I know that I have a 6mm rear break line. Also, I am swapping a ford 9" into the car. So everything after the 6mm line is just 3/16 line. I am now trying to connect the 6mm into the rubber hose that T's off into both axles. It is set up now so that I can run just a 3/8-24 fitting into the hose. I was doing some research and found that 1/4 and 6mm are close together. So could I use a regular 1/4 nut and flare that onto the 6mm hose? If that will work, I can get an 3/16 to 1/4 adapter for the hose.

 

Yeah, you can do that. I don't recall if I had to slightly drill out the tube nut, but it did work.

 

Yes, there is enough material on the 6mm tube to make an inverted flare with a 1/4" tube nut (7/16-24 inverted flare). 1/4" tube nut is a little larger so it's going to be a little loose on the stock 6mm tube.

You don't need an adapter though. The stock hose accepts a M12-1.0 metric bubble.

 

I'm actually using the hose that came with the rear end. So just the stock ford one and it takes 3/8-24 all around.