Hi I have a little bit of a database design problem

The user needs to capture

Form, Length min,length max, width min,width max, gauge min,gauge max(this is simplified).
he is expected to enter the form and at **least** one part e.g. the form and length min and max. He may enter more than one part.

I get the feeling that I should not have 1 table. I was planning on creating a form, length, width and gauge table. The length, width and gauge table will have a foreign key to the form table and my dimensions table will [share the same primary key](https://stackoverflow.com/questions/6046514/how-can-i-share-the-same-primary-key-across-two-tables) (I think this is a 1 to 1/0 relationship). This will allow me to have/ not have certain parts where needed and eliminate null entries. My first problem is, is this good database design? If I need to delete how can I delete without removing the relationship(in plsql)?