What adjustment must be made to the boring bar if the measured bore is +0.003 from the desired dimension?

When a measured bore is +0.003 inches larger than the desired dimension, the adjustment that must be made to the boring bar is to reduce the effective cutting diameter by this amount. The key idea is that the bore is oversize, so in order to achieve the desired diameter, you need to make the boring bar cut less material.

If the adjustment is set to -0.007 inches, it will account for the excess size and further reduce the diameter beyond the current size by an additional 0.004 inches. This combination effectively brings the bore down to the intended dimension.

The rationale here lies in the understanding of how adjustments impact the cutting diameter: if the bore is too large and the goal is to achieve a smaller bore, the adjustment must compensate not just for the excess but also ensure that the final size meets the specifications.