The crosshead is used in large slow speed Diesel engines. The crosshead is a large metal casting which slides up and down on a guide mounted on the crankcase of the engine. The bearing surface of the crosshead is usually Babbit metal which rides on cast iron guides. The crosshead is a transitional component from the reciprocating motion of the piston to the rotary motion of the connecting rod and the crankshaft.

Another consideration with the crosshead engine is in the ease of maintenance when pistons have to be pulled from the cylinder. The piston rod is mounted on the underside of the piston and connected to the crosshead by a single nut.

The pistons on these engines are generally in the order of 600 - 800mm and weigh in the region of half a ton.