Surface finish is checked with:

Surface finish refers to the texture or smoothness of a surface after machining or processing. It is an important aspect in determining the performance, wear, and aesthetic appeal of a manufactured part.

The correct method for checking surface finish is often through a comparison chart. This chart provides a visual and numerical reference for different levels of surface finishes, allowing for a straightforward assessment of the surface quality against established standards. It helps in evaluating whether the surface meets the required specifications based on the desired function of the part.

Other methods, while they may be useful in certain contexts, do not provide as comprehensive or standardized a measure as a comparison chart. Digital gauges can certainly measure surface roughness, but they represent just one technological approach. Visual inspection can give a general idea of surface quality but lacks the precision required for accurate assessments. The pencil test, while a rudimentary assessment technique, is quite subjective and is generally not used in professional settings for accurate measurement of surface finish.