What size is it?

[epretot]

I want to solder a cap to these locations. 1 1/4 copper cap is too tight.

[epretot]

The plumb and hvac supply house were both stumped

[luvrbus]

That is commercial refrigeration tubing size,I bought some Hussman   

[dtcerrato]

The plumb and hvac supply house were both stumped

It almost looks like a "Pex" fitting which ARE! a bustard size. Ask me how I know! You may want to inquire or search 1-1/4" Pex to see what you come up with. Just a guess and an issue I ran into with the same looking fitting in 1" size.
Hope that might help...

[Jim Blackwood]

Sometimes copper tubing swells, especially during freezing temperatures if they have water in them. A cheap set of digital calipers are your friend here if they go to 3 decimal places. You can compare to the new size. If it's just tight but you think it could be made to fit then the tubing has probably swelled. That's not the end of the road as there are many many ways around the problem. Easiest is most likely a rubberflex coupling for lower pressures and I would expect those to work fine for cooling runs (engine radiator and heaters). A tool can be found or made to swage the tubing back to the correct size. The fitting can be expanded to fit the tubing. Or sometimes a compression or other (PEX) type fitting can be used. My choice would be to drive the copper fitting on after cleaning both pieces and then braze them using a fluxless brazing rod for copper plumbing. A propane torch with MAP gas should get hot enough if you don't have an acetylene plumber's torch.

Jim

[Utahclaimjumper]

Are they presently soldered joints or welded,, you could always just measure the OD and fabricate a cap and use JB weld as a welded joint..>>>Dan

[luvrbus]

You can buy freeze plugs for the inside OD they don't have to be copper to solder either