Well, I have frost....

[wdrzal]

You can use teflon tape thread sealer ,but be carful to start it back 2 treads so it doest get cut off and sucked into system. Also you need to wind it closkwise if your looking at the hole in the bottom of the gage. About 2 or 3 turns. Or pipe dope for gases.

You should tighten the gauge into the fitting first,then face it forwards and braze. No problem.

I avoid threaded connections when possible.........buy gauges with flare fittings.