BobCAM allows you to assign geometry to define custom lathe tool inserts for tools that can't be created using the provided insert types.
1 In the graphics area, draw the 2D shape of the insert.
At the position of the attachment point to
the tool holder, place a dashed
circle.
It does not matter which dashed
pattern is chosen, just that the circle itself is not solid.
Place a point at the theoretical tool point.
This point is normally tangent to the forward
and bottom extents of the tool nose radius.
2 To open the Tool
Library, do one of the following:
Right-click 
CAM Defaults,
and click Tool Library:
Turning
Tools, and click Tools.Right-click
CAM Defaults, and click
Tool Library:
Right-click
Turning Tools, and click
Tools.
3 In the Tool
Library, select the lathe tool category that you want to modify.
4 In the list on the
right side of the dialog box, click the tool that you want to modify,
and click Modify.
(If you are creating a new tool, just select the category, and click Add.)
5 In the Create/Modify
dialog box, select the radio button for Custom
Shape.
6 Click Assign
Tool Insert.
7 In the Workspace,
to select the insert geometry, click and drag a window around the entire
drawing.
8 Right-click anywhere
in the graphics area, and in the
shortcut menu, click 
OK.
The holder geometry is now assigned to the selected tool.
Click OK to save the changes and
return to the Tool Library.