7/29/2014 Preferred fits and tolerances (Metric) - Ames

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Advanced Mechanical Engineering Solutions 41

PREFERRED FITS AND TOLERANCES (ISO & ANSI METRIC STANDARDS)

Preferred metric 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.

Supplement: Preferred Fits Advised By ISO And ANSI Standards

ISO Symbol

DescriptionHoleBasis

ShaftBasis

ClearanceFits

H11/c11 C11/h11Loose running fit for wide commercial tolerances or allowances onexternal members.

H9/d9 D9/h9Free running fit not for use where accuracy is essential, but good forlarge temperature variations, high running speeds, or heavy journalpressures.

H8/f7 F8/h7Close running fit for running on accurate machines and for accuratelocation at moderate speeds and journal pressures.

H7/g6 G7/h6Sliding fit not intended to run freely, but to move and turn freely andlocate accurately.

H7/h6 H7/h6Locational clearance fit provides snug fit for locating stationary parts;but can be freely assembled and disassembled.

TransitionFits

H7/k6 K7/h6 Locational transition fit for accurate location, a comprimise betweenclearance and interference.

H7/n6 N7/h6Locational transition fit for more accurate location where greaterinterference is permissible.

InterferenceFits

H7/p6 P7/h6Locational interference fit for parts requiring rigidity and allignmentwith prime accuracy of location but without special bore pressurerequirements.

H7/s6 S7/h6Medium drive fit for ordinary steel parts or shrink fits on light sections,the tightest fit usable with cast iron.

H7/u6 U7/h6Force fit suitable for parts which can be highly stressed or for shrinkfits where the heavy pressing forces required are impractical.

Preferred fits table (ANSI B4.2-1978)

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LIMITS, FITS AND

TOLERANCES

Limits and Fits Calculator (ANSI)

Preferred Limits and Fits (Inch)

Limits and Fits Calculator (ISO)

Preferred Fits (Metric)

Interference (Press & Shrink) Fit

Formulas for Interference Fit

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7/29/2014 Preferred fits and tolerances (Metric) - Ames

http://www.amesweb.info/FitTolerance/PreferredTolerances.aspx#.U9eV3PmSwWw 2/2

BasicHole

Tolerance classes for shafts

Clearance Fits Transition Fits Interference Fits

H6 g5 h5 js5 k5 m5 n5 p5

H7 f6 g6 h6 js6 k6 m6 n6 p6 r6 s6 t6 u6 x6

H8 e7 f7 h7 js7 k7 m7 s7 u7

d8 e8 f8 h8

H9 d8 e8 f8 h8

H10 b9 c9 d9 e9 h9

H11 b11 c11 d10 h10

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

BasicShaft

Tolerance classes for holes

Clearance Fits Transition Fits Interference Fits

h5 G6 H6 JS6 K6 M6 N6 P6

h6 F7 G7 H7 JS7 K7 M7 N7 P7 R7 S7 T7 U7 X7

h7 E8 F8 H8

h8 D9 E9 F9 H9

h9

E8 F8 H8

D9 E9 F9 H9

B11 C10 D10 H10

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

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

Supplements:

Link Usage

Limits, fits andtolerance calculator

Limits, fits and tolerance calculator (metric unit) is designed to calculate thelimits, fits and tolerances according to ISO 286(2010) and ANSI B4.2 (1978)standards.

Reference:

IS0 286-1 (2010) Geometrical product specifications (GPS) - ISO code system for tolerances on linear sizes - Part 1:

Basis of tolerances, deviations and fits

IS0 286-2 (2010) Geometrical product specifications (GPS) - ISO code system for tolerances on linear sizes - Part 2:

Tables of standard tolerance classes and limit deviations for holes and shafts

ANSI/ASME B4.2 (1978) Preferred Metric Limits and Fits

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