Steam Radiator Fittings - Thread Question

Fishin_Rod

I found a replacement radiator for one that had been removed from our home. However, I cannot transition from the radiator 1-1/2" FIP threads to the steam fittings that were left on my pipes.

The house is 106 years old, and I believe the fittings are original. I am also going to use the WRONG terminology, so just try to get the gist of my descriptions.

There is a typical 90 degree brass valve on the steam supply line side. It was originally a flare/union type (?) of connection. (On my other radiators, a nut on the radiator screws onto the threads on the valve.)

The threads on the valve look like 3/4" Male Garden Hose, but they are not.

There is a 90 degree brass steam trap on the condensate return pipe. The traps on my other radiators also have a flare/union type of connection with a nut on the radiator that screws onto the trap.

The threads on the trap are also 3/4", but they are a finer thread (more threads/inch) than typical 3/4" Male Iron Pipe threads. The exit from the steam trap is a 1/2" FIP threaded connection.

The male threaded ends on both the valve and the trap have a small concave cup slightly recessed in the pipe, which is why I am using the word "flare" in my descriptions.

Any advice on the correct name of these types of threads, and where I could find/order transitions?

(The valve works just fine. I don't know about the trap. I would rather not replace the expensive fittings if I can just plumb back into my radiator.)

This radiator is exposed in a bathroom. If I make a "drippy" connection on a less than perfect transition, I will certainly see the drips and be able to avoid any house damages.

Thanks for any advice!

Intplm.

And the question is?