Which is grammatically correct? I can only do so much in this time. Or i can do only so much in this time.

We are getting that only printed. What is the proper way to put it? The question asks for a general answer but gives only one special context. In general, only and but only are not substitutable. *they but only work that way occasionally. The oxford english dictionary defines but only (which can also occur as only but) as meaning Γ’β‚¬Λœ (a) only, merely; (b) except onlyÒ€ℒ, and comments that its use is now poetical.

*they but only work that way occasionally. The oxford english dictionary defines but only (which can also occur as only but) as meaning Γ’β‚¬Λœ (a) only, merely; (b) except onlyÒ€ℒ, and comments that its use is now poetical.