A unique feature of the Heirloom computer is the removable, bluetooth keypad that allows access to integrated features of the computer PCB including the FPGA port.
The Heirloom design supports the keypad between a removable rear panel and a rabbet, or groove, along the the front rail of the computer. Fitting keypads during construction requires a measuring and cutting procedure described here.
Because the keypad is tapered from front to back, the cut made in the front rail rabbet has a sloped bottom surface. An end mill was ground to match the keypad taper. It is used to cut the rabbet on the CNC milling machine.
Each rear panel is made from the wood composite designed for the Heirloom and, due to slight variations from things like veneer thickness, sanding, and mold-shape springback, has to be individually fitted in a table saw operation.
After the rear panel is fitted, a measurement is taken on the CNC mill with an electronic edge finder. This measurement is used to locate the front edge of the rabbet to be cut in the wooden front rail.
Once the rabbet is cut in the front rail, the remainder of the front rail is shaped by hand to correspond to the gentle rollover at the front edge of the keypad. This detail creates a comfortable palm rest at the front edge of the keypad.
After fitting keypads to each of the Heirloom computers, it is time to move on to pre-finishing the wood composite panels in preparation for assembling the enclosures.