My principal is threatening to not sign my articleship completion form.

Respected members,I hope of getting proper help and guidance on this matter. I'm in serious need of it.Thank you! Status : Working as an article assistant. Articleship period : 28.10.13 to 27.10.16. Issue : Threats from the principal regarding non signing of articleship completion form. Extension period : I have calculated the maximum leave allowable (1/6th of no. of days served) and no extension is required to be served by me. That is, the leaves that I have taken plus the leaves that I'm planning to take are the ones I'm eligible for. Leave status : As on 27.08.16, I will be having an eligible leave balance of 60 days. And as my articleship is scheduled to end on 27.10.16, I can take exam leave from 28.08.16 i.e. approximately 2 months. Issue in detail : I requested my principal to grant me my exam leave from the eligible date (28.08.16) but he's refusing to do so and is asking me to serve till 15.09.16. And he has even threatened me that if I refuse to do so, he will not sign the articleship completion form when the time comes. I will be appearing for my final exams in November 16. I informed him about my leave status but he doesn't give importance to such calculations and is threatening me. I have been as cooperative as possible throughout my articleship tenure but it is not possible for me to cooperate in this case. I've requested him immensely but he's taking his stand. Kindly guide me on handling this matter in such a way which creates minimum issues for me as well as my principal.