Replace or rebuild the moldboard if the bottom edge is worn to the bolt holes. The shorter the moldboard height from unwanted wear, the higher the backward blade torque, which results in bolt and blade breakage.
Use S.A.E Grade 8 Plow Bolts
(They will not stretch when tightened)
Number 3 head plow bolts (with self-locking nuts) will greatly reduce the likelihood of blade chatter and bolt failure.
Torque bolts to 220 ft./lbs. (Torque spec. for ⅝″ Grade 8 bolts)
Use S.A.E. Grade 8 Nuts, they are hardened and will not "mushroom" or flatten in use.
Lock Nuts are preferred because they lock to the bolt, and are always Grade 8.
Standard Nuts, if used, should be Grade 8. We recommend you double nut (no lock washer).
Lock washers gouge the backside of the snowplow moldboard because the washer is harder than the moldboard. These hardened lock washers act as a cutting tool, causing unwanted "metal shards" on the moldboard where the nut is to seat.
No matter how hard you tighten the nut, these metal shards will flatten under use, causing the nut to loosen on the bolt and eventually shear the bolt under use.
Use a hardened lock nut to alleviate this condition. If using standard Grade 8 nuts, double nut.