Presentation on theme: "8-7: Surface Texture Designers must accurately describe the required finish to the people actually making the parts."— Presentation transcript:
8-7: Surface Texture Designers must accurately describe the required finish to the people actually making the parts.
Two principal reasons for surface finish control: To reduce friction To reduce wear
Surface Texture Characteristics Microinch: μin is one-millionth of an inch ( inch) Micrometer: μm Roughness: consists of the finer irregularities in the surface texture, usually including those that result from the inherent action of the production process. Roughness-Height Value, roughness spacing, roughness width cutoff, waviness, lay, flaws
Surface Texture Symbol Roughness, waviness, and lay may be controlled by applying the desired value to the surface texture symbol, in a general note, or both. The point of the symbol should be located on the line indicating the surface, on an extension line from the surface, or on a leader pointing to the surface or extension line. When numerical values accompany the symbol, the symbol should upright and readable from the bottom When no numerical values accompany the symbol, the symbol can be positioned to be readable from the right side. For plain surfaces, the surface texture symbol refers to the completed surface For plated or coated surfaces the designer must indicate if the surface texture value applies before, after, or both the plating or coating
Surface Texture Ratings 1. Indicated to the left of the long leg of the symbol – One rating gives maximum value – Two ratings indicates maximum and minimum values 2. Waviness-height rating is located above the horizontal extension of the symbol 3. Waviness-spacing is separated from the waviness-height rating by a dash 4. Lay symbol located to right of long leg of symbol.
Machined Surfaces Cast, molded, or forged parts need symbols to indicate machining or finishing. FINISH ALL OVER may be used as a general note. is the symbol for surfaces produced by machining operations Material removal allowance (amount of material to be removed) is shown in inches or mm to the left of the symbol Material removal prohibited is shown by a special symbol