LINEAR MOTION SOLUTIONS - Brd. Klee A/S

Clearance & Mounting
Linear Ball Bearings
CLEARANCE & FIT
Standard-type Simplicity ® linear ball bearings matched to a
shaft that provides inadequate clearance may result in early
bearing failure and/or rough linear motion. The clearance
adjustable linear ball bearings and open linear ball bearings
can be adjusted when assembled in the housing by controlling
the housing bore. However, too much clearance will increase
the deformation of the linear ball bearing, which will affect
its precision and life. Therefore, the appropriate clearance
between the ball bearing and shaft, and the appropriate linear
ball bearing housing bore are required based on application.
Table 2 shows recommended fit of the linear ball bearing:
TABLE 2
SHAFT & HOUSING
To optimize performance of the Simplicity ® linear ball bearing
it is recommended that a high precision shaft and pillow block
are required.
Shaft
The rolling balls in the Simplicity ® linear ball bearing are
in line contact with the shaft surface. Therefore, the shaft
dimensions, tolerance, surface finish, and hardness greatly
affect the performance of the linear ball bearing. The shaft
should be manufactured to the following tolerances:
1) Surface finish critically affects the smooth rolling of balls;
Shaft surface finish should be 6-8 micro (RA# 7.2 to 10.8 a
1.11 to 1 ratio).
2) Shaft hardness should be HRC 60 to 64. Hardness less
than HRC 60 will decreases the life/load, see page 126.
3) Preload increases the frictional resistance slightly, If the
preload is too tight, the deformation of the bearing sleeve
will shorten the linear ball bearing’s life.
Housing
There are a wide variety of housings differing in design,
machining, and mounting. See Table 2 (above) and the
following section on mounting requirements.
Technical Information
MOUNTING
When inserting the linear ball bearing into the housing, do not
hit the linear ball bearing on the end-retaining ring, but apply
pressure either by hand or arbor on the linear ball bearing
sleeve (See Fig.1) To insert the shaft into the mounted linear
ball bearing, make sure the shaft is chamfered and be careful
not to push on the balls by inserting the shaft at an angle.
NOTE: If two shafts are used in parallel, the parallelism is an
important factor to assure smooth linear movement and not
damage the linear ball bearings.
Examples of Mounting
The popular way to mount linear ball bearings is with a
slight preload. PBC Linear recommends a slight clearance
fit-up to ensure proper life. The examples, Figs. 2 to 6, show
the inserted linear ball bearing using a variety of retention
methods.
FIG. 1 FIG. 2 FIG. 3 FIG. 4 FIG. 5 FIG.6
124
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