Building a Steel String Guitar

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Re: Building a Steel String Guitar

#201  Postby John Platko » Dec 29, 2015 7:24 pm

And getting back into the swing of things ...

Making a compression truss rod

One could buy a compression rod, or many other types of truss rods, but I'll make one from generally available hardware store materials.

I'm going to use a Gibson compression type truss rod. Stewmac sells a version, and LMI sells a slightly different version. I'm going to make my own version.

Start with some 3/16” steel rod.

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I use a die to cut 10-32 threads on the rod.

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I find a bit of lube always helps.

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Turn the die a bit to start the thread, then back off to clear the cut metal.

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Repeat until the thread is complete.

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Gibson uses a brass nut. LMI has a custom nut which you turn with a hex key. You need more space for a socket to get over the Gibson nut so I prefer an LMI style nut.

Here's a coupler that I got at my local hardware store on the newly minted thread.

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Along with the coupler I use a hex screw.

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I put a bit of superglue on the threads of the screw and snug it down on the coupler. Then I drill a hole so that I can pin the screw into the coupler. (ummm - you might want to just buy a bullet truss rod nut or variation of that.)

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Not the best picture but here's the finished truss rod nut.

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At the other end of the rod there's an anchor. I''ll make that out of some steel bar. A tap is used to thread the hole that's drilled in the rod for the bar.

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Here's the drilled bar being tapped. A hacksaw is all you need to cut the rod and bar.

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Here's anchor on the rod, again I used a bit of superglue before putting it on. The rod extends through the anchor a bit (A tad less than this would be better) and then I use a small hammer to peen the end of the rod so it can't come out when you're backing off the truss rod nut.

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After peening

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I should mention that instead of using a separate anchor, LMI just bends the rod at a 90 degree angle and you drill a hole in the truss rod channel at the heel to anchor it. That works well but you have to remove the fingerboard to replace that rod in case it breaks. With my rod and instillation you can replace it without removing the fingerboard.

Just about finished.

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I wrap some tape on the rod to help keep in quiet and fit more snug in its cavity.

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And it's done.

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Re: Building a Steel String Guitar

#202  Postby John Platko » Jan 01, 2016 2:52 pm

Next I'll be working on the fingerboard. For a very long time the most used wood for fingerboards on high end guitars has been ebony. Often Madagascar ebony because it could be found with even dark color, it is stable, extremely hard so it resists string wear. These days it's harder and rather expensive to get. One substitute is West African or Gabon Ebony. Here's a picture of some West African ebony.

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You can read more about it here.

Another good choice is Macassar Ebony. It tends to have more striping and that made it less popular in the past but today it's come into it's own. Here's a picture of Macassar Ebony.

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You can read more about it here.

After Ebony, Rosewood is the next most popular choice for high end acoustic guitar fingerboards. Back in the day it would have been Brazilian rosewood but that's a problematic choice today because it's an endangered species. Today East Indian Rosewood is commonly used. It's lighter in color and not as hard as ebony but it's a great fingerboard choice. It more open pore than ebony so some may not like the feel as much as ebony. Here's a pictue of Indian Rosewood.

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You can read more about it here.

And there are lots of other choices, different rosewoods etc.. Any very hard wood will work but lighter woods will stain over time unless you put a finish over them and that's not a traditional thing to do on acoustic guitars. A hardwood that is very hard but I think too soft for the job of fingerboard is Honduran mahogany- a great neck choice but one that is also problematic as it is now also an endangered species. This shows many of the woods that could be used for fingerboards.

Here's a video of Bob Taylor talking about the state of Ebony in the world and how Taylor Guitars is dealing with it.



And all of this is serious, as you can see by reading:
From
Last week federal marshals raided the Gibson Guitar Corporation in Tennessee. It wasn't the first time. The government appears to be preparing to charge the famous builder of instruments with trafficking in illegally obtained wood. It's a rare collision of music and environmental regulation.

In the hottest part of an August Tennessee day last Thursday, Gibson Guitar CEO Henry Juszkiewicz stood out in the full sun for 30 minutes and vented to the press about the events of the day before.

"We had a raid," he said, "with federal marshals that were armed, that came in, evacuated our factory, shut down production, sent our employees home and confiscated wood."

The raids at two Nashville facilities and one in Memphis recalled a similar raid in Nashville in November 2009, when agents seized a shipment of ebony from Madagascar. They were enforcing the Lacey Act, a century-old endangered species law that was amended in 2008 to include plants as well as animals. But Juszkiewicz says the government won't tell him exactly how — or if — his company has violated that law.

"We're in this really incredible situation. We have been implicated in wrongdoing and we haven't been charged with anything," he says. "Our business has been injured to millions of dollars. And we don't even have a court we can go to and say, 'Look, here's our position.'"


I believe Gibson got their wood back and made some special edition of guitars with it but I haven't followed the story closely.
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Re: Building a Steel String Guitar

#203  Postby John Platko » Jan 03, 2016 1:47 pm

Surfacing one side of the fingerboard


Rosewood or ebony are good choices of wood for fingerboards and the are very traditional. I would like to use a rosewood board to keep the weight down but I'm feeling like the added strength of Ebony is a better choice for this guitar because of the Spanish cedar neck. Here's the ebony blank that I'll start with.

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I check the blank with a straight edge. This is an especially nice fingerboard blank and it's pretty straight. Since it doesn't need much work to get one very flat surface to work from, I'll just touch it up on a flat surface that has sandpaper stuck to it. The surface is a granite block. I'd use a plane if it needed more work.

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Finish off the sanded surface with a scraper.

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Re: Building a Steel String Guitar

#204  Postby John Platko » Jan 04, 2016 5:26 pm

Preparing fretboard binding material

The edge of the fretboard can be left unbound. In that case the edges of the fret tangs are visible. It looks like:

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There are two other options. One is to bind the fretboard the way Gibson does. That is, the frets stop short of the binding and the binding "completes" the fret. This makes for a very smooth feel. It looks like:

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The disadvantage of Gibson style binding is that a refret seems to necessitate a change in binding style- i.e. you loose the nibs. I kind of like Gibson style binding but since it wasn't the style I was taught, and I like using wood binding which may not work so well for Gibson style, I use what I'll call Martin style binding. Which looks like: (the frets tops go over the binding)

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Plastic is traditional binding material for steel string guitars. I like wood. I also like a technique called "self binding" where wood from the fretboard is used for the binding. It makes for very subtle binding, most people wouldn't even notice that the fingerboard is bound but it hides the fret tang.

First I plane a flat surface on both edges of the fingerboard. A shooting board would work great for this but I'm just going to wing it.

The board clamped securely.

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A few passes with a plane.

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I bring back out the rig I used to cut the binding for the body.

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And slice off some binding strips from the fingerboard.

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Now I have some binding for the fingerboard.

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Re: Building a Steel String Guitar

#205  Postby John Platko » Jan 05, 2016 3:45 pm

Making the fingerboard to the correct thickness.

Next I bring the board down to .25” for most steel string guitars. The safety planer is good for that. Ebony is really hard, I only take a bit off at a time.

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And take off the safety planer marks with a scraper. This step isn't too important because the top surface of the fingerboard will get a lot of work later on. But it only takes a second or two minutes or so to do.

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While I'm at it, I clean up the sawed edges of the binding.

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I go back and put a fresh flat edge on the fingerboard. It's best to use two hands on the plane!

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And now we're ready for fret slots.

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And you might be interested in how a factory like Taylor Guitars goes about building a neck.

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Re: Building a Steel String Guitar

#206  Postby John Platko » Jan 07, 2016 3:49 pm

I'm now at the point where I'm ready to cut the fret slots so this seems like a good time to figure out where they need to be located. When you pluck a string that's fixed at both ends, i.e. a guitar string, the string develops a series of standing waves. The longest wave- the one that has the lowest frequency is the fundamental (some call it the first harmonic). The next harmonic has twice the frequency, the one after that 3 times the frequency, then 4, then 5, etc. etc.

The one dimensional wave equation explains the whys of this in detail. I'm not planning on going there but if someone is interested they can read about it here.

For a bit more boiled down explanation go here.

I'm interested in fret spacing so I'm going to start with:

the Fundamental frequency (F) = (T/u)1/2 /2 L
where T is the tension of the string
u = the mass per unit length of the string.
L is the length of the string.

From that equation we see that:

The frequency increases as we increase the tension on the string - although not linearly.

A heavier string with the same tension and length vibrates at lower frequency - hence bigger bass strings.

Decreasing the length of the string increases the frequency - so we get higher pitches as we move up the fretboard. But how do we adjust the fret position to match musical note frequencies?

The Chromatic scale (e.g. - the notes found on a piano, guitar, etc.) is a non-diatonic scale. These notes can be expressed as:
Frequencyn = M Frequency - (note property 1)

Where n represents any note of the scale

n-1 represents the note one interval lower in frequency than note n.

M is a constant multiplier which determines the interval between notes.

For example: the fundamental of C is equal to the fundamental of B * M

The 12 tone chromatic scale also has the property (prop 2) that notes that are 12 intervals apart are an octave higher/lower, that is the fundamental of the higher note an octave above is twice the frequency of the fundamental of the lower note an octave below. Sooooooo.

The fundamental f of C an octave higher = C M M M M M M M M M M M M or
C * M = C#
C# * M = D
D * M = D#
D# * M= E
E * M = F
F * M = F#
F# * M = G
G * M = G#
G# * M = A
A * M = A#
A# * M = B
B * M = C up an octave

or simply

C up an octave = C M12 (prop 2)

An octave up is 2 * the frequency so

2C = C M12
canceling out the Cs and a bit of algebra
21/12= M

Or M = the 12th root of 2. That is, to move from one note to the next, the frequencies in the note are all multiplied by the 12th root of 2 , which is 1.056 or so.

Calculating Fret Spacing

The frequency interval between notes (prop 2) and the equation for string frequency (prop 1) can be used to determine fret spacing.

Let L be the string length from the nut to the saddle (This is ideal- lets go with that for now)
Let L' be the string length from the first fret to the saddle.

Therefor X ( the distance from the nut to the first fret is L -L'

Using prop 2 -

Frequency of First fret = 21/12 Frequency of open string

and substituting the equation from prop 1 into that.

(T/u) 1/2/ 2L' = ((T/u) 1/2/ 2L) * 21/12

Canceling out the common terms yields

1/L' = (1/L) * 21/12 or L/L'= 21/12

A guitar builder is more interested in finding X (the distance from the nut to the first fret)

We know:

L'= L -X and L/(L- X) = 21/12

L = (L-X) 21/12
L= L21/12- X21/12
X21/12= L21/12 - L
X21/12=L(21/12 - 1)

soooooo

X= (L/2 1/12) /(21/12 - 1)

where 2 1/12 /(21/12 - 1) = D = 17.817

So so ...
X = L/D = L/17.817

That is. we find the distance from the nut to the first fret by dividing the original scale length by 17.817

Then we just repeat the above recursively to find however many frets we want. I.e. the length of the first fret to the saddle is now L and we divide that by 17.817 to find the distance from the first fret to the second fret. And so on and so on...

There's a bit more to be said about this but perhaps I've said enough for now. TBC
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Re: Building a Steel String Guitar

#207  Postby John Platko » Jan 08, 2016 2:26 pm

Hopefully I got all the parentheses in the right place in my last comment I :dunno:. But the reasoning is sound and the final answer is correct. and that was:

X = L/D = L/17.817

We can use that to make a quick spreadsheet to calculate all fret distances.

fret, L to saddle, X from last fret
0 25.000
1 23.597 1.403
2 22.272 1.324
3 21.022 1.250
4 19.842 1.180
5 18.729 1.114
6 17.678 1.051
7 16.685 0.992
8 15.749 0.936
9 14.865 0.884
10 14.031 0.834
11 13.243 0.787
12 12.500 0.743
13 11.798 0.702
14 11.136 0.662
15 10.511 0.625
16 9.921 0.590
17 9.364 0.557
18 8.839 0.526
19 8.343 0.496
20 7.874 0.468
21 7.432 0.442
22 7.015 0.417
23 6.622 0.394

And a quick sanity check of this is to look at the 12th fret, which is an octave up from the open strings, and make sure that it is half the length of the open string. -12 12.500 0.743 and it is.

In the above example I use a scale length of 25" because it made the octave length work out evenly but what scale length should be used- does that matter?

Scales lengths typically vary a bit from manufacturer to manufacturer and even the same manufacturer may vary its scale length(s) over the years. Taylor is mostly know for it's 25 1/2" scale length but they make a shorter scale guitar too. Martin is known for a scale length around 25.4" or 24.9". Gibson 24 3/4". this gives the exact details and some explanations.

A longer scale length (with the same string gauge) has more tension in the strings- why can be seen in the equation I gave in the last comment. More tension tends to lead to more energy going into the guitar when you pluck a string. People tend to describe shorter scale guitars as having a warmer sound with more fundamental/lower harmonics.

Of course you can play with string gauge and change things ...

Reality

Up to this point I've been talking about guitar strings as if they were ideal and being used in ideal ways. But that's not reality. :nono:

For one thing, just look at a guitar, all the strings aren't the same length. Because the string spacing is wider at the saddle then the nut, (I imagine for playing convenience) the outer strings are longer. More importantly, the tension of strings change when you push them down to a fret. And this is a pretty big deal. And how much the tension changes depends on the action or setup of the guitar, and what string you're fretting. Electric guitars usually have ways to adjust the length of every string so that these effects can be compensated for.

Acoustic guitars by and large tend to have fixed compensation. Somehow this reminds me of the time I just finished a new guitar and hung it on the wall in our dining room. My wife was admiring it and saying it was beautiful but then she paused and pointed to the saddle and said, but this part is crooked- and she was right.

It bees that way with guitar saddles:

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The higher pitched strings are closer to their maximum tension and they need less compensation when you fret them. So, saddles are tilted at an angle to give the bass strings more compensation. This can be fine tuned a bit, Taylor does this with the B sting.

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You can make a wider saddle that can be shaped a bit to adjust the intonation.

The general procedure is to slant the saddle where the bass side is about 1/8" further back towards the tail than the treble side and the middle of the saddle further back from the desired scale length by 1/8". That get's things close. Doing this is called compensation.

I'll also mention that things are not ideal even for the open string. That is if you tune it to a certain pitch, the harmonics aren't exactly whole number multiples of the fundamental - They're close but as you go up in frequency they go sharper and sharper. As the wavelengths of the harmonics get shorter and shorter the string acts less ideal and behaves as if it is a bit more stiff so the harmonic frequencies are higher than they should be. I measured this at one point and this is certainly true, off the top of my head (which could be very wrong) I seem to recall they went up to about 10% sharp. If anyone cares I could probably find or recreate a graph that demonstrates this.

What else - classical guitars don't use the tilted saddle trick, they just push back the saddle a bit.

Some people have other compensation tricks, e.g. they play with their nut slots to give them their special compensation sauce. No matter what you do, guitars are not perfectly intonated.
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Re: Building a Steel String Guitar

#208  Postby John Platko » Jan 09, 2016 4:23 pm

Cutting the fret slots

Hmmmm. Well this is a bit embarrassing, after all that math, I'm going to be using this fancy miter box to cut fret slots with a hand saw. It includes a template with an index for each slot. There's noting to measure. :oops:

But give a person a fret template and he can build scale, teach a person how to calculate fret spacing and ...

I bought this tool after my first fretting experience in class. Al Carruth handed us a square and a 24" rule and we did it all freehand. Ebony is hard, it's easy for the saw to slip, holding a square and marking the line and then keeping the saw on the line is harder than one might expect. After 18 frets or so I got a bit crooked. So I went out and bought this for future guitars:

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The miter box does a pretty good job of controlling the depth of cut. The top of the saw comes to a stop when it hits the guides. And the depth of cut can be adjusted easily.

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The box also has an indexing system built in. Here's a close up.

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I only have templates for the common fret spacing that I use on acoustic guiars. But it's easy to cut slots accurate enough without a template for other fret spacing. Most of my electric guitars are done that way.

To cut to a custom scale I just tape a mark on the inside of the miter box and them double sticky tape a precision ruler along side the fingerboard to any template. Then I don't use the index key but just read the fret position on the ruler against the mark. I like to do this in metric so I print out a fret scale with metric spacing. I don't print out the fret to fret spacing, you don't want to measure that way because then errors can accumulate. Instead I print out the distance each fret is from the nut and measure that. This way any error I make in aligning the ruler to the mark will only be at that fret and not accumulate. That is, if I'm miss align .02mm each fret then each fret is .02 mm off but I'm not off by .02+.02+.02 by the third fret which is what would happen if I measured fret to fret.

If this is confusing and someone wants a few pictures of the ruler method, just ask. It really does work well and there's no need to buy a template for a few guitars, especially if you vary the scale length that you use. And it's easy enough to build a simple miter box that effectively does what this fancy one does.

I use double side tape to hold the fretboard on the template. The board has to be skewed a bit from the indexing slots so that the nut lines up with the cutting slot when the nut index lines up with the index key. (The tape on the far right of the picture is in the wrong place and I had to move it a bit left.)

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The miter box has good clamps to hold the board in place, especially after you get a few slots in but for the first few slots I add an additional one of my own. Of course the whole miter box needs to be clamped to the bench too.

After the nut position is marked.

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After the first fret slot is cut.

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My fret saw is Western and cuts on the push stroke. I added a handle on the other end so I can put more force into it. Often, I'll turn the saw around and use it like a Japanese saw on the pull stroke. It's harder to cut slots in ebony, much easier with rosewood. These days you can buy Japanese fret saws, i.e. a Japanese saw with a kerf for fret slots.

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And then it's done.

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I should also mention that it's important that the kerf of the saw match the tang of your fret. Your fret supplier will specify this.
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Re: Building a Steel String Guitar

#209  Postby John Platko » Jan 11, 2016 7:40 pm

Tapering the fingerboard

Next I cut the tapered shape of the fingerboard. A table saw can be used for this with the right jigs, I imagine that's a great way to go but I'm more or a router person so that's what I use for this job. Of course, you can just use hand tools too.

I have a template that will get me pretty close to the board I want. Since I'm going to add the binding that was made earlier I need to account for that in the fretboard wedge. This strat template is pretty close to what I want.

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It's best to make any symmetrical templates like this by making a half-template first with guide pins on the center-line. Then make a new full template flipping the half template over to insure symmetry.

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Some double side sticky tape.

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I use a square to align the template to the fingerboard edge. Marks along the template really help with this job.

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And it's on. A bit of sloppy bandsawing to remove the bulk cutoff.

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Clean up with a flush cut bit on a router table.

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And it's done.

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Re: Building a Steel String Guitar

#210  Postby ScholasticSpastic » Jan 12, 2016 4:25 pm

This continues to be a fascinating thread. Thank you very much for making it! :thumbup:
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Re: Building a Steel String Guitar

#211  Postby John Platko » Jan 12, 2016 9:03 pm

ScholasticSpastic wrote:This continues to be a fascinating thread. Thank you very much for making it! :thumbup:


You're welcome, I'm glad you're enjoying it. :cheers:
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Re: Building a Steel String Guitar

#212  Postby John Platko » Jan 12, 2016 9:15 pm

Gluing the binding back on the fingerboard

Now it's time to put the wood that I took off the fingerboard before I slotted and shaped it to size back on. But first, this is a good time to check that the fingerboard is still straight.

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I put some wax paper doubled over in the slots at this point to keep the glue from getting in. It's helps ease the clean up job.

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Some glue on the binding.

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Spread it out and keep the excess to a minimum, again to help keep it from going into the slots.

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Put the binding on the fingerboard and tape in place. The binding was cut before the fingerboard was planed to thickness so it should easily cover the edge. Still, I'm using titebond and it's slippery so make sure the binding overlaps the bottom of the board a bit. It's not too important that the binding overlap the top of the fretboard on a steel string because the board gets an arch later. On a classical, which has a flat fingerboard of course the binding needs to overlap the top and bottom a bit. Even on a steel string you might want a flat board over the body.

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Wrap the board with ranger-rope. (an old inner tub cut in strips)

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And now the binding is well bound. ;)

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Re: Building a Steel String Guitar

#213  Postby John Platko » Jan 14, 2016 1:43 pm

Completing the fretboard

After the glue dries, and with the rubber rope removed, we can see how the binding extends above and below the surface of the fretboard.

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Plane the binding close to flush to the top and bottom surface.

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I like to scrap the last bit flush so I don't nick the board.

Scrape the sides of the binding and check the overall width of the fingerboard. This is a good time to make any necessary adjustment.

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Now I cut off the excess binding.

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And sand flush, being extra careful at the nut end not to touch the fingerboard itself- just the binding.

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And there you have it. The binding technique that I'm using on this guitar if very subtle, most people wouldn't even notice that the fingerboard is bound. But the fret ends will be hidden and it's the look I'm going for. A more traditional binding would also add a mitered strip of binding on the end of the fretboard.

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Re: Building a Steel String Guitar

#214  Postby John Platko » Jan 17, 2016 7:32 pm

A few comments back I explained how to determine where to cut fret slots by using the physics of a vibrating string combined with basic music theory, ie, how Western music notes are spaced in frequency. But that calculation doesn't really convey the complexity of what's going on when you pluck a guitar string, that is, the timbre of the guitar. So I want to drill a bit deeper on that before moving on.

When you pluck a string that's fixed on both ends it vibrates with many modes or frequencies, the frequencies are integer multiples of the lowest frequency. If you want a review of this go here..

But how do you actually relate this to the sound of an Acoustic guitar? If you pluck a string an look at the sound a microphone picks up, i.e. sound pressure and plot it over time you get something like:

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And if you zoom in you see something like:

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And if you look at this in the frequency domain- you can see the amplitude of the harmonics. Which looks something like:

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But that's a picture of what's happening in the frequency domain for a small chunk of time. When you pluck a guitar string the frequencies quickly bloom and then start to decay. You can show a "movie" of this but there's so much going on that I don't find that useful. Instead, I create a chart which shows the amplitude of each harmonic every x msecs. The dots in this chart show those amplitudes for the lower harmonics of a guitar pluck. This chart shows about 22 harmonics - left to right. Vertically you see how that harmonic decays with time. The longer the smear, the faster the harmonic decays.

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And you can see even more harmonics: (which makes it clear that the higher frequency harmonics are decaying faster that the lower ones - that's important to the timbre of a steel string guitar.

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All of that has been mostly review of what I've covered earlier in the thread but I think it useful before I present what is new.

I made a demo where I build up a plucked guitar sound by adding more and more harmonics until something resembling a guitar is created. (ignoring the frequencies added by the envelope I'm imposing on the harmonic.) This kind of thing helps me understand what I'm hearing when I hear a guitar note and what aspect of the sound is due to various harmonics. You can hear the demo here.

And see what the various harmonic additions look like below:

Just the fundamental - I'll call that 1 harmonic.

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Two harmonics:

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Three harmonics:

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Four harmonics:

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Five harmonics:

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Ten harmonics:

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Twenty harmonics:

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Forty harmonics:

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78 harmonics:

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Re: Building a Steel String Guitar

#215  Postby ScholasticSpastic » Jan 18, 2016 8:20 pm

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Re: Building a Steel String Guitar

#216  Postby John Platko » Jan 18, 2016 8:44 pm

ScholasticSpastic wrote:https://en.wikipedia.org/wiki/Fourier_transform


:scratch: Any specific thing we should look for there?
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Re: Building a Steel String Guitar

#217  Postby ScholasticSpastic » Jan 18, 2016 8:57 pm

John Platko wrote:
ScholasticSpastic wrote:https://en.wikipedia.org/wiki/Fourier_transform


:scratch: Any specific thing we should look for there?

I was just thinking that your diagrams looked more and more like the raw data from the FT-NMR (Fourier Transform-Nuclear Magnetic Resonance spectrometer) I used to play with at school. I think that what you were doing with adding the frequencies together is the opposite of a Fourier Transform. I just thought that was fun and kind of cool, and decided to link to the wikipedia article on it just in case anyone else might make the connection.

Basically, just appreciating how much science is in the very olde art of instrument manufacture.
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Re: Building a Steel String Guitar

#218  Postby John Platko » Jan 18, 2016 9:21 pm

ScholasticSpastic wrote:
John Platko wrote:
ScholasticSpastic wrote:https://en.wikipedia.org/wiki/Fourier_transform


:scratch: Any specific thing we should look for there?

I was just thinking that your diagrams looked more and more like the raw data from the FT-NMR (Fourier Transform-Nuclear Magnetic Resonance spectrometer) I used to play with at school. I think that what you were doing with adding the frequencies together is the opposite of a Fourier Transform. I just thought that was fun and kind of cool, and decided to link to the wikipedia article on it just in case anyone else might make the connection.

Basically, just appreciating how much science is in the very olde art of instrument manufacture.


Ahhh.

Yes, my adding the frequencies is a crude inverse FFT.

The picture with the dots smearing down the page is generated by taking a series of DFTs in time and then sifting through the data at the spots where a harmonic is expected to be- plus or minus some wiggle room.

The "crude inverse FFT' is my feedback loop that convinces me that I have a handle on what's going on in the sound. If I get curious about what is involved with a particular aspect of a sound, I'm not convinced I understand what's happening in the frequency domain until I can add a few sine wave together and get something similar.

I think the main point I was trying to communicate with that demo was how complex an actual musical note really is and how important the high frequencies decaying much faster than the low frequencies is to the sound of a steel sting guitar.
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Re: Building a Steel String Guitar

#219  Postby John Platko » Jan 19, 2016 4:07 pm

I'm now at a point in the construction where I create the neck to body joint. The traditional way to do this is with a dovetail joint. Taylor Guitars bucked tradition and made bolt on necks perfectly acceptable for acoustic guitars- at least to most. For many years Taylor used a seemingly simple but very effective neck butt joint Here's a picture of what that looks like, the only one I could find was in for repair. It seems that they sometimes split near the inserts for the metal bolts.

Image

Collings has a slightly different bolt on construction and they put a dowel down the heel to keep it from splitting. That's the type of neck joint I would recommend to most people to use.

Image


Taylor's new neck joint attacks many of the problems of attaching the neck to the body. It's really nice but problematic to build if you don't own precision CNC machines. It's worth hearing about all the issues from Bob Taylor himself.



The new Taylor neck joint:

Image

Martin has a different point of view. Here's their spokesperson giving it.



A traditional Martin neck joint.

Image

When I was studying with Al Carruth he favored Spanish heels for neck joints. which essentially eliminates having a neck joint, the neck is integrated into the body of the guitar. But for the reasons Bob Taylor discusses in the video, that's not such a good idea.
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Re: Building a Steel String Guitar

#220  Postby John Platko » Jan 21, 2016 2:09 pm

Cutting the body dovetail mortise

Well, I can't put it off any longer, it's time to cut a dovetail for the body/neck joint.

While for the many reasons stated by Bob Taylor in the video posted above it makes more sense to use a bolt on neck, I'm going the traditional route. Glued on neck in dovetail.

I'll be using a router to make the basic cuts; along the way to a finished guitar there will be some hand adjustment.

I'll mention that some folks cut the dovetail mortise in the heel block before gluing it to the sides. I imagine that's a bit less stressful, you don't have to take a router to a nearly completed body. Doing the mortise early in the process does make the alignment of the heel block with everything else more critical.

This is a good time to make sure you have a flat surface for the neck to mate to.

A bit of sandpaper on a block.

Image

A straight edge to check.

Image

I'll be using this jig which holds the guitar body securely and has a dovetail mortise template on it.
A few spacers near the heel make sure that the sides sit flat against the template.

Image

The guitar locked and loaded on the jig.

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The jig clamped to the workbench.

Image

A look through the mortise. It's important to have enough free space to start the router without having the bit touch the guitar – really important.

Image

I do a slow pass down the middle and then do the sides of the mortise, from the top of the guitar down. I think some folks like to hog out some of the bulk material with straight bit and appropriate bearing.

Image

It's a good idea to really make sure everything that should be cut away is before removing the guitar from the jig.

Image

And there you have it:

Image

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