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Barrette's Small Engines Inc. - FAQ's

What is a shear bolt? What is a shear pin?

A shear bolt, also known as a shear pin, is a pieace of metal alloy that is designed to "shear" or break under a predetermined amount of force.

Shear bolts are used as a protective device which attempt to counter stress towards critical or expensive components. The most common use of shear bolts for outdoor power equipment is in the auger shaft of snow throwers. Essentially these bolts are designed to be the "weak link" in the system. Should a snow thrower auger become jammed, the objective is for the shear bolt to purposely fail before damage of the stress load created by the jam reaches the auger gear box or other components.

Snow throwers generally have a single shear bolt located on each auger side although some designs may have more. These shear bolts are normally located along the main auger shaft near the center of each auger section. The shear bolts will pass through the outer auger shaft sleeve and the auger shaft, securing them together. The shear bolts are then secured on the protruding side with a lock nut or similar fastener.

Please reference the illustrated parts manual of the unit to determine the replacement part number and exact location of these bolts. To replace a broken shear bolt simply drive out the remaining broken pieces from the auger shaft hole using a punch tool and hammer and then replace it with the correct shear bolt and fastener.

IMPORTANT! Never replace a shear bolt with a standard bolt, hardened bolt or any other bolt as this will defeat the protective purpose of the shear bolt design and severe damage to the gear box may result. The type of stress will ultimately determine the amount of force applied on the shear bolt. A sudden and severe impact (shock load) is more likely to fracture a shear bolt then a slow and progressively larger resistance (soft load). Examples of "shock loads", consist of hitting a large rock or block of ice. "Soft loads" would likely be rope that slowly gets entangled in the auger or a newspaper left on the driveway that slowly gets more jammed into the augers eventually stopping them. Although the shear bolts are a protective device, they are not a guarantee of protection for the gear box. Variations in the types of load or jams will ultimately determine the amount of force being applied to a shear bolt at any given time. When auger gear boxes fail before the shear bolts fail, it is generally the result of a "soft load" resistance.

SERVICE NOTE:  Occasionally, when these bolts shear, the pieces fall out. When this happens all that remains are the holes in the auger sleeve and shaft. If the pieces are gone, the auger holes will need to be aligned using a punch (or similar tool) to facilitate alignment of the holes and insertion a new shear bolt.

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