Preferred Mechanical Tolerances Metric ISO 286

Related Resources: manufacturing

The following defines the preferred tolerance basis for hole and shaft per. ISO 286.

Hole Basis	Shaft Basis	Type of Fit	Description
H11/c11	C11/h11	Clearance Fit	Loose running fit for wide commercial tolerances or allowances on external members.
H9/d9	D9/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/f7	F8/h7		Close Running fit for running on accurate machines and for accurate moderate speeds and journal pressures.
H7/g6	G7/h6		Sliding fit not intended to run freely, but to move and turn freely and locate accurately.
H7/h6	H7/h6		Locational clearance fit provides snug fit for locating stationary parts; but can be freely assembled and disassembled.
H7/k6	K7/h6	Transition Fit	Locational transition fit for accurate location, a compromise between clearance and interferance.
H7/n6	N7/h6	Transition Fit	Locational transition fit for more accurate location where greater interferance is permissible.
H7/p6a	P7/h6	Interferance Fits	Locational interference fit for parts requiring rigidity and alignment with prime accuracy of location but without special bore pressure requirements.
H7/s6	S7/h6		Medium drive fit for ordinary steel parts or shrink fits on light sections, the tightest fit usable with cast iron.
H7/u6	U7/h6		Force fit suitable for parts which can be highly stressed or for shrink fits where the heavy pressing forces required are impractical.

Illustration of Tolerance Zones
Illustration of Tolerance Boundaries

Preferred Fit Hole Basis
Preferred Fits Hole Basis

Preferred Fit Shaft Basis

Related Resources: