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 BASIS	SHAFT BASIS	DESCRIPTION
CLEARANCE FITS	H11/c11	C11/h11	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 location at 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.
TRANSITION FITS	H7/k6	K7/h6	Locational transition fit for accurate location, a comprimise between clearance and interference.
TRANSITION FITS	H7/n6	N7/h6	Locational transition fit for more accurate location where greater interference is permissible.
INTERFERENCE FITS	H7/p6	P7/h6	Locational interference fit for parts requiring rigidity and allignment 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.

PRACTICAL USE OF INTERNATIONAL TOLERANCE GRADES
	FOR MEASURING TOOLS									FOR MATERIAL
IT GRADES	01	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16
							FOR FITS							FOR LARGE MANUFACTURING TOLERANCES

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

BASIC HOLE	TOLERANCE CLASSES FOR SHAFTS
BASIC HOLE	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
H8			d8	e8	f8		h8
H9			d8	e8	f8		h8
H10	b9	c9	d9	e9			h9
H11	b11	c11	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 tolerance classes shown with grey color.

Help support us by using our affiliate links below.