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DAVID NANCARROW · February 23, 2002, 07:18 AM

Perfessr,
Check your data on weight differences between castings and forgings. Take a cast part and a forged part of identical dimensions and the forged part is heavier, as the metal itself is compacted as it is being beaten by the hammer. Good work on the casting explanation. The lost wax method you describe was, IIRC, invented by the Egyptians and used during the time of the Pharoh's, although their manufacturing wasn't in steel, nor were their tolerances as close as what has been achieved in this day and age.
Also, aluminum forgings are more durable than cast aluminum parts, although castings made today with high amounts of silicon are quite durable. Forged aluminum parts have been used in racing engines for decades in some arenas, but endurance racing see's more forged steel for its ability to handle greater stress. In addition to castings being lighter than forgings, a cast part does not expand as much as a forging, so parts subjected to a lot of heat-pistons, for example, can be fitted closer to the cylinder dimension with obvious benefits, such as smaller compression rings, etc.
Forged vs cast may be coming full circle as CNC machines are able to work in much closer tolerances than before, and are becoming competitive with cast parts.

February 23, 2002, 07:18 AM	#12
DAVID NANCARROW Senior Member Join Date: November 5, 2000 Location: Wyoming Posts: 1,761	Perfessr, Check your data on weight differences between castings and forgings. Take a cast part and a forged part of identical dimensions and the forged part is heavier, as the metal itself is compacted as it is being beaten by the hammer. Good work on the casting explanation. The lost wax method you describe was, IIRC, invented by the Egyptians and used during the time of the Pharoh's, although their manufacturing wasn't in steel, nor were their tolerances as close as what has been achieved in this day and age. Also, aluminum forgings are more durable than cast aluminum parts, although castings made today with high amounts of silicon are quite durable. Forged aluminum parts have been used in racing engines for decades in some arenas, but endurance racing see's more forged steel for its ability to handle greater stress. In addition to castings being lighter than forgings, a cast part does not expand as much as a forging, so parts subjected to a lot of heat-pistons, for example, can be fitted closer to the cylinder dimension with obvious benefits, such as smaller compression rings, etc. Forged vs cast may be coming full circle as CNC machines are able to work in much closer tolerances than before, and are becoming competitive with cast parts.