Selection of Bearing Sizes

In general machinery applications, the bearing size for a given bearing arrangement is determined by the load carrying capacity. The selection is made not only in relation to the actual load, but also to the desired life and operational reliability.

The size of the bearing should be selected on the basis of static load ratings. The permissible load for a bearing is determined by the amount of major deformation to the raceway caused by the load. Loads operating on slow oscillating bearing or a stationary bearing or on rotating bearing can produce flat areas on the rolling elements and indentations in the raceways. If the load operates for a number of times, the deformation will increase and will be evenly spread over the whole raceway, which can lead to vibration in the bearing, noise and increased friction. As a result the bearing sizes need to be carefully chosen.

Bearing size is almost always determined by criteria like as follows:

• Load Capacity
• Stiffness of the system
• Fixed dimensions for the tool holder
• Spindle bore

The bearings based on such criteria often exhibit extremely long life.

Ball Bearing Sizes
One of the most popular type of bearing is the ball bearing. Ball bearings have sizes usually in millimeters, and the balls themselves are sized in inches. The Anti-Friction Bearing Manufacturers Association adopted a classification of ball bearings depending on their construction.

Most ball bearings is a 3-digit code which shows the dimensions in millimeters. The first digit refers to the series. There are four main series:

• 100, extra light
• 200, light
• 300, medium
• 400, heavy

The table given displays the sizes up through a bore of 50 mm, but much bigger sizes are defined.

Designation	Bore	Series 100 (x = 1)		Series 200 (x = 2)		Series 300 (x = 3)		Series 400 (x = 4)
		OD	Width	OD	Width	OD	Width	OD	Width
x00	10	26	8	30	9	35	11	-	-
x01	12	28	8	32	10	37	12	-	-
x02	15	32	9	35	11	42	13	-	-
x03	17	35	10	40	12	47	14	62	17
x04	20	42	12	47	14	52	15	72	19
x05	25	47	12	52	15	62	17	80	21
x06	30	55	13	62	16	72	19	90	23
x07	35	62	14	72	17	80	21	100	25
x08	40	68	15	80	18	90	23	110	27
x09	45	75	16	85	19	100	25	120	29
x10	50	80	16	90	20	110	27	130	31

Source: www.sizes.com

Buyers Guide :
Selection of Bearing Type | Selection of Bearing Sizes | Application of Bearings | Lubrication and Maintenance | Mounting and Dismounting