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engineer-mechanical:inventor-dimensions [2019/10/07 17:26]
jjensen [GD&T Symbols]
engineer-mechanical:inventor-dimensions [2019/10/15 14:35] (current)
jjensen [Surface Finish]
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   * [[https://​youtu.be/​20J-WhSDsfY|YouTube - Inventor Tutorial with Isometric Sketches - Advanced part 4 multi-views]]   * [[https://​youtu.be/​20J-WhSDsfY|YouTube - Inventor Tutorial with Isometric Sketches - Advanced part 4 multi-views]]
   * <​HTML><​iframe width="​560"​ height="​315"​ src="​https://​www.youtube.com/​embed/​20J-WhSDsfY"​ frameborder="​0"​ allowfullscreen></​iframe></​HTML>​   * <​HTML><​iframe width="​560"​ height="​315"​ src="​https://​www.youtube.com/​embed/​20J-WhSDsfY"​ frameborder="​0"​ allowfullscreen></​iframe></​HTML>​
 +
 +===== Surface Finish =====
 +  * Texture Characteristics
 +    * machined surface contours can be split into three main components: roughness, waviness, and form
 +    * For most applications,​ roughness is the only characteristic that is specified on prints
 +  * Roughness
 +    * roughness refers to small scale, closely spaced irregularities caused by the cutting process. Marks produced by cutting tools during machining operations are examples of roughness; lines of this type are commonly called 'tool marks.'​
 +  * Waviness
 +    * Waviness has a longer period than roughness and can be caused by any cyclic characteristic of the machine-tool-toolholder combination. Flexure of the workpiece or the tool system is also a cause of waviness. Waviness is at its worst when a critical frequency is reached and chatter occurs.
 +  * Form
 +    * Form errors result from machine characteristics such as slideway variations and from inaccurate tool settings. Form errors can also arise from thermal distortions of the workpiece or the machine during cutting and also inadequate support of the workpiece during cutting.
 +  * Lay
 +    * Cutting tools leave characteristic marks on the surface that may affect the way the surface wears and interacts with mating parts. The general direction of the tooling marks depends on the manufacturing method selected; the general direction may be specified for applications where lay is critical.
 +  * Skewness
 +    * Skewness indicates the degree to which roughness comes from external variation or internal variation. For a contact-bearing application,​ sharp deep valleys separated by wide flat planes (negative skewness) would perform better than sharp spikes (positive skewness), for the same overall roughness value. A surface with positive skewness would contain spikes that would soon wear off, creating wear debris and damage.
 +  * Specification of Surface Texture
 +    * The surface texture symbol looks like a check mark. This symbol provides a uniform and concise way of specifying surface texture.
 +  * Roughness Height, Ra
 +    * surface texture for English prints is specified in microinches [millionths (0.000001) of an inch]
 +    * surface texture for metric prints is specified in micrometers [thousandths (0.001) of a millimeter]
 +<​html>​
 +<​table>​
 +<​theader>​
 +  <​td>​Microinches</​td>​
 +  <​td>​Micrometers</​td>​
 +  <​td>​Typical Uses</​td>​
 +</​theader>​
 +<tr>
 +  <​td>​250</​td>​
 +  <​td>​6.3</​td>​
 +  <​td>​Clearance surfaces (stock surfaces or rough machined)</​td>​
 +</tr>
 +<tr>
 +  <​td>​125</​td>​
 +  <​td>​3.2</​td>​
 +  <​td>​General mating surfaces for parts, sealing surfaces used with soft gaskets</​td>​
 +</tr>
 +<tr>
 +  <​td>​63</​td>​
 +  <​td>​1.6</​td>​
 +  <​td>​Keyways,​ milled threads, gear teeth</​td>​
 +</tr>
 +<tr>
 +  <​td>​32</​td>​
 +  <​td>​0.8</​td>​
 +  <​td>​Slideways,​ journals, sliding mechanisms</​td>​
 +</tr>
 +<tr>
 +  <​td>​16</​td>​
 +  <​td>​0.4</​td>​
 +  <​td>​Pistons and cylinder bores, cam lobes, precision gear teeth</​td>​
 +</tr>
 +<tr>
 +  <​td>​8</​td>​
 +  <​td>​0.2</​td>​
 +  <​td>​Precision heavy-duty rolling surfaces, valve seats</​td>​
 +</tr>
 +<tr>
 +  <​td>​4</​td>​
 +  <​td>​0.1</​td>​
 +  <​td>​Surfaces of fluid seals, pressure-lubricated bearings</​td>​
 +</tr>
 +</​table>​
 +</​html>​
 +  * Symbol Placement
 +    * Surface symbols are normally located so that they touch the object line for the surface that requires the finish. If this is not practical, the symbol is placed on an extension line. And if this is not practical, the symbol is used with a leader line, as illustrated in Figure 8-8 (p. 236). Both the symbol and the inscriptions are oriented for reading from the title block corner. [Hammers p. 236]
 +  * What does "​="​ mean
 +    * It is a lay direction symbol. Lay parallel to the plane of projection of the view in which the symbol is used.
 +  * No Symbol
 +    * Not all machine parts require special surface textures. Many parts are used as normally manufactured. If texture symbols are not shown, surfaces produced by normal manufacturing methods are acceptable.
 +  * Surface Treatment
 +  * Surface Coatings
  
 ===== Symbols ===== ===== Symbols =====
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   * Autodesk Inventor 2019 Help - [[http://​help.autodesk.com/​view/​INVNTOR/​2019/​ENU/?​guid=GUID-E5A07FBB-A7A5-4D4E-9EFC-68F74054E1EF|To Add Special Characters to Text or Prompted Entries]]   * Autodesk Inventor 2019 Help - [[http://​help.autodesk.com/​view/​INVNTOR/​2019/​ENU/?​guid=GUID-E5A07FBB-A7A5-4D4E-9EFC-68F74054E1EF|To Add Special Characters to Text or Prompted Entries]]
  
 +===== References =====
 +  * [Hammers] Hammer'​s Blueprint Reading Basics, 4th Ed by Charles A. Gillis
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