[AutoCAD 2000 & Higher Versions. Level: Advanced]
Hello dear readers,
I tried summarizing Tolerances under 3 headings. In this first article, we'll be learning about the components of a tolerance dimension..
Fig.1
As you can see in Fig.1, tolerance dimensions can be broken down to 5 sections. However, it is the first two parts that are used the most. The remaining ones are primary, secondary and tertiary datum reference letters. Let's find out what they mean.
Geometric Characteristic Symbols:
Tolerance symbols for the geometric characteristics are placed on the left end of the tolerance box. One of these symbols may be placed in there:
Fig.2 List of geometric characteristic symbols that may be used.
Let's see a few examples:
Fig.3 Linearity tolerance.
Fig.4 Flatness tolerance (of the surface).
Fig.5 Angular Tolerance.
Fig.6 Cylindrical tolerance.
Fig.7 Profile tolerance.
Fig.8 Positioning tolerance.
As you can see, the tolerance dimensioning stars with the geometric characteristic symbol at the left end. The second box contains the tolerance values and material quality values.
- M: MMS = Maximum Material Cond
- L: LMC = Least acceptable material condition (Least Material Cond.)
- S: RFS = Regardless of Feature Size
Fig.9 Examples of material condition values.
Let's move on to more complex tolerances.
Complex Tolerances:
These are tolerances that contain boxes of "Datum" (a letter for describing the feature).
Fig.10
You can see a table showing the possible combinations for complex tolerances below, in (Fig.11).
Fig.11 Frames for more complex tolerances.
Fig.12
Single letter tolerance data can also be used, as in Fig.12.
We learnt about geometric tolerances and features of tolerance dimensions in this article. In our next article, we will be placing tolerances on drawings with the LEADER command.
In this article, British ROYMECH's geometric tolerance page was used as a reference. Link for those who want to have a look.
