This parameter holds the Diameter of the currently selected tool.
The field can be edited if you wish to temporarily change the value of the currently selected tool. Changing this field does not change the value of the tool in the tool list! It is for temporary editing only.
This value will affect the size of the lead-in and lead-out on most cut cycles, but will not affect the offset of the tool paths.
If you are using the Cut-SIM (Tool Simulation Software), this will change the size of the tool reported to Cut-SIM and result in a back plot that is inaccurate.
The diameter value is the largest diameter value of the tool if more than 1 option is available, for instance on a shaper type tool. Some common tools and their measurements are shown here.
In each of these tools L is the Tool Length, D is the Tool Diameter, and R is the Tool Radius.