Hello Narayana,

Since you have achieved 57 marks in the gate examinations, you have a chance to get admission in the IIT's or the NIT's.
but as u mentioned in OBC category, you still might get a chance.

Also, want to tell you that what course or subject you wish to study also plays a vital role,

and for further details, you can even visit our website, where there is a detailed description of all the major courses offered by the IIT's and which one would be the best for you.

https://engineering.careers360.com/iit-mtech-admissions

 few of IIT colleges for mechanical engineering

 IIT Madras
 IIT Bombay
 Indian Institute of Technology Delhi
 IIT Kharagpur
 Indian Institute of Technology Kanpur
 Indian Institute of Technology Roorkee
 Indian Institute of Technology Guwahati
 NIT (National Institute of Technology) Trichy