DIN v. Yoke! Fight!

[Centrals]

I was diving at Maldives several yrs ago and all the tanks on the liveaboard were using convertible valves.
The boat captain did not have to worry about the compatibility of the 1st stage with the tank.

 

[The Chairman]

That was probably the only thing you could do to try to save the valves. The bad news is that chrome plating on the threads is now compromised or totally gone. The live of the threads has now been shortened. The exposed brass can also collect more grit than the original plated threads.

Yeah, I am looking at that, but now I have a tap that I can screw in to clean off any verdigris! As for collecting grit: not on my watch.

The worst part is that any corrosion on the threads can scratch the finish on the mating threads of the regulator.

Why would I allow corrosion to accumulate?

You probably planned on replacing your regulators (or the threaded ring) before this becomes a major issue, but I recommend you keep a nylon brush handy and keep the threads clean.

I like a soft brass instead but I rinse my valves after every dive so I rarely need it. If you let the salt water sit on them, you might have an issue. Of course, I rebuild my valves every year when I inspect the tank. This includes a complete dis-assembly, replacing two o-rings (three on a yoke), a 20 minute bath in my ultrasonic cleaner and then re-assembly with Christo Lube.

Is the tap that you use a thread chaser (thread repair tool) or a regular cutting tap?
Where did you get it?

I doubt they make a thread chaser for that size. Thread chasers are fairly inadequate and usually sold to DIYers at a reduced cost. I bought a set of Snap On thread chasers twenty years ago and it's one of the few tool purchases I regret. I think I need to Ebay them. I got the tap from NAPA here in Key Largo. They were cheaper than the Internet and they had it in two days. I used it on two of my valves and two for a shop.