To Delete a Custom Units System
You can delete a custom system of units that you previously created. You cannot delete a system-provided system of units. Use caution when deleting units systems; you cannot undo the deletion. Before you delete the units system, make sure it is not the set system for the current part or assembly.
1. Click File > Prepare > Model Properties. The Model Properties dialog box opens.
2. Click change in the Units line. The Units Manager dialog box opens to the Systems of Units tab, which lists all available custom and system-defined units systems. A description of the selected units system appears under Description.
3. Select a custom units system that you want to delete, and then click Delete. A warning message appears and lists the units system you have selected for deletion.
4. Click Confirm to delete the units system.