Official Luthiers Forum!

So far I've used sound hole access on my guitars but I don't care for drilling a hole in the UTB as well as routing the slot into the top. It seems like it would cut out a couple of annoying steps to go with the other style and cover it with a magnetized cover. Does the truss rod need to be longer if I do this? What other considerations are there?

From the repair point of view, peghead access weakens the neck on those guitars with an angled headstock, has one or more extra parts to detach and reattach when the truss rod is adjusted, and the cover often appears to me to be an afterthought...especially where there is an inlay scheme present. Keep in mind that a peghead-adjustable rod also requires some additional steps to mill the recess and fit up the rod, so as one of the many little 'motivational' postings around the shop remind us, there is no such thing as a free lunch!

In terms of building, a hole in the UTB is not required...an appropriate-sized wrench can be bent up as many custom builders do (and sell to repair shops). If a hole in the UTB is used, 1/4" is more than large enough for anything up to a 6mm, and has very minimal impact on stiffness (the shop's building guide notes that the UTB is left 1/64" higher to address any loss of stiffness).

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For the times they are a changin'

- Bob Dylan

I'm on team soundhole. I've done both, and I feel that putting it at the soundhole end leads to fewer problems.

Me 3. I just completed my first head stock access rod via Gibson style. Came out OK but #NEVERAGAIN!

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"I've been had again"
Tim Benware
Creedmoor, NC

Soundhole for me, including hole in UTB for truss rod. Not much loss of strength, as mentioned a tiny adjustment in height will regain it, and it makes life easier for the end user not to have to find a fancy wrench.

My UTB gets butted up and glued to a fretboard reinforcement piece. This is one of the reasons I've been considering a change.



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I will only use a peghead adjustment when I have to, as in "electric guitar", but many fine builders do the peghead thing will no ill effects. So, like they say in poker, it's dealer's choice.

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Joe Beaver
Maker of Sawdust

Joey, I use a trapezoid brace similar to your fingerboard brace. I also use Martin 2-way rods which are installed directly below the fretboard. A 5/16" hole drilled at an angle through the neck block gives good access to the rod with a Martin ball end wrench without the need for a hole in the UTB.

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Good judgement comes from experience. Experience comes from poor judgement.

Do you pre-mill the channel in the filler piece and neck block? It seems like a 5/16" square channel would not meaningfully reduce stiffness of the filler piece, and would minimize the work to achieve truss rod access.

_________________
For the times they are a changin'

- Bob Dylan

That's interesting. I haven't seen or used that style of truss rod. Where do you get yours?

I've been waiting until I get the neck fitted and centered and then setting up my Bosch colt laminate trimmer on a track like jig to route the channel. It works well but takes a bit of time to set up and get right. I'm not overly worried about losing strength in the UTB since it's glued right to the mahogany fretboard extension support or whatever you want to call it. I was just thinking that the nut access could be a little more streamlined than what I'm doing now. Sounds like it might be more work but I would like to give it a try on one of these rounds of builds sooner or later. I notice that Tom Bills, Mike Greenfield and a few others use the access at the nut version and thought there might be a reason for it that I was missing.

Martin. Part number G13NR0009 for 14 fret, G13NR0013 for 12 fret.

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Good judgement comes from experience. Experience comes from poor judgement.

I build archtop guitars with the typical fingerboard extension. It would be pretty radical to have access at the body end of the neck. That said, I wonder if anyone has ever done that.

Anyone in this vast brain trust ever see a truss rod on an elevated fingerboard that was adjusted in the body end.


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Sweet, thanks. Dirt cheap too!

The shop has produced two guitar-shaped octave mandolins (with Morelli Guitars) with Martin Size 5/Terz length two-way body-adjustable truss rods; both instruments are carved top/flat back, so certainly an unusual configuration, but one that works well according to the owners. I came across the shop drawings for the octaves recently while organizing the collection of plans and vintage instrument documentation, and will see if I can take a few snapshots of the arrangement, as well as look for any other photos we have. As seen in the photo, there is a channel milled in the extension block on the underside where it mounts to the body, allowing access with a standard length post-2005 Martin 5mm wrench. The end of the extension block has a reverse bevel (hard to see in the shot), with the channel dying just short of that point to hide the access.

If the top looks a bit pieced together, both instruments were built for under $150 each as part of some sort of low priced building competition...the tops came out of two perfectly quartered red spruce 2x4's. With the burst and normal lighting, it is hard to see that this instrument has an 8 piece top and the other a 6 piece top.

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For the times they are a changin'

- Bob Dylan

The old Epiphone archtops had their truss rod access under the fretboard extension......

If anything I think you need a longer rod for sound hole access rather than peg head.

Call me a heretic, but I like my truss rod access on the peghead. I hate working around the strings and into a blind hole to make adjustments. I'd rather do them under string tension. Pulling a couple of screws from a cover plate is a minor inconvenience. And I'm probably going to be tarred and feathered for this, but I also don't buy into the argument that it significantly weakens the neck. Sure, accidents happen resulting in a broken headstock. And we all see and hear about breaks in headstocks with truss rod access...equating it with a severe weak point. But it seems that there are a lot more guitars out there that have peghead truss rod access, so I'd expect to see more breaks on that style guitar. I'd like to see a controlled study where 100 necks are tested, half with a peghead TR and half without. But I'd hate to see all that wood and work go to waste!

But in the end I probably do the peghead TR access because it feels a lot easier to do.

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Tony Thatcher
Bozeman, Montana

I made my first archtop guitar with the truss rod adustable from the neck end. The only problem is that fitting a pickup to the end of the fingerboard may be a problem. In this case the pickup I originally fitted was fine but it was subsequently changed to one with adjustable pole pieces which was deeper and meant the pickup had to be detached to adjust the rod. I don't have any pictures that really show what's going on but I used a low profile, Martin style truss rod. Next one I built with conventional adjustment at the headstock. On flat top guitars I always use soundhole adjustment - I've seen too many broken headstocks with the adjuster at the headstock end.

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"There is hope in honest error .... ". Charles Rennie Mackintosh.
http://www.ianchisholm.co.uk

The Martin rods are sized to terminate prior to the end of the dovetail or tenon, so the longer truss rod wrench with ball end is the usual tool for access when body access is used. Total rod length is about the same as a single-action Gibson-style rod when the length needed to allow for the anchor and truss rod nut is taken into account.

The main difference for us is in the required length of the adjusting tool - the Martin rod requires close to a 6" long ball-end 5mm hex, while rods that project a ways into the body cavity, such as the older Martin single-action Gotoh-made rods terminate closer to the UTB, so take a much shorter wrench. While we have used the Martin rods in replacement necks which are peghead-adjustable, it requires some careful planning (usually a full-sized drawing) to determine the best layout.

Every broken peghead that has come through the shop in the 2-1/2 years I have been here have been a Gibson, Epiphone, or a clone, and out of the hundreds of broken pegheads repaired here over the years, very few have been body-adjusted truss rod necks. Taylor seems to take a bit more care with material selection and installation, and the scarfed joint or finger joint used is quite a bit more robust than Gibson's approach. We have a nice slope-shouldered 1966 J-50 that is getting a whole new neck after three breaks over the years...the grain through the neck-to-peghead transition runs upward towards the tuners, so there is little that can be done, outside of splining and back-strapping (which also have their weaknesses). It is not that peghead accessed truss rods need to necessarily result in a weaker neck joint or be more trouble-prone in terms of breakage, but it works out that way because of the sheer number of instruments with Gibson-style construction. But as the boss says, please continue using that design approach, as it provides repair shops with a very steady stream of income.

_________________
For the times they are a changin'

- Bob Dylan

A couple of thoughts. First off, from an efficiency standpoint, having the access in the body puts the rod at a mechanical disadvantage as the rod needs to work more at the nut end than the other and many folks with more knowledge than me say they work better at the nut end. Second, it's a pain in the ass to access them in the sound hole; third, with a predominance of builders using allen key style rods, the opening at the nut isn't what Gibson style rods require; fourth many builders using carbon fiber neck reinforcement that goes past the nut, strengthens the area and negates any weakness from headstock access. Lastly, a peghead break isn't a warranty issue, its a handling problem. The peghead broke because of poor handling not because it wasn't strong enough for the job.

Perhaps an actual mechanical engineer will weigh in here with some discussion of compression rods versus bending rods, given that - while the movement of the neck is greater due to the reduced cross-section towards the nut - the rod sees just tension or bending. Perhaps friction effects?

The notion that poor handling is the culprit in so many more neck breaks on peghead-adjusted truss rods versus soundhole-adjusted truss rods agrees with my own observation that Gibson and Epiphone owners are perhaps a 100 times clumsier than owners of other brands, and uniformly so...I suspect a genetic link of some sort will eventually be identified.

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For the times they are a changin'

- Bob Dylan

Woodie, you're twisting my words and inferring where none was intended. The reality is that a peghead break is negligence. There are other manufacturers that use a nut-end truss rod that don't have Gibson and Epiphone's history of breaks. Furthermore, in my comments I specifically mentioned the change in style of rods predominantly used today as well as CF reinforcement as reasons it shouldn't be a problem.

Twisting your words, Mr. Berkowitz? I think not.

Order in a paragraph may imply subordination (i.e., each element of the list is dependent and related to the last), but your construction was an enumerated list of issues (i.e., "first...second, ...lastly), structured to separate your thoughts as independent ideas coupled together only so far as they were a) your thoughts, and b) they related to the more general topic per the OP's title. Given your paragraph construction, I am unsure as to how a reasonable person would conclude that your last sentence and a half should be considered as applying solely to those necks modified with carbon fiber reinforcement, etc., rather than the more general class of truss rod arrangements most closely associated with Gibson, et alia.

Absent the sort of paragraph construction which guides the reader towards your true intent, my quoted comment was both reasonably humorous and more than gentle in its lampooning of the notion that Gibson and Epiphone necks are no more or less prone to breakage than any other marque.

_________________
For the times they are a changin'

- Bob Dylan

"So far I've used sound hole access on my guitars but I don't care for drilling a hole in the UTB as well as routing the slot into the top. It seems like it would cut out a couple of annoying steps to go with the other style and cover it with a magnetized cover. Does the truss rod need to be longer if I do this? What other considerations are there?"

As mentioned, using a rod that requires a smaller opening to access the adjuster, splicing the peghead, and adding a reinforcement to the transition from neck wood to peghead wood (thicker peghead overlay) might make a stronger and ultimately more successful construction. Reasonable care by the end user solves a lot of potential problems.