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Posted by David Sherman [216.18.131.213] on Sunday, January 31, 2010 at 01:27:36 :
In Reply to: On castings... posted by Chewie [207.199.226.126] on Sunday, January 31, 2010 at 00:34:46 :
Good idea. I have a very old (1880s) planer on which somebody dealt with a broken casting long ago by putting the two broken pieces together and using them as a pattern to sand-cast a replacement out of brass. This must have been done a long time ago since welding or brazing apparently wasn't an option, but casting was relatively easy. The reason I know the brass piece was a repair is because there's a mirror-image part on the other side of the machine that is iron, and the crack line showed up in the brass replacement. So, that would be another approach to reproducing old cast iron parts -- use the actual casting as a pattern to make a copy out of brass or bronze. Strength would be equal to cast iron, cost would be more for materials but less for tooling and labor. I have not tried any red metal casting yet, but I'm saving all my broken pipe valve bodies as raw material. Obviously, using the iron part as a pattern only works if it was a simple mold without a core. Not sure how you could copy a gear housing without cutting the original in half. Maybe a rubber molding compound like the art foundry people use?