Weeks 12-13: Neck work

This post covers another two weeks of work in the shop - pretty much all on the neck now.

Roughing out the Neck

Prior to gluing on our fingerboards, which we previously trimmed down to the correct widths at the nut and 14th fret (where it will  meet the body), we cut down the neck blanks to the size of the fingerboard.  This was done on the bandsaw after the lines defining the top and bottom edges of the fingerboard on top of the neck were transfered to the back.
The headstock shape I'm using is based on a classic Guild headstock, like the guitar I've had since I was 16 (a late 60s or early 70s Guild D-35).  I traced that design as best I could, but then had to work it down to a slightly smaller size to fit the material  I had.  I had to join up two pieces of the extra walnut from my back and sides to have a piece large enough to glue on for the headplate, and this became a limit on the size of my design.  The design was rough cut on the bandsaw and will be finished by some combination of a rasp, file or sandpaper.

Gluing on the Fingerboard

The fingerboard position has been kept in the correct position by a couple of pins that were inserted at the 1st and 13th fret.  The truss rod was also glued into the neck groove we did in the previous class at the same time that the fingerboard was glued on to the neck.

The glue up is straightforward with a generous amount of glue laid into the groove for the rod, and then all over the neck.  The fingerboard was held in place with a long caul so that clamping pressure was even across the length of the fingerboard's edges.

Inlay

The only inlay on this guitar is for the fingerboard dots at the 5th, 7th, 9th, 12th, 15th and 17th frets.  Two dots are used at the 12th to designate the octave.  The dots I used are mother-of-pearl with a 5mm diameter.  The inlay just requires marking a center position and then using a hand drill to make a shallow hole for the dot.

Each dot is set with some super glue.  Then all of the dots and the fingerboard were sanded.  I still need to go over mine one more time with som 00 steel wool. There are some small dots put in with plastic along the top of the fingerboard as well.  These holes were made on the drill press, then a small plastic stick was inserted in the holes and cut off.

 

 

Frets

The fingerboards we are using were fully serviced before we got them: a radius had been applied and the slots for the frets were pre-cut.  Our job is just to install the frets.
We're using standard nickel-silver fret wire.  Each fret is cut a little long for the slot and then hammered into place with a 'dead-blow' hammer that kicks back very little.  Each fret is tapped in at the top and bottom so that the tang grabs into place.  Then a series of taps from the middle out to each side sets the wire fully into the slot where it is held by the tang.




After the frets are installed, they are trimmed to length with a pair of nippers.  A small straight edge is used to check that none of the frets are sitting
higher than the others.  Any found to be proud are given some extra taps to set them in deeper.  Then a mill file is run along the edges to dress and clean the frets.  The file is held at a 60 degree angle in order to create a bevel .  Each fret can also be dressed with a small file to create a slight horizontal taper at the ends.  Out necks our now ready for carving.

Finishing

We have also begun sealing the top, back and sides with a couple of coats of thinned shelac (a 50-50 mixture of shelac and grain alcohol).  The top was sealed first in order to keep any color that might leach out of the sides from getting into the lightly colored spruce.  This can be a significant issue for rosewood, but didn't seem like a big problem for the walnut I  am using.

Moving on: Weeks 9-11

I've been having a hard time keeping up with this journal due to the arrival of homework for my fluid mechanics class.  May be a little over committed on the education front right now.  This entry will catch up over the last three weeks of finishing off the body by installing the bindings and setting up the neck and fingerboard.  We've also begun finish sanding the bodies.

Top and  Bottom  Bindings

In preparation for laying in the bindings, the excess top and bottom wood overhanging the sides was trimmed off with the router using a flush bit.  No special jig is required, as this operation is just in preparation for routing the ledges for bindings and purflings.

Once the excess was removed, a ledge was routed for the binding.  Again, a straight, downward spiraling bit with a guide was used to create the ledge on the top and on the back.





On the bottoms, I am using the koa wood binding by itself.  It is installed with yellow wood glue.Here is a different guitar set up for the installation of an ivroid plastic binding along the bottom ledge.   The two pieces of the binding are squared off to create a clean joint at the neck end of the guitar.  One side is glue most of the way in and then trimmed to meet at the center line under the end graft.  The second piece can then be laid in and trimmed for the cleanest joint possible.

For my top, as well as the koa binding I'm also using a decorative purfling strip.  In order to install the purfling, an additional shallow ledge is required.  Here a second router is adjusted to the correct depth with a bit offset from the guide to match the width of the purfling strip.  This creates a "staircase" ledge.  As usual, the router gave me some trouble and I ended up with a deeper secondary ledge.

This provided the opportunity to use a slightly thicker purfling with an extra color band through it.  It happens that this  additional band is koa and so matches my guitar well.  It also has some consistency with the elaborate rosette that I ended up with.  The picture to the right shows both the purfling and the staricase ledge for the binding and purfling.

	I worked at home to finish installing the purfling and binding.  This is an operation that requires a considerable amount of masking tape.  The challenge on this operation is to glue in all four pieces, 2 stretches of purfling and bindings each, in a single operation.  To set up, masking tape is laid out in 1 inch intervals.
I was fortunate that by working at home I would have the skills of the new master luthier in the family.  Still, getting all of the pieces laid down and then 'clamped' in by the tape within the 5 minutes of open time allowed by the glue was a challenge.  One advantage of working on the top is that a joint is only required at the butt end by the graft.  The neck end does not have to meet as it will be covered
	by the neck and fingerboard. Here's Jonah showing off our work.  Kind of reminds me of a post-operative patient from a nose job - can't see the results until the bandages come off.
Here's the patient without the  bandages, ready to go back to the shop.  I have a few narrow gaps between the top and the purfling strip, generally less than 0.5 mm that I'm in the process of filling with a mixture of sawdust and glue .

Neck Setup

This picture shows the neck and fingerboard blanks that we are starting with along with Edward's new jig for figuring the angle of the neck with respect to the sides.  This is never exactly 90 degrees, so this joing helps to set a horizontal line along the top, matching a tangent to the slight curve of the top.





As you can make out in the photo to the left.  A small amount of clearance, about 9 millimeters is left between the bottom of the finger board and the top of the guitar at the bridge.  The fingerboard will actually dip down slightly when it is glued on.  My neck angle did not require adjustment.  Using this jig, however, does allow for slight increments to be identified on the front of the neck blank to be removed in order to get the tight fit with the body.  material was removed from the front by sanding it against a circular sander using a thin wedge to change the angle of the neck.

Once the neck joint was put in the correct plane, the holes in the neck block were used to identify the location of the two bolts in the neck.  These were drilled out and self-tapping insert installed for receiving the end of the neck bolts.

 

Fingerboard

 

The fingerboards we are using come set with a scale length of 25.4 inches (the length of the first octave from the nut to the twelfth fret).  The blanks for these are rectangular (see example on LMII) and must be cut down to the proper shape.  The fingerboard tapers up from approximately 1.75"/ 45 mm at the nut up to 25 11/16"/59 mm at the 20th fret.  Here is my fingerboard cut to those specification.  Two lines are marked at the 14th fret which marks the division between the body and the neck.

A centerline has been drawn down the fingerboard to match the centerline of the body which has also been extended down the neck.  A small wire brad has been used to pin the fingerboard to the neck at the 13th fret (small white circle in the photo) and another one at the 1st fret.

 

Bridge

 

Setting up the bridge is one of the most important steps for getting the guitar ready to play.  The bridge must be centered property and the line created by the bridge saddle must match the scale of the fingerboard to ensure the guitar is tunable and playable.
With the fingerboard set in place, the bridge can be aligned from top to bottom using reference lines off the sides of the fingerboard.  Two long straightedges are placed along the sides of the neck and their center is checked against the centerline of the body.  The bridge is centered between these two straightedges and the side positions marked with masking tape.  The bridge can then be moved along the centerline between these pieces of tape.


Using a thing ruler laid in the tweflth fret to define the location of the first scale, the bridge can then be offset vertically from this location.  Theoretically, the distance from the 12 fret to the bridge saddle, a second scale, should be equal to the first.  This distance is increased slightly, a technique known as compensation, to allow for the
depression of the strings and for eventual compression of the guitar due to tension along the neck and body by the strings.  In the case of this project we are compensating by an additional 2 millimeters at the 1st string (high E) and 4.5 millimeters at the 6th string (low E).  Different tunings or string types would affect the amount of compensation used.  With the bridge in place, two holes are drilled through the 1st and 6th string holes, the top, and the bridge place to permanently place the bridge; although it will not be glued on until later.

 

Truss Rod set up

The neck of a steel string guitar is supported by an adjustable truss rod that serves to counteract the tension placed along the neck by the steel strings.  The truss rod (here is an example from LMII) runs from the headplate through the neck into the body of the guitar where it ends up close to the transverse brace.  In order to insert the rod, the groove is routed out using the jig shown at left.  The jig is aligned at the neck joint and along the centerline of the neck.  A plunge router is used in two or three passes to rout the groove out to full depth.




As we switch to working on the neck, we're also sanding down the bodies in preparation for finishing.  The first sanding was with 120 grit paper; this removed excess glue and any major irregularities in the surface of the wood.  My top is light enough that this sanding was sufficient for developing the final tap tone on my guitar.  Some tops are sanded down a few more hundredths of an inch along the bottom and outside edges in order to increase response, especially in the bass range.  I've also started to fill some small gaps with a mixture of sawdust from excess pieces of spruce or walnut to fill gaps along the binding and purfling.  The next sanding will be with 220# as a final step prior to finishing.

Class 8 and 8.5

Last week and during a short class last night we worked to finish our tops and on gluing them to the body.  I have to say that I find myself challenged to perform even basic steps cleanly at the moment.  I'm not sure why things have been so difficult for me - unreasonable expectations, false sense of skill, general winter malise - but I've been messing up on some very basic steps.   Anyways, the work over the last two weeks is not presented in chronological order since I've been moving back and forth between tasks over the two classes.

Triming the Back 

One further step before finishing work on the top was to flush trim the back that we had already glued on.  It's been put face down so that the edges could be trimmed flush.  I've marked the direction that I want to move the router, working in from the top of the curves, so that I don't rout against the grain.  The router is equipped with a flush trimming bit - a guide below the bit sized to the bit prevents the router from traveling in any deeper than the sides against which the guide runs.  Hence the back is cut flush to the sides.

Trimming worked fine.  To prepare the body for gluing on the top, we also sanded the sides and kerfing on the top on a sanding dish with a 45' radius.  This slight curve is meant to add more stength to the top and can improve tonal qualities.   However, this was another area where I got myself into trouble.

It's a little hard to see in this picture, but despite using the sanding dish, I managed to overwork my sanding and end up with one side sanded down more than the other.  The picture shows the  remaining difference after Edward helped even things out using a wooden block plane to remove small amounts of wood from the high points.  It will be hard to see in the finished guitar, but the trebble side of my guitar will be slightly deeper than the bass - creating a slight wedge shape.  Edwads suggested that maybe it will be easier to play as a result.....

Finishing the top

Below I've tried to illustrate some of the further steps taken in the process of paring down the bracing with the intent of keeping the top strong while bringing out its 'tap tone'.  Tap tone refers to the sound eminating from the top when held up and tapped.  The goal in our process is to try to get 4-5 seconds of sustain out of the tops, with a good clear sound that has strength in the lower and middle ranges.

Initially, much of the work done was to plane down the X-brace and scallop a  smooth spiral curve into the ends of most of the braces.  Generally, this is a step I can handle at this point, but still with some challenges discussed below.
	The scalloping on the X-brace and tone bars was also done in the middle of these longer pieces of wood.  Wood is also removed with a chisel from the sides of the braces, trying to created a domed  'cathedral' shape along the cross section.  Trying to do this with any elegance with a rounded chisel has been giving me fits.
The small finger braces and the tone bars are actually curved down on the outside edge to become flush with the top.  Inside the braces are down to just a couple of millimeters for a total thickness including the top itself of about 5 millimeters.
	The ends of the transverse brace are also scalloped and the middle is 'cathedralized'.   The end of the X-brace at the bottom of the picture gave me problems.  When I tried to scallop the end, the grain gave me problems and took a bit of a nosedive.  I  was left with sort of a flat angle down leaving very little wood at the end.
The flat brace above the transverse brace needs to have a groove rounded out for access into the truss rod with a wrench.

Gluing the top

Through this process we got a resonable tap tone out of my top.  I haven't been especially  happy with the cleanliness or the elegance of my carving.  And generally, I continue to be hard on my top, adding a couple more dings.  I'm not sure why this has been so difficult for me this time around.  As with the bottom, notches are cut out of the top to fit the braces (X-brace and transverse) into the sides.

These allow for a stronger fit with the sides.  Initially, the notches are sized for fit horizontally, then further wood is filed out so that the main surface of the top makes a flush fit with the kerfing.

A bead of glue is laid all the way around the kerfing and over the end blocks and then the top is put on and clamped.  Next week we'll finish off the bodies by flush triming the top and doing some initial sanding of the sides.  Then we'll rout out grooves around the bottom and top seams to allow for the  bindings.  Despite my travails, I still think the guitar will look alright.

Class 7: Back from Break

Class met again last week for the first time in four weeks following a two week winter break and a snow day.

Over the Break

I went in once over the break to work on catching up; I glued most of the bracing on my top and installed an end wedge from a piece of Koa that should match the bindings I'll be using.  There are two purfling strips surrounding the wedge; the wedge shape is used to try and get a tight fit with the sides.  By cutting in this shape, the wedge can be pushed into the sides until it fits.  I ended
up with a slight difference in the angle of my wedge and the angle of the slot in the sides, so the fit wasn't as tight as it could have been, but  cosmetically it should be fine.  This week I cut the excess wood and purflings flush to the sides with a back saw.

Fitting the Back

Another step tonight was notching out the sides and kerfing so that the braces on the back would fit snuggly within the sides.  This increases the instruments strength (in case it's dropped).  The notches are made by laying the back onto the sides while they are in the mold and marking the sides of the braces.  The notches are then cut out by making a shallow incision in the side for each notch, then using a small chisel to cut out the notch.
The trick, which is hard for me, is to not overcut the notch with the saw.  It's better to start with a shallow notch and to work it out and deeper with a small file.  The fit with the back can  checked by putting a small light inside the mold and then placing the back on top.  The seam between the back and sides can then be checked for light, indicating a brace that may need to be made deeper.

Glue Up

The sides are back were glued up by running a generous seam of yellow glue all the way around the kerfing.  Leaving the sides in the mold, the back is placed onto the sides and secured with a generous serving of clamps (that's about 2 dozen wooden cam clamps at about $18/clamp in this picture).  Clamping pressure is exerted down the sides with the bottom of the clamp pressing on the side, not on the mold.




Here's the results.  Some clean up of the squeezed out glue is still needed.  Also, the back still extends out past the sides - but
it's a good milestone.

Progressing the Top

When I came in over the break I glued on most of the top bracing.  At the start of class I still had two long braces to glue on, extending out from the X-brace.  Once these dried I began the process of planning and curving the braces.  These are the first steps in tuning the top - probably the single most determinate process in giving life to the guitar.  The goal is to remove wood from the braces in order to lighten the top and allow for greater sustain of the sound.  The top is the vibrating membrane that gives the guitar depth and volume of sound.


At the same time, there needs the braces need to remain strong enough that the top can resist the longitudinal forces applied at the bridge by the strings.  This is a compressive force that tries to bring the neck and body together.  Removing wood from the braces, therefore, must be done with an eye towards retaining strenght.  The initial step is to plane down the X-brack and curve the ends of the other braces.  From there we'll go towards scalloping the braces - adding horizontal curves to complement the vertical curves.  We'll also finish the tuning next week by sanding the top.

Unfortunately, I've set my top up to need some extra sanding.  While working on curving and planning the braces, I left wood fragments between the top and my work surface, thereby adding a bunch of small imprints and one good divit.  The little ones will hopefully sand out, but the larger divit is probably there to stay.  All in all, lutherie remains a challenge.  I'm not yet at the point where I've anywhere near full command of the steps
that I'm executing - probably be a number of years (and a few more instruments) to get towards any basic command of the tools and skills.

Class 6: Progessing the body

 Last Wednesday's class (12/15) had me working on all parts of the body: sides, back and top.

Sides

The sides that I glued up with the end blocks last week were ready to prepare for gluing on the top and back.

The first step was to sand the back side on a circular sanding dish (seen to the right) with the same 15 foot radius curve used throughout the back.  This will prepare the edges of sides, and
especially the blocks at the neck and heel, to hold the same curve that the back is being set to.







Following the sanding, I started to glue in the kerfing that will run along the inside edges of sides along both the top and back.  The flexible kerfing provides a surface to which the top and back can be glued, extending the glue surface past the 3-4 millimeter thickness of the sides themselves.
This is a fairly simple operation, but one, as seen in these pictures, that make extensive
use of clamps.

End piece

Edward gave a demonstration during the class of fitting an tail piece in the body.  The shape of this piece is angular (long trapezoid) so that the piece of contrasting wood can be fit tight into the cutout made in the body.

This cutout is right over the heel block; the tail piece is decorative but also used ot hide a less than perfect fit of the sides.  The side joint at the neck end will be covered by the neck itself.  The notch is cut using a pull saw, then cleaned out
with a chisel.  I'll be using a piece of Koa to match the bindings, and will probably add black purfling strips for contrast.

Carving back braces

I worked on carving the braces on the back of my guitar.  Carving the braces reduces their mass while trying to preserve their strengths, hence the use of a curve.  The braces are tappered down to 5 mm at the edges where the ends of the brace will be fit into the sides.


Carving is done with a chisel, in successive strokes until the top of the curve is set about 60 mm from the edge of the top.  The trick to get a gentle cuve that preserves mass towards the center of the  back.  My braces tend to be carved a little on the steep side.

Top

I worked further in this class on gluing in the braces on the top.  In the picture, the transverse brace is being glued on.  This brace has a 1/4" hole drilled through the center to accomodate the end of the neck truss rod.  The hole is centered 4 mm above (below) the top, so that the outside edge of the hole is just inside the brace.

I also cut and glued the bridge plate from a scrap pice of walnut.  This is glued directly under the bridge to accommodate the ball ends of the steel strings which pull back up against the top.  The plate protects the soft spruce.  The piece is cut slightly off the direction of the grain so that the ends do not pull against a single fault line in the grain.

Back fitting

Edward provided a final demonstration of how to fit the back to the sides.  I'll be working on this when I return from our break.
The back is centered over the sides and the location of the braces is marked with a pencil on the outside of the sides.  It's important to remember the cuts for the braces run straight  across, not perpendicular to the outside curve of the side.










Next a back saw is used to make very shallow cuts for the edges of the notches.  Better to cut to shallow than too deep.

















The notches are then cut out with a small chisel.  Each joint can be tested by placing a small light inside the guitar and placing the top over the sides to see if any light comes through between the back and the side.










I'm hoping to come in once over our winter break to get everything else finished up on the sides and top so that I can begin fitting my back once class starts up again.

Class 5: Muti-tasking

Half of our class was missing this evening, which made it a little easier to spread out and get a number of tasks done.  Tonight I finished out the soundhole rosette, did the layout for the bracing on my top and back, cut the X-brace for the top, and glued up the back strip and braces on the back.

Finishing the Rosette

Completing the rosette at this point was down to just bringing the strips of paper and veneer added the week before down to the level of the sound board.  The strips were riding about 1/16th to 1/8th of an inch higher than the sound board, so using a sharp chisel, I worked them down to be closer to flush.  From there, sanding with a small block at 80 and then 120 grit brought the trim level.  A final sanding, prior to later final sanding for tap tuning and finishing, was down with some 220 and a block.  The complete rosette, I'm happy to report, no longer looks like an accident.  I'll try not to go down this course next time.

Gluing up the Sides
Here's a couple of shots,  from the bottom and the top, of the sides being glued up with the end blocks.  Spring clamps were added to the heel block to bring the sides up tight.  Cam clamps were used, three for each block, to bring the whole a assembly together.
The entire assembly is now sitting in the mold in the shop until next week.

Laying out the Top
The heart of the guitar, so to speak, is really the sound board.  This is the component that provides the core vibration and response that give the instrument the bulk of its character.  The top must be flexible, but strong enough to stand up to the longitudinal forces created by the pull and compression of the steel strings.  The layout of the bracing underneath the sound board, therefore, is perhaps the single defining design.

The design used by Edward on his steel string guitars is built around a classic 'X-brace' pattern developed by Martin (and possibly others) in the 1930s or 40s.  The 'X' is the two long braces running from the lower to the upper boughts, crossing and joined underneath the sound hole.  This pattern has been transferred from a template onto my guitar.  The transverse brace runs across the opposite side of the sound hole, and numerous finger braces spread out from the primary X.

After laying out this pattern, I did several test cuts of the X-brace joint before finally cutting this joint in two pre-cut
braces.  Top braces do not have a radius along their length, even though the top will be glued up on a support that will help to provide a curve with a 30' radius.  This curve is gentle enough it does not require the curvature to be set into the  braces before gluing.



Setting Back Braces
The back curvature, however, is more defined than the top.  We are using curvature with a radius of 15 feet.  In order to give some additional support to the back, a center strip of think spruce is glued down the middle of the back.  All of the supports for the back are glued on using a support that already has this curvature.  This is one of the many unique pieces available working in a shop that new luthiers must develop.  There is a caul with the same 15' curve that will be clamped over the back strip in order to provide support during the gluing.

First the back strip is put in place with some help
from masking tape. Masking tape is a great help to lutherie, but one of only a few tools that are cheap and readily available.   In addition to the back from and caul, we are using prebuilt templates and molds for the sides along with additional jigs (such as the router circle cutting jig that got me in to so much trouble) to help move the process ahead.

Another essential element of lutherie is the use of clamps.  Shown here and below are the standard wooden cam clamps that are used throughout the process of gluing braces and many other parts of the guitar.  They can easily run $15 to $20 each, and as you can see in the pictures below, we can easily use 12 or more at a time. 

After the back strip has dried, it needs spaces
set into it for the braces.  These braces, as mentioned, already have a curve set
to their bottom and have been given a preliminary shape on top as well.  Four are glued in to the back to give strength.  Setting clamps for gluing is its own art forms could all be set at the same time.






 Below I found space for 17 clamps on the back so that the braces could all be set at the same time.

 

Another subtle skill, as in all woodwork, is getting just the right amount of glue to ensure a firm joint, but not so much that things get messy and look sloppy.  An example of the latter is shown in the close up below.

Next week I will be fitting and gluing on the top braces as well as putting in kerfing strips along the sides to create a glue surface for the back and later the top.  There is a bunch of work ahead in carving are braces and tuning up the tops to complete the assembly of the guitar body.