position tolerances

POSITION TOLERANCES

USED TO SPECIFY THE REQUIRED LOCATION ACCURACY FOR FEATURES OF SIZE

ONE FEATURE CONTROL FRAME CAN BE USED TO SHOW THE POSITION OF A SINGLE HOLE OR AN ENTIRE PATTERN OF HOLES

MOST COMMONLY USED FOR HOLES/SLOTS

POSITION TOLERANCES

DATUM FEATURES ARE IDENTIFIED –

LOCATES THE DATUM REFERENCE FROM WHICH THE HOLE LOCATIONS ARE MEASURES

BASIC DIMENSIONS LOCATE THE TRUE POSITIONS FOR THE HOLES

FEATURE CONTROL FRAME DEFINES THE SIZE OF THE TOLERANCE ZONE

POSITION TOLERANCES

POSITION TOLERANCE

A POSITION TOLERANCE

ZONE WILL USUALLY HAVE

A DEFINED SHAPE, SIZE, LOCATION, AND ORIENTATION.

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A DIAMETER SYMBOL INDICATES SHAPE

BASIC DIMENSIONS & TRUE POSITIONS

THE TRUE POSITION IS THE LOCATION ON WHICH TO CENTER THE SPECIFIED TOLERANCE ZONE.

POSITIONRELATIONSHIPS

THE NEED FOR POSITIONAL TOLERANCES

FEATURE CONTROL FRAME

POSITIONAL TOLERANCING

THE EFFECTS OF MATERIAL CONDITIONS ON POSITION

RFS APPLIED TO POSITIONAL TOLERANCING Page 166

THE SPECIFIED TOLERANCE VALUE REMAINS CONSTANT REGARDLESS OF THE PRODUCED SIZE OF THE TOLERANCED PART

MMC APPLIED TO POSITIONAL TOLERANCING

IF THE CONTROLLED FEATURE IS PRODUCED AT ANY ALLOWABLE SIZE OTHER THAN MMC, THE POSITION TOLERANCE VALUE INCREASES AN AMOUNT EQUAL TO THE MMC.

HOLE POSITIONING AT MMC

LMC POSITIONING

THE POSITION TOLERANCE VALUE INCREASES AN AMOUNT EQUAL TO THE DEPARTURE FROM LMC

HOW FIT AFFECTS POSITION TOLERANCES

DEPARTURE FROM MMC INCREASES LOCATION ERRORS

THE PERMITTED POSITION TOLERANCE INCREASES BY EXACTLY THE SAME AMOUNT AS THE FEATURE DEPARTS FROM MMC

POSITION TOLERANCING USING AXES

DATUM REFERENCES FOR POSITIONING

MEASUREMENTS TAKEN FROM THE DATUM REFERENCE FRAME MAY BE SIGNIFICANTLY DIFFERENT FROM MEASUREMENTS FROM THE ACTUAL PART-

USE MEASUREMENTS FROM THE DATUM REFERENCE FRAME

POSITIONAL TOLERANCING

POSITION TOLERANCES RELATIVE TO DATUM FEATURES

POSITIONING HOLES

MMC TOLERANCE USING DATUMS

ZERO POSITIONING TOLERANCES

POSITIONING SLOTS

TOLERANCE ZONE

ROUND TOLERANCE ZONES PROVIDE AN INCREASED TOLERANCE ZONE COMPARED TO SQUARE TOLERANCE ZONES

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COMPOSITE POSITION TOLERANCES

A COMPOSITE TOLERANCE HAS ONLY ONE POSITION TOLERANCE SYMBOL

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COMPOSITE POSITION TOLERANCES

COMPOSITE TOLERANCES

WHENEVER DATUM REFERENCES ARE SHOWN IN THE SECOND LINE OF A COMPOSITE TOLERANCE, THEY MUST BE REPEATED AS SHOWN IN THE FIRST LINE WITH THE SAME MATERIAL CONDITION MODIFIERS.

COMPOSITITE TOLERANCING

CONTROLLING COUNTERBORES

COUNTERBORE HOLE POSITIONING

HOLE PATTERNS

HOLE PATTERNS

PATTERNS

PATTERN AT MMC

CHECKING POSITION

CHECKING POSITION

CHECKING POSITION

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CHECKING POSITION

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FEATURES VS.POSITIONING

FLOATING FASTENER

FLOATING FASTENER

T = TOLERANCE

H = HOLE DIA AT MMC

F = FASTENER DIA AT MMC

FLOATING FASTENERPRACTICE CALCULATION

FLOATING FASTENER –EXAMPLE 2

CALCULATE THE POSITION TOLERANCE FOR A FLOATING FASTENER APPLICATION.GIVEN HOLE DIAMETER = .328 +/- .004”FASTENER DIAMETER = .312” MMCT = H – F

.324 - .312 = .012

T = .012”

FIXED FASTENER

FASTENER LOCATION CAN BE FIXED BY THREADS, PRESS FIT, OR TAPER THAT PREVENTS MOVEMENT OF THE FASTENER

FIXED FASTENER CALCULATION

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FIXED FASTENER CALCULATION

CALCULATE THE POSITION TOLERANCE FOR A FIXED FASTENERHOLE DIA = .296 +/- .003”FASTENER DIA = .250” MMC

T = (H – F) /2

T = (.293 - .250) /2

T = .043/2

T = .0215

FIXED FASTENER

COAXIAL HOLE PATTERNS

COAXIAL HOLES CAN HAVE DIFFERENT DIAMETERSA COMPOSITE TOLERANCE CAN BE APPLIED TO COAXIAL HOLES OF DIFFERENT DIAMETERSTHE ALIGNMENT OF THE COAXIAL HOLES MUST BE ACCURATE ENOUGH TO INSERT THE SHAFT THAT PASSES THOUGH THEM.

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COAXIAL FASTENERS

COAXIAL POSITIONING

CONCENTRICITY

CONTROL OF ONE AXIS TO ANOTHERONLY USED WHEN THIS IS THE ONLY MEANS TO MANUFACTURE A USEABLE PARTCOMMON MISTAKE TO USE A CONCENTRIC TOLERANCE INSTEAD OF A RUNOUT TOLERANCE

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CONCENTRICITY

APPLIED TO A CYLINDER OR ANY OTHER SYMMETRICAL SHAPE WITH AN AXIS

CONCENTRICITY

SYMMETRY

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A CONDITION WHERE FEATURES ON EACH SIDE OF A CENTER LINE OR CENTER PLANE ARE EQUAL

COMMONLY USED

ON HOLE PATTERNS

SYMMETRY

CAN BE APPLIED TO FEATURES OF SIZE

SHOWS THAT THE RAIL IS SYMMETRICALLY LOCATED TO THE BASE OF THE PART

SYMMETRY

SYMMETRY

SYMMETRY AT MMC

CHECKING INTERFERENCE

PROJECTED TOLERANCE ZONE

PROJECTED POSITION TOLERANCE

PROJECTED POSITION TOLERANCE

BONUS TOLERANCES

USED TO INCREASE THE AMOUNT OF ACCEPTABLE ERROR

CAN BE USED TO REWORK HOLES THAT ARE OUT OF TOLERANCE BY REDRILLING HOLES TO A LARGER DIAMETER

ALLOWABLE INCREASE IN THE TOLERANCE IS KNOWN AS THE BONUS TOLERANCE

BONUS TOLERANCES

THE BONUS TOLERANCE AND THE SPECIFIED POSITION TOLERANCE ARE ADDED TOGETHER TO DETERMINE THE ALLOWABLE POSITION TOLERANCE.

BONUS TOLERANCE

BONUS TOLERANCES

POSITION TOLERANCES APPLIED TO EXTERNAL FEATURES ARE AFFECTED BY MATERIAL MODIFIERS IN THE SAME MANNER AS TOLERANCES ON HOLES/INTERNAL FEATURES

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