Symbols of surface finish which are providing at the finishing stage which gives value of surface finish. The symbols to indicate the information in connection with surface roughness are represented by symbolically. This is the important characteristics for surface finish.
Grade of Surface Roughness
Grade of surface roughness value is expressed as Ra in microns. The Ra value is considered as the main surface roughness in practice. In this process The grade of surface finish Ra value is from zero to stated value is acceptable.
Value of Ra and Rz
Value of Ra is the arithmetical mean deviation in mm are from selected from. 0.025, 0.05, 0.1, 0.2, 0.4, 0.8, 1.6, 3.2, 6.3, 12.5 and 25.
Values for ten points of height of irregularities Rz in mm are. 0.05, 0.1, 0.2, 0.4, 0.8, 1.6, 3.2, 6.3, 12.5, 25, 50 and 100.
Scales of Sheet Sizes
- Full Size 1:1
- Enlargement 2:1, 5:1, 10:1
- Reduction 1:2, 1:2.5, 1:5, 1:10
Engineering Drawings maybe prepared full sheet size. Sheet sizes are enlarged or reduced in size according to drawings. Size of scale is must be used in engineering drawings.