Welding Tips and Tricks

Have a semi-urgent need to make a fitting/adapter.
Not having an oxy torch, pondered tig brazing with silicon bronze (have the filler rods here somewhere)

1-So can I do this copper to copper?
2-Copper to brass?
3-Do I need any flux?

Needs to be fairly clean, will argon purge. (no N2 or He here) And hold a vacuum.
(not medical level clean, but HVAC would be a close proximity)

TIA

OK - I don't do it much & much prefer oxy but ! Copper to copper yes - as long as everything is clean & you have decent shielding ( think 10 / 12 cup if available ) regular argon is all you need - copper to brass NO - it will just vaporize the zinc out of the base metal & make a mess ( ask me how I know ! ) - if it were me I would make a decent slip joint on the parts using the lathe & silver solder this combination together - if this is a HVAC application there are guys on here do it all the time can give you the preferred method - hopefully one will chime in.

Thanks.
Its not exactly an HVAC applications. Just making an adapter to use a HVAC vacuum gauge (sorry, _refuse_ to call it a micron gauge; and it ain't since i'll be using mbar ) to work with a CNC laser, for a vacuum check and system calibration.

I've had luck with a map torch and Stay-Silv in the past, but not sure I'll have the room/part length not to over heat it. Thought the tig might keep the heat concentrated a bit better.

Yes I’ve done it several times refrigeration grade, R22 head pressure around 275psi average, and on steam, less than 75 psi. Also done copper to steel and steel to brass. Just used Argon and dc. I’ve used 45%silver, 15% silver, and a product from Harris called Blockade. It’s a high silicon brazing rod.