| abstract | - A crankcase often has an opening in the bottom to which an oil pan is attached with a gasketed bolted joint. Some crankcase designs fully surround the crank's main bearing journals, whereas many others form only one half, with a bearing cap forming the other. Some crankcase areas require no structural strength from the oil pan itself (in which case the oil pan is typically stamped from sheet steel), whereas other crankcase designs do (in which case the oil pan is a casting in its own right). Both the crankcase and any rigid cast oil pan often have reinforcing ribs cast into them, as well as bosses which are drilled and tapped to receive mounting screws/bolts for various other engine parts. Besides protecting the crankshaft and connecting rods from foreign objects, the crankcase serves other functions, depending on engine type. These include keeping the motor oil contained, usually hermetically or nearly hermetically (and in the hermetic variety, allowing the oil to be pressurized); providing the rigid structure with which to join the engine to the transmission; and in some cases, even constituting part of the frame of the vehicle (such as in many farm tractors).
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