Design of bearing arrangements

Axial displacement

Y-bearings are not intended to accommodate axial displacement of the shaft relative to the housing. The distance between bearing positions should therefore be short to avoid excessive induced axial loads as a result of thermal expansion of the shaft.
Design for small axial displacement
To accommodate small axial displacement, the bearings should be supported by resilient sheet metal support surfaces or walls (fig. 1).
Design for larger axial displacement
In applications where there are slow speeds and light loads, a Y-bearing with grub screws can be used to accommodate axial displacement. The shaft at the non-locating bearing position should be provided with one or two grooves 120° apart, to engage a modified grub screw:
  • Hexagon socket grub (set) screws with a dog point, in accordance with ISO 4028:2003, but with a fine thread according to the product table. The grub screw should be secured by a nut and spring washer or star lock washer (fig. 2).
  • Slotted pan head screws in accordance with ISO 1580:2011, but with fine thread according to the product table, locked with a spring or star lock washer (fig. 3).

The screws and groove(s) accommodate changes in shaft length and prevent the shaft from turning independently of the bearing. The ends of the grub screws should be ground and the sliding surfaces in the shaft grooves coated with a lubricant paste.

Shaft tolerances

Recommended fits for Y-bearings are listed in table 2. Fig. 4 illustrates the relative position of the upper and lower limits of the most commonly used ISO shaft tolerance classes for Y-bearings, except for those with a standard inner ring. The values for these tolerance classes are listed in table 3.
For Y-bearings on an adapter sleeve or SKF ConCentra Y-bearings the total radial run-out of the shaft seat should be IT5/2 for tolerance class h9Ⓔ. The values for the ISO tolerance class h9 are listed in table 3.
For Y-bearings with a standard inner ring, the same recommendations apply as for standard deep groove ball bearings (table 2). The values for these ISO tolerance classes are listed in table 4 and table 5.
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