#### Answer

The difference between the cutting-edge width of the two chisels with the widest blades is $\frac{1}{4}$.

#### Work Step by Step

The cutting-edge width of the two chisels with the widest blades are $1”$ and $\frac{3}{4}”$. The difference between them is computed by subtraction:
$1 - \frac{3}{4} = \frac{4}{4} - \frac{3}{4} = \frac{4-3}{4} = \frac{1}{4}$.