Machinery's Handbook, 31st Edition
Surface Texture
817
Surface Texture Symbols and Construction
Symbol
Meaning
Basic Surface Texture Symbol. Surface may be produced by any method except when the bar or circle (Fig. 7b or Fig. 7d ) is specified.
Fig. 7a.
Material Removal By Machining Is Required. The horizontal bar indicates that material removal by machining is required to produce the surface and that material must be provided for that purpose. Material Removal Allowance. The number indicates the amount of stock to be removed by machining in millimeters (or inches). Tolerances may be added to the basic value shown or in general note. Material Removal Prohibited. The circle in the V-shape indicates that the surface must be produced by processes such as casting, forging, hot finishing, cold finishing, die casting, powder metallurgy or injection molding without subsequent removal of material. Surface Texture Symbol. To be used when any surface characteristics are specified above the horizontal line or the right of the symbol. Surface may be produced by any method except when the bar or circle (Fig. 7b and Fig. 7d) is specified.
Fig. 7b.
3.5 Fig. 7c.
Fig. 7d.
Fig. 7e.
3 X
3 Approx.
3 X
1.5 X
OO
O.OO
OO OO
1.5 X Letter Height = X
60°
60°
Fig. 7f. Applying Surface Texture Symbols.— The point of the symbol should be on a line repre senting the surface, an extension line of the surface, or a leader line directed to the surface, or to an extension line. The symbol may be specified following a diameter dimension. Al - though ASME Y14.5-2018, “Dimensioning and Tolerancing,” specifies that normally all textual dimensions and notes should be read from the bottom of the drawing, the surface texture symbol itself with its textual values may be rotated as required. Regardless, the long leg (and extension) must be to the right as the symbol is read. For parts requiring extensive and uniform surface roughness control, a general note may be added to the drawing that applies to each surface texture symbol specified without values as shown in Fig. 8. When the symbol is used with a dimension, it affects the entire surface defined by the dimension. Areas of transition, such as chamfers and fillets, shall conform with the rough est adjacent finished area unless otherwise indicated. Surface texture values, unless otherwise specified, apply to the complete surface. Draw ings or specifications for plated or coated parts shall indicate whether the surface texture values apply before plating, after plating, or both before and after plating. Only those values required to specify and verify the required texture characteristics should be included in the symbol. Values should be in metric units for metric drawing and non-metric units for non-metric drawings. Minority units on dual dimensioned drawings are enclosed in brackets.
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