Hi. Using the technique I mentioned earlier, I was able to successfully weld a broken cast iron C-clamp. I used a small oxy propane torch and cast iron welding flux. The weld had no porosity. Oxy propane has a porosity problem with steel welding due to the heat being in the wrong part of the flame. But, there was a problem. EBay had 3/8" cast iron welding rod, but I was afraid it was too thick. That turned out to be correct. I found a cracked piece of cast iron pipe and hacksaw a 3/8 x1/4" rod from it. I couldn't get enough heat, so I ended up cutting it in half lengthwise and welding the two pieces together. This took a long time, but it worked great. I found out that piston rings aren't cheap! Hopefully I'll find some at a garage sale.

 

If you know any mechanics that overhaul engines, see if they will save the used piston rings for you. At one time I had about 20 pounds of them for free.

Wow. I overhauled an engine once, and just threw the old ones away. I don't have any friends who do this now, since the engines last so much longer. For now, I'm going to just use old pieces. But I will forge a tiny pair of tongs to feed the pieces since pliers don't work well and aren't safe.

Where DID I put those old rings?

Got an automotive program at a high school or VoTech?

I looked extensively at Craigslist and EBay, but only found expensive new rings. I've never seen these at garage sales. Then, at a storage unit clean out, I finally succeeded. They were seized and brittle, but I managed to break a couple out. They spark tested as cast iron, so that's good. They seemed a little hard, but a file will cut them. The third ring groove had a wavy thing and two thin springy rings which sparked as spring steel. I guess I can repurpose the pistons as pistonium as soon as I get a foundry setup working. Thank you for the suggestions. I'll report back on how well they work, but I have seen good results reported from the web.