I bought a tool similar to the one you are using hurt it was unusable until I sanded down the mating surfaces and cleaned up the threaded parts.

Lubrication is needed on the flare surface when doing steel but I was able to make fine flares on steel even though I didn't need to I replaced both of the rear main lines.

Did you buy steel line or are you trying to splice into factory line (I do not recommend).

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)