HELLO,

NO, 70 % score in Board exams as an OBC category candidate is not enough for securing admission in IITs or NITs through JEE advance .

1. JEE Advanced Eligibility :- The minimum requirement to give JEE Advanced is 75 % in your class 12th board exams for general and OBC categories and 65% for SC/ST candidates.

2. IIT and NIT admission:- Even if you get qualified to give JEE advanced still you need to meet the specific eligibility criteria for IIT and NIIT that includes minimum 75% for boards for OBC and general category

3. Top 20 Percentile:- A more approach to eligibility is that you may be eligible if you are within the top 20 percentile of successful candidates in your respective board exams .

You could consider private engineering colleges for admissions if you want.

visit the link for any other details :- https://engineering.careers360.com/articles/jee-advanced-eligibility-criteria

Hope that Helps!