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New Luna Ukulele Is Bent Out Of Shape

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Sophie’s aunt wanted to do something to further her niece’s continuing education and eventual career in music therapy.  This nice Luna ukulele was a thoughtful gift.  Unfortunately, there were many dead notes.  Could the Unbrokenstring Crew bring those notes back to life?

Inside the bag is a ukulele, some picks, a tuner, and an instructional DVD!

 

The words for “Peace” in forty-four languages are engraved into the soundboard of this instrument. All you hippies will recognize the peace sign in the sound hole.

 

Sure enough, there are several notes on the fret board, near the nut, that are muted out.

 

Name, rank, and serial number, please.

 

I am not sure what this number is…

 

The fret rocker shows a very tiny difference in fret height, when checking between adjacent frets.

 

However, a straight edge reveals that the neck is back-bowed. The tape just keeps the machinist’s scale upright so I could take the picture.

 

I recorded the string height for all posterity. This is not far from right for a ukulele. Some authorities say it’s too high, others say too low. Whatever.

 

The fret wire height is not adequate to support a fret level job. The back bow is just too much. Yes, the back bow is more than 0.040 inch on each end of the fret board!

 

My guess is, the fret board will need to be reshaped. Here, I’m recording the width of the fret wires.

 

Concert ukuleles are tuned A – E – C – G, with the bottom string, sometimes called String 1, the highest pitch. This G string diameter is about 0.022 inch.

 

The C string is about 0.030 inch.

 

The E string is the largest, measuring about 0.035 inch.

 

The drone string is tuned to A above the G. This string measures about 0.025 inch.

 

Interestingly, the fret board has about a 20 inch radius, while the nut and saddle are absolutely flat. The Luna Guitars Web site specs this instrument with a flat fret board, too. I’ve decided to re-flatten the entire fret board. The nut must come off. Here, I’m cutting the finish so that the nut can be removed cleanly.

 

I love whacking musical instruments with a hammer. I find it strangely satisfying.

 

The saddle slips out of its slot. You can see that there is no radius in the saddle at all.

 

The Smoking Gun. There is not enough string tension in the world to straighten this neck. It also has a twist. It doesn’t matter that this instrument has no truss rod because it wouldn’t help.

 

Visually, we can see the wavy fret board and a clear radius. How did this instrument leave the factory?

 

Let’s get the tuners out of the way.

 

I made this fret remover from an inexpensive set of end nippers from Harbor Freight.

 

These frets over the body are easily removed.

 

Before the woodworking begins in earnest, let’s tape everything off.

 

Some cardboard protects the entire soundboard.

 

The strategy is to flatten the fret board on the belt sander.

 

This little belt sanding station came from Harbor Freight.

 

Some of the safety covers were removed to enable the instrument to set flat on the sanding belt. Do not attempt this at home, kids!

 

The eighty-grit sanding belt begins to make an impression on the fret board. This fret board appears to be rosewood, but the Web site says that this instrument is all mahogany. Dunno about that.

 

With a twist that bad, we can easily inspect our progress.

 

Now I am wondering what I got myself into.

 

Back to it! Many thanks to my wife Glenda for taking these pictures.

 

Serious amounts of sanding dust are produced, so we are outside today.

 

Another check shows that we are not there yet.

 

The sanding belt is doing its work.

 

What is it going to take to get this straight?

 

Sanding dust is going everywhere. No scorch marks yet!

 

I am pleased that the fret markers are still intact.

 

Very light pressure is used now to clean up the surface.

 

Now we’re getting somewhere.

 

Continuing on, producing sanding dust like crazy.

 

Now I’m thinking that I need to be careful not to go too far.

 

Most of the fret board is flat. There is still some fall-away over the body of the ukulele, which is OK with me.

 

Last few strokes on the belt.

 

The twist is gone and most of the fret board is absolutely flat. I thought that the noise of sanding would drive the cats away, but we see Jack on the bottom step in the lower left corner of this picture.

 

The luthier’s scraper shows that the fret board is flat.

 

The sharp scraper is an excellent tool to finish raw wood.

 

The fret slots at fret six and seven are almost gone. I really don’t think that this fret board is mahogany.

 

Fret slot ten is almost gone.

 

One end of the fret slots over the body IS gone. Yes, it was that bad.

 

My fret saw was set to 0.054 inch, which is the depth of the new fret tangs.

 

Every slot was taken down to about 0.055 inch.

 

These short sections of small fret wire are perfect for this instrument.

 

Each fret was installed, and nipped to length after installation. The long ends were the pieces at the end of the short strips that weren’t long enough to fill another fret. They get nipped off separately.

 

After nipping, this file embedded in a block of nylon files the fret ends 90 degrees to the fret board. Moving the file to another slot allows the fret crowns to be filed to a 60 degree angle to the fret board. I love eBay!

 

Checking for flatness, these frets are ABSOLUTELY flat, which is not surprising.

 

The fret ends are shaped and burnished by hand, and the fret wires are lightly sanded. As with a classical guitar, the frets are not polished, but finely sanded in the same direction as that of the string.

 

The original nut was reused, and re-slotted to restore the original 0.060 inch string height. The nut was just right as it was. The fret board was oiled. New strings complete the job. All the notes are present and accounted for!

Thanks for reading all the way to the end!

CONTACT – David Latchaw EE

281-636-8626

Squire Jagmaster Gets a Total Make-over And Then Some! Part Four of Four

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In Part Three of this project, The Unbrokenstring Crew installed a unique cut-out switch in the pick guard of this guitar. One more thing… Now that the instrument is play-able, the original plastic Squire nut is cracked. Grrrr…

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The old Squire nut came out in pieces.

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Let’s make a new one from Vietnamese water buffalo bone. The blank we’ll use today is shown above the old Squire plastic nut.

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Not to brag or anything, but these bone nuts are truly a renewable resource that I am privileged to legally import from overseas. CITES can go bite it.

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The eighth inch chisel easily cleans whatever glue Squire used to install the original plastic nut.

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This slot is ready for the new nut.

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Sorry, that’s as clean as I can get it.

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The new blank nut is thickness-sanded to fit the slot. I’m doing this by hand because the blank is very close to the proper dimensions to begin with.

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The inside radius is established by using the actual neck as a radius block.

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The side contour is also established by hand, on the actual instrument.

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The actual height of the fret wires is measured in order to calculate the depth of the string slots. This dial indicator measures the installed height of the fret wire above the finger board.

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Here, we’re gluing the new nut right to the finger board using hide glue. A water-based adhesive could cause the wood to swell; shrinkage over the next few months as the wood dries out would throw off the accuracy of the nut slot depth. Can’t have that!

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The old nut is used as a template to establish string spacing. A couple of old strings are used to align everything.

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Now that we know the fret height, string gauge, and string spacing, we can begin establishing the string slots. At the nut, the string slot depth is constant across the radius of the finger board, regardless of the string diameter.

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With a set of old strings in place, the top of the nut can be quickly contoured so that the top of the nut will not protrude above the strings. The geometry of the top of the nut is established in part by the diameter of the strings, which is, of course, not constant across the radius of the finger board. This three-cornered triangular file belonged to my father.

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This old triangular file is just the thing to contour the nut further, smoothing out sharp corners and preparing the nut for polishing.

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Note that the string centers are just below the top of the nut, and that the top of the nut is no higher than any string.

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This is the instrument, as delivered. The Vietnamese water buffalo bone is a spectacular material for musical instruments: incredibly hard, uniform throughout its bulk, and capable of a fine polish without additional waxes or oils, making a visually attractive nut and providing a stable, polished string slot that allows for smooth and stable tuning without binding or sticking. What more could you ask?

I think we’re finally done with the Jagmaster Make-Over!

Thanks for reading all the way to the bottom!

CONTACT – David Latchaw EE
281-636-8626

MIJ Fender Precision Bass Gets a New Nut and Setup

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Lisa’s marvelous Fender P-Bass needed attention.  Some of the open notes were dead, and the electronics needed some attention.  Could the Unbrokenstring Crew sort it all out?
I just love the pale yellow finish.  Except for a string, everything is here.

 

Yes, it really is Made In Japan.  Back in the day, ‘made in Japan’ was another word for cheap imported junk.  Nowadays, this is some of the better stuff, particularly in guitars.

 

Name, rank, and serial number, please!

 

An electrical test shows that we have no output.

 

A quick look under the hood does not reveal an immediate problem.  Hmmm…

 

Oh, this is it.  The ground point for the whole unit is this potentiometer body.  However, the ground wire to the output lead does not connect to the potentiometer body anywhere.

 

With that fixed, the remaining ground wires are cleaned up a bit.

 

The bridge ground wire made an intermittent connection to the bridge.  We need to remove the green corrosion.

 

OK, the electronics are now all up to snuff, and actually look pretty nice.

 

While we’re here, we’ll tighten the output jack and potentiometers a bit.

 

The knobs go on now.

 

Final test is performed with a signal generator and another bass pickup.  The signal generator excites the windings in a bass pickup from an Aria Pro II bass, which will be featured in a future blog post.  The test pickup is brought near the instrument’s pickups, and the magnetic field carrying a test tone is coupled into the instrument’s electronics.

 

The dead open notes are traced to a cracked nut.  Here, we’re cutting the finish around the old nut so that it can be removed cleanly.  The Exacto knife gets a new blade for this operation.

 

The old nut comes out in two pieces.  The crack expanded until the nut broke in two.  That’s why we’re replacing it.

 

Here is the new nut that the customer wanted installed.  Good stuff!

 

Oops.  Houston, we have a problem  This new nut does not fit the neck.

 

The new nut is just a tiny bit smaller than what is required for this neck.  What gives?

 

We can clearly see the difference in the sizes between the old nut and the new one.  This neck is the width of a five string bass, but it was delivered as a four string bass from the factory.  So, we will make a custom nut for this instrument.

 

A Tusq blank is radiused to match the radius of the fretboard.  I’m using an Exacto knife as a scraper.

 

The Tusq blank is cut to rough length with a fine saw.

 

It doesn’t take long to slice through the Tusq material with this blade.

 

This is a saw blade set that I use for sawing fret slots and general fine work on wood.

 

The blank is now shaped on the disk sander.  A piece of birch plywood serves as a raised table that can be placed very close to the abrasive surface of the disk, necessary when shaping small parts.

 

The blank is now pretty close to the rough shape we need.

 

The first trial fit shows that we haven’t cut it too small, yet.

 

This is a little better.  The ends are flush and smooth with the edges of the fret board.

 

In AutoCAD, a drawing is created showing the cross sections of the four strings and the width of the fret board in actual size.  The distance between the edge of the outside strings and the edge of fret board, established by factory specs, is drawn, and the position of the outside strings fixed.  We then subtract the diameters of the four strings from the width remaining.  This result represents the space between strings, which shall be three equal spaces.  This establishes the center lines of the inner strings.  The spaces between the strings are the same, not the center-to-center distance.

 

But, to cut the string slots, we need to know where the edge of the fret board is, and where the center lines of the strings fall.  These solid lines represent that information.

 

The lines which represent the centers of each string are transferred to the nut.

 

A shallow file cut is made at each string center.  Here, we are checking these cuts against the template.

 

These shallow cuts represent the eventual center of each string.

 

These cuts were made with a triangular mill file.  Nothing special, but accurate enough.

 

Here, we’re polishing up the sides and faces of the nut, in preparation for gluing the new nut in place on the neck.

 

The nut depth is established by the fret height plus a constant which is established by Fender (and can be adjusted a bit by a good luthier, like me, for best play-ability.)  This is the Secret Sauce of making an instrument a great instrument.

 

The slot depth is now established by this stack of feeler gauge shims.  They are held in place with rubber bands wrapped around the back of the neck.  I’ve taped off the head stock so that I don’t scratch it up with the end of a file.

 

When the file touches the stack of feeler gauges, continuity will be detected by this multimeter, and it will beep.  This is another check of slot depth, besides my eyeballs.

 

Here, the slots are cut.  With a little cleanup and polish, this will be a good nut!

 

The nut is all done and polished.  Looks good!

 

The action on this instrument at the twelfth fret is pretty high…

 

We have a metal neck shim between the neck and body, made from a piece of the machinist’s feeler gauge of the proper thickness to reestablish proper neck geometry.  The metal shim is the hardest practical material for this purpose, with an accurate thickness, and better mechanical stability and hardness for greatest vibration transfer between the neck and body than a guitar pick or a piece of business card.  This results in the best tone.  And a set of feeler gauges are less than five bucks.

 

A quick adjustment gives us just the right amount of neck relief.  (Sharp-eyed readers will spot the fact that the strings are off in this picture.  This is the only pic I took of the truss rod adjustment, setting the neck flat while the neck shim was being sized.  Who cares if my pics are out of chronological order?)

 

To set intonation, we needed to work on the bridge.  Here is the underside of the bridge, probably not seen for decades.

 

The intonation screws were dinged.  Here, we are chasing the threads with a die to clean them up.  Yes, they are English/Imperial threads, not metric.

 

The bridge is tightened down and ready to go!

 

The moment we’ve all been waiting for!  Add strings, tune up, intonate, and play!

Thanks for reading all the way to the end!

CONTACT – David Latchaw EE
281-636-8626