"My fitting"............now that's the problem. What fitting? Where did you get it? Have you tried properly installed teflon tape? Can we see the fitting. Is it for direct flare tubing? or pipe? straight threads? or what? Please post good clear pics of it and it's nose. Some fittings are supposed to bottom out. Some folks call bottom out as the outside nut is hitting, some mean the inside nose is hitting. Which are you?
We can't guess a solution before we see the parts.
If the soft Zink/Aluminum cast carb needs tapped or worked, time to get a new carb or section.
I will say this as delicately as I can........
1. If it's leaking it means you are planning on using it on a motor. Yipes!
2. That carb needs to be cleaned, examined for cracks, then thrown away.
