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Barrette's Small Engines Inc. - SmallEngines.ca FAQ's
I recently broke the blade adapter on my walk-behind mower and now the new one has failed, why would the new one fail so soon?
Blade adapters are designed in strict accordance with federal safety guidelines. They must be weaker than the cutting blades and yet strong enough to withstand the engines normal RPM and resulting blade torque and vibration. They also must meet several other federal guidelines regarding stress and load tolerances too numerous to be detailed here.
When the mower hits a stationary object at 3,000+ RPM, the forces exerted on the blade and associated parts can be quite considerable. Sometimes a series of lesser impacts eventually results in enough vibration and combined stress that the blade adapter finally fatigues and fails. Broken blade adapters are most frequently the result of one or more of the following:
A) The mower blade hitting a stationary object resulting in significant torque or vibration to the adapter and possibly also transferred through to the engine crankshaft.
B) The mower blade being unbalanced, damaged or from the use of an unapproved NON-OEM* cutting blade.
C) The engine or engine crankshaft being damaged and thus resulting in excess vibration being transferred to the blade adapter.
All of which may result in excess vibration and subsequent blade adapter failure.
It is good service practice that whenever the blade adapter is fails that BOTH the blade adapter and the cutting blade be replaced with new OEM* parts. The blade should also be replaced, as it may have defects undetectable to the human eye that may result in a future blade failure and/or blade adapter failure. If the blade adapter has failed and the blade adapter and blade have BOTH been replaced with new OEM* parts and then the blade adapter fails again in a short period of time, it is likely that the engine has a bent engine crankshaft. Installing another blade adapter on an engine with a damaged crankshaft will simply result in another blade adapter failure, until the engine crankshaft has been properly serviced. Click Here for more information on damaged engine crankshafts.
*The acronym OEM stands for Original Equipment Manufacture. Always use OEM approved parts for service.