I used the roller chain and made a nice billet today which fell apart three times in the process but I ended up with two nice billets which I formed into knife blanks. My method was to fold the chain over on itself until I had a piece roughly 2" wide by 6" long and about 1/2" thick. I wired it together and just kept adding borax and smacking it together. I kept the chain pins parallel to the ground (read that online somewhere) I think that was the right idea because it mostly held together. Like I said, it fell apart a few times and I ended up with a couple of billets about 1/2" x 1/2" and about 3-4" long.
My forge welding needs more improvement as there are a few open cracks in my knife blank, but I thought I continue all the way to see what I'd end up with. So, I've shaped and shined and heat treated, what should I acid should I use to etch? A search turned up ferric chloride as the recommended but I'm not sure where to find it. What can I find at a local place that will etch? I've got a wal-mart, menards, rural king (like a Tractor Supply) in town.