Using a Laser Cutter/engraver to Make a Hawai`ian Steel Guitar

The Hawai`ian steel guitar provides the signature musical sound of Hawai`i. The most common type of Hawai`ian steel guitar has a solid body constructed from a single plank of wood, and use an electrical pickup to detect the movement of the strings. The name “Steel Guitar” is derived from the steel slide that is used to alter the length of the string, and hence its pitch, as the guitar is being played. Over the past four years, more than three-hundred middle and high school students in Hawai`i have constructed solid body steel guitars while participating in University of Hawai`i “Makery” programs. The Makery is a collection of tools, machines, materials, and know-how that empowers individuals to use computer numerically controlled (CNC) machines to make real products.
Solid body guitars require an amplifier to make the sounds produced by the strings audible and this creates a problem for students who can’t afford an amplifier, or who live in remote locations, where batteries are very expensive. The cost of amplifiers and batteries became an issue when we were planning a recent summer guitar building program for all forty-eight of the sixth grade students living on the island of Lanai and led to the creation of the acoustic model shown here.

Traditional guitar construction methods involve a great deal of manual and/or CNC carving. Holding parts securely, and changing tools, is challenging and time-consuming when using small CNC machines for classroom activities. For the Lanai program, we decided to explore the possibility of making as many of the parts as we could on a laser cutter. This inscrutable shows how we were able to use a thirty-Watt, sixteen-inch by twelve-inch laser to cut out all of the parts except for the long side panels that were cut out with a CNC router. A larger laser, such as one of the Hurricane machines that can accommodate a thirty-inch work piece, could cut out the complete guitar.

If we were to win one of the large Hurricane lasers, It would be housed in a not for profit “tech space” where individual students could perform all of the steps involved in constructing a guitar. It would also increase opportunities for them to work on other STEM learning projects, such as making name badges, awards, boxes, trinkets, clocks, puzzles, educational toys and 3D engraving artworks. This would significantly increase the number of students we can introduce to the magic of turning their very own ideas into tangible objects.

There are many options in the choice of features, materials, and finish for the guitar described in this Instructable. Some of the photos show a purely acoustic version and some show a combined electric/acoustic version. The main purpose of the instructable is to show that a laser cutter/engraver can be used to fabricate all of the required parts. Some of the choices for the models shown in the photos were dictated by the capacity of our laser and the alternatives available to us for making the parts that could not be fabricated with the laser. A larger laser can cut out every part of the guitar.

High-quality tone woods can be very expensive, especially in small quantities. We have been able to find planks of maple, mahogany, and koa, for example at architectural wood suppliers, demolition sites and places that sell recycled wood. We have also obtained some very good wood as offcuts from furniture factories. Old furniture is often made from fine woods like cherry that work really well. Go online to learn about which woods work best for musical instruments and find what is indigenous to the area in which you live. We use a band saw and a drum sander to prepare thin sheets of wood that can be used in the laser for student projects.

Since the front panel of the guitar is too long to fit into our laser, we fabricate it as two separate parts called the fret board and the sound board. The attached photos show two variations of the basic design. One uses mahogany for both parts and the other uses mahogany for the fretboard and sitka spruce for the soundboard. A bracing strip is required under the join in each case. With a larger laser, we would make the top panel from a single sheet of quality tone wood.

The design we have shown here is a work in progress. Rather than providing a set of drawings that could easily become outdated, we invite you to call or email us to get the latest drawings in a version that matches the options you wish to include. We do our detailed designs with Autodesk Inventor and transfer these to CorelDraw for controlling the laser.

Components such as the tuning heads and pickups are readily available on-line. We have found that low cost replacement bridge pickups for the Stratocaster work well for the steel guitar.

For additional information and copies of the latest drawings, please contact William Weichert (billw60@gmail. com)

The frame is constructed from a hard wood such as mahogany or maple. It is shaped like an A frame with its pointed end truncated. To ensure that it can be easily assembled with the correct shape, we used rebated joints in which the shorter parts have square ends and the rebates (slots) are cut into the side panels at an angle. To create the angled rebates, we made a jig that held the side panels at an angle of eleven degrees and cut horizontal slots with the CNC router. If you don’t have access to a CNC router, the same result can be achieved by using a dado blade in a table saw set to a tilt of eleven degrees. Another alternative is to use a band saw with the crosscut fence set to the correct angle.

The short cross pieces must be accurately cut to length since any errors will cause the sides to bow in or out when the frame is assembled.

The bottom panel is made from a single piece of one-eighth inch thick mahogany measuring 30 inches long and six and one- quarter inches wide. It is not necessary to cut it to shape before assembling it to the frame as the excess parts are easily trimmed off with a band saw later. Use a good quality wood glue to assemble the frame. It is important that the top and bottom edges of the frame are completely flat to ensure there will be an airtight seam where they join to the top and bottom panels. To achieve this, we placed the bottom panel onto a piece of three-quarter inch MDF and assembled the frame on top of it. Use clamps to hold all of the parts firmly together while the glue dries. It is not necessary to use any nails or screws for the assembly.

When the frame is complete and the glue has hardened, trim the edges of the back panel to within one eighth of an inch of the sides.  The excess wood will be automatically removed later when we use a hand-held router to round off the corners.

The fret board is cut out and engraved on the laser from a sheet of 0.090” hardwood. The top surface of the sheet must be sanded to a very smooth finish before it is cut and engraved with the laser to ensure even cutting and to minimize the amount of sanding required after the inlays have been inserted.  The outer edge is cut through the .09” thick panel all the way around.

The fret board markings are engraved to a depth of 0.020” using the raster setting. Blue painter’s masking tape may be used to minimize burning of the surface face. There are several options for increasing the visual contrast between the frets and the background material. If desired the engraved frets and markers may be inlayed with a contrasting hardwood such as maple or ebony, or with shell such as abalone or mother-of-pearl. The inlays are cut to size with the laser. Some trial and error is required to achieve a tight fit for the inlays due to the different burn rates on the various materials. It is important to use an adequate amount of glue when inserting the frets so that they don’t pop out during the sanding process. Tinted epoxy can be used as a faster alternative for inlaying the frets and markers. Simply over-fill the fret slots with the tinted epoxy and then sand off the excess after it has set.

Two versions of the fret board are shown. the first is simply engraved with the laser. The second has ebony inlays for the frets and abalone for the markers. The frets were cut out of thin sheets of ebony wood and and inlays from a processed form of abalone shell called "Ablam" that can be purchased online.

The soundboard can be made from the same material as the fret board or of a contrasting and/or more tone-producing material such as sitka spruce. The outer edge is cut through the .09” thick panel with the laser. The inner sound hole is cut out also as well as the holes for the bridge, string pins, pick-up and pick-up controls. Again, blue painter’s masking tape may be used to minimize burning of the soundboard surface. Carefully sand the surface after the soundboard is cut out since it is very difficult to sand it after the bridge and pickup have been attached.

Two additional parts make up the soundboard. A bridge and string peg brace and a pick-up brace (only required if a if an electronic pick-up is installed) is glued to the underside of the soundboard. The braces are laser-cut from the same material as the soundboard  but have the grain running at right angles to the soundboard.  We use small bolts and nuts to align the holes in the braces with those in the soundboard and, at the same time, to clamp the parts together while the glue dries. The braces shown here are on a sitka spruce sound board that has mounting holes for a pickup, volume control, and tone control.

The nut and the bridge are the points at which the strings are suspended and ring at their tuned pitch. They transfer the sound of the string to the resonance of the guitar body and soundboard. They must be stable and precise.  The design we are using here is a four piece assembly where each part serves a specific purpose. Using the laser cut out the two sets of four pieces to form the nut and bridge. They fit together as shown. The notches cut in the bottom of both leading edge pieces (ie the piece whose edge gives the string its point of contact for vibration) will fit over the dowel pins to secure the position of each assembly.

The nut and bridge have the same basic construction and are basically mirror images of each other. They must be assembled carefully because the dimensions are carefully matched to the diameters of each string to ensure that the top surface of each string lies in the same plane so that the Steel will have even contact with all of the strings.

On a flat surface carefully glue the four pieces of the bridge together, checking that they are in correct order and seated evenly to the flat work surface. Repeat this for the nut assembly. Prior to assembly the pieces may be lightly sanded but BE VERY CAREFUL NOT TO ALTER THE LEADING EDGE of both the nut and the bridge. The top surfaces these pieces are precisely stepped to compensate for string thickness and the leading edge facing the string length on both the nut and the bridge must remain sharp and unchanged.

The joint between the fretboard and soundboard is supported by the crossbrace that divides the sound box from the neck compartment. Use adequate glue to ensure all of the joints will be solid and airtight before aligning and clamping the parts. If, for any reason, the top surface of the frame is distorted or not flat, we found that carefully running the complete bottom assembly through the drum sander prepared the surface for a good joint to the top panels. As a precaution against damaging the inlays, we placed a sheet of carpet on the top surface with solid blocks of wood on top of the carpet to distribute the pressure and prevent the faces of the clamps from marking the surfaces.

Before installing the nut, bridge, and machine heads, you should shape and sand the body of your steel guitar. We use a hand held router with three different radius round-over cutters to smooth all of the corners on the body, except for the top edges of the tuning box.

Use a 1" radius round-over cutter to fillet the vertical corners at the wide end of the guitar

Use a 1/4" round-over cutter to fillet the the vertical corners at the narrow end of the  guitar

Use a 1/8” radius round-over cutter to fillet the edges of the back panel and the edges of the soundboard and fret board.

Note that the top edges of tuning box are not filleted.

If you don't have access to a set of round-over cutters, you can can use a disk or belt sander to create the large fillets at the ends of the guitar and a hand held sander, such as a  Dremel Multitool oscillating sander to form the small radius fillets. While it will take a lot more effort, you can also create the fillets by hand with a sanding block.  

Sand all surfaces of the body beginning with 220 grit and working up through 340 grit, 400 grit and 600 grit. (NOTE: do not sand on the top surfaces of the bridge and nut). The more patiently and carefully you do the sanding the better the final finish on your guitar.

There are many options when it comes to oiling the guitar. If you have the patience, French polishing provides a superb and durable finish but requires thin coats of shellac to be hand rubbed on every day for several months. If you want something quicker than French polishing, you can use Tru Oil or Gunstock oil. This provides a very good finish after about 6 to10 coats. If this is still too long for you, you may want to use Danish oil, a combination of oil and varnish that creates a good finish after only three coats.  Regardless of which oil you use, it is good practice, to lightly rub down the surface with very fine steel wool (0000 gauge) between coats to remove any bumps or blemishes. If you have access to a buffing machine, you can use it to apply a final hard wax polish the provides a very smooth and shiny surface. You can also use a buffing wheel in an electric hand drill or Dremel to apply the wax and polish the surface.  Wipe-on Poly is an alternative to waxing and buffing when you want a durable shiny finish. It is a self-leveling polyurethane varnish that is designed to go over Danish oil. Up to three coats may be required to get an even surface shine.  If all of these options are too much for you, you can spray on a few coats of clear lacquer from an aerosol can.

The two holes in the narrow end of the fret board mark the position of the nut. Clear out any glue that may have leaked into the holes by carefully drilling into the block under the fret board using a 1/8” bit. Glue two pieces of 1/8” dowel into the holes. When the glue has set attach the nut to the dowels and fret board with glue. Make sure you are facing it the right way with the high leading edge facing the fret board. Clamp carefully and let dry.

The bridge is also attached to the soundboard with two 1/8” dowels and glue. Carefully clamp in place and let dry.

The two sets of paired machine heads pictured are positioned as shown. Take care not to turn them around because they are designed to use the tension of the string to pull the gears together to prevent backlash. The position and size of the holes needed for the installation are included in the drawing. Measure and drill the six holes as accurately as possible so that the shaft that anchors the string can turn freely. Accurate tuning of the strings is difficult if the shaft is stiff to rotate. Use a small (1/16”) drill bit to make shallow pilot holes for the small screws that secure the machine head assemblies to the body. Also, use a small screwdriver to limit the torque while you are inserting these tiny screws. They easily shear off inside the wood and it is almost impossible  to get the broken shaft out without messing up the wood.

This steel guitar is designed for these string gauges: .014 - .017 - .020 - .026 - .032 - .036

Place the steel guitar on your lap with the machine heads to your left. Have your strings, string winder, wire cutters, needle nose pliers and string pegs all within reach. Start with the string furthest from you. That is the thinnest string (.014) and is called the 1st string. Put the ball end of the string into the hole on the far side behind the bridge. Insert a pin so the slot fits the string and push down. Pull string gently as you secure the pin into the hole. That should hold the string from coming out. Put the other end through the hole in the first machine gear pole (nearest the nut on the far side). Cut the string so that 3” - 4” of string extends past peg when pulled taut. Position string winder on the tuning peg. Pull out string so the cut end extends 1/2” out of hole in machine gear pole. Turn the peg clockwise to tighten.
Bend the 1/2” of string under the first wind so it catches and locks the string. Continue winding and tightening the string keeping some tension on the string with the other hand. As the string tightens take care to position it into the slotted string guides on both the nut and the bridge. Continue until the bow is out of the string. Do not tighten to pitch yet.

To help stabilize pressure on the bridge and nut, install the thickest string (.036) next, also called the 6th string. Follow the same procedure. First secure the ball end in the hole nearest to you with a pin. Insert string through the hole in the near peg closest to the nut. After pulling taut cut at 4”, back it out so 1/2” or more protrudes from hole, position winder and turn clockwise. Use needle nose pliers if needed to tuck end under first wind to lock the string. When locked continue tightening applying some tension with other hand. Be sure to get the string in the correct slots closest to you in the nut and bridge string spacer. Tighten until bow is out of string but not any more.

Use the same technique with the 2nd string (.017), then the 5th string (.032) on the 2nd pegs (middle pegs), and the 3rd string (.020) and then the 4th string (.026) on the 3rd pegs.

While the steel guitar is essentially a melody instrument, its distinctive sound and emotional impact relies on the use chords (groups of notes that are played simultaneously).  Because the notes on a steel guitar are defined by placing a straight cylindrical bar across the strings, it is challenging to form all of the chords that may be required within a particular tune. Over the years, steel guitar players have figured out how to tune the strings in ways that enable them play the chords they need. This has resulted in many variations in the style of the guitars and different string tunings, each of which provides a particular selection of chords. Another way to increases the options for forming chords on a steel guitar is to increase the number of strings. Versions with six, seven, eight, or ten strings are available.  Advanced players often change their string tuning for each tune they play. Some players use guitars with two or three necks, each of which has a different tuning. The pedal steel guitar is another variation in which the player uses foot pedals to change the tension on individual strings or groups of strings to form complex chords.

One of the most versatile and popular tunings is based on a C6th chord (E-C-A-G-E-C).  This tuning provides a great starting point for learning to play Hawai`ian music.  It is vital that you learn how to tune your guitar accurately and regularly.  It is more difficult to play and sounds bad when it is out of tune.  There are a variety of ways to find the notes to tune to. The obvious choice is the piano, but more portable options include: pitch pipes that you blow into, electronic tuners, or apps you can download into your cell phone. The Cleartune app for the iPhone, for example, costs $5 and works as well as electronic tuners that cost ten times as much.

We will tune the steel guitar to a C6th tuning. The highest note will be on the thinnest string (.014), the 1st string. That will be an E above middle C on the piano. You can also use an electric tuner or a pitch pipe.  (The correct way to tune a string is to turn the tuning key anticlockwise until the pitch is lower than what you are aiming for and then slowly turn it clockwise to bring the string up to pitch. This technique prevents problems caused by backlash in the gears of the tuning machines.) Next tune the 5th string (.032) to E an octave lower. Then the 2nd string (.017) to middle C and the lowest string (.036) to the C an octave below. Tune the 3rd string (.020) to A below middle C and the 4th string (.026) to G below middle C. Now check the tuning on all strings and adjust as the body is compressed  and the strings stretch out.

Strum the strings and listen to your Hawaiian steel guitar.

Congratulations!

Get a lap steel bullet nose tone bar 2 3/4” long and 5/8” diameter or thereabouts. Get a plastic thumb pick and two steel finger picks and learn to play if you don’t know already.

Sixth-grade students and their teachers constructed fifty of the guitars described in this instructable during a recent summer guitar building camp the island of Lanai. A single 16" x 12" 30 Watt laser cut out all of the sound boards, fret boards, nuts and bridges.

An electronic pickup is an optional addition to your steel guitar. The attached photo shows the required components. This option must be incorporated in the initial design of the sound board as additional braces and holes are required in the soundboard.