To prepare the blockboard for the final quality Brian May Red Special guitar body I bought two 8′ x 4′ x 3.6 mm thick hardwood plywood sheets from my local Travis Perkins and bought two blocks of spruce tonewood intended for making acoustic guitar bracing from Exotic Hardwoods (Timberline) in Essex. This timber had very close grain structure and was essentially free of flaws. I also invested in a Makita 2704 table saw so that I would not have to reply on a third party to prepare my timber to the desired dimensions. I fitted an 80 tooth Makita branded saw blade with thin kerf (2.3 mm) to obtain a fine cut.
I cut each plywood sheet into ten 18″ x 16″ panels yielding twenty in total. I then assessed each panel for thickness, warp and voidage and rejected any that were unsuitable. Unfortunately, the quality of this second batch of plywood was worse than the original sheet I bought. Nevertheless, I was able to find sufficient sheets to make several upper and lower body section panels. I weighted down those with slight warp to try to flatten them.
To obtain a true 3/4″ (19 mm) thick blockboard panel, I had to accurately measure the actual thickness of the plywood (typically 3.35 mm) and cut the spruce into strips of thickness equal to 19 mm minus 2 x 3.35 mm minus two glue layers. I assembled a test block to determine the likely thickness of the glue layers which was around 0.2 mm. This meant that the spruce strips required to be around 12.1 mm thick. I cut them to around 41 mm wide to satisfy the two constraints of (a) efficiently using the spruce blocks which measured 90 x 90 x 550 mm taking into account wastage from the blade kerf and (b) getting an even number of strips per 16″ (406.4 mm) wide panel with a small stickout for the quick release clamps to grip onto.
As previously, I laid up the blockboard by generously coating the plywood panels and all sides of each spruce strip in an even layer of Titebond Original wood glue, assembling, clamping laterally with two 18″ Irwin quick release clamps then weighting down the board with an MDF sheet, standard house bricks stood on end, another MDF board acting as a load spreader then a single large heavy object (a fire safe). The pictures in the gallery illustrate the lower body section blockboard timber, the uncut spruce on my table saw and the cut spruce strips. The YouTube video embedded below illustrates use of my CNC machine to final thickness the spruce strips from approximately 12.5 mm to 12.1 mm.