After making the bakelite nut for my Brian May Red Special replica guitar, I moved on to install the roller bridge, tremolo hardware, string up the guitar and set the playing action by thicknessing the Tufnol (phenolic resin) bridge shim to size. I also installed and shimmed the pickups and redesigned and cut a new semicircular tremolo cavity cover plate to fit the installed hardware.
The first issue was that the 2 3/4″ (70 mm) long tremolo bolts were around 3/32″ too long to fit in the tremolo cavity (they wouldn’t fit past the fulcrum plate in any orientation) so I had to grind them down. As an aside, I struggled to obtain 1/4″ UNF x 2 3/4″ hexagonal head self colour set screws (i.e. fully threaded bolts). 2 1/2″ and 3″ were easy enough to find but the shorter length proved unsuitable. I eventually sourced these from the Arun Fastener Company in Arundel, Sussex who stock a large variety of fasteners in imperial dimensions.
To carry out basic playability checks including checking string spacing, string distance from the edges of the fretboard and action with the supplied bridge shims, I temporarily affixed a cosmetically imperfect Bakelite nut using double sided adhesive tape on the front face of the fretboard and strung up the guitar with an inexpensive set of steel strings in Brian May’s preferred string gauges, i.e. 0.009, 0.011, 0.016, 0.024, 0.032 & 0.042” then tuned to EADGBE. I fitted the bridge with its 1/16″ brass shim plate and thicknessed tufnol shim plate on top of the pickguard cut out section. I used two pieces of 0.5 mm plastic gasket material as shims to centralise it.
With any newly built guitar, let alone a replica of a unique DIY built instrument, no assumptions can be made about any of the physical dimensions such as when setting up a factory built standard design. The first step was to measure the action at the 17th fret and reduce the thickness of the 1/16″ tufnol shim plate supplied with the bridge. I found that the action at the 17th fret was 2.0 mm compared to my desired height of 1/16″ (1.6 mm). To help determine the required Tufnol shim thickness to achieve this, I loosened the strings, removed the shim and measured the action again. Without the 1/16″ thick tufnol shim in place, the action had reduced to 1.0 mm. I ended up at half thickness, i.e. 1/32″ (0.8 mm) to achieve the desired action. At this point, somewhat inevitably, several strings buzzed when played open and there was a degree of tuning instability when operating the tremolo, presumably as a result of string resistance on the nut slots which I had cut quite tight to the deployed string gauge. I will address this at a later date.
Having achieved a satisfactory playing action, I then estimated the thickness of shims required to set the pickups to the accepted distance from the strings. I have previously set up my converted Fender Stratocaster and Guyton RS Transporter using the straightforward method of fretting the high and low E strings at fret 24 then adding shims until all the pickups are at a set distance (around 1.0-2.0 mm) from the strings while allowing sufficient clearance for string vibration amplitude. However, Greg Fryer published a set of measurements from his restoration of Brian’s original guitar in 1998 which do not confirm to this scheme. The playing action was not referenced and the measurements were taken from the unfretted strings to the pickup casing. I decided to set up my RS to these measurements using custom made shims made from 8.5 mm diameter PTFE tube. Evidently, this scheme should only yield similar tones to the original if the electromagnetic characteristics of the pickups are very close to those of the original guitar. The pickups I fitted to this guitar are “Original BM/Guyton spec.“ Burns Tri-Sonics I bought retail in January 2016 from Adeson and were hand made to match Brian May’s original set as closely as possible.
To estimate the necessary shim thicknesses, I first measured the distances from the guitar body to the high and low E strings. Because I designed in staggered rebate heights as I estimated the original to have, this yielded consistent values of 16.0 mm for the neck pickup, 16.5 mm for the middle pickup and 17.0 for the bridge pickup. Subtracting the pickup height between mounting tab and casing (generally 11.0 to 11.5 mm for this Adeson set) yielded unshimmed distances of 5.0 to 5.75 mm. Subtracting the measurements quoted by Greg Fryer gave me shim measurements ranging from around 1.5 mm at the neck to around 4.0 mm at the bridge. I made these by sanding down slices of PTFE tube, checking the thickness with digital calipers. I installed the pickups with small wood screws; I designed in an aperture in my pickguard to allow the pickup screw head to protrude on the treble side but the bass side screw head will require a small rebate to be milled out of the bass side. This was also known from previous Red Specials I had owned but I elected to deal with it at the final assembly stage.