ABIS Miniature and Precision Ball Bearings

Importance of Correct Fitting of Bearings

With bores of 0.6 to 90mm and precision grades to ABEC 7

General Information

Importance of correct fitting of bearings

A bearing can only perform to its full capacity when it is correctly fitted on the shaft and in the housing. Insufficient interference on fitting surfaces could cause bearing rings to creep in a circumferential direction. Once this happens, considerable wear occurs on the fitting surface and both shaft and housing can be damaged. Furthermore, abrasive particles may enter the bearing causing vibration, excessive heat and damage to raceways. It is therefore necessary to provide bearing rings under rotating load with an adequate interference fit to prevent creep. When using thin-type bearings under low load, the bearings should be fastened by a nut. Statically loaded bearings generally do not need to be fitted with an interference fit. Only when subject to a high degree of vibration do both inner and outer rings require fitting with an interference fit.

Fitting of Bearing and Shaft
Condition (Steel Shaft)		Shaft Bore Diameter	Shaft Tolerance Class
Condition (Steel Shaft)		Shaft Bore Diameter	Thin-Type	Others
Inner ring rotating load or indeterminate load direction	Light load ≤ 0.06C or fluctuating load	10 ≤ d ≤ 18 18 ≤ d ≤ 30 30 ≤ d ≤ 50	h5 h5 h5	js5 js5 js5
Inner ring rotating load or indeterminate load direction	Standard load = 0.06 – 0.11C	10 ≤ d ≤ 18 18 ≤ d ≤ 30 30 ≤ d ≤ 50	js5 js5 js5	j5 k5 k5
Outer ring rotating load	Necessary for inner ring turning easily around shaft	All bore diameters	g6	g6
Outer ring rotating load	Unnecessary for inner ring turning easily around shaft	All bore diameters	h6	h6

Fitting of Bearing and Housing
Condition (One-Piece Housing)		Axial Directional Movement of Outer Ring	Tolerance Class of Housing Seats
Condition (One-Piece Housing)		Axial Directional Movement of Outer Ring	Thin-Type	Others
Inner ring rotating load	Varying loads	Easy to move	H7	H7
	Light or standard loads	Easy to move	H8	H8
	High temperature of inner ring and shaft	Easy to move	G7	G7
	Light or standard load Precision rotation	As a rule, impossible to move	K6	K6
	Light or standard load Precision rotation	Possible to move	JS6	J6
	Quiet operations	Easy to move	H6	H6
Indeterminate load direction	Light or standard load	In general, possible to move	JS7	J7
	Standard or heavy load	As a rule, impossible to move	K7	K7
	Large shock load	Impossible to move	M7	M7
	Light or fluctuating load	Impossible to move	M7	M7
Outer ring rotating load	Standard or heavy load	Impossible to move	N7	N7
Outer ring rotating load	Thin-type housing seats heavy or large shock load	Impossible to move	P7	P7

Characteristics of Load and Fitting
Rotating Ring	Load	Load Condition	Fitting
		Inner ring rotating loadOuter ring static load	Interference fit for inner ringClearance fit for outer ring
		Inner ring rotating loadOuter ring static load	Interference fit for inner ringClearance fit for outer ring
		Outer ring rotating loadInner ring static load	Clearance fit for inner ringInterference fit for outer ring
		Outer ring rotating loadInner ring static load	Clearance fit for inner ringInterference fit for outer ring
In case of fluctuating load direction or unbalanced load	Rotating or static	Indeterminate load direction	Interference fit for inner and outer ring