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.
RECOMMENDED FIT OF LINEAR BALL BEARINGS
Shaft
Housing
Model
Division
Normal Fit
Transitional
Loose Fit
Tight Fit
JP
High Precision High Precision High Precision
g6 g6 h6
h6 h6
H7 H7 H7
J7 J7 J7
IP
EP
j6
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 linear ball bearings 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 Ra 8-10.
2. Shaft hardness should be HRC 60 to 64. Hardness less than HRC 60 will decreases the life/load. 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 mounting requirements below.
Mounting
FIG. 1
FIG. 3 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. 5
FIG. 6
FIG. 4
FIG. 2
FIG. 2
FIG. 3
FIG. 4
FIG. 5
FIG. 6
pbclinear.com • Engineering Your Linear Motion Solutions 155
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