Ramblings of an Ex-Cad Engineer and Cad Drafter experienced in Mechanical Cad with His Autocad Tutorial
August 28th, 2010 — AutoCAD Tutorials
A composite tolerance specifies two tolerances for the same geometric characteristic of a feature or features that have different datum requirements. One tolerance relates to a pattern of features and the other tolerance to each feature within the pattern. The individual feature tolerance is more restrictive than the pattern tolerance.
August 28th, 2010 — AutoCAD Tutorials
Projected tolerances are specified in addition to positional tolerances to make the tolerance more specific. For example, projected tolerances specify the perpendicularity tolerance zone of an embedded part.
August 28th, 2010 — AutoCAD Tutorials
The tolerance values in the feature control frame are followed by up to three optional datum reference letters and their modifying symbols. A datum is a theoretically exact point, axis, or plane from which you make measurements and verify dimensions. Usually, two or three mutually perpendicular planes perform this task best. These are jointly called the datum reference frame.
August 28th, 2010 — AutoCAD Tutorials
Material conditions apply to features that can vary in size. At maximum material condition (, also known as MMC), a feature contains the maximum amount of material stated in the limits. At MMC, a hole has a minimum diameter, whereas a shaft has a maximum diameter. At least material condition (, also known as LMC), a feature contains the minimum amount of material stated in the limits. At LMC, a hole has maximum diameter, whereas a shaft has minimum diameter. The third material feature condition, regardless of Feature Size (, also known as RFS), means a feature can be any size within the stated limits.
November 20th, 2009 — AutoCAD Tutorials
Geometric tolerancing shows deviations of form, profile, orientation, location, and runout of a feature. You add geometric tolerances in feature control frames. These frames contain all the tolerance information for a single dimension. You can copy, move, erase, scale, and rotate feature control frames. You can snap to them using the object snap modes. You can use DDEDIT to edit feature control frames, or you can edit them with grips.
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