[MW:4006] cutting of 90 deg elbow in to 45 deg elbow

hi,

I am new to this group. In our project we have one problem. For
shortage of 45 deg elbow, they want to cut the 90 deg factory made
seamles elbow ( 52" size) in to 45 deg elbow. Is this allowed by the
code or any restriction in the code. For this which code we should
refer. please help me in this issue.

regards,

Gulam Kader