The phrase 'bordering on obsession' is correct and usable in written English.
It is a way to describe something that is close to an obsession, but not quite an obsession. For example, you could say, "My mother's interest in gardening was bordering on obsession."
Considering the hours he puts into even the smallest pictures, which are just a few inches tall and wide, this means a persistence bordering on obsession, and one always feels the claustrophobia and passage of time in the work.
And although there were many initial responses, one of the most memorable was my need, bordering on obsession, to become a collector (perhaps even hoarder) of all my father's stuff.
For some, that fandom may well be bordering on obsession.
Many residents hate them with a passion bordering on obsession.
He soon acquired a reputation for assiduousness bordering on obsession.
It was a love like I had never experienced before, bordering on obsession.
He believes in the passions bordering on obsessions that drive films noirs.
Ms. Hart's earlier show, "Shells," which she wrote with Nick Chase, involved the love life of a character named Michelle Hoffman, a self-absorbed woman whose preoccupation with one particular date she had bordered on obsession.
If it was a hobby, it was an interest that bordered on obsession.
That was the beauty of Pettitte, whose competitive alter-ego bordered on obsession to the point that the Yankees' pitchers jokingly called him by another name, Lloyd, on days that he pitched.
With a passion for physics that bordered on obsession, she also worked for the division of war research at Columbia University during the second world war, where she became a highly productive researcher and later professor.
