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In addition to the size of the bond-bridge, the fracture mode is also critical. The bond must be strong enough to hold the grains under normal grinding conditions, but under higher stress it must allow the grain to fracture in a controlled way. The bond should not be so strong relative to the grit strength that the abrasive glazes and leads to burn.
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Micro
fracture
FIGURE 6.7 Pullout, stable breakdown, and glazing regimes in grinding. (Based on a drawing by Rappold 2002. With permission.)
One method to regulate this is by adding fine quartz or other particles to the bond to control crack propagation. Another is to recrystallize the glass creating nucleation centers that act in a similar fashion.