Selecting the Correct Bearing
Craft Bearing makes a standard duty (S1 series), heavy duty (S2 series), and an extra heavy duty (S3 series) bearings. Bearings from 1-1/2 to 12 inch (or equivalent metric size) are standard stocking items. Larger bearings are often in stock, but special orders can quickly be provided for bearings up to 32 inches.
Shaft Size and Tolerance
Craft split bearings are designed and manufactured to a close tolerance. Over time, actual shaft diameter in the field can vary by as much as a few thousandths of an inch in different bearing positions on a single shaft.
Shaft to bearing fit becomes more critical as load and/or speed increases. Before mounting a bearing, the journal should be checked for diameter, roundness, taper, and conformity to a straight edge. Roundness and taper should be held within 0.001” along the length and diameter of the bearing seat. The faster an application, the tighter the shaft tolerance should be.
In an engineered piece of equipment such as a roller bearing, shaft tolerance and condition are of highest importance. A bearing is no better than the shaft it is on. Therefore, shaft condition directly affects bearing performance and life.
In ordering a bearing for a particular application, it may be necessary to know the bearing dimensions (height, width, length). Additionally, the expected load and RPM of the application determines the bearing series need (S1, S2, or S3). The Bearing Dimension section provides dynamic, static, and axial load ratings and maximum speed for each bearing size and series.
All calculations to determine the load carrying capacities of the Craft split bearing are based on and in accordance with ABMA and International Organization for Standardization (ISO) standards. Bearing life is a fatigue calculation that estimates the ability of a bearing to carry a load, commonly known as L10. The L10 is the basic life rating of a bearing, generally given in hours or millions of revolutions, and is the minimum expected life for 90% of a group of like bearings. Median life is where 50% of the group will complete or exceed the life rating, and is approximately five times the life rating.