LIMITS, FITS AND TOLERANCES

LIMITS, FITS AND TOLERANCES

Preferred tolerances and fits for hole and shaft basis systems which are given in ISO 286-1 (2010) and ANSI B4.2-1978

standards are summarized in the following tables. The usage of these tolerances is advised for economic reasons.

Preferred fits table (ANSI B4.2-1978)

ISO SYMBOL
HOLE BASISSHAFT BASISDESCRIPTION
CLEARANCE FITSH11/c11C11/h11Loose running fit for wide commercial tolerances or allowances on external members.
H9/d9D9/h9 Free running fit not for use where accuracy is essential, but good for large
temperature variations, high running speeds, or heavy journal pressures.
H8/f7F8/h7 Close running fit for running on accurate machines and for accurate location at
moderate speeds and journal pressures.
H7/g6G7/h6 Sliding fit not intended to run freely, but to move and turn freely and locate
accurately.
H7/h6H7/h6Locational clearance fit provides snug fit for locating stationary parts; but can
be freely assembled and disassembled.
TRANSITION FITSH7/k6K7/h6Locational transition fit for accurate location, a comprimise between clearance
and interference.
H7/n6N7/h6Locational transition fit for more accurate location where greater interference
is permissible.
INTERFERENCE FITSH7/p6P7/h6 Locational interference fit for parts requiring rigidity and allignment with prime
accuracy of location but without special bore pressure requirements.
H7/s6S7/h6 Medium drive fit for ordinary steel parts or shrink fits on light sections, the
tightest fit usable with cast iron.
H7/u6U7/h6 Force fit suitable for parts which can be highly stressed or for shrink fits where
the heavy pressing forces required are impractical.
PRACTICAL USE OF INTERNATIONAL TOLERANCE GRADES
 FOR MEASURING TOOLSFOR MATERIAL  
IT GRADES01012345678910111213 141516
  FOR FITS FOR LARGE MANUFACTURING TOLERANCES

Preferable fits of the hole-basis system (ISO 286-1:2010)

BASIC
HOLE
TOLERANCE CLASSES FOR SHAFTS
CLEARANCE FITSTRANSITION FITS INTERFERENCE FITS
H6     g5h5js5k5m5 n5p5      
H7    f6g6h6js6 k6m6n6p6r6s6t6u6x6
H8 e7f7h7js7k7m7s7u7
d8e8 f8h8
H9d8e8f8 h8
H10b9c9d9e9 h9
H11b11c11d10 h10

Preferable fits of the shaft-basis system (ISO 286-1:2010)

BASIC
SHAFT
TOLERANCE CLASSES FOR HOLES
CLEARANCE FITSTRANSITION FITSINTERFERENCE FITS
h5G6H6JS6K6M6 N6P6
h6F7G7H7JS7 K7M7N7P7R7S7T7U7X7
h7 E8F8H8
h8D9E9F9H9
h9 E8F8H8
D9E9F9H9
B11C10 D10H10

 

Note: For economic reasons, the first choice for a fit should, whenever possible, be made from the tolerance classes shown with grey color.