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That's actually a very good observation. Sharp inside edges that aren't rounded after casting will cause the stresses in the material to crack the parts to relieve the internal stresses. When castings come out of the molds and cool to quickly they're liable to build up a lot of internal stress. Cracks are propagated from the sharp edges when the castings cool. And keep in mind henry was scratching the surface when it comes to
Metallurgy. And our model T's are what he experimented on.