Reading and writing to different files on the same time - can multithreading be useful?

I'm reading text form a huge file, line by line, perform some operations on them and then store results in different files. If I will have two thread, one that read the data from one file, will other thread be able simultaneously write data to another file? Or as they are o the same hard disk multithreading won't make sense as they will wait for each other?