A modular bone mill system for converting bone stock into bone chips, the system comprising: a base module; and a milling module, said milling module comprising: a shell adapted for releasable attachment to a base module that includes a motor, the shell having: an inlet opening through which bone stock is introduced into the shell; an outlet opening through which bone chips are discharged from the shell; and a milling element disposed in the shell between the inlet opening and the outlet opening for converting bone stock into bone chips, wherein the shell includes: a lid that is removably attached to a foundation, the lid including the inlet opening of the shell; and the foundation being adapted for releasable attachment to the base module, the foundation including the outlet opening and a catch tray removably seated in the foundation adjacent the outlet opening to receive bone chips discharged therethrough, characterised in that the base module also includes a sensor, wherein the lid includes a first detection component positioned to be detectable by the sensor in the base module and the foundation includes a second detection component, wherein the base module is configured to selectively power the milling element of the milling module based on whether the sensor in the base module detects that the first and second detection components (140, 236) are arranged relative to each other indicating that the lid is correctly attached to the foundation, the catch tray is correctly seated in the foundation, and the foundation is correctly attached to the base module. a base module; and a milling module, said milling module comprising: a shell adapted for releasable attachment to a base module that includes a motor, the shell having: an inlet opening through which bone stock is introduced into the shell; an outlet opening through which bone chips are discharged from the shell; and a milling element disposed in the shell between the inlet opening and the outlet opening for converting bone stock into bone chips, wherein the shell includes: a lid that is removably attached to a foundation, the lid including the inlet opening of the shell; and the foundation being adapted for releasable attachment to the base module, the foundation including the outlet opening and a catch tray removably seated in the foundation adjacent the outlet opening to receive bone chips discharged therethrough, characterised in that the base module also includes a sensor, wherein the lid includes a first detection component positioned to be detectable by the sensor in the base module and the foundation includes a second detection component, a shell adapted for releasable attachment to a base module that includes a motor, the shell having: an inlet opening through which bone stock is introduced into the shell; an outlet opening through which bone chips are discharged from the shell; and a milling element disposed in the shell between the inlet opening and the outlet opening for converting bone stock into bone chips, an inlet opening through which bone stock is introduced into the shell; an outlet opening through which bone chips are discharged from the shell; and a milling element disposed in the shell between the inlet opening and the outlet opening for converting bone stock into bone chips, wherein the shell includes: a lid that is removably attached to a foundation, the lid including the inlet opening of the shell; and the foundation being adapted for releasable attachment to the base module, the foundation including the outlet opening and a catch tray removably seated in the foundation adjacent the outlet opening to receive bone chips discharged therethrough, characterised in that the base module also includes a sensor, wherein the lid includes a first detection component positioned to be detectable by the sensor in the base module and the foundation includes a second detection component, a lid that is removably attached to a foundation, the lid including the inlet opening of the shell; and the foundation being adapted for releasable attachment to the base module, the foundation including the outlet opening and a catch tray removably seated in the foundation adjacent the outlet opening to receive bone chips discharged therethrough, characterised in that the base module also includes a sensor, wherein the lid includes a first detection component positioned to be detectable by the sensor in the base module and the foundation includes a second detection component, wherein the base module is configured to selectively power the milling element of the milling module based on whether the sensor in the base module detects that the first and second detection components (140, 236) are arranged relative to each other indicating that the lid is correctly attached to the foundation, the catch tray is correctly seated in the foundation, and the foundation is correctly attached to the base module.