Before wringing, the mating surfaces of slip gauges should be wiped clean with

Grade - 2

Slip gauges are graded according to their accuracy as Grade 0, Grade I and Grade II.
Grade 0 is used in laboratories and standard room which serves as standard for periodically checking the accuracy of Grade I and Grade II gauges.
Grade I is of higher accuracy and used in inspection departments.
Grade II is intended for use in workshops during the actual production of components, tools and gauges.

More than 63 HRC

Inspection room

Slip gauges are graded according to their accuracy as Grade 0, Grade I and Grade II.
Grade 0 is used in laboratories and standard room which serves as standard for periodically checking the accuracy of Grade I and Grade II gauges.
Grade I is of higher accuracy and used in inspection departments.
Grade II is intended for use in workshops during the actual production of components, tools and gauges.

112 pieces

As per Indian standards a special set of slip gauge is used consisting of 112 pieces.