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Interested in learning about blacksmithing? Read this!

--News & Announcements--
Upcoming projects:
Continuation of the Mandola project
Conclusion of bookbinding
Metallurgical Science behind Heat Treating

Sunday, August 28, 2016

Bookbinding Revisited

A few years back, I journeyed down the road towards binding books by hand, and although the result was I suppose successful the entire experience was not wholly satisfactory. Due to the thickness of the spine and general inexperience, there were a few pieces to the method that I wanted to change, and now I have come to a project which allowed me to explore these differences. In the interest of pursuing more traditional methods and materials, this time I used a few particulars which, although not necessary, will hopefully add a note of authenticity in appreciation for the approach.

For this round of binding, resulting in a sketchbook, I used the following materials:

-Linen paper
-Cotton thread
-Linen tape (ribbon)
-Hide glue

To being, I took the linen paper and oriented it so the texture all aligned to the same direction. This was for nothing more than consistency throughout the process. With a stack of somewhere around 200 sheets, I began to fold them in half and make stacks of 5 sheets, resulting in folios of 20 sides each.

Five of the original sheets seemed to be a good number for the thickness of the folios at the fold, allowing the edges on the opposite side to have the look and feel of depth to them without the farthest (innermost in the folio) protrude excessively far from the shortest (outermost in the folio).

Here is where I spent a great deal of time deliberating on what to do next. For a few weeks I thought over how to punch eight holes in each of the hundreds of sheets with exacting consistency. Doing them all by hand, separately, would take far too long and be far too inconsistent to make the stitching of the spine come out with any amount of respectability. In the end, this is what I came up with. In short, it is two boards connected by a hinge, the top of the two with eight nails driven through it. When the folio is inserted into the jig and the top board pressed down, the tips of the nails punch through the paper.

For an idea of how far the nails come out, see above. It is not much. Had I smaller nails, I might have used those, but after a lot of trial and error, this depth was the best for puncture consistency, hole size, and not having the nails sink into the opposing board too far. The advantages I have found using this jig are this. First, the hinge itself has several lines which can be used to align the centre (where it was folded) of each folio. More, it is also a hard stop for how far the folio is inserted into the jig. After getting a feel for it, I marked a few lines on the non hinge size of the bottom board to align the crease of the folio. In the beginning, I expected to have to punch the folios one sheet at a time, but after adjusting the depth of the nails, I was able to easily and cleanly (important) punch all five sheets at once. As a result, I punched a few thousand holes in just about a minute, all with perfect accuracy and repeatability. The spacing of the nails was measured such that the folios can be inserted in either direction and the hole spacing will remain the same, but this is also unique for this length of paper. Should I bind other sizes of folio, I will need to make another top board for the jig.

The bottom folio of the above stack of paper is a bit off kilter and was one of the ones used in testing out position, but after learning the tool, the nails fell centre in the fold every time. This will make stitching the folios together incredibly easy and predictable.

With the stack of folios punched for stitching, it's time to gather everything for the actual binding. Simply put, all you really need is thread. The linen tape helps keep the folios aligned and straight, but it is not strictly necessary.

With the linen in place, it is a bit easier to see the reason behind how I spaced the holes. There are two on the ends that tie the folios together, then three pairs of two which are spaced at the width of the linen.

The end of the thread receives a barrel knot, an overhand knot, or really any simple stopper knot to keep it temporarily from pulling through the first set of holes. This knot will later hold another knot on the second folio and affix the two together, which will be explained later.

To begin the stitching, first start on the outside of the spine and push the needle into the first hole at either end. I happened to start on the left side but there is no difference. Then, simply follow the hole pattern going in and out to either side, trapping the linen tape when you reach those sets of holes as shown above. It is important for a tight binding to pull the thread tight through each of the holes. When doing this, pull only in a line parallel to the folds, or the thread will very quickly cut through the pages.

This is what the inside of the first stitched folio looks like. To hold the folios in place, I use a metal straight edge or anything flat with a little bit of weight to it. Open the folio and set it on the stack such that the inside of the folds are accessible.

Now we come to the second folio. Because of the number of holes, the thread will be coming out of the first folio at the spine as shown above. Just like with the initial threading, pass the needle into the second folio from the outside towards the inside of the fold.

This next bit may be a little confusing at first but is actually quite simple. When the thread comes out of the second hole, the an overhand knot that captures the thread of the first folio that holds the linen tape in place. The reason for this is to keep the folios tight together at the middle of the pages as well as the ends, which are naturally held together by the thread direction. If you do not do this, the binding will still work, but the linen tape will be the thing keeping it together rather than the thread. With the subsequent hide glue over the spine, it is possible to do without the binding knots, but I would advise using it as the glue is strictly a chemical binding rather than a physical one, and can fail after repeated opening and closing of the book.

Once the knot is tied, continue the threading as normal, repeating this knot every time the needle comes out of the spine (one for each of the linen tapes).

At the far end of the second folio, tie another overhand knot, this time capturing the stopper knot at the original end of the thread. This pulls the two spines of the folios tight together.

Onto the third folio, now everything becomes repeated through to the last folio. The only difference between this one and the second folio is that the end knot simply passes between the two folios beneath it, again cinching the folios tight together.

Finally, the stitching is complete. Notice how the stitches across the linen forms a Z pattern. This is because the thread comes out of the spine on alternating sides of the linen and thus which side receives the knot. Hopefully that makes sense.

Thread complete, it's time for the mull. This is in essence a very loose weave fabric that adds some structure to the spine. it helps act as a surface which the glue adheres to, allowing for a stronger binding between the cover and the pages.

I decided to use hide glue, although any white PVA glue will also work. Since this is the first time I have ever used hide glue, I cannot comment on the durability of it, but the PVA glues I have used in the past are excellent. Hide glue burns under direct heat, so it must be heated either in an electric glue pot or in a simple double boiler. I went for the latter.

Cut the mull so it extends past the linen tape and covers the majority of the spine. I left a it a tad short of the edges for aesthetic reasons, as I did not want the chance that it would later be visible once the cover is on.

Apply glue to the spine only at this point. Glue over the mull and press it down so that it becomes entrapped in the glue layer. Try to avoid excess glue from dripping or spilling over to the front and back of the pages.

Next, take some waterproof layer such as tin foil or wax paper and place it between the pages and the mull/linen tape.

Between the foil and mull/linen, place a half sheet of paper or whatever size page you are binding with. Align the loose sheet with the bound pages as closely as possible, as this will serve as the interior cover of the book.

Place the pages on whatever you are using as a cover, in my case ~2oz leather. Brush on a layer of glue on both the leather and the loose sheet of paper, leaving a clear space where the spine of the bound pages will sit. This is one of the lessons I learned from my previous experiences with binding. Having the cover attached to the spine makes it difficult to bind the cover to the front and back while having it still be able to open fully.

With everything aligned, fold the cover onto the pages and apply even pressure while it dries. I used a granite block with another weight on top. Having a flat surface pressing down while it dries is important to keep the pages from drying strangely, and the foil barrier keeps the moisture of the glue from the pages beneath.

Once the first side is done, flip it over and do the same thing on the second side. Pull the cover material tight before gluing or there will be excess leather over the spine.

When the glue is dry, which takes a bit longer because of the leather and foil preventing moisture from evaporating, remove the weight and trim  away the excess cover material. Later, I will be adding some embellishment and a touchmark to the the sketchbook, but for all practical purposes, the book is now bound.


Saturday, July 30, 2016

on Iron [Part III]

Continued from:
     Part I
     Part II

To the bladesmith, heat treating is, in short, the effect of time and temperature on steel to produce a change in either the grain or microstructure phase. The four main modes of heat treatment used in the processing of steel are annealing, normalization, hardening, and tempering.

Throughout this examination of heat treatment, I will be using a variety of terms and ideas discussed in the previous two parts linked above. As an introductory look at the various interactions between the forms of the iron carbon lattice and relevant temperatures, please briefly examine the graph below detailing phase states for various carbon contents and temperatures.

**Unless otherwise noted, all figures are from from "Metallurgy of Steel for Bladesmiths & Others who Heat Treat and Forge Steel", by Verhoeven et. al.


Annealing is the general process of relieving internal stress in the metal lattice and results in a softer, more ductile member. The primary goal of annealing is to diffuse dislocations within the lattice into a state of equilibrium and, where possible, remove them entirely. Technically, normalizing is a form of annealing, but the differences in process and resulting material properties will necessitate a separate examination.

Annealing can generally be thought of as a thermodynamic cycling where the metal is heated above the critical temperature until the carbon contained in the cementite regions fully diffuses into an equilibrium state with the carbon deficient ferrite regions, yielding homogeneous austenite. After forming this austenite, the steel is slowly cooled such that only cementite and ferrite are formed as it drops below the A3 temperature, or the temperature at which ferrite begins to precipitate out of austenite. The following slow cooling allows for a higher equilibrium state in the resulting ferrite and cementite, making for a stable lattice of greater uniformity

Steels of higher hardenability, and by inference higher carbon content to an extent, require slower cooling to prevent the precipitation of Martensite. Alloyed effects have similar requirements on annealing times due to the separation of the Martensite start temperature Ms (when Martensite begins to precipitate from austenite) and Martensite finish temperature Mf (when Martensite lower temperature limit after which Martensite will no longer precipitate). The widening of the Ms and Mf temperatures mean that Martensite is able to precipitate for a longer amount of time (allows for slower quench speeds) and therefore necessitates a longer duration of cooling to prevent that same martensitic precipitation.

One of the principle consequences of annealing, and often the reason it is done, is the relief of internal stresses. When the austenite reaches equilibrium and higher energy dislocations are allowed to become unpinned, those places which would have become nucleation sites for the formation of grains are relieved. Larger grains are typically undesirable for hardened steels, but in softer members it is of little consequence because of the increased malleability and ductility resulting from the refined ferrite and cementite. Not only does annealing soften the metal and make it easier for subsequent machining operations but it also helps relieve stresses from prior machining that results in surface dislocations which more easily lead to sites for stress fractures and brittle failure.

Because I rarely ever anneal, I will not discuss the process at great length to avoid distributing misinformation.


Similar to annealing (and as a form of it), normalization is also a thermodynamic process used to manipulate grain size and the lattice's chemical equilibrium. Unlike the previously described annealing, normalization refines the grains into smaller, uniform patterns.

Like annealing, normalization requires the steel to be heated past its critical temperature and thus allow the formation of austenite. The longer the steel is soaked (to an extent), the more homogeneous the austenite will become. High alloy steel requires longer soak times due to the higher energy required for those larger substitutional atoms to diffuse through the iron lattice. Similarly, normalizing results in a softer steel of lower stress and improved ductility, malleability, and toughness. The notable difference between the two processes lies in the rate at which the steel is cooled. Instead of a very gradual lowering of the temperature, normalizing is generally done in still air. This is significantly more rapid and, as a result, can also yield a harder piece than one that has been annealed.

Normalizing also has the key benefit of reducing grain size and therefore a more consistent response when the steel is subsequently hardened. For the bladesmith, this is extremely important, as improperly worked steels tend to warp, crack, or otherwise act unpredictably when hardened without normalization. Irregularities in the micro structure from forging are allowed to be relieved through normalization which also cause that unpredictable response to hardening.

Because the cooling is more rapid than in annealing, austenite tends to precipitate into pearlite more rapidly and therefore with a shorter distance between interspersed cementite plates (resulting in a finer grain structure).

In the application of heat treating blades, normalization has another key benefit. Throughout the process, the phenomena of decalescence and recalescence can be observed. For reasons discussed in the section on quenching, it is best to harden a steel as close to the critical temperature as possible (without going below) and that visual indication of phase for the given lighting conditions is made clear through the process of normalization if precise temperature controlled kilns or furnaces are unavailable.


Courtesy of University of Cambridge, Department of Metallurgical Engineering

This is where the majority of the study of this examination will take place, in addition to a look at tempering. Due to the complex nature of phase transformation and meta-stable thermodynamic states involved with the quenching and subsequent tempering processes, there will be a fair bit of technicality to this.

Before talking about all that, to put it simply, quenching is the hardening of steel by rapidly cooling it in order to achieve a state of the metal lattice's microstructure which would ordinarily not exist. This quenching process is what hardens the steel.

A quick note on the critical and curie temperatures:
-Curie temperature is the temperature at which a material becomes non-magnetic. The cause of this is the introduction of sufficient thermal energy for the magnetic dipoles become unaligned with respect to their neighbours. This happens in countless materials other than steel, including pure iron (which cannot form austenite) and is lower than and independent of the critical temperature.
-Critical temperature is the temperature at which ferrite cementite transform into austenite. While austenite is paramagnetic by nature, it is not because its formation happens at a temperature above the curie temperature.
-In a eutectic, binary iron-carbon lattice, the curie temperature and critical temperature are within a few degrees. However, the addition or loss of carbon widens the difference between the two, and the introduction of additional elements into the lattice makes the disparity larger still. Using a magnet, therefore, to judge whether a steel has transformed into austenite can serve as an approximation but an approximation alone. There are more accurate ways of determining the phase transformation.

In the context of this larger discussion, quenching forms either Martensite or bainite, depending on the methods, mediums, and temperatures used. As with annealing and normalization, steel is quenched from an austenitic steel, or a steel whose metallic lattice is above the critical temperature and thus given the opportunity for its substituent ferrite and cementite to homogenize after transforming into austenite. When quenched from this austenitic state, that austenite undergoes a forced converted to Martensite as a super saturated body centred tetragonal crystal of approximately 1,5% carbon or greater. Because of the martensitic structure is thermodynamically unstable (meta-stable), that carbon would ordinarily have diffused into cementite upon more gradual cooling. Inside this Martensite, there is a tremendous amount of internal stress and pinned shear dislocations, which give it its relative strength and hardness, which is about 1,75x harder than pearlite. In addition to a change in micro structure and hardness, there is also a change in density. The Martensite has a lower density than the previously exhibited austenite, and therefore the steel expands during this phase transformation. It is the irregularities in formation of Martensite that lead to warps, cracks, and sori (curvature of a blade towards or away from the edge during hardening). 

Unlike the formation of pearlite, which holds to the same decomposition mechanisms from austenite regardless of the change in temperature, Martensite precipitates from austenite depending on the rapid change of temperature and the final temperature at which it is cooled. This faster cooling produces a few similar results as with the stable forms of the micro structure- the faster growth of individual grains and smaller grain sizes due to the increased number of nucleation sites along previous austenitic grain boundaries. The major difference between slow cooling and rapid quenching is that there lies a disparity in the formation of Martensite that heavily depends upon the rate at which it is actually cooled. Where pearlite will entirely replace the austenite from which it came insofar as the final temperature is below the eutectic temperature, Martensite will not form at all unless the temperature at which it is cooled is below the Martensite finish temperature. In the phase diagram of the iron-carbon lattice, there are only three possible phases the steel can occupy, ferrite, cementite, and austenite. While there are combinations of these three phases, they will not appear as something else in a thermodynamically stable system. The Martensite, however, begins to form between the Martensite start and finish temperatures, provided a sufficiently fast rate of change of temperature. If the quenched temperature of the steel lies between those two temperatures, a portion of the austenite will remain untransformed, and is called retained austenite. This reduces overall hardness due to the difference in structure of austenite and Martensite, and that remaining austenite can later transform into ferrite and cementite, which also reduces hardness. Because austenite is able to dissolve more carbon than Martensite, a steel of increasing carbon content is increasingly susceptible to retained austenite. Fully lath martensitic steels generally will not have significant amounts of retained austenite, which occurs in steels of ,60%C or less; but fully plate martensitic steels tend to be dramatically increased amounts of retained austenite, which occurs in steels of 1,0%C or greater.

As would seem intuitive, steel is fully hardened when the maximum amount of Martensite is precipitated within the piece across its entire length and cross section. In order to achieve this maximum theoretical Martensite content, the rate of cooling must exceed a rate (unique to each grade of steel) throughout all of the present austenite. Due to the nature of heat transfer and thermal boundary layers and internal convection, the surface of a piece will always cool faster than the centre. If the quench speed is not fast enough to lower the temperature of the steel below the Martensite start temperature, other phases of the iron-carbon lattice will form in place of Martensite, and therefore be softer in afflicted regions.

As previously discussed, grain refinement is an important part of heat treatment. After normalizing, grains will be smaller and more uniform. During quenching, Martensite precipitates along prior austenitic grain boundaries. Uniformity and predictability in the formation of Martensite during the quench is important to the overall shape and integrity once the quench temperature has been reached. Smaller grains lead to greater uniformity in martensitic distribution, which leads to normalized stress distribution. For thin pieces such as blades, unwanted distortion presents a significant problem. Although crack formation and embrittlement correspond to carbon content and quench speed across the Martensite start and finish temperature band, there are a few additional factors which can lead to catastrophic quench failure.  First, temperature uniformity dictates how a piece will react. If there are hotter regions alongside colder regions, that temperature banding will determine when the formation of the various phases can occur. Note that once pearlite or bainte (discussed later) precipitate from austenite, that portion of the lattice will not form Martensite without first being converted back to austenite. Second, the speed at which the steel is quenched can have a dramatic effect of stress introduction. Martensite precipitates from austenite at a speed close to the speed of sound in iron. Faster quenches mean more Martensite is forming within the steel in a shorter period of time, and therefore introduce high amounts of internal stresses more rapidly.  This is generally why (in addition to a few effects of substitutional alloying) steels quenched inappropriately into water or brine have a much higher chance of failure. Third, when steel is quenched into a volatile liquid, the thermal boundary layer can cause an insulating effect and flash that liquid to vapour. The difference in temperature and density of the vapour compared to the bulk modulus causes an extremely complicated analysis of heat transfer, but in short tends to lead to warping and sometimes cracking.

There are several liquids into which steel can be quenched, ranging from water and brine to molten salts, oil, and even liquid metals. Each have their own advantages and disadvantages, but the main difference between them is the severity of the quench experienced by the steel. Oil tends to be slower and more forgiving, water faster but with the more significant introduction of the vaporous jacket, and brine which is extremely fast but can mitigate some of the vapour effects. I may delve deeper into this at a later time, but for now I will leave it at that.

Retained Austenite
When austenite is unable to fully transform into Martensite during the quench, a portion of that austenite remains as a metastable crystal within or around the Martensite. Due to the changes of volume that come with changes in the microstructure, retained austenite imparts a tremendous amount of internal stress to the steel. Steels containing more than ,30% C have a Martensite finish temperature below room temperature, which is why some heat treatment methods employ freezers, liquid nitrogen, or other cold receptacles, as austenite may remain until the steel is cooled beneath the Martensite finish temperature.

If warps appear during the quench, it is because of retained austenite's softness that they can be straightened for a brief period of time before additional retained austenite transforms to Martensite. However, if the quenched steel is not cooled sufficiently, subsequent cooling may initiate the transformation of retained austenite to Martensite. The density of austenite's face centred cubic structure is higher than Martensite's body centred tetragonal structure, so that retained austenite's degradation will push the neighbouring Martensite outwards, causing warps or even cracks. The tempering process generally helps alleviate the possibility of the retained austenite's transformation at some point imminently or indefinitely in the future by providing enough energy to the metastable crystals to transform instead into stable ferrite and cementite.

There is a specialized approach to quenching known as marquenching or martempering, in which a piece is quenched into a high temperature liquid (usually salts) long enough to equalize the piece's temperature at a point just above the Martensite start temperature. After this uniformity is achieved, the steel is allowed to cool across the Martensite start and Martensite finish temperature band. Although often done in still air, this requires a fairly thin cross section for the centre to precipitate Martensite quickly enough before other phases begin to form.

Austempering and Bainite
Austempering introduces another meta-stable form of the iron-carbon lattice called Bainite. The two variations, upper bainite and lower bainite, form by holding the steel at a temperature slightly above the martensitic start temperature without first forming ferrite and cementite from the austenite which it precipitates from. Generally, the steel is quenched from just above critical to the martensitic start temperature, where it is held in a medium such as molten salts at a consistent temperature for a long period of time. Because bainite is not formed rapidly like Martensite, thick cross sections can have extremely long decomposition times to form fully bainite parts.

Similar to pearlite, bainite is comprised of ferrite and cementite. Instead of pearlite's lamella patterns of alternating ferrite and cementite, bainite forms acicular cementite formations surrounded by the softer ferrite. 

Bainite exhibits an increase in hardness as the temperature at which it is precipitated is lowered. That bainite, lower bainite, is stronger than upper bainite, which precipitates closer to the Martensite start temperature. In both cases, bainite has a higher toughness, ductility, and reduced distortion when compared to Martensite tempered to achieve the same hardness. Because the bainite formation does not need to be tempered to relieve the Martensite issue of brittleness, the lack of regions of pearlite means that there is also superior wear to Martensite of a comparable hardness.


Transformation products of Austenite and Martensite (eutectic steel)
From "The Handbook on Mechanical Maintenance" by K.P. Shah

Tempering is, simply put, heating steel to a certain temperature and holding it there for a certain duration. The temperature more than the time effects how much Martensite is converted back to the stable forms of the iron carbon lattice, but both work together to give energy to the metastable Martensite and allow it to overcome the threshold energy by which it decomposes. As temperature increases, a greater percentage of Martensite is able to degrade (those crystals of a certain required dislocation degradation energy and all those with a lower threshold). As time increases, some crystals 'pinned' by lower energy crystals may drop into lower energy decomposition states. The decomposition of Martensite leads to a decrease in hardness but increase in ductility and toughness.

During the tempering process, high stress Martensite decomposes, and the subsequent reduction in lattice unit size relieves the associated volumetric strain. First, metastable carbides precipitate within the Martensite crystals, followed quickly by the decomposition of retained austenite to the stable ferrite. If the temperature is high enough, the initial carbide formation will instead yield cementite. Carbon migration out of the Martensite allows it to form ferrite, which is stable and of much greater ductility and toughness.

Excessive tempering times, usually at higher temperatures, the Martensite is entirely degraded into ferrite and cementite, but instead of forming lamellar pearlite, the cementite collects into spheres. This spheroidized state is extremely malleable and often times exceeds the softness of a fully annealed piece of the same alloy.

It should be noted that introducing additional alloyed elements into the steel dramatically changes the rates of dislocation diffusion, pinned dislocation energy, and the response of Martensite to tempering.

Additional Concepts

Effects of Temperature on Diffusion
As temperature increases, both interstitially and substitutionally alloyed elements into the iron lattice are better able to and therefore more rapidly move across concentration gradients. Homogenization therefore is an effect of both time and temperature. The most prominent case of diffusion is that of carbon on the surface of steel. Whether by the introduction of excess oxygen in the forge atmosphere to strip carbon for the formation of CO2, or the introduction of carbon to carburize steel, there will form a gradient on the surface of the steel of regions either carbon rich or carbon deficient. The depth of this gradient before reaching homogeneous steel increases approximately linearly with time, but exponentially with temperature. Finally, interstitially dissolved atoms such as carbon are better able to move through the lattice as opposed to substitutionally dissolved atoms, such as chromium and manganese, which take significantly longer to diffuse.

Hot Short
Hot shortness is a phenomena where impurities in an alloy, such as sulphur, bind with iron and liquefy. There are a variety of elements which, when bonded with iron, will form a liquid at temperatures well within the range of normal forging conditions. This liquid, usually Iron Sulphide, melts and is drawn into the grain boundaries of the steel. Having a thin film across the grains drastically weakens their bond to neighbouring grains, and causes the steel to crumble when forged. Even extremely small amounts of sulphur, phosphorous, and other impurities can cover incredibly large areas. To combat this, the introduction of manganese instead causes these impurities to bond with it instead of iron. That Manganese Sulphide or equivalent compound melts at much higher temperatures, virtually eliminating the hot short problem. 

Tuesday, June 21, 2016

The Luthier: Part XIII- Finish, Hardware and Strings

It's been a little while since I've shown any progress on this, and I was honestly expecting to be done by now. This was intended to be the final post, but due to the back order of the material for inlay on the fretboard, it may be some time yet before that has arrived. Between then and now, I also decided to try out some amplification options (since it was originally going to be purely acoustic) so that will be coming at a later time as well. Finally, the unforeseen delays will also give me an opportunity to record some of what this actually sounds like.

For now, I'll be finishing up a few details on the overall construction, applying the finish, and adding some hardware.

First up is cutting down the nut block to final size. The material is some sort of synthetic bone and is extremely hard. There was no good option for shaping it, so I eventually resorted to chisels and a bit of light file work to get it flush with the wood.

With the ends to the width of the neck, I also needed to round over the far edge. Since stringing and playing it a bit, I have since made some adjustments to the height of the nut and the depth of the strings with regard to the first fret.

To string it, I needed to carve out six equally spaced grooves for the strings to sit in. Later on, I actually spread them out a little farther by reducing the empty space between the outermost strings and the edge of the nut. The first stringing revealed that they were too close together for it to be played without extreme difficulty in pressing strings without hitting the ones beside it.

To establish a groove on the nut, I used the point of a triangular file, then opened it with a thin dovetail saw. Having the corner that the string is pinned on through its tension needs to be on the fretboard side of the nut rather than the headboard side. Without matching or even exceeding the angle of the headboard, the strings rattled quite a bit even when under full tension.

Now that the last of the shaping is done (still rough on the depth of of the slots in the nut), it's time for finishing. Over the process of building this, I read somewhere that the fretboard is typically not finished with the same product as the rest of the wood. Not sure why or if this is even true, but I went with it. After all, it is easier to add more finish to plain wood than it would be to remove it later. So, I masked off the entire fretboard face (leaving the edges exposed to they will receive finish), making sure to press the tape into the corners of the frets so the finish does not wick into that small space.

The finish I used is a semi gloss instrument varnish from Luthier Mercantile International. I expected this to be much more glossy than it actually turned out to be, but I think I actually like it better this way now that I've looked at it for a while.

To apply it, I used a folded paper towel for the first few coats (for lack of anything else available) and eventually moved to a foam brush. I've found that the direction of the strokes greatly impacts how light reflects off the surface, and may end up going back and adding a few more to even things out.

Between coats, I sanded the entire thing with 600 and 1200 grit sand paper. The first few coats were a bit rough, as the wood's grain variance tended to absorb the finish with a great variety. Once the entire surface was sealed, it grew easier and more consistent. All in all, I put on somewhere between 8 and 10 coats, but it's been so long now that I cannot entirely remember.

In spite of my efforts to prevent wicking into the frets, a bit of the finish found its way in there. A quick touch with chisels and sand paper brought it all back into order.

Here we are with the worst of the capillary action. Fortunately it was not worse than this!

Now that it's all sealed and sanded, I can install the tuning pegs. For lack of an electric drill, I once again use the brace and egg beater. Although the screws are small, I do not want to risk cracking the sapele of the neck stock. A few pilot holes and we're in business.

Screwing it into place was trickier than I expected. These little screw drivers are awful at having any sense of torque because the shaft is precious larger than the shank. In the end, I put a driver bit in the egg beater and screwed it in that way.

Next on the agenda is the tailstock. I did not keep this one, but I did not take any pictures of installing the second one because the holes were more or less the same. Aligning the tailstock with the strings was tricky because the heel of the instrument is not perfectly flat. As a result, moving the tail to the left actually twisted the string end to the right, to an extend, before swinging back around to the left. It took a lot of trial and error using thread as test 'strings' for alignment. Once the outermost two sat evenly on the lowest edge of the fretboard, I taped the tailpiece in place and drilled some pilot holes.

And now we're finally stringing it! Many, many months of work has led me here and I was a bit nervous that it would collapse under the tension (which spoiler, it did not).

Stringing from thickest string to thinnest seemed the most logical approach to me, as those would require more tension on the neck to tune, thus pulling the other strings out of tune the most. It probably did not matter, as I went back and forth a bunch anyway as it settled.

Since the tailstock was not in place when I did the rough filing on the nut, I had to finish them one at a time as I strung it. Ultimately, I was looking for an equal spacing for each string between the bottom of that string and the top of the first fret. This distance is important in determining how easy it is to play (how far down you need to press to engage a fret). Too much, and it is really difficult. Too little, and the strings will probably rattle when strummed or plucked, which is no good.

Some more adjusting, using the saw at an angle so the string is pinned by the corner on the right side of the picture (fret side) rather than the left (peg side, which would cause it to rattle).

It's finally strung! Since I did this semi-concurrently with the stuff in the last post, I did not initially have the bridge made for this moment. I was extremely worried that the entire thing was a horrific failure when it did not produce any sound  when played beyond a faint death rattle of a whisper. The bridge resonance into the body is insanely important.

The last piece of hardware for this post is the strap posts. After some design deliberation, I found these ones. They are tapered ovals as opposed to the more common circular posts, and I am quite fond of them. They make for a nice and secure hold for a strap without protruding very far from the body.

Installing them was a bit difficult, as the brace could only turn about 2/3 of the way before I had to lift it out of the screw and return it to the initial position. In the end, it all worked out.

Here we are with the ebony/bone bridge in place. I have to do some work on this one, as it is a bit too tall. I did not realise how important it is to account for neck angle and bridge height when I began, so the strings still sit a bit far off the body end of the fretboard. There is not much more I can do to lower that (lowering the bridge makes the strings slide and rattle because the tension angle is so small) but I have learned to adapt when playing it.

Next up, I'll hopefully have the fret markers and the internal pickups for connecting this to an amp. And, maybe then you'll finally be able to hear what it sounds like!