Hi,
I'm not at all familiar with Bobcam however most CAM programs offer a thread milling toolpath.
In that circumstance the Gcode lowers the tool into the hole on center and then move outward radially to start the groove.
In a thread the groove is a helical path, but as you want a straight groove then nominate the 'pitch' of your 'thread' to be zero.
The CAM should handle how the get the tool in and out of the hole thereafter.
Craig