MET 349 - Stringed Instrument Design and Manufacture



Mark French

121 Knoy Hall

desk: 765-494-7521

mobile: 765-714-9382




Technology of the Guitar


ISBN 978-1-4614-1920-4





This class meets for lecture twice each week and for lab four times each week. Initially, labs will be divided between CAD work and fabrication in the guitar lab.


The central task for the semester is designing and building solid body electric guitars. You will work in teams of 5-7 people and each team will design its own instrument. Each team must complete one instrument for each team member. You will each have a body blank to start with.


The teams will have a parts and materials budget of $225 per instrument. Any team staying below this budget can use the remainder for gig bags or cases.


There are three allowable suppliers for major components: Stewart MacDonald, Guitar Fetish (no, I don't know who names these companies) and Amazon. The difference between the lab fee and your budget is used for consumable materials like glue, bits, blades and replacement parts.You will also able to get basic hardware, like neck and pickup screws from McMaster-Carr.Again, only one order.


No parts orders will be placed until all teams have 2D layouts completed and approved. There will be one parts order from each supplier. Successful manufacturers plan their operations carefully; if additional orders are required because of poor planning, students will have to order the parts themselves. Additional orders required for reasons beyond the control of the build teams will not be penalized; you pay for your mistakes, not mine J.


Finally, this syllabus is likely to change during the semester. If we finish a subject sooner than expected, that might make room for learning other things.Alternately, if we need some extra time on some subject, I want the freedom to spend that time.


Lessons Learned for Summer 2017:


         Budget and schedule must be kept current.If itís after the due date and your schedule says you were done 4 days ago, Iím not going to be impressed.

         Everything takes longer than you think it will, necks especially.

         Itís easy to throw away days or even a week at the beginning of the semester.By about week 5 you will be worrying about days rather than weeks.By week 8, you will be worrying about hours rather than days.By the absolute last day (the last day you are able to squeeze out of me), you will be worried about minutes rather than hours Ė trust me, Iíve seen this movie before.By then, what would you give for one of those days you threw away so casually weeks before?

         Last day of class is hard due date.Points will be deducted for missing the due date.You future customers will charge you money (sometimes lots of it) for missing dues dates.

         Inventor for CAD and HSM for CAM are OK.Necks are made with Inventor/HSM.Bodies are made with VCarve.

         It takes as long as 45 minutes to mill a body and about the same to make a neck.There is no Ďprint buttoní on any CAD program.Plan for realistic milling times.

         You must make alignment features when putting blanks on the CNC routers.Just drawing a couple pencil lines on the blank and the table is not acceptable.

         Necks are harder than they look.They take between 3 and 6 weeks to make.If all the necks are not complete by week 6, it is likely that the team will miss the due date.

         If the necks are not done by week 7, I will require that you make them by hand after rough cutting them with Vcarve.

         If you are dropping tens of thousands of lines of G code from HSM something is very wrong.

         Do not try to cut bodies and necks with small bits.ĹĒ flat end or ball end mills are a good choice.ľĒ mills are OK for truss rod slots and pickup pockets.

         Make a shallow pocket for the bridge in order to place it accurately.Trying to align it by hand will drive you crazy and introduce unneeded build variation.

         Tinted finishes are fine, but must be sprayed by week 7.They take time and you canít just ask for one to be thrown on in 15 minutes.That only works on TV or YouTube.

         Do not apply finish to any surface that is to be glued.Glue, especially wood glue, does not stick to finish.

         You must make a cutaway drawing showing me how the neck and bridge placement will give you the correct string heights.Do not just try to show me something scribbled on a sheet of notebook paper.

         If you decide to make design changes in week 6 or week 7, you are just looking for ways to miss the due date.

         Donít try to wire the guitar with heavy gauge wire.Youíre not trying to jump start a truck.You can wire the whole thing with 22 gauge stranded wire and it will turn out fine.Fender has done it this way for 60 years.Do not use solid wire.

         Neck through designs are fine if you remember two things:Not fault tolerant - if you mess up a neck, you may also have to discard a body that is correct (and vice versa).If you want me to spray your guitar, you have to make a solid stand that holds the guitar horizontal and allows me to rotate it.Spending 5 minutes nailing a stick to a board is not acceptable.

         When your question starts with the words ďMy buddy told me...Ē, I cringe a little on the inside.I know the advice is well intended, but there is a lot of dubious information floating around the guitar world.Do your best to verify advice before acting on it or asking me about it.There are two books available to you with tons of relevant information.You can start there.

         It turns out that not everything on the internet is true.Donít naively base your design on something you found on some web site, especially when you have the ability to do a calculation to check it.

         Buy more material and components than you think youíll need.If you break a potentiometer or lose a capacitor, I probably donít have extras for you.

         Build in alignment features.Why would you not use the CNC router to put alignment features on the instrument only to have to put pencil marks on it during assembly?



Lecture Schedule




Lecture Topic



Homework Due Date



Intro to class

Selection of build groups

History of the guitars

Ch 1



Intro, notes and scales

Ch 2.1




Scales and Chords, Fret Layout

Ch 2.2







Inductive Pickups




Forces in Necks,Guitar wiring

HW #1:


1 - Find the notes that make up:

         C major scale

         D major scale

         A minor scale

2 - Find the notes that make up:

         C major chord

         D major chord

         A minor chord

         F major chord

         G major chord

         E minor chord

3 - Find the notes for a major scale starting at A2 and the corresponding frequencies.Calculate these values donít just copy them from the book.

4 - Repeat for a major scale starting at C2

5 - Complete Instrument Budget for Each Group.Each group member should attach a copy to the HW set.



Due Date:






Aesthetic Elements of Instrument Design




Sound Pressure Level,

String Tension

Ch 2.3,2.6



Real strings


HW #2:


Calculate the fret layout for the following scale lengths:

1.    25.5 inch guitar

2.    24.75 inch guitar

3.    34 inch bass

4.    600mm classical guitar

5.    13.7 inch mandolin

6.    28 inch baritone guitar


         Report answers in both mm and inches

         Calculate the positions of the first 24 frets

         Report distances from the nut






String Tension


HW #3:

1 - If a sound has an RMS pressure of 0.50 Pa, what is the sound pressure level in dB?

2 - If a sound has an SPL of 110 db (really loud), what is the RMS pressure?

3 - If a sound has an SPL of 94 dB, what is the RMS pressure?

4 - Go on the interwebs and find the standard SPL for microphone calibrators. What RMS pressure does this correspond to?Note, some calibrators have more than one setting.Pick the most common setting.

5 - If a steel string with a diameter of 0.012 inch is tuned to 330 Hz, what is the tension? Assume E=205 GPa and a density of 7850 kg/m^3. Scale length is 647.7mm. Report the answer in both Newtons and pounds.

6 - What if the string has a diameter of 0.008 inch?

7 - A plain steel string has a diameter of 0.011 inch and a length of 711.2 mm (28 in). If it is tuned to 330 Hz, what is the required tension?


Do problems 5-7 in both English and metric units from the beginning.Donít just convert at the end





Sound Pressure Levels


String stretching and changes in pitch





No Lecture




No Lecture







Resistance and impedance

Input and Output Impedance

HW #4:

1 - For a voltage divider where R1 is the output resistance of a pickup and R2 is the input resistance of an amplifier. If Vin=12V, find Vout for these values:

a)    R1=1MΩ, R2=100kΩ

b)    R1=1MΩ,


c)    R1=100kΩ, R2=1MΩ

d)    R1=15kΩ, R2=500kΩ


Due: 7/28


Note: The frequencies for the open strings on a guitar at standard tuning are:

E - 84.2 Hz

A - 110

D - 146.8

G - 196

B - 246.9

E - 329.6


HW #5:

1 - A steel G string has a diameter of 0.43mm. If the scale length is 647.7mm, find the predicted frequency, using the real string equation, for the open string and the string being played at the 12th fret. Assume E=205 GPa and a density of 7850 kg/m3.Use tension predicted by ideal string equation

2 - What changes in length would be needed for the frequencies to be correct at the 12th fret and the 18th fret?

3 - A Nylon G string has a diameter of 1.023mm and E=1.95GPa.Find the tension assuming it is an ideal string and density is 1100 kg/m3

4 - Find real string frequency for the open string and the string being played at the 12th fret

5 - For the real G string in problem 1, how far would the saddle need to move for the string to be at correct pitch at the 12th fret? What would be the resulting tension?


Due: 7/31



Review for Exam


Practice Problems


Use the real string equation for all 4 problems


1 - Calculate the frequency error for a 25.5 inch nylon G string (E=10^6 psi) with a diameter of 0.040 in, stopped at the 12th fret. String Tension is 11.7 lb. Calculate the error due to inharmonicity. Assume that nylon is 1250 kg/m3.

2 - Calculate frequency error for a steel G string (E=29*10^6 psi).String diameter is 0.023 in. String Tension is 27.2 lb.Assume steel is 7850 kg/m3.

3 - Calculate the saddle offset needed for the nylon string using frequency at the 12th fret

4 - Calculate the saddle offset needed for the steel string.

1 - How far from the nut would the 12th fret be on a guitar with a 24 in scale length?


2 - If a string is 700mm, is made from steel and has a diameter of 0.4mm, what tension is required for it to be at a frequency of 150 Hz?


3 - What are the notes in an F major scale?


4 - What are the notes in an A# chord?


5 Ė If a guitar has an output impedance of 16 , what is the input impedance of the amplifier required to drop 90% of the signal across the amp input?




Open Book, Open Notes












Exam: ††††††††††††††††† 20%

Homework: †††††††† 15%

Guitar: ††††††††††††††††† 55%

   Design: completeness, accuracy, creative solutions to design problems, aesthetics

   Construction: accuracy, organization, meeting build schedule, build process, jigs and fixtures

   Final Product: accuracy, playability, finish, balance, sound, aesthetics

Peer Grade††††††††† 10%