CREATE TABLE table_204_828 (id DECIMAL, "whitworth size  ( in ) " DECIMAL, "core diameter  ( in ) " DECIMAL, "threads per inch" DECIMAL, "pitch  ( in ) " DECIMAL, "tapping drill size" TEXT)

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