Hardware DNA: Electric Guitar Teardown
Guitars have an incredible amount of craftsmanship applied to each individual instrument. The detail of every perfectly sanded edge, intentionally placed fret, and expertly applied pickup all amount to a product that both looks and sounds beautiful. (To see just how much detail goes into the making of a guitar, check out this How It’s Made video from the Science Channel.)
For this issue of Hardware DNA, we’re taking apart an Epiphone electric guitar. These instruments can amount to a value of thousands of dollars, but we chose a beginners model with a value of around $100 as a good starting place to better understand how guitars are made.
To start, we cut the strings off (with care to reduce the tension first!).
Next we remove the bridge with 2 flat head screwdrivers. At first it looks like the bridge has been dipped or painted to achieve the chrome finish, but after dremeling through we can see the copper coating underneath, which tells us the piece is in fact chrome plated.
Throughout the teardown we find chrome-plating metal components to be quite the theme (bling bling).
Next up we remove the pickup, which has power and ground attached and is essentially a big magnet and works like a mini microphone, picking up the sound vibrations of the strings and sending them over to an amplifier and then a speaker.
The base of the pickup is brass stamped sheet metal with threaded posts on the inside and outside.
These threads, coupled with springs, allow you to adjust the height of the pickup — a very simple, low cost height-adjustment mechanism.
Removing the height adjustment screws, we find our first injection molded piece! This is a simple, very inexpensive 2 part injection mold and in the photo we can clearly see the 4 ejector pin marks.
Side note: This thing is oily! Machine grease everywhere…
Inside the pickup we remove 2 layers of electrical tape… electrical tape! We find undeath the wires haven’t even been soldered, but held in place using only the tape. Remember this is a cheap guitar, so the cost of hand-soldering during assembly isn’t a great investment when slapped on electrical tape will do the trick!
Beneath the electrical tape we find a ton of tightly wound copper wire with a gauge of 0.04 mm, which equal 40 microns or the width of a human hair. For reference, our high res 3D prints (polyjet) are produced at 16 micron layers.
Here we have 3 potentiometers, which each manipulate current to adjust resistance. The way an electric guitar works is the pickup, soldered to these potentiometers, grab sound vibration entering the magnetic field. The pickups then transform these vibrations into electrical signals which get sent out to the amp + speaker.
Here we have a three state logic switch. Yay, we love simple mechanisms! This switch allows the user to choose the desired pickup (front, back, or both).
Finally we use a dremel to open up the body of the guitar and find a single piece of wood — either mahogany, poplar, or maple, which are all lightweight woods that provide the right balance of treble, mid-range, and bass vibrations.
This block of wood would have started as a large plank and then planed down to the desired width and CNC’d on a 2D router to create the shapes and pockets.
The body of the guitar is finished with up to 22 coats of lacquer, which gives it the high-gloss finish. To make it even glossier, after a 6-week curing period the guitar is wet sanded, buffed until it’s really glossy, and polished with wax.
Onto the neck of the guitar! This is where the fine tuning occurs and where tension and rigidity are the most critical features.
As we take off the tuning keys, we thought it was interesting to see one of the screws was actually stripped. It’s fun to see the human element behind a product; you realize products are actually made by people and don’t need to be 100% perfect to be great.
The metal housings here are all press fit as you can see the groves in the wood from when they were pressed in.
The tuning keys use a worm gear to transfer rotation from one axis to the other in order to transfer torque. This is why it doesn’t feel strenuous to turn these components despite the immense string tension; the keys leverage the efficiency of the worm gear. Worm gears operate at ~90% efficiency for transferring torque.
Further down the neck, we lift up the wood to find it’s a solid piece with a welded steel rod, called a truss rod, inserted in the center to increase rigidity. Then the finger board is simply secured on top using wood glue.
If the neck starts to bend inward, from high-gauge strings for example, you can actually use an allen key to re-straighten out the neck by adjusting the protruding end of the rod.
The frets themselves, made of nickel and lead, are also press fit into the neck and have an inner wall thickness of 1mm.
We were surprised at how many components go into making a guitar and really love the intersection of organic materials like wood and injection molded and machined parts.
It’s important to recognize that these instruments, even today, are mostly man-made with a great deal of attention, deal, and most of all time that goes into production. For example, after cutting the wood into the body shape, it needs to go into a drying room for 2 months before it can be painted. So next time you wonder why your guitar costs so much… well, that’s why.
Originally published at fictiv, a hardware development platform for engineers and designers.