Such apparatus may be used to machine internal and external surfaces of a polygonal or other non circular contour, and is especially suitable for {HEAD ~ the machining dies} used in {TAIL ~ the casting} of hexagonal bolt heads, more particularly domed bolt heads wherein a hexagonal rim merges into the domed surface of the head 
Such apparatus may be used to machine internal and external surfaces of a polygonal or other non circular contour , and is especially suitable for { HEAD ~ the machining dies } used in { TAIL ~ the casting } of hexagonal bolt heads , more particularly domed bolt heads wherein a hexagonal rim merges into the domed surface of the head
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