The Shear Boost Reaction sets an amount of time by which the shear boost should fire early--the larger the time, the earlier the boost output fires.
When timed correctly with a properly calibrated boost, the die appears nearly weightless when the cutoff hits the material.
Note: This parameter is not used to obtain accuracy. Instead, it improves the quality of the cut--a larger boost reaction keeps the die from buckling the leading edge of the part, while a smaller boost reaction keeps the die from tearing the material on the trailing edge of the part.