Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_204_828 ( id number, "whitworth size (in)" number, "core diameter (in)" number, "threads per inch" number, "pitch (in)" number, "tapping drill size" text )

### Question ###
how many more threads per inch does the 1/16th whitworth size have over the 1/8th whitworth size ?

### Accurate SQL ###

SELECT (SELECT "threads per inch" FROM table_204_828 WHERE "whitworth size (in)" = '1/16') - (SELECT "threads per inch" FROM table_204_828 WHERE "whitworth size (in)" = '1/8')