With the Cross-Roller Bearing, cylindrical rollers are arranged crosswise, with each roller perpendicular to the adjacent roller, in a 90 ゜ V groove, separated from each other by a spacer retainer. This design allows just one bearing to receive loads in all directions including, radial, axial and moment loads.
| Part Number | RA7008 Bearings |
| Bearing Type | Crossed Roller Bearings |
| For Load Direction | Combined Radial; Thrust; and Moment |
| Construction | Single Row |
| Interchange Brand | THK,IKO,TKW,China |
| ABEC Rating | ABEC-5 ABEC-7 ABEC-9 |
| Ring Material | Steel |
| Roller Material | Steel |
| Shaft dia. mm | 70 |
| Mass(kg) | 0.1 |
| Bore Dia (d) | 70 |
| Outer Dia (D) | 86 |
| Width (B) | 8 |
| Greasing hole(a) | 2 |
| Greasing hole(b) | 0.8 |
| r(min) | 0.5 |
| Shoulder height ds(max) | 73.5 |
| Shoulder height Dh(min) | 80.5 |
| Basic load rating (radial)C kN | 5.98 |
| Basic load rating (radial)Co kN | 9.8 |
| Lubrication | Required |
| Shaft Mount Type | Press Fit |
| Temperature Range | 0 -230 |
● High Rotation Accuracy of RA 7008 Cross Roller Bearing
The spacer retainer fitting among cross-arrayed rollers prevents rollers from skewing and the rotation torque from increasing due to friction between rollers. Unlike conventional types using steel sheet retainers, the Cross- Roller Ring does not cause displacement or locking of rollers and provides a stable rotation torque.
Since the inner and outer rings are designed to be separable, the bearing clearance can be adjusted. In addition, highly accurate rotary motion is ensured through adjusting the bearing clearance to provide a preload.
● Easy Handling
The inner and outer rings, which are separable, are secured to the Cross-Roller Ring body after the rollers and spacer retainers are installed. This procedure prevents the rings from separating from each other. Thus, it is easy to handle the rings when installing the Cross-Roller Ring.
● Skewing Prevention
The spacer retainer keeps rollers in their proper position, thereby preventing them from skewing. This eliminates friction between rollers, and therefore secures a stable rotation torque.
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| Major dimensions | Shoulder dimensions | Basic load rating | Mass |
| Shaft diameter |
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| TKW | Model No. | Inner diameter | Outer diameter | Roller pitch circle diameter |
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| d | D | dp | Width | Greasing hole |
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| C | C0 |
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| B B1 | a | b | rmin | ds | Dh | kN | kN | kg |
| 50 | RA 5008 | 50 | 66 | 57 | 8 | 2 | 0.8 | 0.5 | 53.5 | 60.5 | 5.1 | 7.19 | 0.08 |
| 60 | RA 6008 | 60 | 76 | 67 | 8 | 2 | 0.8 | 0.5 | 63.5 | 70.5 | 5.68 | 8.68 | 0.09 |
| 70 | RA 7008 | 70 | 86 | 77 | 8 | 2 | 0.8 | 0.5 | 73.5 | 80.5 | 5.98 | 9.8 | 0.1 |
| 80 | RA 8008 | 80 | 96 | 87 | 8 | 2 | 0.8 | 0.5 | 83.5 | 90.5 | 6.37 | 11.3 | 0.11 |
| 90 | RA 9008 | 90 | 106 | 97 | 8 | 2 | 0.8 | 0.5 | 93.5 | 100.5 | 6.76 | 12.4 | 0.12 |
| 100 | RA 10008 | 100 | 116 | 107 | 8 | 2 | 0.8 | 0.5 | 103.5 | 110.5 | 7.15 | 13.9 | 0.14 |
| 110 | RA 11008 | 110 | 126 | 117 | 8 | 2 | 0.8 | 0.5 | 113.5 | 120.5 | 7.45 | 15 | 0.15 |
| 120 | RA 12008 | 120 | 136 | 127 | 8 | 2 | 0.8 | 0.5 | 123.5 | 130.5 | 7.84 | 16.5 | 0.17 |
| 130 | RA 13008 | 130 | 146 | 137 | 8 | 2 | 0.8 | 0.5 | 133.5 | 140.5 | 7.94 | 17.6 | 0.18 |
| 140 | RA 14008 | 140 | 156 | 147 | 8 | 2 | 0.8 | 0.5 | 143.5 | 150.5 | 8.33 | 19.1 | 0.19 |
| 150 | RA 15008 | 150 | 166 | 157 | 8 | 2 | 0.8 | 0.5 | 153.5 | 160.5 | 8.82 | 20.6 | 0.2 |
| 160 | RA 16013 | 160 | 186 | 172 | 13 | 2.5 | 1.6 | 0.8 | 165 | 179 | 23.3 | 44.9 | 0.59 |
| 170 | RA 17013 | 170 | 196 | 182 | 13 | 2.5 | 1.6 | 0.8 | 175 | 189 | 23.5 | 46.5 | 0.64 |
| 180 | RA 18013 | 180 | 206 | 192 | 13 | 2.5 | 1.6 | 0.8 | 185 | 199 | 24.5 | 49.8 | 0.68 |
| 190 | RA 19013 | 190 | 216 | 202 | 13 | 2.5 | 1.6 | 0.8 | 195 | 209 | 24.9 | 51.5 | 0.69 |
| 200 | RA 20013 | 200 | 226 | 212 | 13 | 2.5 | 1.6 | 0.8 | 205 | 219 | 25.8 | 54.7 | 0.71 |
Crossed roller bearing is a special type bearing with split inner ring and rotating outer ring. Since the divided inner ring or outer ring is installed with rollers and spacers, it is fixed with the cross roller ring to prevent separation from each other, so it is easy to operate when installing the cross roller ring. Since the rollers are arranged in a cross, only one set of cross roller rings can bear loads in all directions. Compared with the conventional model, the rigidity is increased by 3 to 4 times. At the same time, because the inner ring or outer ring of the cross roller bearing has a two-part structure, the bearing gap can be adjusted, and even if preload is applied, high-precision rotational movement can be obtained. Moreover, due to its special structure, it is usually used as a joint bearing in industrial robots.
When you purchase the crossed roller bearings, please confirm the designation first.
1. Model RU (Integrated Inner/Outer Ring Type)
2. Model RB (Separable Outer Ring Type for Inner Ring Rotation)
3. Model RE (Separable Inner Ring Type for Outer Ring Rotation)
4. USP-Grade Series of Models RB/RE
5. Model RA (Separable Outer Ring Type for Inner Ring Rotation)
6. Model RA-C (Single-Split Type)
Features of Crossed Roller Bearings RA7008
1. Excellent rotation accuracy
2. Simplified operation and installation
3. Withstand large axial and radial loads
4. Significantly save installation space
5. High speed capability
EASIER designs and manufactures a variety of crossed roller bearings that can handle radial, thrust and moment loads at the same time. These compact bearings feature rollers crossed at right angles between inner and outer rings.
-- Widely used in machine tools, industrial robots and medical equipment because of their high rotational accuracy.
-- Roller guide options include a cage or separator as well as a full complement design. Both the cage and separator styles offer a small coefficient of friction for high-speed rotation. Full complement bearings handle heavy loads at low speeds.
-- Sealed and open designs are available. Sealed bearings incorporate synthetic rubber seals to protect against dust, dirt and grease.
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