Engineering Drawing

B. Griffiths

Method of indicating surface finish and texture

Thu, 03 Mar 2011 13:37:23 | Engineering Drawing

Section 6.3.1 above described parameters using lTnN\ However, no information was given concerning how these are added to features on a drawing. The methodology to do this is described in ISO 1302:2001. It is based on what is termed a 'tick symbol' that defines the SF and points to the surface in question via a leader line.

Figure 6.13 shows the tick symbol with various descriptors surrounding it. The tick symbol is placed on the surface or an extension drawn to it. The basic tick comprises two lines at 60° to each other. This basic open tick (Figure 6.13a) has no significance of its own. Closing the tick symbol (Figure 6.13b) indicates that the surface must be machined. If machining is prohibited for some reason, for example, residual stresses must not be added, a circle is placed over the tick (Figure 6.13c). When additional information is to be added, a horizontal line is added to the right tick arm (Figure 6.13d). When the same surface texture is required on all surfaces around a workpiece, represented on an orthographic 2D drawing by a closed outline, a circle is added to the symbol at the junction of the tick and the horizontal line (Figure 6.13e). It is the symbol that means 'all surfaces around a workpiece outline'. For example, consider the gauge shown in Figure 6.14. A surface roughness 'tick' symbol is added to the top face. Because the tick has the small circle on it, the surface roughness requirement applies the eight faces around the front view but not the front face, shown as face (a), nor the back face, shown as face (b).

Additional information can be added to the closed tick symbol and arm as shown in Figure 6.15 as follows:

■ Positions 'a, b and c' - the surface texture parameters, numerical values, transmission band and SL information are placed at