I just finished drilling the holes in my new chainplates. I went with aluminum bronze. The alloy is called C61400. I purchased it from Atlas Bronze.
After talking to Tom Smith, who is the owner I think, I was convinced that this was the best bronze to use.
It wasn't cheap. But I don't believe I will ever have to change out chainplates again.
I am doing all the fabricating myself, but since they had to cut the material from plate, I had them cut to length. So all I have to do is grind, drill, polish and bend them a little.
I also upsized them. From 1/4" x 1.5" to 3/8" x 1.5. Way bigger than I needed, but I don't want them to be the weak link.
My boat can handle the extra weight.
The address for Atlas Bronze is 445 Bunting Ave. Trenton NJ 08611 and the phone is 800 478 0887.
I have no affiliation with them other than this recent purchase, but I will say that they are very helpful and nice to deal with.
Since I wanted to use the same alloy for the bolts but couldn't find any. I am purchasing round stock from them and am going to make my own bolts by threading both ends. They will all be made the exact length.
The bolts on most of the chainplates are visible inside the boat so I am going to use acorn nuts on the inside so that they all are uniform. The outside will be regular silicon bronze nuts.
Edit: The total cost of the material is around $675.00 including the round stock, but not the nuts.