position tolerances
TRANSCRIPT
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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