Lapping is a machining process in which two surfaces are rubbed together with an abrasive between them, by hand movement or using a machine. Lapping process gives best surface finish.

Lapping is a machining process in which two surfaces are rubbed together with an abrasive between them, by hand movement or using a machine. Lapping process gives best surface finish.

The lower critical temperature is same for all steels Lower critical temperature for steel’s austenite-to-pearlite transformation is 1333 ºF (723 ºCelsius). Below this temperature, austentite doesn’t exist.

The important dimensionless numbers in fluid mechanics are

1. Reynold’s number

2. Froude’s number

3. Weber’s number

4. Euler’s number

5. Mach’s number or Cauchy’s number

**Reynold’s number**: Reynold’s number is the ratio of inertia force to the viscous force.

**Froude’s number**: Froude’s number is the ratio of inertia force to the gravity force.

**Weber’s number**: Weber’s number is the ratio of inertia force to the surface tension force.

**Euler’s number**: Euler’s number is the ratio of inertia force to the pressure force.

**Mach’s number or Cauchy’s number**: Mach’s number or Cauchy’s number is the ratio of inertia force to the elastic force.