"Christopher Tidy" .(clip) I would guess that the forged couplers will be
stronger. Forgings are usually very strong because of the alignment of the
grains in the metal.
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Another reason forgings are generally stronger is that the dies can be
shaped so that the metal varies in thickness as needed for strength.
Reinforcing webs and radii can be designed in, to reduce stress, increase
stiffness and improve fatigue life. In a stamping, the dies can stretch the
material, making it thinner, but they can't make it thick and strong next to
a hub, for example.