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Formulae For Fundamental Deviations of Shafts up to size 500-3150mm


SHAFTHOLESFORMULAE FOR DEVIATION IN MICRON
SHAFT DESIGNATION FUNDAMENTAL DEVIATIONSIGN HOLE DESIGNATIONFUNDAMENTAL DEVIATIONSIGNFor "D" in mm
des-DEI+16D0.44
ees-EEI+11D0.41
fes-FEI+5.5D0.41
ges-GEI+2.5D0.34
hesNo SignHEINo Sign 0
jsei-JSES+ 0.5ITn
kei+KES- 0
mei+MES- 0.024D+12.6
nei+NES- 0.04+21
pei+PES- 0.072D+37.8
rei+RES- Geometric mean of the values "p" and "s" or "P" and "S"
sei+SES- IT7+0.4D
tei+TES- IT7+0.63D
uei+UES- IT7+D

ISO 286 Tolerance Band "IT8" To "IT16"


Tolerance Band Given Below (IT8 To IT16) In Micrometer=(10-3)mm


NOMINAL( BASIC) SIZES (mm) INTERNATIONAL TOLERANCE GRADES
OVER UP TO INCL.IT8IT9IT10IT11IT12 IT13IT14IT15IT16
03142540 60100140250400600
36183048 75120180300480760
610273668 9060220360580900
1018274370 1101802704307001100
1830335284 1302103305208401300
30503962100 16026039062010001600
50804674120 19030046074012001900
801206487140 22035054087014002200
12018060100160 250400630100016002500
18025072115185 290460720115018502900
25031581130210 320620810130021003200
31540089140230 360570890140023003600
40050097155250 400630970150025004000
500630110175280 4407001100175028004400
630800125200320 5008001250200032006000
8001000140230360 5609001400230036005600
10001250165260420 66010601650260042006600
12501600195310500 78012601950310050007800
16002000230370600 9201500230037006000920
20002500280440700 1100175028004400700011000
25003150330540860 136021003300540080001350


Calculation of International Tolerance Grades:


As mentioned before IT Grade have 18 standard tolerance. These IT Grades have their own numerical values for each dimater step given in the tables above. IT Grades IT01 to IT5 are the most accurate and used essetially for gauge. IT Grades IT6 to IT 16 are less accurate and are used for nonmating dimensions. International Grade can be calculated as given below;


T:International Tolerance grade in (m)


D:Geometric mean dimension in millimeters (mm)


ITG:IT Grade (a positive integer)


Also T:International Tolerance can be showmen as;


"i": is standard tolerance unit/factor."i" for IT5 to IT 16 values can be calculated with the formula below;


Unit tolerance in (m). To calculate D;


where, D (mm) is the geometric mean of the lower and upper diameters of a particular diameter step within which the chosen the diameter D lies. Standard Tolerance Unit/Factor the formula has parabolic relationship with the size of the products. As the size increases, the tolerance within which a part can be manufactured also increases.


The Standards Tolerance values corresponding to IT grades IT01, IT0, IT1, see the chart below


INTERNATIONAL TOLERANCE GRADES
Values In MicronsIT01IT0IT1
Values For D In mm0.3+0.008D0.5+0.012D0.8+0.020D

The Standards Tolerance values corresponding to IT grades IT5 to IT16, see the chart below


INTERNATIONAL TOLERANCE GRADES
Values In MicronsIT5IT6IT7IT8IT9 IT10IT11IT12IT13IT14IT15IT16
Values For D In mm 7i10i16i25i 40i64i100i160i250i400i 640i1000i

EXAMPLE:


Lets chose the diameter of the shaft 60mm, and Tolerance grade H8f7; Calculation for Fundamental deviation, Tolerances and Limit of size for Hole and, Shaft. Calculation of the Standard tolerance Unit;


The size range for 60mm Diameter would be 50-80mm from the ISO 286 table


D=√ 50 +80 mm=63.25mm

i=10-3 50 +60 +0.01x63.25=1.865micron or i=0.001865mm

For Shaft of f7 "i" value standard unit from the table;

Tolerance=16i=16x1.865=0.030mm

For Hole of H8 "i" value standard unit from the table;

Tolerance=25i=25x0.001865=0.046mm

Since design based on Hole basis, the fundamental deviation of hole is zero. Fundamental deviation for Shaft;


=-5.5xD0.41


=-5.5x63.250.41

=-30.114 microns=0.030mm


Shaft;
Higher Limit=Basic size-Fundamental Deviation=60-0.030=59.97mm
Lower Limit=Higher Limit-Tolerance=59.97-0.03=59.94mm

Hole;
Lower Limit=Basic Size=60mm
Higher Limit=Lower Limit+Tolerance=60+0.046=60.046mm


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