Mounted ball bearing units...
consist of ball bearings with spherical outer diameter mounted in either a pressed steel or ductile cast iron housing, and are further categorised by the method of attachment to the shaft
- Set screw mounting type - the most popular and most widely used consisting of 2 setscrews 120o apart
- Adaptor sleeve locking type - more usually found on large or high speed units
- Eccentric locking collar - usually found on units with reversing shafts
The specially heat treated inner ring is wider than that of a standard ball bearing to increase stability and more effective lockscrew locking.
Limiting speeds
The limiting speed of ball bearing inserts is mainly determined by the quality of fit between the bearing and the shaft. Usually a shaft with h7, h8 or h9 tolerance is recommended for light loads and slow speeds, whilst a tight j7 fit is recommended for higher speeds and heavier loads.
The limiting speeds for a variety of fits are tabulated below. The j7 (h9/IT5) figures apply to adapter mount ball bearing inserts, the others to setscrew and eccentric locking collar type units.
|
shaft (mm)
|
200 Series
|
300 Series
|
|
Shaft tolerance
|
Shaft tolerance
|
|
j7 (h9/IT5)
|
h7
|
h8
|
h9
|
j7 (h9/IT5)
|
h7
|
h8
|
h9
|
|
12
|
6700
|
5300
|
3800
|
1400
|
-
|
-
|
-
|
-
|
|
15
|
6700
|
5300
|
3800
|
1400
|
-
|
-
|
-
|
-
|
|
17
|
6700
|
5300
|
3800
|
1400
|
-
|
-
|
-
|
-
|
|
20
|
6000
|
4800
|
3400
|
1200
|
-
|
-
|
-
|
-
|
|
25
|
5600
|
4000
|
3000
|
1000
|
5000
|
3600
|
2600
|
900
|
|
30
|
4500
|
3400
|
2400
|
850
|
4300
|
3000
|
2200
|
800
|
|
35
|
4000
|
3000
|
2000
|
750
|
3800
|
2800
|
2000
|
700
|
|
40
|
3600
|
2600
|
1900
|
670
|
3400
|
2400
|
1700
|
630
|
|
45
|
3200
|
2400
|
1700
|
600
|
3000
|
2200
|
1500
|
560
|
|
50
|
3000
|
2200
|
1600
|
560
|
2600
|
2000
|
1400
|
500
|
|
55
|
2600
|
2000
|
1400
|
500
|
2400
|
1800
|
1300
|
450
|
|
60
|
2400
|
1800
|
1200
|
450
|
2200
|
1700
|
1100
|
430
|
|
65
|
2200
|
1700
|
1100
|
430
|
2000
|
1500
|
1100
|
400
|
|
70
|
2200
|
1600
|
1100
|
400
|
1900
|
1400
|
1000
|
360
|
|
75
|
2000
|
1500
|
1000
|
380
|
1800
|
1300
|
900
|
340
|
|
80
|
1900
|
1400
|
950
|
340
|
1700
|
1200
|
850
|
320
|
|
85
|
1800
|
1300
|
900
|
320
|
1600
|
1100
|
800
|
300
|
|
90
|
1700
|
1200
|
800
|
300
|
1500
|
1100
|
750
|
280
|
|
95
|
-
|
-
|
-
|
-
|
1400
|
1000
|
700
|
260
|
|
100
|
-
|
-
|
-
|
-
|
1300
|
950
|
670
|
240
|
|
105
|
-
|
-
|
-
|
-
|
1200
|
900
|
630
|
220
|
|
110
|
-
|
-
|
-
|
-
|
1200
|
800
|
600
|
200
|
|
120
|
-
|
-
|
-
|
-
|
1100
|
750
|
530
|
190
|
|
130
|
-
|
-
|
-
|
-
|
1000
|
670
|
480
|
180
|
|
140
|
-
|
-
|
-
|
-
|
900
|
600
|
430
|
160
|
Housing strengths
One of the most common design errors is to base the selection on the bearing strength only. The "tear out strength" of the housing must be considered. The housing strength is a fraction of the bearing insert static capacity, and it is recommended that a safety factor of 6 is applied.
Seals
In general, bearing inserts have a single steel/rubber lipped seal that offers low friction, good grease retention and good protection against external contaminants. However, there is a small clearance between shaft and seal that will inevitably increase after hours of use.
For extreme environmental conditions we recommend use of the triple lip seal arrangement which impinge slightl;y on the shaft forming a tighter seal. A far better barrier to liquid and solid contamination is thus formed. This type of seal is typically found in machinery used in mines and quarries.
Lubrication & Maintenance
Inserts are sealed and factory lubricated with a standard lithium based EP2 grease suitable for operation between -20o C and 120o C, and are generally considered to be sealed for life. However, operation at temperatures > 70o C will seriously reduce grease life and this must be taken into account.
Recommended relubrication intervals take into account the operating speed, operating temperature and the environment. Some of the grease will find its way into the bearing through the lubrication slot (if provided) and regreasing holes in the outer ring, while some will simply extrude between at the bearing/housing interface.
Note dm = (ID+OD)x rpm/2
| dn value |
Environment |
Temp oC |
Relube interval |
| <40 000 |
Clean |
-15 - +65
+65 - +100
|
6 - 12 months
2 - 6 months
|
| < 70 000 |
Clean |
-15 - + 65
+65 - +100
|
2 - 6 months
1 month
|
| Any |
Dirty |
< 65
>65
|
1 week - 1 month
1 day - 2 week
|
| Any |
Very dirty |
Any temp |
1 day to 1 week |
| Any |
Water splash |
Any |
Daily |
Mounting bolts and shaft mount gribscrews should be checked from time to time as vibration may cause them to loosen in service.
Tolerances for spherical housing bores
The dimensional tolerance for the inner diameter of the sphere is H7 which will normally give a clearance fit with the bearing insert. By special order a tighter tolerance J can be specified which will result in an interference fit.
Information extracted from TR catalogue E03-1999