GD&T

The practice of Geometric Dimensioning and Tolerancing, commonly called GD&T

A national drafting standard defined in the American Society of Mechanical Engineers document ASME Y14.5M- 1994

It is a language of symbols that communicates complex relationships between part features and

requires study and practice to apply correctly

Feature Control Frames

A feature control frame can include a tolerance symbol, one or more tolerance values, one

or more datum references, and a datum identifier

1. Geometric Characteristic

    flatness, roundness, parallelism, or perpendicularity

2. Tolerance zone size and form

3. Material Condition

4. Datum References

5. Projected Tolerance Zone

6. Datum Identifier

Feature Control Frames specify the part feature’s form, size, and allowable variation 变化 from both, and also the allowable variation between part features

Geometric Tolerance dialog box

1. Geometric characteristic symbol (menu)

2. Tolerance zone form (toggle)

3. Tolerance zone value

4. Material condition symbol (menu)

5. Datum reference 1 of 3

6. Datum reference 2 of 3

7. Projected tolerance zone symbol (toggle)

8. Projected tolerance zone value

9. Datum identifier