Aboothman please don't muddy up this thread.
Spackyscooby, Crystal is using 2(pi)R1 - 2(pi)R2 = circumference difference between a cylinder with a torque plate and one without it. He simplifies this equation by stating distortion difference x pi = true circumference difference. This equation would work if the cylinder did not distort and only the radius changed.
When Crystal applies this equation incorrectly he is exaggerating the effect of a torque plate. This exaggeration leads members on this site to believe they need to buy a torque plate to set their rings. Torque plates are only needed for boring and honing where exact tolerances are required. Setting ring gaps is not exact enough for the slight distortion to effect the rings.
Builders in this forum that are only setting ring gaps do not need to waste money on a torque plate.