Terry Docherty Guitars

“A Work in Progress” This is a brief, stage by stage pictorial blog on the building of a custom copy of Gibson’s J50 steel string guitar. It is in fact the blond headed version of the iconic J45 which first made an appearance in the 1940’s and is still in production today. A dark sunburst finish was used on the J45 at a time when good materials were scarce and the sunburst was used to hide flaws in the wood but the blonde J50 signalled the use of better grade materials. This guitar was commissioned by local guitar maniac, Mike Slaughter. Mike’s a great performer who knows a thing or two about guitars and he also knows what he likes so after some deliberation, he asked me to make him this guitar as the twin to his J45 which he loves so much and to which I recently fitted a Fishman Matrix Infinity under-saddle transducer system. The J50 will eventually have the same system installed. Stage 1: This guitar will be made from AAA grade Indian Rosewood with a very special top of Adirondack or Eastern Red Spruce. The photos here are of the top and back, jointed and thicknessed. This very stiff top wood has been taken down to 2.5mm with the sides the same and the back at 2.3mm. The herringbone rosette was inlaid before thicknessing as was the back centre strip of rosewood and boxwood.
Stage 2: The sides are soaked in water for a few hours then bent to shape on a heated aluminium pipe, using the mould as a template, which is split in two at this stage to cope with the overlap to be trimmed off later. The sides are clamped hard in the mould and left to thoroughly dry out after which they “set” to shape with little or no spring tension. It takes practice but the bending operation can be done surprisingly quickly. The mould itself is made of four layers of plywood glued as two blocks and then using a half template for perfect symmetry, the body shape is scribed onto the blocks followed by some very careful cutting out on the band saw. The two halves are joined at each end and set onto a datum line drawn on a base board. The mould is kept perfectly centred while the mahogany heel and tail blocks are glued in place and indeed for the whole of the construction process.
Stage 3: Completing the carcass The carcass is now complete with linings and side struts installed. The side struts will stop the progress of any cracks should the instrument be subject to accidental damage."
Stage 4: Bracing the back and Top. The curved bracing for both back and top is made from vertical grained Adirondack spruce. The long plywood cauls and flexible backing plate spread the load evenly along the length of the braces and ensure a tight fit and a very thin glue line. The centre joint of the back is strengthened with a cross-grained strip of spruce. Notches are cut in this strip with knife and chisel where the braces cross it
Stage 5: Bracing the back and top. The back is braced in standard transverse pattern with the ends of the braces scalloped to "loosen" the back and to allow the brace ends to be fitted snugly into the linings. The top is the "business" end of any instrument and I'm using using a standard "X" brace pattern. There are various ways to shape and scallop the profiles of the bracing but I get best results with the "taper" method which leaves the cross section square whilst progressively loosening the top toward its perimeter. I feel this allows the sound waves to pick up speed as they travel outwards from an oscillating bridge and the top to vibrate increasingly strongly towards its edges. Its all matter of judgement, depending on the initial stiffness of the top, as to how much wood is removed from each brace. The pitch of the top when "tapped", becomes progressively lower as wood is removed and the top is loosened up. The same applies to the back but ideally, I want finish up with about a tone difference between the two plates when tapped. In this case, the back taps to a D with the top sounding to a C so I'm very happy at that. .
Stage 6: Fitting the back and top I normally fit the back first though the plates can be fitted in any order. I begin by making sure that the plates are centred to the pencil marks on heel and tail blocks. I do this by carefully laying the mold and carcass onto each plate and marking with a very sharp pencil on both the braces and the linings, the points at which braces and linings touch. The ends of the braces are trimmed to fit inside the sides of the carcass and then with junior hacksaw, knife and chisel, the notches that will house the braces are carefully cut, making sure that the depth needed to do this, is not exceeded. The photos show the notches for the top bracing, clearly. This is very exacting work and sloppiness is not permitted. The plates must fit tightly without force and once done, the plates must remain dead centre. Because the plates are arched over curved braces, a certain amount of wood must be planed from the sides and linings at the upper and lower bouts as well as some adjustment to the blocks. Fitting the back to a guitar is probably the single most difficult operation in the whole construction process and the back must fit neatly and without forcing any part of it down onto the linings as this will cause counter stresses which will distort the smooth transverse and longitudinal arch of the back which will then stick out like a sore thumb. Its the part of any guitar that I check first as it says so much about the level of craftsmanship and care of the maker. As with the back, I've taken great care to ensure the fit and alignment of the top before glueing and clamping (Photo attached) and I've done at least one dry run to make sure there's no distortion of the top and everything is as it should be before going anywhere near the glue pot. After about 3 hours the clamps are removed and the overlapping edge trimmed off. Its at this stage that you will really know how good your work is when checking for symmetry and true alignment. I'm well satisfied with both in this case and can move on to the binding stage
Stage 7: Binding the Soundbox Binding a guitar with wood is a very different proposition to the use of plastic found on most factory produced guitars. There are few shortcuts and it takes time to get it right, especially if you hold to the principles of the classical guitar makers in which the back and sides are seen as 4 integral panels which join up uniformly at the tail of the instrument. With this guitar I'm using rosewood binding strips (same material as the sides) to which I've superglued very fine boxwood flats, 0.6mm deep which will produce fine "gold" lines that will eventually define and accentuate the shape of the instrument and because they are wood, they must be bent to shape using the same method as the bending of the sides, (plastic does not require this). A bit of time can be saved by clamping the four wet strips at each end with bulldog clips and bending them around the iron as one, before clamping them in the mould to dry (photos 1 & 2) but take care to orientate the strips correctly to ensure you end up with 2 left and 2 right or you will be starting all over again Channels must now be routed into the edges of the soundbox to house the binding strips as well as the back boxwood purfling strips and the herringbone strip that will eventually decorate the top edge of the instrument. I described this process in my cittern construction blog where there are also photos to be seen so no need for repetition here. Suffice it to say that the utmost care is required not to overcut any of the channels and ledges but to leave everything a little proud to be scraped flush after gluing. Always practice on scrap to get the height and depth of cut right before showing the router cutter to the soundbox. Also, when cutting the ledge for the herringbone strips, the depth must not exceed the thickness of the top or you will weaken the joint between the top, sides and the linings. I always glue the herringbone separately before fitting the binding strips but it must also have a separate inner "flat" of ebony or black-dyed sycamore to give it definition and would look decidedly odd if the inner edge were left "open". After applying glue to the ledges, all the wood bindings and purflings are held tightly in place with strips of clear sellotape until the glue is dry. It's a messy operation because of the glue squeeze-out and while you can clean some of it away with a clean, damp rag as you proceed, there's always a lot of clean up required after the glue has dried and tape has been carefully removed, using scraper, thumb plane and garnet paper, the results of which you can see in this series of photos. I've deliberately left out information on the very tricky jointing and mitering of the binding strips which I'm happy to supply to anyone who wishes to enquire. Also, a good scraper, like a sharp chisel, is a joy to use and putting an edge onto a scraper is an art worthy of a separate paragraph at a later time. A final word of warning when removing tape from a spruce top. Try to identify the direction of grain run-out and pull the tape in that direction. This will avoid pulling out strips of softer, summer growth and avoid a lot of unnecessary sanding. As always, I'm happy to supply more info on this to individual enquirers.
Stage 8: The neck The neck for the J50 is being constructed from a 1metre long piece of vertical grained Central American Mahogany, famed for its lightness, strength and above all, stability. The neck blank is 80mm wide and 25mm thick and will also provide the pieces used to laminate the heel. Because these are stacked in exactly the same order and orientation as they were cut from the blank, the vertical grain will match up precisely through the vertical length of the heel. Also, when the heel is carved to a finish, the horizontal joints of the glued laminations will be barely visible and be every bit as strong as a one piece heel, if not more so. A 6mm dowel will also be glued into a hole drilled vertically through the 4 layers for additional strength but will stop just short of going all the way through. I'm putting the peghead and heel together using exactly the same method as described in my cittern blog so I'll skip some of the detail here and leave it to the photographs. The plywood cauls enclosing the heel laminations prevent the pieces from sliding out of alignment on the glue and please note the liberal use of grease-proof paper to prevent the assembly from gluing itself to the cauls and baseboard. This paper is essential to many of the gluing operations throughout the construction process and no luthier should be without a good supply readily to hand. In the same photographs you can see the head veneer being glued together prior to its installation on the upper face of the peghead. The outer veneer is a 2mm thick piece of Indian rosewood which is being underlain with a 0.5mm thick veneer of sycamore which will provide a thin cream-coloured decorative line around the whole peghead, in keeping with the rosewood/boxwood bindings to the soundbox. I don't always add the sycamore veneer but it's a nice touch that maintains a consistent decorative theme which I feel adds to the elegant simplicity that I'm always trying to create in my instruments, a theme which will be continued when I come to add the ebony heel cap and which is once again, in keeping with the best traditions of the classical Spanish guitar maker. The third photograph shows the head veneer now being glued to the peghead. The edge of the veneer that will eventually butt against the bone nut, was sanded to a 15 degree angle on the belt sander tilt table so that when in place, that leading edge moves to the vertical because of the 15 degree angle of the peghead itself. I should also add that although not visible in the photographs, the truss rod channel was routed into the neck at an earlier stage, after the peghead had been constructed. In the stages to follow you will see a novel yet very effective method of joining the neck to the body but first, the neck angle must be "set" and centrally "aligned" and the fingerboard made.
Stage 9: The Fingerboard I started with a squarish piece of AA grade ebony which needed to be levelled on both sides. This was done with several passes through the thicknessing sander, the same machine used to thickness back, sides and top. The finished thickness was 6mm. I then straightened one edge of the board before carefully sticking it down with double sided tape to a specially made steel template designed to give two common scale lengths. In this case I'm using the scale length of 24.9 inches. The template fits neatly into an aluminium mitre box and the edge of the template is machine notched along its edges, the notches fitting to a locating pin in the floor of the box. By moving the template notch by notch, the correct position for each fret is located and having accurately set the depth stop and width of cutting slot for the saw, each fret slot is neatly and cut to the correct depth using a special Japanese saw which cuts on the back rather than the forward stroke, with no need for marking out the fret positions on the board itself. Japanese cabinet makers are famed the world over, not just for their supreme craftsmanship but also for their unconventional and unique tools. Its the first time I've used this recent purchase of mitre box and saw and it made what is generally an arduous and unpleasurable task, an absolute joy and I could kick myself for not having gone for it sooner. It remains to be seen how many ebony boards the saw will cope with as ebony "eats" fretting saws. After the board was slotted, I marked on the correct taper, working from the centreline. The nut end will finish at 43mm wide and the board will be 53mm wide at the 14th fret. These lines are very carefully and accurately marked with a hard, sharp pencil followed by a knife-cut with a very sharp blade just outside the pencil line because its easier to see against the black and to follow when cutting out the taper on the bandsaw. Once sawn out, the board is clamped in the vice and each edge is straightened using an aluminium level with garnet paper stuck to its edge with double-sided tape. The sawn edge is a whisker outside the knife cut which I then make "disappear". You can see the fine hair-like sliver of ebony left by the knife cut as you approach the size required and once that's gone completely, the board is perfect. Playability is everything and you must strive for extreme accuracy with every dimension of the fingerboard. I'll trim the bottom end off the board later when I'm absolutely sure where the tongue of the board will lie when glued to the neck. That's because I don't want to see any of the rosette joint when the neck and fingerboard are finally fitted to the soundbox. The next job is to install the 4mm mother-of-pearl position dots to the face of the board as well as the side dots for which I use 1mm diameter brass wire which shine like gold when finished and which I prefer to any other material when it comes to the side dots. ( 2 photos of finished board - face and edge views)
Stage 10: Finishing off the soundbox. The final job is to rout the channel for the "through soundhole" truss-rod. It will be a "two-way" rod which can be adjusted to correct a back bow in the neck as well as its more conventional use in counteracting the forward bowing of the neck when under full string tension. The 6mm wide channel is marked with a knife and the spruce is removed first with knife and chisel, exposing the top of the mahogany heel block and the empty space between it and the main cross brace which has an arch filed out of it where the adjusting allen nut of the truss rod pokes through just inside the soundhole. Its this empty space which needs to be filled with a spruce block with a blind channel cut into it to encase the free end of the truss rod. This block is important also because when tightly fitted and glued between the cross brace and the heel block, it will make this portion of the soundbox very stiff and strong against any possible downward pressure from the tongue of the fingerboard when the guitar is under full string tension. I made the block earlier from vertical grained spruce but with the grain running at right angles to the grain of the top, for added strength. I also made it slightly oversized to be carefully trimmed and tried before glueing. This is made easier because I can see as well as feel the fit of the block through the open portion of the channel and because it is also slightly wider than the fingerboard at this point, it will minimise the risk of the top cracking where the edges of the fingerboard lie, a fault I've often seen on guitars which are inadequately strengthened and supported at this crucial part of the soundbox. The first photo shows the spruce block being glued in place with one clamp though the soundhole. The second photo shows the dremel used to rout the channel, fitted into the circle cutter which forms the level base needed to do the routing. The channel is cut with successive light passes until the correct depth is achieved, bearing in mind that the upper, flat surface of the truss rod will lie just below the under surface of the top. The photo also shows the spruce block just behind the darker coloured mahogany heel block. Job done.
Stage 11: The neck The mahogany neck was fabricated using the same method as in the cittern blog after which the truss rod channel was cut with the bench-mounted router and the double peghead veneer added. With the advent of modern glues it is possible to glue a neck to a guitar body directly, without recourse to a mechanical joint such as a tapered dovetail but the gluing face of the neck heel must be absolutely flat and set at the precise angle required to achieve optimum string height at the bridge when the finished instrument is under full string tension. If done correctly, this is as good and safe a method as any other and I've never yet had a neck fail, using it. Suffice it to say that through careful measuring, the "set" angle is achieved using a bench-mounted belt sander and tilt table after which everything is double checked for alignment and string height. The long straight edge tells me that the truss rod channel is in perfect alignment with the centre joint of the top and with the fingerboard clamped where it will finally lie, not only does it lie dead centre on the neck but the straight edge again tells me that the string height at the saddle will come in at 12mm plus or minus 1mm with a necessary bridge thickness of around 8 - 9mm. I'm very happy with all of that and can proceed to thickness and partially carve the peghead, after which the head is marked out to receive the holes that will house the tuners. Final carving of the lower shoulders of the peghead will take place once the fingerboard is glued in place. Because this is a custom copy of Gibson's J50, I've decided to use a peghead design which strongly implies "Gibson" but which is not an identical copy of the distinctive Gibson headstock. The subtle difference at the crown, I feel makes a necessary statement about this handmade guitars' uniqueness and it will carry my logo. Finally, I have also checked the truss rod for fit, alignment and length and all is in order. It will be buried in the neck under a fillet of mahogany and its upper surface will lie just below the underside of the top. The corresponding gap seen between the truss rod and the underside of the fingerboard will be filled by the same mahogany fillet mentioned above. Once the truss rod and fingerboard are glued to the neck, the rest of the neck will be accurately thicknessed, followed by final carving of the heel, neck and peghead. The whole finished assembly will then be glued to the soundbox and for the first time, it will look like a guitar, minus the bridge.
Stage12 With everything in perfect alignment and secure in the knowledge that the finished string height will be correct, its time to pin everything together so that it all goes back in exactly the right place when its time to glue up. I drill two 1.5mm holes down through the 1st, 13th and 15th frets through which pins are inserted to prevent the parts sliding about on the glue. These holes will not be seen when the frets are installed. This is done only after the truss rod has been secured in its channel and the mahogany fillet glued over it and planed and scraped level with the face of the neck The fingerboard is then glued onto the neck and the 2 pins inserted at the 1st and 13th frets, coated with soap to prevent them getting stuck. A hardwood caul is used to spread the clamping pressure as the fingerboard is glued in place, cleaning up the squeeze out as you go. Once dry and with the pins removed, the neck, truss rod and fingerboard assembly can be tried on the sound box where it is held by the two pins at the 15th fret. I clamp the tongue down tight and check that the heel is tight against the body, that the fingerboard is lying level along its length with no dips or rises anywhere and that the string height at the saddle will be as predicted. With everything as it should be, the neck assembly is removed and final carving can begin. With the fingerboard in place, the whole neck assembly is clamped face down an a narrow base-board which is clamped to the bench, and carving can begin. The pattern of the heel is traced onto the gluing face and the heel sawn out using a coping saw. I've already removed as much of the excess neckwood where it overlapped the fingerboard, on the bandsaw and using a combination of various gouges, chisels, rasps and files, the heel is carved first before moving on to the neck, the peghead shoulders and neck terminus. Particular attention is paid to the transition areas between heel and neck, and neck and peghead. The photos show the neck 90% done with a little more attention yet to be paid to smoothing out any last lumps and bumps until everything is as it should be and the profile of the neck fits my templates at the first and tenth frets. The neck and fingerboard will be finished to a combined thickness of 22mm and then smoothed down with 100 grit garnet paper. The neck assembly will then be glued permanently to the body using a most interesting method which I will demonstrate in the next section. Meanwhile, I've tried the neck on again, using the locating pins shown earlier, just to make sure everything remains perfectly in alignment and that the centre of the heel lies on the centreline of the back, as per the photo. Its at this point that you can see from the photos, how tightly the gluing face of the finished heel butts against the body of the instrument, without gaps. This will be a very good joint when completed. The whole thing now begins to take on the appearance of the finished article though there's still a bit of work to do, including radiusing the fingerboard, installing and dressing the frets and making and locating the bridge where it will eventually be glued after finishing. There's a huge amount of very exacting work goes into a guitar neck and fingerboard, the accuracy and feel of which has such a huge bearing on the instruments playability and intonation which you get wrong at your peril.
Stage 13 - Gluing on the neck This now becomes a quick and straightforward operation involving one clamp and a tourniquet comprising of a length of shock cord looped between the strap button temporarily installed at the tail, and an eyelet screwed into the heel. With a liberal coating of Titebond to the underside of the fingerboard tongue and heel, the neck assembly is slotted into place and the locating pins coated with soap are inserted. The tongue is clamped down hard using a hardwood caul, the underside of which has been filed slightly concave so that pressure is exerted towards the edges of the fingerboard when the caul is clamped flat. Flipping the instrument over, the loop is tightened as shown until really taut, pulling the heel hard against the sides of the soundbox. The hardwood caul at the tail prevents the shock cord from digging into the binding and leaving unsightly grooves. Glue squeezeout is cleaned with a damp cloth and the whole assembly left undisturbed for several hours. A light sand with 120 grit garnet will remove all watermarks. The joint is immensely strong and permanent but like every other operation, its success lies in meticulous checks and preparation. The next stage will see the fingerboard radiussed and fretted.
Stage 14 - Fretting the board I first put a 16" radius on the fingerboard with a radiussed block and various grades of garnet paper from 80 to 280 grit and finished it to a gloss with 0000 wire wool. Making sure the fret slots were clean of all dust and debris, I installed the frets via the traditional method of hammer and hard wood caul to avoid leaving hammer imprints in the ebony. Every stage of the fretting process involves great care not to mark or scratch the fingerboard. I bevelled the fret ends with a special file held at 45 degrees in a block which is drawn along each edge and ensures an even job along its length. The frets must then be levelled with a special machine-ground steel box section with emery paper attached, The flat spots left are the removed with a special crowning file after which the frets are polished with 280 grit garnet and wire wool. At each stage, the work is checked with a straight edge and strong backlight. Finally, the heel cap is installed. It is a decorative touch which has the clear practical purpose of sealing the open end of the heel and keeping the back binding firmly in place. The fine sycamore underlay lines up with the boxwood strip on the binding. To achieve this the heel had to be cut very precisely and left completely flat but with a slight angle sloping upwards toward the underside of the neck, purely for aesthetic effect. These are small but important details to which the luthier must pay close attention if the finer points of his work are to be appreciated and the finished instrument is to look right.
Ready for lacquer
Finished and collected by its new owner ............ "Absolutely flawless build quality. Thoughtful, beautiful materials, outstanding volume, tone, clarity and projection. Put simply it looks the part, plays the part and sounds the part. If you're even thinking about investing in a personal custom guitar, immediately add Terry to your "absolutely must go-to" guitar guys.One very satisfied, very fortunate and very grateful customer from start to finish" Mike Slaughter