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Fundamental Deviations Letter For Hole and Shaft Basis.


The Value for the Hole from "A" to "H" are positive (+), for the Shaft from "a" to "h" negative (-). The Value of the Hole from "J" to "K" either positive (+) or negative (-), for Shaft form "j" to "k" either positive (+) or negative (-).






Applications with ISO 286/ANSI B4.2-1978 International Tolerance Grade.


For best fit selection for a specific applications many factors can be effective. Such as speed, temperatures, length engagement, materials, lubrications, humidity, bearing load and etc. To satisfy extreme conditions the best preferred fit must be considered. The tolerances indicated by the International Tolerance (IT) Grades are general guide to machining process given in ISO 286/ANSI B4.2-1978 showmen in the below table.



APPLICATIONS and PROCESS IT Grade Range
 LAPPING AND HONING  IT1,   IT2,   IT3,   IT4,  IT5,  
CYLINDRICAL TURNING AND DIAMOND TURNING IT4,   IT5,   IT6,  IT7
PLANE/ SURFACE GRINDINGIT5,   IT6,   IT7,   IT8, IT9
BROACHING AND REAMINGIT5,   IT6,   IT7,   IT8, IT9
 BORING AND TURNING IT6,   IT7,   IT8, IT9,   IT10,  IT11,  IT12
SAWING  IT9,  IT10,  IT11
POWDER METAL-SINTEREDIT7, IT8, IT9,IT10
MILLINGIT9,IT10,IT11, IT12, IT13
PLANING, SHAPING, COLD ROLLING AND DRAWING IT10, IT11, IT12, IT13,IT14,
COLD ROLLING AND DRAWING IT 4, IT5, IT6,IT7
DRIILINGIT11, IT12,IT13, IT14
DIE CASTINGIT12,;IT13,IT14, IT15
PUNCHING AND FORGING IT13,IT14, IT15,IT16
HOT ROLLING, FALME CUTTING AND SAND CASTING IT1 4,IT15, IT16
  


ISO 286 TOLERANCE BAND IT01 To IT7


Tolerance Band Given Below (IT01 To IT7) In Micrometer=(10-3)mm


Example: IT1 For Nominal Size 0-3mm;  0.8μm=0.8x(10-3)=0.0008mm


NOMINAL( BASIC) SIZES (mm) INTERNATIONAL TOLERANCE GRADES
OVER UP TO INCL.IT01IT0IT1IT2IT3 IT4IT5IT6IT7
030.30.50.8 1.2234610
360.40.61 1.52.545812
6100.40.61 1.52.546915
10180.50.81.2 23581118
18300.611.6 2.64691321
30500.811.6 2.647111625
50800.81.22 358131930
8012011.52.5 4610162235
1201801.223,5 5812182540
180250234.5 71014202946
2503152.546 81216233262
315400357 91318253657
400500468 101620274063
5006304.569 111622304470
6308005710 121825355080
80010005.5811 152129405690
100012506.5913 1824344666105
1250160081116 2129405478126
1600200091318 2635486592160
20002500111622 30416777110175
25003150131826 36606993135210

Equation Chart to Calculate Fundamental Deviation of Shaft Size Up to 500mm (Geometric Mean Dia "mm")


FORMULAE FOR FUNDAMENTAL DEVIATION FOR SHAFTS SIZES UP TO 500 mm
UPPER DEVIATION (es)LOWER DEVIATION (ei)
Shaft DesignationIn Microns (for D in mm)Shaft DesignationIn microns (for D in mm)
a= -(265 + 1.32D) for D ≤ 120
              ;and
= – 3.52D for D > 120
j5 to j8No formula
jsITx1/2
k4 to k7=+ 0.6x  3 D 

b = – (140 + 0.852D); for D <160
             ;And
= – 1.82D for D > 160
k for Grade  ≤3 and ≥4=0
m= + (T7-IT6)
c= – 52D0.2 for D ≤ 40
= -(95 + 0.82) for D> 40
n= + 5D0.34
P= + IT7 + 0 to 5
cdG.M. of values for c and dr= geometric mean of
values for p and s
d= – 16D0.44
s= IT8 + 1 to 4; for D ≤50
= + 7T7 to + 0.4D; for D > 50
e= -11D0.41
efG.M. of values for e and f
f= -5.5D0.41t= + IT7 + 0.63D
fgG.M. of values for f and gu= + IT7 + D
g= -2.5D0.34V= + IT1 + 1.2525D
h= 0X= + IT7 + 1.62D
y= + IT7 + 2D
z= + IT7 + 2.52D
za= IT8 + 3 + 3.152D
zb= + IT9 + 4D
zc= + IT10 + 4D

ALL DEVIATIONS EXCEPT THOSE GIVEN BELOWGENERAL RULE:
Hole limits are identical with the shaft limits of the same symbole (Letter and Grade)but disposed on the other side of the zero line.EI=-es (EI is equal upper deviation of shaft of the same letter symbol but of opposite sign.)
  NIT9 and Closer GradesES=0
For Size Above 3mmJ,K.M, and NUp to Grade IT8 Inclusive SPECIALS RULES:
ES= Lower deviation ei of the shaft of the same letter symbol but one grade finer and of opposite sign increased by the difference between the tolerances of the two grades  in;
ei+ITx=ES+ITn and ei-ITn= ES-ITx (x=n-1)
   
For Size Above 3mm P to ZCUp to Grades 7  inclusive

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