Page 42 - Y-bearing-units

Design of Y-bearing

arrangements

Axial displacement

Y-bearing units do not accommodate axial dis-
placement of the shaft and are therefore not
normally suitable for non-locating bearing
(free unit) arrangements. The distance between
bearing positions should therefore be short or Fig. 1
the units should be supported by resilient sheet
metal support surfaces or walls to prevent them
from being subjected to excessive stresses as a
result of thermal elongation of the shaft
(† fig. 1).
In applications where there are low speeds,
light loads, and the distance between the bearing
positions is too long or the operating tempera-
tures too high and one bearing position has to
accommodate thermal elongation of the shaft,
the following arrangement is recommended.
The shaft on the non-locating side should be
provided with one or two grooves 120° apart,
to engage one of the following:
• grub screws with a finger, e.g. in accordance
with ISO 4028:2003, but with fine thread
according to table 1, secured by a nut and
spring washer or star lock washer († fig. 2)
• flat head screws in accordance with
ISO 1580:1994, but with fine thread
according to table 1, locked with a spring or
star lock washer († fig. 3)
The finger(s) and groove(s) accommodate
changes in shaft length and prevent relative
rotational movements between the shaft and
bearing bore. To help provide trouble-free oper-
ation, the ends of the grub screws should be
ground and the sliding surfaces in the shaft
grooves coated with a lubricant paste.

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