I’ve fabbed and re-rehabbed dozens of flex hoses from sense lines to process lines to high press apps like brakes and hydraulics. It is not that hard but I will say that the
proper mandrels are a must. They must be threaded to engage the b-nut (? Check my terminology. It’s been a while) the perpendicular through holes or wrench flats are a must. Some can take some considerable torque. Without such, it would not be hard to damage the inside liner. The two most important criteria IMO
roper gap on the collar
Proof pressure test
The inner Al parts expand/contract faster than the material which expands faster than the outside collar. Without that gap, the resulting strain from differing thermal expansion rates can easily make the part fail. The gap is more essential than would appear.
I’m a tool jumkie so I only sell my duplicates. I can at least help out my hangar neighbors that aren’t converts yet or locked in by their aircraft TCs.