The type of blade on your lawn mower depends on the type of mower you own. Rotary mowers powered by gasoline or electricity have blades that rotate on the same plane as your lawn. These types of mowers use either a straight blade or a mulching blade. Other rotary mowers do not have engines; this type of mower has a horizontally mounted drum with five or six blades that revolve and cut when pushed by hand.
Straight Rotary Blades
Straight mower blades are the simplest and least expensive type. The blade mounts to a shaft that extends through the mower deck from the lawn mower's engine, whether gas or electric. Straight rotary blades have sharpened edges that cut the grass. Keeping these edges sharp is important to maintaining your lawn's health. If your mower blade is dull, it will not cut the grass cleanly. Straight rotary blades are the easiest type of mower blade to sharpen yourself.
Mulching Rotary Blades
Mulching rotary blades mount the same way as straight rotary blades. However, mulching rotary blades are curved to create suction. This suction holds the grass clippings in the path of the blades longer, allowing the blades to cut the clippings into smaller pieces. These smaller pieces fall deeper into your lawn and break down more quickly, allowing you to use your grass clippings as a direct lawn fertilizer. Keeping mulching rotary blades sharp is as important as keeping straight rotary blades sharp. However, because of their curve, mulching blades might require a number of different files to sharpen at home. They can, however, be easily sharpened at many mower-service companies.
Reel mowers predate rotary lawn mowers. Developed in the 19th century, reel mowers use a series of blades mounted horizontally on rotating drums to cut grass. The blades spin against a fixed metal plate and use a scissor-type action to cut the grass. Reel mowers can range in size from small push mowers to large, commercial lawn mowers pulled by a tractor. Older reel mowers might need to be sharpened once or twice a year. Mowers that are more modern keep the blades slightly away from the cutting bar and might not need sharpening for five years or more. Sharpening a reel mower blade requires a sharpening kit, but it is not difficult.