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Tolerancing Vocab 1
| Term | Definition |
|---|---|
| Actual Size | the measured size of an object |
| Allowance | the intentional difference in the dimensions of mating parts to provide for different classes of fits |
| Basic Dimension | an exact untoleranced value used to describe the size, shape, or location of a feature |
| Basic Size | the size of a part determined by engineering and design requirements |
| Chain Dimensioning | a dimensioning system in which successive dimensions are placed in a "chain" from point to point to locate features, rather than each originating at a datum. AKA point-to-point dimensioning |
| Datum | a point, line or surface assumed to be exact size and shape, and in an exact location for establishing the location of other features. |
| Datum Dimensioning | a dimensioning system in which every feature of a part is dimensioned from a common point or plane. |
| Design Size | the size of a feature after an allowance for clearance has been applied and tolerances have been assigned. |
| Feature Control Frame | a compartment containing divided areas for specifying a geometric tolerance for a feature. |
| Fit | a general term referring to the range of "tightness" between mating parts. |
| Form Tolerances | Tolerances that control or the geometric shape of features of a part. |
| Bilateral Tolerances | allow variations in both directions from a design size |
| Lay | the direction of the predominant surface pattern of a part. |
| Least Material Condition (LMC) | a condition that is present when a feature contains the least amount of material within the tolerance range. |
| Reference Dimension | an untolerated dimension placed on a drawing for the convenience of engineering and manufacturing personnel |
| Limits | the extreme dimensions allowed by a tolerance range. |
| Tolerance | the total amount of variation permitted from the design size of a part. |
| Unilateral Tolerances | allow variations in only one direction from the design size. |
| Clearance Fit | has a positive allowance or "air space." |
| Interference Fit | has a negative allowance or "interference." |
| Transition Fit | the limits of size are defined so that the result may be either a clearance fit or interference fit. |
| Basic Hole Size | the basic size of the hole is the design size, and the allowance |
| Basic Shaft Size | the design size of the shaft is the basic size and the allowance is applied to the hole. |
| Limit Dimensioning | only the maximum and minimum dimensions are given. |
| plus and minus tolerancing | the tolerances are generally placed to the right of the specific dimension |
| running & sliding fit | fit that allows ease of movement. Designated by RC1- RC9 |
| Locational Fit | relate to the location of mated parts. Designated by LC, LT & LN symbols |
| Force Fit | designed to describe pressures between mating parts. AKA Force Fit. Designated by FN1- FN3 |