So that it is clear what motions & components I am talking about in future build posts, I will outline here the axis conventions that I will use throughout. They are as per section 5.2.3 of Manufacturing Automation (2nd Ed) by Yusuf Altintas:
Machine tools are programmed in a Cartesian coordinate system. The Z axis is always aligned with the direction of spindle. The primary X motion is normally parallel to the longest dimension of the primary machine tool table. The Y axis is normally parallel to the shortest dimension of the primary machine tool table. Characters A, B, and C designate angular motions around the X, Y, and Z axes, respectively.
With this in mind, the axes of movement that the machine will be designed to use are X, Y, Z, B & C.
Manufacturing Automation contains a great deal of information on metal cutting mechanics and CNC design and I expect it will prove to be an invaluable resource throughout this project.