No, I’ve never attempted to do that. But the pressure rating on steel brake line is much higher than brass. Pretty sure it is seamless tubing.
Diameter would be issue, but probably can be found.
Since it is illegal, I’ll never attempt it.
But could if I had to.
We have a lath at farm. Old but functional. I don’t have a milling machine or head. Would like to.
Keep thinking I’ll find an old machine shop closing and acquire more equipment.
I’ve been a Ham Op for many years. Electronics is my 2nd language.
Have spent far too much time with PCs in past 20 years. Not enough time with my projects. Built my first PC in 1982.
Been running Linux since 1984. Used them all: DOS’s, Window’s, AS400.
Cost of a mill is not too bad. Its the collets, bits and other attachments that kill ya.
I am a mechanical engineer but electronics was an avocation. Fixed TVs for fun and would sell them at garage sales.
And built a few inverted sinwave sync suppressed converters to unscramble early pay TV.
Also wrote a communications program to hack into the local real estate MLS system in the days of 300 baud modems. I don't think hack was a term even used in those days.
Fun times. ;o)