A frame allows you to assign a value to each radio button, so they would be 1-6 and you could store that value in a single field for each question.
Example:
AnswerTable;
AID autonumber
QID Long (Ties to question table)
RespondentID (ties to who took the questionare)
Answer (1-6 depending on what is selected)
But you need to use frames (and the associate frame box with it) for the easiest solution. Think of the frame a group of radio controls, only one is allowable for selection and each has a unique value within the group).
The attached file is kind of an example.