Service tax on job work

THIS IS A QUERY RELATING TO APPLICABILITY FOR SERVICE TAX ON JOB WORK.

SOME OF OUR CLIENTS DO JOB WORK ON BRASS PARTS USING SOME OF THEIR OWN MATERIALS EVEN.  T/O OF THERE DURING P.Y. EXCEEDS RS. 10,00,000 TOO. BILLS ARE RAISED FOR LABOUR CHARGES ON PIECE RATE BASIS.

MY QUESTION IS WHETHER LABOUR CHARGES RECEIVED FOR THESE WORKS COVERED UNDER JOB WORK.???

WILL THEY LIABLE TO PAY SERVICE TAX????

ARE THERE ANY CIRCULARS/NOTIFICATION/CASES SUPPORTING???