Oracle Database Discussions

I am very new to oracle and am working with the minus operator to run a query. I could use some help!

Here is the query I am working on:

select suppliername, partname
from quote
where partname = 'hammer'
minus
select suppliername, partname
from quote
where partname = 'hammer';

HOW DO I GET THE QUERY TO DISPLAY ONLY THE ROWS OF SUPPLIERNAMES THAT SUPPLY ONLY HAMMERS?
I WOULD GREATLY APPRECIATE SOME CLARIFICATION.