Notes and observations

In the heat of the moment when you are working as fast as possible to position and clamp the bridge while the glue remains hot, don't forget that the saddle part goes in the front, and the tie block goes in the back ! Its a mistake everyone makes at least once.

There are a variety of bridge types in use in the ukulele world. There are slotted bridges, pin bridges and thru-hole bridges. And there are as many different designs as there are builders. Which style is best ? Its a matter of opinion. I like the tie style bridge because it is light weight, the strings attach securely and don't creep, it accommodates a large range of string sizes, it doesn't require a bridge plate to protect the underside of the sound board from string knots or pin ends, and there are no parts to misplace or lose. Tie style bridges are a tradition that comes from the classical guitar and lute world.

In the last couple of notes i showed you how i make bridges and lay out their position on the soundboard.
The bottom of a bridge should be thoroughly cleaned with a soft rag moistened with lacquer thinner or acetone before glueing. In the first photo, you can see that quite a lot of oil came off the bottom of this ebony bridge. In the second photo, you can see everything set up and ready, waiting for the glue pot to heat up. Those black soundhole clamps are really handy for this purpose because they have adjustable feet that allow use over the crossbracing inside a top. They're sold by Stewart McDonald. The 5 inch size work well for my tenor ukuleles but they are too big for a concert or soprano. It'd be nice if StewMac would bring out some smaller and lighter weight soundhole clamps for ukulele makers.

I'm laying out the bridge location on Jimmy's tenor this evening. The distance from nut to saddle is determined by the scale length of the instrument, to which is added a small compensation factor. The lateral location is determined by stringing thread through the two outside string holes. The thread is taped at the nut and the tail block and the bridge position is centered. Once the bridge position is established, masking tape is laid down on the soundboard to mark the location, the bridge removed, the soundboard slightly rough sanded in the glueing area, the bottom of the bridge degreased with a rag dampened with a bit of solvent, and the bridge is then glued, clamped and left to dry overnight.

I just love it when i get this close to hearing a new tenor ukulele for the first time !

I use tie style ebony bridges on all of my ukuleles. While making a couple of tenor bridges yesterday i took some photos to illustrate the process. I resaw African ebony fingerboards for bridge blanks using the bandsaw and then dimension them to approximately 115mm x 20mm x 6mm using the drum sander. The saddle slot and groove between the tie block and the saddle block is cut on my shaper, set up as a router table with appropriate cutters. This sequence of photos begins with a bridge blank after initial routing, showing the different steps to complete a finished bridge by hand. At some point, i need to find the time to jig up with special fixtures and cutters to do most of this on the shaper, but for now they are very much handmade, one or two at a time.

[ Editor's note: that brown wood benchtop visible in many of the following photos is a 16/4 (4") thick x 18" wide by 6' long piece of old growth tight grain beautifully colored Spanish cedar serving a dual function while waiting patiently for its primary destiny to manifest - neck blanks for fine classical and flamenco guitars and ukuleles. There are a few more chunks of it scattered around the workshop ! ]

The string hole locations are marked and then drilled on a drill press, using a 2mm brad point bit.


Then the wings of the bridge are sawn on the bandsaw.


A dozuki (Japanese dovetail saw) is used to remove the scrap wood on the bridge wings.


Next, the round bridge ends are marked by tracing around a nickel, which is just the right size.


Then the bridge ends are shaped using a drill press mounted sanding drum.


Here you can see the bridge ends after shaping.


The bridge wings are now rounded and smoothed, using a hand file and sanding sticks.


Next, the back of the saddle block is beveled with a Japanese push chisel.


The front of the saddle block is rounded with a push chisel.


The string hole exits are opened up with a jeweller's round burr held in a pin vise. I drill the holes as low as possible in the bridge to maximize the string break angle over the saddle. My overall bridge height is only 6mm and the top of the saddle typically adds a couple more mm. Its a very low profile bridge setup designed to minimize the weight of the bridge.


The hole entry on the back of the bridge is slightly countersunk with a jeweller's stone setting burr held in a pin vise. After all the basic shaping the bridge is smoothed with 320 grit sandpaper.


The bottom of the bridge is arched to match the slight arch of the soundboard. This bridge arch is started with a small round bottom violin maker's plane fitted with a toothed blade.


And the arch is finished using an adjustable sanding bow.


Here you can see the finished bridge being checked for fit on Jimmy's Indian rosewood and Swiss spruce tenor. I'll be glueing it soon, using hot hide glue. I glue the bridge before lacquering the instrument so that i can string and play it during top tuning. When finished, i'll mask the bridge and lacquer the instrument. After the lacquer finishing process is complete, the bridge will be treated with a tung oil based sealant and then waxed, leaving a soft black satin sheen to the ebony.

Fine Indian rosewood displays a nice dark color and delicate spider webbing in the grain. It is an excellent wood for the back and sides of classical guitars and ukuleles.

I spent part of yesterday and today joining, glueing and profiling a few sets of curly koa and rosewood for tenor and concert sized ukuleles. Here you can see 4 tenor ukulele top and back sets and 1 concert ukulele top and back set. These haven't been sanded yet and they still have glue and tape marks visible. They are mostly 5A grade koa with nice color and beautiful full curl. Check back next month to see what they look like under a nice lacquer finish on the completed instruments.

A tenor ukulele top or back is usually made from two bookmatched halves, glued together along the center seam. I shoot the joint on each half on my shaper using a sliding table i made for the purpose. It produces a nice straight and square edge. After joining the two bookmatched pieces, they are glued using hot hide glue and set aside overnight to dry. When they are dry, i trace the body outline using the plywood template i've made during the initial model design process, and then cut the top or back to the approximate shape on the bandsaw.

The joined and profiled backs are now ready for sanding on a drum sander to close to final thickness. The fronts will be sanded just enough to provide a smooth surface and then the rosette will be inlayed. After the rosette is inlayed, they will also be sanded to approximate final thickness on the drum sander. The tops then will receive individual attention to graduate them to final thickness before bracing.




Rosewoods tend to have a high resin content. When joining rosewood plates for backs it is important to remove as much of this resin as possible on the edges to be glued. Some lacquer thinner on a rag is effective. In the second photo you can see how much resin came off the edge of these two bookmatched Indian rosewood plates. They are now ready to be glued. I'm waiting for the hide glue pot to come up to temperature as i write this note.




In the third photo, you can see the bookmatched Indian rosewood glued and taped, with the glue pot top left.



In the fourth photo you can see two 5A grade curly koa top and back sets for a small Nunes style soprano glued, taped and drying. I'm tempted to try some bling on one of these 5A sopranos, just to see how deeply a precious fetish can be satisfied, nay encouraged ! I have some pretty Awabi shell blanks that could look mighty fine on this colorful curly koa. On the other hand, i think wood mosaic purfling can rival shell for bling, particulary if it details out the colors of the koa and echos the motif of a tasteful wood mosaic rosette. Hmmm ... another conundrum ... maybe i should do one in Awabi and one in wood mosaic trim ! That would make a cute and unique pair of sopranos, particularly with little crowns inlayed in the ebony fingerboard as position markers !

Luthiers, as a group. are blessed with the opportunity to work with rare and beautiful woods daily. But as precious as Brazilian rosewood, top grade curly koa, fine Swiss spruce, milo or some of the more unusual spalted hardwoods are, they pale in rarity and price to the wood of the most precious tree of all, the Aquilaria tree, an evergreen tree native to northern India, Laos, Cambodia, Malaysia, Indonesia, and Vietnam. Aquilaria wood is also known as agarwood, aloeswood, eaglewood, jinko, gaharu, cheng-xiang or oud.

"One of the legends of the east has an agarwood cutting being the only plant Adam was allowed to take from the Garden of Eden." writes Trygve Harris in her article Gem of Truth on agarwood.

An article sourced from Kyozaburo Nakata of the respected Japanese incense company Baieido, which was formed in 1657, describes the different grades of aloeswood used in the Japanese kodo or incense ceremony. Legend has it that it was aloeswood and myrrh that was burned at the burial ceremony of Jesus by his disciples, and that he was embalmed in aloeswood oil. The 'Wood of the Gods', aloeswood has been used in Buddhist, Shinto, Hindu, Muslim and Christian religious ceremonies and in Chinese, Tibetan and Ayurvedic medical practice for many centuries.

In Buddhism, the most precious Buddhist string of beads is made with agarwood and the standard bead string contains 108 beads. One story tells of a monk's sacrificing spirit. He carried his bead string and traveled around the country. Whenever he saw the ill, he would take out a bead and give it to the ill. After grinding and taking the agarwood bead, most seriously ill recovered. The monk's wish was to give away all his beads before he died.

Today, fine aged Aloeswood or Oud oil sells for more than its weight in gold and rumors abound of Middle Eastern Princes paying tens of thousands of dollars a pound for the highest quality wild harvested aloeswood. Recently the Aquilaria tree has been threatened with extinction but now a research project at the University of Minnesota is helping to establish commercial cultivation of the trees.

Aloeswood is truly a rare and precious wood ! Internet vendors like Scents of the Earth sell the Baieido aloeswood incense products, Eden Botanicals and others sell agarwood oil extracted from cultivated trees and ebay vendors like QT's sell exceptional agarwood oils and wood from around the world.

Fingerboards on Joel's and Jimmy's tenors sit drying. I use fingerboard shaped cauls with recessed centers when clamping fingerboards so that most of the mild clamping force is imparted along the edges of the board.

I had my first ukulele back for repairs recently. It was a deep body long scale 14 fret concert in koa and Adirondack spruce, the first one i made in the A4v5 series. The customer, who had purchased it from its original owner in 'as new' condition, emailed me to say that the /gasp/ top was cracking /gasp/. I was surprised, because i'd had this instrument back shortly after purchase to touch up a couple of spots in the french polish that 'printed' from the webbed case strap being caught tightly inside the case and against the soundboard during shipping.

In any case, i was pretty familiar with this instrument by the time i got it back almost a year later with complaints about the top cracking. On first examination, i noted a separation in the center seam just above the tailblock about .001" (one thousandth of an inch) wide and about a quarter of an inch long. Not the sort of thing you'd notice visually because it was about as wide as the glue line, but i could feel it with my fingernail. The top is fan braced, and a 4-5mm wide brace runs along almost the entire center seam. The seam separation ran from the bottom end of the brace to the tailblock, with no risk of it continuing further. I also noted a similiar (.001" wide) center seam separation about 1/4" long running from the top end of the center fan brace to the lower side of the bottom cross brace below the sound hole, again with no risk of extension. And curiously, both seam separations were barely wide enough to get a .001" feeler gauge into, and only obvious when felt with the nail.

Of course, i'm curious how this happened because this piece of fine grained air dried master grade Adirondack (Red) Spruce had been in the workshop for at least 5 years. I had purchased it from a supplier in Canada who also supplies Martin with wood. And i'd never had a problem with it. Or a problem with top cracking in anything, anywhere, at any other time.

The current owner of the instrument lives in a modern house in the Pacific Northwest, which experiences pretty broad variations of temperature and humidity. I'm guessing the house is centrally heated with hot air circulation but i don't know. The instrument arrived in a soft case with a sponge in a plastic bag in which holes had been punched.

I use hide glue to join my top and back plates. Because the seam separation was very limited, and there was no chance of it spreading, i decided that the appropriate repair was to sand down the polish in the affected areas, reglue the separation with cyanoacrylic glue, and refinish the top. There were no other signs of damage or failure, either to the neck, fingerboard, headstock, the curly koa back and sides, or elsewhere.

Sitting at the bench the other night sanding down the french polish i happened to catch the top in just the right light and saw what looked like /gasp/ small cracks all over the top /gasp/, some quite long ! I took a deep breath, and did a double take. On closer inspection, the cracking was not running with the grain of the wood but with a mind of its own ! One particularly long one ran in a curve about 1/2" in from the lower bout ! The french polish was cracking. And cracking in such a way that it was obvious to me now that the top had probably been through some extreme expansion and contraction cycles, causing the finish to stress. The Adirondack spruce itself was just fine, except for the two small seam separations. The french polish was fine elsewhere.

I'm going to finish sanding down the french polish, reglue, refinish the top of the instrument with lacquer, and return it to its adoring owner. It sounds really pretty and as the 1st in my A4v5 series it may even have historical value someday

I can not over-emphasise too much that fine hand made musical instruments should not be exposed to extremes of temperature or humidy, left outside in the sun on the porch or in a hot car. And they should always be stored in their case when not in use.

An African ebony fingerboard for a 14 fret long scale (~460mm) tenor ukulele with 5mm slotted square mother of pearl inlays. Flat, 36mm at the nut, 44mm at the 14th fret and just a little under 4mm thick. I glue fingerboards with hide glue so that they can be removed at a later date if necessary.

For neck and bridge production, general tooling and mold manufacturing, profiling of bracing, arch top and back roughing for acoustic jazz guitars and mandolins, and just to keep the shop humming lets add a couple of Techno-Isel LC series 48 x 48" CNC routers with the 800"/min option, AC spindles and automatic tool changers. Add a laser scanning module or digital probe to one machine to make design acquisition easier. Add the 4th axis option to one machine for doing neck profiling. If we can get a rotary 5th axis on the tool head of one machine that would be very useful. We'll also need an assortment of carbide cutters, a cutter grinder/sharpener and CAD/CAM design software too.


We'll need a roots style vacuum pump housed in a noise proofed room along with the dust extraction fans, air conditioning, heating, small particle air filtration system and air compressors just so the shop doesn't get too noisy. And we'll need plumbing for all this to the shop. Of course, we'd need 3 phase wiring to the shop too.

Needless to say, you don't house this kind of equipment in your garden shed, so we'll need an extension to the workshop, dedicated to the CNC routers and other large woodworking equipment like the Hitachi resaw bandsaw, Grizzly rotary head planer and Performax drum sanders.

I haven't got the quote back yet from Techno-Isel but lets conservatively budget (I'm guessing) $60-100K for the CNC routers and ancillary tools and equipment.

[ Editor's note: The first part of this series on the well equipped workshop highlighted the Xenetech 1625 rotary engraving machine. ]

Jimmy and Joel's tenor ukuleles get fitted for fingerboards. Jimmy's (Indian rosewood/Swiss spruce with curly koa body binding) is a 36mm nut width, Joel's (Dark master grade koa/Mediterranean cypress with curly maple body binding) a 38mm nut width with curly maple binding. They'll both come up quite a lot darker after treatment with a tung oil sealer and a lacquer finish.

After i inlay the position markers, i'll glue the fingerboards on. When dry, i'll level, fret and dress 'em. Then its bridge time ! I'm looking forward to hearing both of these soon.

A number of recent technological developments have converged at this moment in human history to create a fertile ground for the emergence of small boutique style micro-businesses with a knowledge intensive and specialized product or service focus and with global marketing and product delivery reach.

In the developmental taxonomy of such micro-businesses, continuous growth is not a primary business objective. The same developments that create a fertile ground of operations and provide the tools for their success also require constant innovation, new product development and change. The life cycle of products grows ever shorter, and the customer's expectations of value ever greater. As a result, the primary business objectives becomes profitability, sustainability and quality of lifestyle for the participants.

In these businesses, the demands on productivity, cost competitiveness and custom product design, development and production flexibility brought about by these same techological forces can best be met by the capital intensive adoption of CNC manufacturing technology, just in time material sourcing and software intensive operational management.

Although i spend a lot of time here talking about traditional methods of production in the one man home workshop, i'm going to occasionally take a look forwards and spotlight equipment and techniques on my short list for acquisition as resources allow and i am able to lay the groundwork for something more, ummm, interesting.

This morning, we feature the Xenetech 1625 CNC engraving machine. Complex custom fingerboard and headstock inlays ? No problem. Only $15K. Add a computer, CAD/CAM software, training time, design time, hold down fixtures, inventory of shell blanks, specialized solid carbide micro-cutters, and so on and so forth and some rather cost effective, classy and unique things become possible.

In this contemporary micro-business model, where does the capital for equipment procurement come from ? Profitability. Retained earnings.

I finished binding Joel's koa tenor ukulele and Jimmy's rosewood tenor ukulele this morning. Minoru's is not far behind !

The curly maple binding against the dark koa and golden cypress of Joel's instrument and the curly koa binding against the dark Indian rosewood and Swiss spruce of Jimmy's tenor both present a rich contrast and a nice design detail.
Joel's ebony fingerboard will be bound in curly maple too ....