Sag corrections in dial setting are applied only to what type of readings?

Sag corrections in dial setting are specifically related to vertical rim readings because these readings are affected by the weight of the components involved and the gravitational forces acting upon them. When measuring components that are mounted vertically or are intended to operate in a vertical orientation, any sag in the system – caused by the weight or installed configuration – can lead to inaccuracies in the measurements.

The purpose of the sag correction is to ensure that the dial gauge reflects the true condition of the machinery by compensating for any deflection that occurs under load. In contrast, horizontal rim readings and face readings may not experience the same type of deflection since they are oriented differently with respect to gravity or load. Combined rim readings are generally considered a mix, but without focusing on the vertical aspect, sag correction is primarily pertinent to vertical measurements. Therefore, applying sag corrections specifically to vertical rim readings helps achieve higher precision and accuracy in alignment and level checks in millwright operations.