The petrol chainsaw is a hand-held machine saw

While chainsaws may be powered by a number of means, petrol chainsaws are driven by internal combustion two-stroke gasoline engines. The device gets its name from its cutting edge, which is a chain constructed, like a bicycle chain, from metal segments which in this case have sharp metal blades, or teeth. Like most two-stroke engines the machine is lubricated by its fuel, which takes in about 3% oil in its composition. The oil reservoir is generally designed to outlast the gasoline, so that it should not be possible to run out of lubrication before fuel, saving a great deal of damage and wear on the machine. Lubrication must also be applied to the chain, its guide bar, and the drive links under the teeth that carry the lubrication around the chain. A great deal of oil is used, as it is flung off the chain as it rotates, as well as being soaked up by the sawdust. Care must also be taken to regularly clear out the air intake filter, which quickly becomes clogged with sawdust.

The guide bar is made from toughened steel and there is an edge slot which protects and guides the chain with its chromium plate steel teeth. Left- and right-hand teeth alternate on the chain for maximum efficiency. The teeth should be kept as sharp as possible; the user should not need to push hard on the machine to drive it into the timber, and a blunt chainsaw is more likely to 'bounce' off its target and cause an injury to the operator.