TOLERANCING NOTES

Tolerances

• it is necessary today to hold precise tolerances to insure the interchangeability of parts.
• toleranceing is the process of determining the amount a dimension can vary from its theoretical size.

Terms

• NOMINAL SIZE: the number used to identify a dimension
• BASIC SIZE: the exact theorectical size of the dimension
• TOLERANCE: the amount that a deimension can vary from the basic size
• FEATURE: used to  identify the grometry of the drawing being referenced
• ALLOWANCE: the limit where the smallest clearance or largerst interference occurs. measured at MMC

Types of Dimensioning

• Limit Dimensioning (LIMIT)
• +/- Dimensioning (DIVIATION)

Terms(con't)

• maximum material condition (MMC)
• the limit of a dimension where the maximum material is left on the part
• least material condition (LMC)
• the limit of a dimension where the least material is left on the part

Type of Fit

• CLEARANCE: all dimension combinations will produce clearance between parts
• INTERFERENCE: all combinations of dimensions will produce a force fit
• TRANSITIONAL: different combinations of dimesions will produce different kinds of fits