Few manufacturers equip modern mowers with the simplest cutting blades. Today's brands offer numerous styles of rotary mower blades, each type claiming some superior feature in comparison to a less expensive version. Three main categories offer real differences in performance, but blade design affects mowing less than does blade maintenance and quality of steel. Cheap blades seldom hold an edge well and may not even hold their shape. More expensive blades with advanced designs stand up to heavy use and perform well if sharpened regularly.
Formed from either straight flat steel stock or channel-reinforced steel, the straight cutting mower blade slices through grass with less agitation than other designs. For mowers with less horsepower, these blades cut without placing too much strain on the engine. Straight cutting blades leave longer sections of cut grass behind and do not mulch clippings. Raking the yard clean after a heavy mowing will be necessary. Mow frequently for cleaner results.
With a section of steel stock turned up behind the cutting edge, high lift styles intensify the upward draft created by the revolution of the blade. This updraft lifts grass pushed down by the forward motion of the mower so the blade leaves a more uniform lawn behind. Clippings also circulate in the mower deck longer, creating some mulching action. High lift blades reduce clipping buildup under the deck and in discharge ports, allowing longer periods of trouble-free operation. High lift blades also improve the performance of grass catchers, putting more air volume behind the flow of clippings to the storage bag or bin.
Mulching blades lift and circulate clippings under the deck, cutting and re-cutting clippings into fine mulch. Ideally the mulched grass sinks into the yard's thatch, fertilizing the lawn. Mulching places the highest strain on the mower, requiring slower operating speeds and repeated passes in heavy grass. Damp conditions cause clippings to stick beneath the mower deck, bogging down blades and even stalling engines. Special mulching blades with raker teeth formed in the raised portion of the blade's back edge increase the grinding effect of the blade and decrease operating problems.
Combination blades offer some of the advantages of both high lift and mulching blades. Though makers claim these blades do everything, minor differences in blade design don't make large differences in performance. On any equipment the quality of the cutting edge affects the quality of the cut most dramatically. Even straight-blade mowers mulch well enough if owners mow frequently and keep the blades sharp.