Glossary of Terms
Feature
Feature - general term applied to a physical portion of a part
Feature - general term applied to a physical portion of a part - any observable geometry
Feature of Size (FOS)
Feature of Size (FOS) - a feature with opposed surface(s)
Feature of Size (FOS) - a feature with opposed surface(s) - may be planar or cylindrical
Feature of Size (FOS) - a feature with opposed surface(s) - may be planar or cylindrical - is measurable; associated with a size dimension
Examples of Features of Size:
Examples of Features of Size: Cylindrical FOS
Examples of Features of Size: Cylindrical FOS Internal Cylindrical FOS
Examples of Features of Size: Cylindrical FOS Internal Cylindrical FOS ………… Hole
Examples of Features of Size: Cylindrical FOS Internal Cylindrical FOS ………… Hole External Cylindrical FOS
Examples of Features of Size: Cylindrical FOS Internal Cylindrical FOS ………… Hole External Cylindrical FOS ……..….. Shaft
Examples of Features of Size: Cylindrical FOS Internal Cylindrical FOS ………… Hole External Cylindrical FOS ……..….. Shaft Planar FOS
Examples of Features of Size: Cylindrical FOS Internal Cylindrical FOS ………… Hole External Cylindrical FOS ……..….. Shaft Planar FOS Internal Planar FOS
Examples of Features of Size: Cylindrical FOS Internal Cylindrical FOS ………… Hole External Cylindrical FOS ……..….. Shaft Planar FOS Internal Planar FOS ………..… Slot
Examples of Features of Size: Cylindrical FOS Internal Cylindrical FOS ………… Hole External Cylindrical FOS ……..….. Shaft Planar FOS Internal Planar FOS ………..… Slot External Planar FOS
Examples of Features of Size: Cylindrical FOS Internal Cylindrical FOS ………… Hole External Cylindrical FOS ……..….. Shaft Planar FOS Internal Planar FOS ………..… Slot External Planar FOS ……….… Tab
Examples of Features of Size: Cylindrical FOS Internal Cylindrical FOS ………… Hole External Cylindrical FOS ……..….. Shaft Planar FOS Internal Planar FOS ………..… Slot External Planar FOS ……….… Tab The uses the term: Fit Design Analyst TM
Examples of Features of Size: Cylindrical FOS Internal Cylindrical FOS ………… Hole External Cylindrical FOS ……..….. Shaft Planar FOS Internal Planar FOS ………..… Slot External Planar FOS ……….… Tab The uses the term: Fit Design Analyst TM - “Hole” as an analog to refer to any internal FOS
Examples of Features of Size: Cylindrical FOS Internal Cylindrical FOS ………… Hole External Cylindrical FOS ……..….. Shaft Planar FOS Internal Planar FOS ………..… Slot External Planar FOS ……….… Tab The uses the term: Fit Design Analyst TM - “Hole” as an analog to refer to any internal FOS - “Shaft” as an analog to refer to any external FOS
Nominal Size
Nominal Size - designation used for the purpose of general identification
Nominal Size - designation used for the purpose of general identification - usually expressed in common fractions
Nominal Size - designation used for the purpose of general identification - usually expressed in common fractions 1 Nominal Size is Ø 2
Basic Size or Basic Dimension
Basic Size or Basic Dimension the theoretical (ideal) size to which a tolerance is applied
Basic Size or Basic Dimension the theoretical (ideal) size to which a tolerance is applied limit dimensions result from the application of a tolerance specification to a basic dimension
Basic Size or Basic Dimension the theoretical (ideal) size to which a tolerance is applied
Basic Size or Basic Dimension the theoretical (ideal) size to which a tolerance is applied Tolerance Specification, applied to the basic dimension Basic Dimension
Basic Size or Basic Dimension limit dimensions result from the application of a tolerance specification to a basic dimension
Basic Size or Basic Dimension limit dimensions result from the application of a tolerance specification to a basic dimension Resulting limit dimensions
Basic Hole System
Basic Hole System A widely-used fit system employed when standard tools (e.g., drills, reamers) are used to produce holes
Basic Hole System A widely-used fit system employed when standard tools (e.g., drills, reamers) are used to produce holes the small hole (lower limit) is assigned the basic size (typically the nominal size), to which the hole tolerance and fit allowance is applied: “the small hole is basic”
Basic Hole System A widely-used fit system employed when standard tools (e.g., drills, reamers) are used to produce holes the small hole (lower limit) is assigned the basic size (typically the nominal size), to which the hole tolerance and fit allowance is applied: “the small hole is basic” The toleranced shaft size is then designed around the resulting hole limits in order to achieve the desired fit
Basic Shaft System
Basic Shaft System A less widely-used fit system typically employed where shafts are purchased in standard sizes or where two or more fits are required on the same shaft
Basic Shaft System A less widely-used fit system typically employed where shafts are purchased in standard sizes or where two or more fits are required on the same shaft the large shaft (upper limit) is assigned the basic size to which the shaft tolerance and fit allowance is applied: “the large shaft is basic”
Basic Shaft System A less widely-used fit system typically employed where shafts are purchased in standard sizes or where two or more fits are required on the same shaft the large shaft (upper limit) is assigned the basic size to which the shaft tolerance and fit allowance is applied: “the large shaft is basic” The toleranced hole size is then designed around the resulting shaft limits in order to achieve the desired fit
LIMITS
LIMITS the maximum and minimum sizes indicated by a toleranced dimension
LIMITS the maximum and minimum sizes indicated by a toleranced dimension called the “upper limit” (large) and “lower limit” (small) dimensions
Tolerance
Tolerance - the total permissible variation of a dimension
Tolerance - the total permissible variation of a dimension TOL = UPPER LIMIT DIM - LOWER LIMIT DIM
Tolerance - the total permissible variation of a dimension
Tolerance - the total permissible variation of a dimension TOL = UPPER LIMIT DIM - LOWER LIMIT DIM TOL = 1.006 - .996 TOL = .010
Maximum Material Condition (MMC)
Maximum Material Condition (MMC) the limit of size of a feature which results in the feature having the maximum amount of material
Maximum Material Condition (MMC) the limit of size of a feature which results in the feature having the maximum amount of material MMCSHAFT = upper limit (large shaft)
Maximum Material Condition (MMC) the limit of size of a feature which results in the feature having the maximum amount of material MMCSHAFT = upper limit (large shaft) MMCHOLE = lower limit (small hole)
Least Material Condition (LMC)
Least Material Condition (LMC) the limit of size of a feature which results in the feature having the minimum amount of material
Least Material Condition (LMC) the limit of size of a feature which results in the feature having the minimum amount of material LMCSHAFT = lower limit (small shaft)
Least Material Condition (LMC) the limit of size of a feature which results in the feature having the minimum amount of material LMCSHAFT = lower limit (small shaft) LMCHOLE = upper limit (large hole)
ALLOWANCE
ALLOWANCE the minimum clearance (or maximum interference) between mating features
ALLOWANCE the minimum clearance (or maximum interference) between mating features the allowance represents "the condition of tightest permissible fit" between mating features
ALLOWANCE the minimum clearance (or maximum interference) between mating features the allowance represents "the condition of tightest permissible fit" between mating features ALLOWANCE = SMALLEST - LARGEST HOLE SHAFT
MEAN DIMENSION
MEAN DIMENSION the arithmetic average of the upper and lower limit dimensions
MEAN DIMENSION the arithmetic average of the upper and lower limit dimensions the mean dimension is used to create geometry in computer-aided design (CAD)
MEAN DIMENSION the arithmetic average of the upper and lower limit dimensions the mean dimension is used to create geometry in computer-aided design (CAD) note: the mean dimension is not necessarily equal to the basic dimension
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