Chapter-10 | Surface Metrology

Surface Metrology specifies the function of the surface. The important parameter is surface roughness.

In manufacturing industries, a surface must be within a certain limit of roughness.

Therefore, measuring surface roughness is vital to quality control of machining a work-piece.

By Surface Measurement, we can predict the performance of the component and control the manufacturing process.  

Basic Terminology in Surface Measurement

Flatness

Flatness is defined by the distance between peak and depth point of the surface plate.

Rigidity

It is the property of a solid body to resist deformation.

Leveling

It is the process of Level the table by its support system.

pink granite surface plate
Grade-00 surface plate

Types of Surface Plate

According to Material used, There are three types of Surface Plate

  1. Granite Surface Plate(IS 7327,ISO 8512-2)
  2. Cast Iron Surface Plate(IS 2285,ISO 8512-1 )
  3. Glass Plate(IS 14900)

Granite Surface Plate

Granite surface plate has more rigidity for the same depth with the absence of corrosion. They provide a high modulus of rigidity and are moisture free.

Metallic objects like manufactured components/jobs can easily slide on their surface. The usual range available from 400*250*50 mm to 2000*1000*250 mm.

surface plate grade 0

Grading System

Grade-00 (Prefer for Metrology laboratories )
Grade-0 (Prefer for General work in Quality Control)
Grade-1 (Prefer for tool room)
Grade-2 (Used for Shop Flore)
Grade-3 (Also, used for shop Flore depend upon needs of the customer )
the grading system of granite surface plate

Cast Iron Surface Plate

Cast-Iron surface plates used after rough machining is done followed by seasoning for a suitable period. Then, heat treatment for relieving internal stress.

CI surface table
CI Surface table

The accuracy of this surface plate is +/- 0.002 mm to +/-0.005 mm for the surface plate diagonal of 150 mm.

CI surface plate available in 2 grades,

Grade-1 (Maximum flatness is 5 microns for 300mm*300 mm plate)

Grade-2 (Maximum flatness is 20 microns for 300mm*300 mm plate)

Glass Surface Plate

Glass surface plate commercially available. These are comparatively light in weight and free from burr and corrosion.

Accuracy varies in the range 0.004 to 0.008 mm. They are available in size of 150mmx150mm to 600mm*800mm.

Measurement of Surface Roughness

Inspection and assessment of surface roughness of machined work-piece can be done by different measurement techniques.

  1. Pocket Surf
  2. Electronic Level

Pocket Surf

The Pocket surf is a pocket-sized device used for surface roughness measurement. It can be used confidently in production, on the shop floor, and in the laboratory.

Some important features of pock surf are

  • Solidly built with a durable cast aluminum housing to provide years of accurate, reliable surface finish gauging.
  • It can operate in any position(horizontal, vertical and upside down)
  • Four switchable probe position(axial or 90 degrees, 180 or 270 degrees)
  • Even difficult to reach surfaces such as inside and outside diameters accessible.
  • Easy to read LCD
  • Out of range(high or low) and battery indicator also displayed.

Next, Chapter-11| Basics of Screw thread Metrology

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