SKF ConCentra - Design of bearing unit arrangements

Design of bearing unit
arrangements
Axial displacement
SKF ConCentra ball bearings can accommo-
date only limited axial displacement as a
result of thermal shaft elongation. The
distance between bearing positions should
therefore be short or 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
Misalignment
SKF ConCentra bearing and SKF ConCentra
ball bearing units can accommodate initial
misalignment of up to:
5° when relubrication is not required•
2° when relubrication is required•
Additionally, operational shaft deflections of
a few minutes or arc can be permitted.
Shaft tolerances
SKF ConCentra ball bearing units can be
used with solid or hollow commercial grade
shafts. The shaft should be machined to at
least an h9 tolerance class with a cylindricity
tolerance of IT5. The limits are listed in
table 1.
Support surfaces
To maximize the service life of an SKF
ConCentra ball bearing unit, SKF recom-
mends finishing support surfaces to a
roughness of Ra ≤ 12,5 μm and a flatness
(planicity) that meets IT7 specifications. For
moderate demands IT8 may be satisfactory.
Fig. 1Table 1
Recommended shaft tolerance
Bearing size
1)
Shaft tolerance h9 Shaft tolerance
From to high low Cylindricity
mm
μm
–
05 06 0 -52 IT5
07 10 0 -62 IT5
11 13 0 -74 IT5
1)
For Example: bearings size 07 includes all bearings based on a Y 207 e.g. YSP 207 SB-2F, YSP 207-104 SB-2F,
YSP 207-106 SB-2F, YSP 207-107 SB-2F
Attaching to the support
surface
To attach SKF ConCentra ball bearing units
to the support surface, SKF recommends
using 8.8 class bolts or studs and a washer
to ISO 7089:2000 or 7090:2000 and a
spring washer. Hexagonal head bolts in
accordance with ISO 4014:1999 are appro-
priate. Alternatively, hexagonal socket head
cap screws in accordance with ISO
4762:1988 can be used († fig. 1).
Appropriate fastener sizes are listed in the
product tables.
SKF ConCentra ball bearing units with
plummer block housings have two bolt holes
in their base for attachment bolts. If the
11
B