Digital fabrication tools such as 3D printers, computer-numerically controlled (CNC) milling machines, and laser cutters are becoming increasingly available, ranging from consumer to industrial versions. Although these tools have enabled a completely new crowd to take part in manufacturing, they are still limited in their use and the workflows they provide. As an answer to this, users are modifying and customizing their machines by changing the work envelope and adding different end-effectors. However, customizing, modifying and creating digital fabrication machines require extensive knowledge within multiple different engineering domains, and is non-trivial. In this paper, we present \textit{The Fabricatable Axis}, a high-level parametric model that aims to simplify the process of experimenting, customizing and implementing digital fabrication machines. This model encapsulates the knowledge of an experienced machine designer into a model that less experienced machine builders can use to design and customize linear and rotary motion axes which can be combined into different machines. The model receives high-level input parameters such as axis type, length and speed-parameters, and outputs a CAD model of a motion axis consisting of \textit{fabricatable} parts (parts that are readily available or parts that can be fabricated using accessible tools such as a CNC milling machines). To validate our contribution, we first present a constructed scenario were we use the model to implement a specific machine. Secondly, we present an evaluation of our tool through a series of interviews with users who have been using the model to create different types of machines.