NECK AND NECK

Martin Guitar Necks

Sizes, Shapes, Reinforcements, and Neck Sets
Ebony and Steel Truss Rods

The following information taken from Mike Longworth’s transcription of the Martin Shop Orders indicates which wartime Martins were built with Ebony truss rods
in place of the usual steel rods due to wartime restrictions on the use of steel.  

I’m presenting this here as a general guideline since Mike Longworth’s work, while tremendously helpful, did include quite a few errors.  The contemporaneous Shop Orders
may include errors as well.  So the guitars themselves should always take precedence, and info from the logs should be verified by looking at the guitars. 
Fortunately, guitars are our friends and never lie!  Put a magnet to you guitar’s neck, and it will tell you immediately if it has a steel truss rod buried inside or not!

Observation, in fact, was the basis of Longworth’s ongoing work.  What most folks mistake for the “Martin logs” is actually Mike’s transcription of the logs used as a starting
point for adding his notes from observation of the guitars he inspected in person.  He was always looking to verify and add to what he saw in the original shop orders
While most guitar listings from the wartime period are followed by an “(E)” or an “(S)” to indicate “Ebony" or “Steel", quite a few are not.  In some cases where we have a
long string of “(E)”’s with a few in between with none, It seems fair to say that the lack of an “(E)” would indicate the opposite, but we can’t know for sure. 
I’ve indicated here with an * which of these are not noted but may be reasonably presumed from context.  
Please let us know if any of your guitars can help clarify the ambiguous listings.

Ebony neck reinforcement was introduced in 1922.  Earlier guitars have no neck reinforcement.
The “Bar frets” wedged into the fingerboard on Martin guitars built before 1934 have the additional benefit of keeping the neck straight.  So all Martins built before
August 9, 1934 #57305 have ebony neck reinforcements or no reinforcement at all.  

When Martin switched to T frets, a steel T bar was added to the neck’s interior to help keep the necks straight.


Ebony Rods were used again beginning in February of 1942 to save metal for the war effort, and became more regular from March of 1942, with some exceptions, until late January of 1945.

Then we see Ebony again from late May until late September of 1945. 

Ebony appears again in early May through late December of 1946.

Ebony reappeared in late October through late November of 1953.

Interesting that Martin went back to Ebony rods - soon after the Korean war, but mostly due to a steelworkers strike - at the same time that they were using the “mystery spruce”, producing guitars that sounded more like their wartime Guitars.

Classical Martin guitars, and also the tenor guitars kept Ebony rods throughout.
Guitars with the following serial numbers should have ebony neck reinforcements due to wartime restrictions:
1942
#80585-609
#80715-39
#80752-76
#80813-37

 #80863 - 83107
except:
81118-29*  (*not noted - presumed S)
81242* 
81771-895*
81921-94*
82045-81*
82567-72*

 1943    

All have ebony truss rods. 
1944    

All have ebony truss rods. 
except:
87077-88*
88207-12*
 89244-55*

 1945    
#90150 - 90360
except:
90560-91441*

 #91442-66

#91492-541
91542-66*
91567-91 “T”
91592-622*
#91623 - 92495
except:
91960-71 (partial - 4 with E, 8 with S)
92147-71*
92172-96*
92347-58
#92546-70

92758-82*
93083-107*
93133-157*

#93233 - 93623**  (**not noted - presumed E)
except:  
93283-307
1946
Jan 1 - May 3 
# 93624-95295 -- not noted - presumed S
except:
#95144-68 (E)
#95296 - 97909 (E)
 except:
95321-45
95396-420
95910-21
96703-27
97364-75
97860-84

1947

All have steel truss rods
 
except:
98862-86**
99191-202**
101207** (lefty)
101731-80**
101831-55**
101881-905**
102306*
103082*   (lefty)



 Neck Sizes and Shapes

So what makes a neck feel thin or fat?


I have lots of Martin guitars, from 1834 to the 1960's, with lots of neck sizes.  And I have some that I'm really in love with, such as my early January, 1930 OM-28

which has an unusually wide 1 13/16" wide neck which feels extremely shallow, and Gibson necks from c. 1930 that have a similar feel. 

While most folks are fans of the 1 3/4" necks from the '30's, and I'm used to wide necks - I grew up with a 12 fret 1964 00-21NY with a big neck, and can even

handle my 2 1/8" Roy Smeck - the 1 3'4" doesn't feel as comfortable in my hand, and the wartime necks feel great to me.  Some folks consider the Gibson AJ to be the

Holy Grail.  I'm allergic to it's neck.  If I don't get it out of my hand immediately, I'm in pain with cramped hands.

When I started to catalog the details of my guitars, I learned something interesting.  Wartime Martin necks that felt "fat" to me, actually measured exactly as deep

as necks that felt much thinner, front to back.  This is when I learned that it's all about the "Shoulders".  While some necks have an obvious "V" and others are round, there are

many gradients in between.  And it's the contour of the shoulder- the part of the neck that's missing in a "V", not the depth of the dead center

back of the neck, that usually determines how thin or fat a neck feels. 



The Move to Thinner Necks

Martin phased in steel strings between 1922 and 1926.  They apparently didn't see any need at all at the time to change the neck size, either to accommodate steel strings,
or because steel strings allowed them to do so.  
The neck was slimmed, however, in 1929, from 1 7/8" to 1 13/16", for Perry Bechtel's OM "prototype".  Evidently, this was not considered enough, or they simply realized
they could go further, so the production guitars were tweaked further to 1 3/4".  A 1/8" change from 1 7/8" to 1 3/4" is considerable, and I do believe this decision to
have been clearly influenced by banjo players.  The 14 fret neck was requested by Al Esposito for the 4 string Carl Fisher tenor guitar, which we know was fashioned to
attract banjo players as the banjo waned in popularity.  Even in the months before Fisher, the tenor guitar was introduced by Martin for banjo players with a 1 1/4" neck, a tiny
neck compared to any previous Martin.  I believe that this idea is reinforced by the fact that Martin continued to produce the 12 fret with the exact same 1 7/8" neck width, with
no changes at all after nearly a century, allowing Martin to offer the traditional wide neck to traditional players, and the new thinner neck to these newer converts to the guitar.
Martin has seldom made changes on their own accord, but almost always due to customer demand, either by the market in general, or more often in response to specific requests. 
In 1939, the market spoke again, as musical styles changed from those based on traditional right hand finger style playing, along with a more intricate left hand technique, to
playing with a "plectrum", often with simple strumming and "cowboy chords", as a simple accompaniment to singing.  So Martin responded in 1939 with a relatively minor 1/16"
tweak from 1 3/4" to 1 11/16".  As tastes and musical styles and techniques have changed once again with the times, Martin has more recently tweaked their product line back
in the direction of 1 3/4" necks.  
On the left is Martin's first unsuccessful attempt at a longer neck on a tenor guitar, with no doubt designed for banjo players.
 


Neck Sets


The “action” or string height of a Martin guitar can rise over time, making a guitar difficult to play, for one of two reasons. 

The first is a curvature of the neck caused by the tension of the strings pulling up on the neck over time.  In 1920, Martin added an Ebony truss rod to help prevent this. The nickel-silver alloy bar frets were also an important part of the system which helped to keep the neck straight.  If the neck did develop a curvature, it was often remedied by removing the frets  and sanding the fretboard flat. 

An innovative method was later developed to shim the frets, as Matt Umanov’s shop in Greenwich Village did to my 1939 D-28 in the late 1970s. In the past, bar frets that were worn down could be shimmed underneath to raise a low fret higher. In this case, a thin slice of metal was added next to the fret to make it wider, thus spreading out the top surface of the fingerboard to reduce the curvature in the neck.  Eventually, bar fret material became available in multiple widths, and this job became known as the “compression refret”. Today compression refrets can also be done with modern T-frets. 

In 1934, Martin Guitars moved from bar frets to “T frets”. To compensate for the loss of outward tension the bar frets provided to stiffen the top surface of the neck, Martin added a steel T-bar truss rod to the neck, similar in form to the rail or runner of a sled. By this time they transition from gut strings to increasingly heavier “wire“ strings was exacerbating the problem. The T-bar certainly helped, but did not entirely eliminate the problem.  
While competing Gibson Guitars had adjustable truss rods, Gibson had filed an exclusive 17 year patent in 1923. Martin responded by simply claiming that their Guitars did not need one.  Even after the Gibson patent ran out, Martin refused to add the adjustable neck rods.  Martin switch to a 3/8” square steel tube in 1967, and finally gave in to accepting adjustable rods in 1985. 

While not solving the root problem, both bridges and saddles were often shaved down to lower the action. 

The other major cause of unacceptably high string height or action is due to the relative angle of the neck in relationship to the body of the guitar. This is not due to any change in the neck joint as some may think. The dovetail neck/body joints are extremely solid.  

The angle of the neck in relation to the body of a Martin guitar will change due to a distortion of the body developing over time, usually in the form of the top rising and forming a slight belly under the bridge, and the neck and neck block together as a unit pulling forward, slightly caving in the body in the area of the fretboard extension.

Some of Martin’s better earliest Guitars had a clever Clock key adjustment to adjust the angle of the neck. 

The changes in the neck angle were also addressed by shaving down bridge and saddle until luthier Jon Lundberg developed a method of “slipping the block”.  After Lundberg moved to Berkeley California in 1960, this method became known as the “California neck set”.  This method involves separating the neck block from the back of the guitar and re-gluing the block to the back slightly further down, without touching the neck/body joint.  While this method is often looked down upon as being crude today, it is still useful in some cases, and some well done examples can be quite good.  

By 1975 or so folks were starting to follow Don Teeter’s method of sawing apart the fretboard and separating the neck joint by injecting water, slipping in a table knife, and then heating the knife to melt the hide glue.  Soon after, folks learned that they could remove the first fret after the body joint, drill a hole, and inject steam from a pressure cooker. This later changed to steam from an espresso maker.  

Once the neck is removed, chisels and sandpaper are used to adjust the dovetail on the heel of the neck, so the neck fits at a more appropriate angle. Thin wooden shims are added on the sides, so the neck fits tight.  

It is unusual for a Martin Guitar to require more than one neck set in its lifetime as the body can only distort by so much. Do-overs are usually to correct overset necks that have been set too far back.  

These days, many better luthiers routinely do a full compression re-fret at the same time as the neck set to make sure the guitar is properly set up for playing well.  

A proper neck angle can be determined by laying a straight edge across the top of the frets. The end of of the straight edge should land just about at the height of the top of the bridge.  The added height of the saddle should give the strings proper room to vibrate without buzzing. 




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