Deflections vs. Flatness & Straightness

If flatness obstructions (e.g. dings, dust, dirt and machined contours along the bearing surface) are at the same pitch as the bearings, deflections are generated linearly in a vertical direction only. Where, the deflection amplitude equals the height of the bumps (a).
If flatness obstructions are not at the same pitch as the bearings, deflections are generated both linearly in a vertical direction and rotationally about a point equi-distant between the points of bearing contacts.
Where the deflection amplitude (b) is less than the height of the bumps and linear position (c) is affected by the pitch angle.

(see angular conventions on the Additional Error Causing Conditions page)