question here:

How would I find out the maximum depth (the center portion of the cut) of the curve?

I know that from simple trig that a^2 + b^2 = c^2

b in this case is half of the 4 inches, so b is 2. c can be approximated to be the segment between the two tangents of the block (the center part and one of the
ends) which is tangent alpha = 2 / 5.53125

the length of the arc of the curve is the diameter x pi x (alpha/360)

I am still befuddled as to the true value of c, not the approximated one.

Can someone help me out here?

Thanks