The stop bolts are designed to limit the scraper from over adjusting beyond the wear limit of the blades. When limit is reached, the spring adjuster is restricted by the stop bolts from advancing the blades any further.
This allows the maximum wear of the blades without the blades wearing beyond the recommended limit. The stop bolts eliminate the possibility of the metal arms coming in contact with the conveyor belt.
In some cases, the stop bolts limit the rotation of the shaft, not allowing the blades to be aligned with the service opening. In this situation, the stop bolts need to be released and the shaft rotated to align with the service opening in the chute.