I place a PTEX sidewall and a 2cm ash stringer along the length of the effective edge. In order for this to match the sidecut and thickness profile of the board perfectly, this material is added to the core blank as the first step of the process. The core blank is placed on the CNC machine and alignment holes are drilled through the blank and into the CNC table. This allows me to remove the blank from the table and reposition it later perfectly. Trenches are then routed along what will become the effective edge of the core. These trenches are wide enough to hold the ash and the PTEX sidewall together.
Next, I rip strips of ash from a 2cm thick ash plank. The width of the strip is just a little wider than the thickness of the core blank - about 0.010”.
Strips of sidewall material are also ripped from a half inch thick plank of PTEX. The PTEX material is sanded and flamed on both bonding sides before being glued into the blank. The polyurethane glue is insufficient to create a reasonable bond on its own. Failure to perform this step often causes the PTEX to delaminate from the blank during CNC machining of the core, which is unacceptable.
The prepared PTEX strips are turned on their side and inlaid into the trenches of the core blank. The ash strips are laid in the trenches, next to the PTEX strips, closer to the center. The ash and PTEX are glued in with the same polyurethane glue used to create the blank. This provides a sufficient bond for the blank and shaped core to survive the rest of the process through to lamination. The epoxy used when the board is pressed provides the final structural bond between these components.
Wood shims covered in wax paper are placed on both sides between the core and the body of the clamps to prevent the glue from sticking to the clamps.
The blank is then re-clamped for a minimum of 12 hours to ensure a very good bond with the PTEX. This prevents them from separating before lamination.
Here is a short video which shows each step of shaping a core from blank to final core, including inlay of the ash edge stringer and sidewalls.