Not to put too fine a point on it
Definition 1 of 1
Pro Tip 1/3Directness
The phrase is used to be blunt and doesn't beat around the bush, meaning the speaker gets straight to the point. 
Not to put too fine a point on it, your work has been unsatisfactory.
Pro Tip 2/3Softening Blow
Despite its directness, it often signals that the speaker wants to soften the impact of a critical statement that follows. 
Not to put too fine a point on it, but your argument is flawed at its core.
Pro Tip 3/3Colloquial Use
It's a conversational phrase, used more in spoken English or casual writing, not in formal texts. 
Not to put too fine a point on it, but we're in a bit of a mess here.