with properly sized and shaped access hole with really no sanding or filing.

One variation on this process I remember reading is use of—I think—a 3/8” bit on a long flexible shaft. Laid in the router channel, and drilling toward the headstock BEFORE the front is shaped, or you’d almost certainly get blow-out when the bit emerged from the wood. This method virtually guarantees straight alignment with the routed rod channel. These bits are used by alarm and other low-voltage system installers.

Like Marty, I always had trouble with bits wandering, especially climbing up the transition trying to do it the way Freeman shows. My guide block would slip, or not be quite the right angle and need some very fussy shimming, which would slip, then the block would wear and be sloppy, there are some guys here who have made some very good jigs for this one operation, with metal inserts to align the bit, and multiple clamps to hold the neck in a death grip, but I just didn’t want to be bothered with all that jiggery.

BTW, You may have already answered this, but I overlooked it, can you get Bitterroot rods shipped to SA? They’re a good value, and I’ve always had good luck with them. Slightly more of a PITA to install because of the 3 diameters needed, but once you break the code on that, you’re good to go.

 

[TRexF16]

For Rick and Marty, I want to be real careful not to come across like the Nomenclature **** or as pedantic on the installation technique I was demonstrating. I made the point about "core box" vs. "roundover" just in case someone who reads this decides to order a bit for the purpose without a picture of the bit to reference. For the same reason I was kind of self-flagellating over having called the bit I use 5/16". If somebody orders a 5/16" core box bit to do this job they'll get a bit twice as big as they should, and likely more expensive too. It's also worth noting the cutting length/depth on the 5/32" core box bit I pictured above. Many core box bits stop the cut at the "hemispheric" point, for lack of a better term. I think having the bit cut beyond that point is helpful.
It only takes two bits to do it the way I do it, and the execution could hardly be easier, so I might post a little bit more elaboration on that after I get in the shop and take a few pics this morning. No disrespect meant to Rick but "PITA" is the last descriptor I would ever choose to reference the installation of the Bitterroot rod this way. It's easy-peasy. A bit more to follow later.
Spoiler - you can do in on an already profiled neck too - it does not have to start with a full width neck blank.

Cheers,
Rex

 

[TRexF16]

More words of warning. Bitterroot sells two different kinds of truss rods that work in both directions. I see their images are copyrighted so I will not attach one, but here is the link to their site.
https://www.bitterrootguitars.com/
The image of the two different truss rods are on the first page of the site.
Everything I have been writing and all that follows refers to what they call the "dual action" truss rod - the one where the hex nut is fixed and welded directly to the active rod. Their other rod, the "two-way" rod might have slightly different dimensions to the adjuster nut and it might have slightly different depth and diameter requirements. I don't know - I've only used the dual action rods.

First, in all of the talk so far we have described routing the channel for the truss rod when the neck blank was still basically a rectangular board, and we were using one edge of the board as our registration edge against the router table fence. Well we don't always have that luxury, especially for guys like me, who are, like my father before me, a touch "thrifty." I like to get as many pretty necks as I can out of a nice piece of wood and may crowd them in like cutting biscuits on rolled out dough.

In this case I go ahead and cut out the neck and profile it first. Then I double stick it to a piece of 1/4 hardboard, with the centerline of the neck aligned to a reference mark on the hardboard that is parallel to both sides of the hardboard.

The main use of this hardboard plate is to sit in my fret cutting miter box and keep the profiled neck centerline perpendicular to the fret saw, but I use it for two other purposes:
1) to cut the nut slot, which I make on my table saw since its blade leaves a 1/8" kerf. I just set the blade to the desired depth of the nut slot and make a single pass with the hardboard plate registered against my table saw crosscut sled. Then, I lay out the fret slots and cut them by hand.
2) But before any of that I also use it to register against the router table if I need to rout for a truss rod in a neck that is already profiled as a result of my "thriftiness." So this process, though ideally done on the neck board before it is profiled, need not be and will still work fine if you just create a reference edge parallel to the neck centerline.

Now to set up the router table. I recommend anyone doing truss rod work on the router table view Fletch's great video tutorial here:

He starts the router table stuff at about 6:28. I use his techniques to lay out and mark the start/stop cut line on the table an neck. If using my hardboard plate as described above, I already have the reference marks permanently inked onto the board.

Once you have set the router fence and marked the start and stop cut references, just (for the Bitterroot Dual Action Rod) set the depth of cut to 3/8" and use the router's plunge settings to secure that depth. I rout a couple test slots on a scrap board to double check that it's just right to fit the rod just a hair below flush. Then, save that test board as a future reference to setting the router depth. I use a 1/4" spiral up cut bit (Freud #75102) for this cut but any bit that cuts a flat bottomed 1/4" slot can be used. The 5/32" radius core box is the only other bit needed. The depth for that rout needs to be a bit more than 3/8" as the bottom of the nut on the "dual action" rod is about .025 lower than the bottom of the minimum acceptable flat bottomed rout for the rod itself. I recommend about .425 deep for the core box rout. this gives you just enough clearance all around the edges of the adjuster nut that you can get some finish buildup un the access slot and it'll still turn fine.

So while you are setting up these depths and test cuts on your scrap board, go ahead and create a clone of the final 10-12 inches of the rout. It'll end up looking like this:

The rod is in backwards here just testing the depth for that section.

Once it is all the right size, go ahead and make a shallow cut on the end of your test board that will serve as a future reference for easily setting the depth of the core box cut. Save this board - it now allows quick set-up of both bits.

Now cut it on your neck itself. DO NOT try to cut it to full depth in one pass. I do three passes, deepening each to sneak back up to the final depth I already set and locked in on the plunge settings during the test cuts.
This is a lot of words but it is actually very easy. Only two bits are needed. You can do it on an already profiled neck if you make a reference plate to double-stick it to. Turns out pretty classy looking. Heel adjust would be a lot easier but that's a pain to use unless you use a spoke wheel, and if that's your plan just follow everything Fletch shows in his video.
Questions? Let me know.
Comments, especially room for improvement, please post.
Cheers,
Rex

 

[Freeman Keller]

Rex, great description and probably the best way to do it. I cheat a bit, almost all of my necks are angled heads so I just start at the head and route the channel as far as it needs to go, either stopping at the heel or just running it out and making a filler. Then I bump the fence on the router table "a hair" and hit the entrance to the channel for an inch or so, then turn the neck around against the fence and come in from the other side. All I'm trying to do is widen the slot enough to clear the adjuster. If I was thinking I would also give a hair twist to the vertical adjustment so the channel is a bit deeper.

Your round nosed bit is a bit (no pun) more elegant, I don't own one so I use what I have.

There is a mark on the router table at the joint in the fence - that is the centerline of the bit. That way I know where it is relative to the neck as I push it forward.

 

[TRexF16]

Thanks Freeman, I have an angled Batwing style headstock (think Epi Crestwood) in the future and need to really start thinking it through and gathering ideas like yours above. It'll be my first angled headstock - probably a through-neck but that part of the design is still in flux.

 

[Freeman Keller]

As I have said over and over and over again, I am totally sold on scarf joined heads - I have fixed way too many broken heads that fractured along the grain of a sawn neck. Having the grain run parallel to the face of the head just makes so much sense. A contributing factor to all the broken Gibbie heads has to be the big route for the nut on the tension style rod - a small allen head adjuster seems like the best way to go. I'm also a believer in double acting rods for a lot of different reasons.

I've never built a neck thru guitar - that seems to add so much complexity to the geometry. With a normal set neck you can fiddle around with neck angle and overstand until you get it nailed, with a thru neck you are pretty much committed when you make the first cut. On a practical matter having that neck sticking out while you try to work on the body, or for that matter carve the neck, just seems like a hassle (I did build one classical on a solara and the neck was always in the way).

The last part of neck planning is to really think about your sequence of steps. Make every cut you can with square sides so you can use a fence on your band saw or router - even some of the angled cuts at the heel should be done with square sides. Don't glue wings on the head if it makes it wider than the rest of the neck. I'm doing an acoustic build right now (a few picks at the WOYWBT thread) and I've tried using my Safety planer for some preliminary thicknessing - worked pretty well. If you look at that first picture, the idea is to thin the neck from heel to nut, but at an angle. Recent threads and pictures at OLF.

Looking forward to your build. If you want to bounce ideas off of me let me know. Also, I assume you know that Hiscock has a thru neck as one of his builds.

 

[eallen]

Thx Eric this is what I meant. Any chance of more pics of this, like what the finished headstock looks like

First, the guys are correct on bit terminology and radius. The Frued bit I happen to have is labeled by Frued as "round nose bit". The one in the pic is a 1/4" finished diameter version I had still in the package.

Here is a finished headstock as requested.

Eric

Sent from my SM-G892A using Tapatalk

 

[TRexF16]

Eric - did you do that adjust access hole using a round nose / core box bit is some manner? Or is it drilled? It's beautiful regardless. Thanks.

Freeman - One planning factor I have picked up on a through neck is to do the "think it through" thing as you mentioned, and then do every possible operation while the neck is still just one long narrow piece, before the body wings are glued on. This would include the neck carve and potentially the fretting and fret level as well. Depending on the width of the through neck portion it could also include all the pickup routs. While a through neck seems to be kind of a solution in search of a problem, I suppose it is needed if one must do an "authentic" Firebird, for instance. It might give a little more freedom in shaping the neck-to-heel transition but I don't see that this would be fundamentally different than a set neck that was designed with a particular heel transition in mind.

Cheers,
Rex

 

[Slowtwitch]

Thx guys for detailed tutorials!

confirming my cheap bit is 6/32 radius or 6/16 dia. here's a pic of it referenced to a drilled access hole on a cheap neck. I compared it to my MIA Fender strat, and the Fender's access hole is much smaller because it has a larger filler wood dowl insert, but the larger hole looks fine. Structurally I don't think there's much compromise

And on rods, in South Africa we can get the Allparts double action rod which looks the same rod as the Bitterroot dual action rods. Is there a reason the Allparts rods are not mentioned in any of the research I've done? I understood Allparts products to be acceptable build quality on this forum in general.

 

[guitarbuilder]

Bitteroot is recommended because that's what people keep recommending and use. They are the lowest cost in lots of 5. Before Bitteroot, it was the stewmac hotrod which was the rod of choice for a double rod because that was easily available ,( I prefer those for the couple dollars more). Allparts tend to be more expensive unless you are a dealer.

 

[dickjonesify]

One thing I’m confused about here... if I’m doing the traditional curved truss rod route from underneath with skunk stripe, do I use a 3/16” bit or 1/4”? 3/16” would fit the rod but the skunk stripe seems to measure 1/4”.

 

[guitarbuilder]

I use a 7/32 bit and/or the stewmac bit for hotrods. I don't want an interference fit of the rod in the channel. You make the skunk stripe a few thousandths less than the slot you cut.

 

[netgear69]

One thing I’m confused about here... if I’m doing the traditional curved truss rod route from underneath with skunk stripe, do I use a 3/16” bit or 1/4”? 3/16” would fit the rod but the skunk stripe seems to measure 1/4”.

Why not just do the skunk stripe the same diameter as the bit you have

 

[dickjonesify]

Why not just do the skunk stripe the same diameter as the bit you have

I already have a carbide 3/16” spiral bit for my G-style truss rods so I’ll probably just stick with that.

Just wasn’t sure why the drawing’s skunk stripe was 1/4”.

Mine might be a little short, though, now that I think about it...

 

[GunsOfBrixton]

Why not just do the skunk stripe the same diameter as the bit you have

Short answer. Glue. (as in, you don't want to starve the glue joint on the sides.)

 

[guitarbuilder]

I already have a carbide 3/16” spiral bit for my G-style truss rods so I’ll probably just stick with that.

Just wasn’t sure why the drawing’s skunk stripe was 1/4”.

Mine might be a little short, though, now that I think about it...

Here is the dimension. It's not 1/4 it is .220"

 

[dickjonesify]

Here is the dimension. It's not 1/4 it is .220"

View attachment 578522

How does it get to .220 when 3/16” is .1875”? Is that an additional route? Or is the rod actually .220?

 

[guitarbuilder]

How does it get to .220 when 3/16” is .1875”? Is that an additional route?

Well this is Ed hawleys drawing from his neck. I'm guessing the slot is .220 too. Otherwise you'd be hammering the rod into the slot...ie interference fit. Metal rods would be +/- the .1875. When you think about how the rod works, the skunk stripe is just decorative. The rod tightens between the anchor and the nut trying to straighten, and with that force pushing upward against the maple above it. The skunk stripe doesn't really get that force.