Not only is a Brian May Red Special neck the most challenging part to design, it is also the most challenging part to make, either using hand tools and templates, or in my case by CNC followed by manual finishing. This would be the pièce de résistance of the CAD/CAM/CNC effort because manually carving a neck to a standard that I knew I would be satisfied with would likely take many months of effort and several unsuccessful attempts.
The 2 1/2 foot (30″) length of the Brian May Red Special long tenon neck was the biggest influence on the form factor of the CNC machine I needed. The Stepcraft 2/840 bed length could easily accommodate the Y axis travel required. The Z (vertical) axis dimension of the neck with the fretboard surface horizontal is 1 3/8″ (35 mm) so a stock 1 9/16″ (39-40 mm) thick can also be accommodated with clearance for suitable length cutters. It is possible that the thickness of the fireplace mantelpiece influenced Brian and Harold’s choice of fretboard and headstock angles.
I chose to make my neck from a vintage mahogany fireplace surround, not simply to slavishly copy what Brian and Harold did out of necessity, but because it is a sustainable, ecologically sound way to get well-seasoned mahogany on a budget without creating a demand for new timber. This is certainly feasible because there are many for sale at reasonable prices compared to quarter sawn AAA grade South American mahogany tonewood neck blanks. In July 2015, I eventually found a suitable fireplace surround on eBay whose seller was prepared to package and ship it via courier. It cost £135 + £50 shipping so cost about the same as three mahogany tonewood neck blanks.
Before committing to cutting the final neck, I spent a considerable amount of time planning how to execute the neck cut, and then carried out several test cuts on two inexpensive but good quality quarter sawn African Mahogany (Khaya ivorensis) neck blanks on 23 April 2017. This was possibly an extravagance but I believed that I should use a similar material during testing to be sure that the system parameters would be directly applicable to the final cut. On 19 June 2017, I cut my Mk 1 design neck from the vintage mahogany fire place and then in August 2021, I cut a replacement neck to a revised design. This process is illustrated in the embedded video below:
In the Mk 2 revised design, I corrected some original sin errors and incorporated a significant number of improvements (‘kaizen’), most notably to the thickness of the mahogany in the main section and the headstock. I also reinterpreted the region where the headstock lozenge shape meets the elliptical profile of the main section to improve the fidelity. Having improved my TurboCAD techniques in the five years or so since I began this project, I also simplified the methods I use to design each part of the neck (tenon, main section and headstock) to achieve a better result.
I took every opportunity to improve the cutting and drilling processes including CNC cutting two large 2 degree and 4 degree wedges for drilling machine heads holes in the headstock and fixing screw and bolt holes in the tenon. I also made an extended bed for my mini drill press from 19 mm plywood to accommodate them. To maintain precise axial alignment for both the upper and lower side toolpaths, I fitted a “L”-shaped alignment bracket water-jet custom cut from 20 mm thick aluminium to the T-slot machine table. Credit to Jon Underhill for providing this. Latterly, I deployed direct dust extraction by means of a Delta dust shoe and Dyson DC39 Animal vacuum cleaner. To make subsequent assembly easier, I CNC cut a slot for the brass plate which the truss rod tensioner bolt butts up against and corrected the position of the rebate which accommodates it. I also drilled six dowel locating holes to mount a perspex template which I will use to align the fretboard precisely to the the mahogany.
The original piece of timber is worthy of note. The bulk wood colour is not entirely indicative of mahogany, a buff colour yet the sawdust is a sandy red/brown colour reminiscent of terracotta and there is a slightly fruity smell when you drill into it. The density is 0.67 g/cm^3 which is nearly bang on for Cuban (genuine) mahogany (Swietenia mahogani); see http://www.engineeringtoolbox.com/wood-density-d_40.html)
Most fireplace surrounds of this era (late 19th, early 20th century) were made from genuine mahogany. As you can see from the image gallery below, the mantelpiece is not quarter sawn timber which affects the grain structure and therefore the cosmetic appearance of the cut item as you can see on the headstock where where the grain direction is diagonal. It was pointed out to me that the grain pattern on the original guitar’s headstock is diagonal too.