I have never used 304 before, so take all this with a grain of salt. My thoughts are in no particular order.
1) Could you single point thread them? It would solve your expense with taps, though single point threading an internal thread that small may be fiddly.
2) Maybe substitute 303 for the 304? 303 is more machinable. 304 will work harden readily and that equals bad times.
3) Maybe try a HSS tap. Most common taps I have seen are carbon steel. HSS may last a little longer.
The last thing is that 30x SS is not supposed to be hardenable through heat treating, so I doubt the did anything to it when you brazed it. In any case, the one you finished looks great. How many more?
1) Could you single point thread them? It would solve your expense with taps, though single point threading an internal thread that small may be fiddly.
2) Maybe substitute 303 for the 304? 303 is more machinable. 304 will work harden readily and that equals bad times.
3) Maybe try a HSS tap. Most common taps I have seen are carbon steel. HSS may last a little longer.
The last thing is that 30x SS is not supposed to be hardenable through heat treating, so I doubt the did anything to it when you brazed it. In any case, the one you finished looks great. How many more?