Description of Common Terms used in Crossing Assembly
1. Theoretical nose of crossing (TNC):
It is the point of intersection of the gauge line of a crossing and is used as a reference point for all calculation for turn outs or other track connections.
2. Actual nose of crossing (ANC):
This is a point at which the spread of the gauage lines is sufficient to allow for an adequate thickness of the point, for consideration of manufacture and strength. For built up crossings, the thickness of the nose is generally kept equal to the web thickness of the rail section used.
3. Throat of vee crossings:
It is a point at which the converging wing rail of the crossing are nearest to each other.
4. Throat of obtuse crossing:
It is the point at which the converging elbow rail and the check rail of the obtuse crossing are closest.
5. Flat bearing plates and canting of rails:
In the Indian Railways, all rails on points and crossings are kept vertical i.e. without any cant. Flat bearing plates are therefore used under rails on turnouts.