A bearing cage keeps the balls separated and evenly spaced and helps guide the lubricant. Polymer cages are injection-moulded or machined from engineering plastics; polyamide cages are often called nylon cages.
Compared with pressed steel cages, polyamide cages are lighter, more elastic and lower in friction, and are less likely to seize when lubrication is marginal. That is why they are widely used in electric motor, automotive and appliance bearings.
NLHB supplies cages in four materials:
| Material | Typical colour | Temperature level | Strengths | Typical applications |
|---|---|---|---|---|
| PA66-GF25 | Black or natural | Baseline | Cost-effective, the standard choice | Electric motors, appliances, general bearings |
| PA46 | Brown or black | One step above PA66 | Stiffness and creep resistance at temperature | Automotive engine-area and hot-running motor bearings |
| PEEK | Beige or black | High | High temperature and most chemical media | High-temperature, vacuum and corrosive environments |
| PAI | Amber | High | Strength and wear resistance at temperature | High-speed, high-temperature, poorly lubricated bearings |
Material is only the first step; the compound matters as well. For unfilled, 30% glass-fibre and 30% carbon-fibre PEEK, a resin producer's data sheets list heat deflection temperatures of about 152 °C, 328 °C and 336 °C, with the same 343 °C melting point. Neither melting point nor heat deflection temperature is the cage's continuous operating temperature.
Polymer cages come in two main designs.
When ordering, confirm the number and diameter of balls, the pitch diameter, pocket shape and guidance (ball-guided, inner-ring-guided or outer-ring-guided). A similar outline does not make two cages interchangeable.
Structure examples only. The materials shown in these pictures do not indicate the cage materials supplied.
There is no single maximum temperature for a polyamide cage. It depends on four things:
Major bearing manufacturers' public catalogues commonly give 120 °C as the continuous limit for glass-fibre reinforced PA66 cages, and some specify 100 °C for continuous use; PA46 allows about 15 °C more than PA66; PEEK shows little ageing below 200 °C. These are reference values; the actual limit is set by validation of the specific design and lubricant.
| Polyamide cage | Pressed steel cage | Machined brass cage | |
|---|---|---|---|
| Weight | Lightest | Medium | Heaviest |
| Noise | Low | Medium | Medium |
| Marginal lubrication | Resists seizing | Wears | Fairly tolerant |
| Temperature | Limited by material | High | High |
| Vibration and shock | Moderate | Moderate | Good |
| Cost at volume | Low | Low | High |
NLHB has more than 1,800 moulds for polymer deep groove ball bearing cages, from miniature to medium-size bearings, with pitch diameters from 2.6 mm to over 110 mm. The chart lists 150 common types, sorted by pitch diameter.
| Bearing type | Ball dia. mm | Balls | Pitch dia. mm | Cage OD mm | Cage ID mm | Other ball/count options |
|---|---|---|---|---|---|---|
| 681 | 0.6 | 7 | 2.64 | 2.95 | 2.3 | — |
| 68/1.5 | 0.8 | 6 | 2.66 | 3.03 | 2.2 | — |
| 672 | 0.6 | 7 | 2.99 | 3.25 | 2.7 | — |
| MR52 | 0.8 | 7 | 3.45 | 3.8 | 3 | — |
| 692 | 1 | 7 | 3.95 | 4.5 | 3.45 | 1 |
| MR63 | 0.8 | 8 | 4.35 | 4.73 | 3.9 | — |
| MR144 | 1 | 7 | 4.7 | 5.25 | 4.15 | — |
| MR83 | 1.2 | 7 | 4.94 | 5.43 | 4.37 | — |
| MR73 | 1.2 | 7 | 4.97 | 5.43 | 4.37 | — |
| 683 | 1.2 | 7 | 5 | 5.5 | 4.5 | 2 |
| 693 | 1.588 | 6 | 5.3 | 6 | 4.7 | — |
| MR74 | 0.8 | 9 | 5.4 | 5.8 | 5 | 1 |
| MR93 | 2 | 5 | 5.5 | 6.3 | 4.7 | 1 |
| MR84 | 1.2 | 7 | 6 | 6.55 | 5.45 | 3 |
| MR85 | 0.8 | 13 | 6.36 | 6.75 | 5.9 | 1 |
| 684 | 1.588 | 7 | 6.4 | 7.05 | 5.55 | 1 |
| 623 | 1.588 | 6 | 6.5 | 7.4 | 5.7 | — |
| R2 | 1.588 | 7 | 6.5 | 7.3 | 5.7 | 3 |
| MR95 | 1.2 | 10 | 6.9 | 7.42 | 6.3 | 1 |
| R166 | 1.588 | 8 | 7.1 | 7.9 | 6.3 | — |
| MR104 | 1.588 | 8 | 7.31 | 7.95 | 6.6 | 2 |
| MR105 | 1.588 | 8 | 7.35 | 7.95 | 6.75 | 3 |
| 685 | 1.588 | 8 | 7.5 | 8.25 | 6.85 | — |
| 694 | 2 | 7 | 7.5 | 8.45 | 6.6 | 1 |
| R212 | 2 | 7 | 7.5 | 8.34 | 6.65 | — |
| 604 | 2 | 7 | 7.62 | 8.57 | 6.5 | — |
| MR106 | 1.2 | 10 | 8 | 8.6 | 7.34 | 2 |
| MR115 | 1.588 | 9 | 8 | 8.7 | 7.3 | 1 |
| 624 | 2.381 | 6 | 8.5 | 9.7 | 7.2 | 2 |
| 695 | 2 | 8 | 8.7 | 9.7 | 7.85 | 4 |
| R3 | 2.381 | 6 | 8.7 | 10 | 7.4 | 1 |
| 605 | 2.381 | 7 | 9 | 10 | 8 | — |
| MR117 | 1.2 | 10 | 9 | 9.62 | 8.38 | — |
| MR126 | 1.588 | 8 | 9 | 9.64 | 8.32 | 2 |
| 686 | 2 | 8 | 9.5 | 10.5 | 8.5 | 4 |
| MR128 | 1.2 | 12 | 10 | 10.45 | 9.35 | 2 |
| MR137 | 1.588 | 9 | 10 | 10.64 | 9.32 | 1 |
| 625 | 3.175 | 6 | 10.2 | 11.9 | 8.5 | 7 |
| 696 | 2.381 | 8 | 10.3 | 11.3 | 9.3 | 3 |
| 687 | 2 | 9 | 10.5 | 11.5 | 9.5 | — |
| R4 | 2.381 | 8 | 10.5 | 11.6 | 9.5 | 2 |
| MR148 | 1.588 | 10 | 11 | 11.78 | 10.12 | 1 |
| 606 | 3.5 | 6 | 11.3 | 12.8 | 9.8 | 1 |
| MR149 | 1.588 | 12 | 11.5 | 12.15 | 10.85 | — |
| 688 | 2.381 | 9 | 12 | 13 | 11 | 3 |
| 697 | 2.381 | 8 | 12 | 13 | 10.75 | — |
| 626 | 3.969 | 6 | 12.5 | 15 | 9 | 9 |
| 6700 | 1.588 | 11 | 12.5 | 13.3 | 11.65 | — |
| 689 | 2 | 11 | 13 | 14.1 | 11.9 | 4 |
| 698 | 3.5 | 7 | 13 | 14.8 | 11.2 | 2 |
| 16800 | 2.381 | 10 | 14.5 | 15.5 | 13.5 | — |
| 6800 | 2.381 | 9 | 14.5 | 15.7 | 13.3 | 4 |
| 699 | 3.175 | 8 | 14.5 | 16 | 13 | 1 |
| 608 | 3.969 | 7 | 15 | 17.05 | 12.95 | 7 |
| 6701 | 1.588 | 13 | 15 | 15.8 | 14.15 | 1 |
| 609 | 4.763 | 6 | 15.5 | 17.8 | 13.4 | 1 |
| R6 | 3.969 | 7 | 15.85 | 17.6 | 14.1 | — |
| 628 | 3.969 | 7 | 16 | 18 | 14 | 6 |
| 6900 | 3.175 | 9 | 16 | 17.35 | 14.3 | 1 |
| 6801 | 2.381 | 12 | 16.5 | 17.55 | 15.45 | 1 |
| 629 | 3.969 | 8 | 17 | 18.7 | 15.3 | — |
| 6000 | 4.763 | 7 | 17.7 | 20.4 | 15.3 | 4 |
| 6702 | 1.588 | 14 | 18 | 18.85 | 17.18 | — |
| 6901 | 3.175 | 10 | 18 | 19.7 | 16.35 | 4 |
| 61802 | 2.381 | 14 | 19.5 | 20.8 | 18.35 | — |
| 6802 | 2.381 | 14 | 19.5 | 20.8 | 18.4 | 1 |
| 6703 | 1.588 | 16 | 20 | 20.75 | 19.3 | — |
| 6200 | 4.763 | 8 | 20.3 | 22.5 | 18.1 | 9 |
| 6001 | 4.763 | 8 | 20.5 | 23.1 | 18.7 | 3 |
| 6704 | 2.778 | 12 | 21 | 22.4 | 19.6 | — |
| 6803 | 2.381 | 15 | 21.5 | 22.8 | 20.3 | 1 |
| 6902 | 3.969 | 10 | 21.5 | 23.6 | 19.4 | 2 |
| 6201 | 5.953 | 7 | 22.2 | 24.5 | 20 | 4 |
| 6002 | 4.763 | 9 | 23.5 | 25.6 | 21.3 | — |
| 6300 | 6.35 | 7 | 23.5 | 26.5 | 20.6 | 3 |
| 6903 | 3.969 | 11 | 23.5 | 25.6 | 21.4 | 1 |
| MR203 | 2.778 | 15 | 23.5 | 24.55 | 22.35 | — |
| R8 | 4.763 | 9 | 24.3 | 26.7 | 21.9 | 2 |
| 6301 | 7.938 | 6 | 24.5 | 28.3 | 20.5 | 5 |
| 6202 | 5.953 | 8 | 25.2 | 27.8 | 22.6 | 7 |
| 6003 | 4.763 | 10 | 26 | 28.1 | 23.6 | 4 |
| 6804 | 3.175 | 14 | 26 | 27.7 | 24.6 | 3 |
| R12 | 4.763 | 10 | 26 | 28.1 | 23.6 | — |
| 6904 | 3.969 | 12 | 27.5 | 29.5 | 25.5 | 5 |
| 60/21 | 3.969 | 13 | 28.3 | 30.5 | 26.1 | — |
| 6203 | 6.747 | 8 | 29 | 32.4 | 26.3 | 5 |
| 6302 | 7.938 | 7 | 29.5 | 33.1 | 25.9 | 2 |
| 16004 | 5.556 | 10 | 30.8 | 33.6 | 27.7 | — |
| 61805 | 3.5 | 15 | 30.8 | 32.55 | 29.4 | 1 |
| 6004 | 6.35 | 9 | 31 | 34 | 28.1 | 2 |
| 6805 | 3.5 | 15 | 31 | 32.4 | 29.6 | 5 |
| 6303 | 8.731 | 7 | 32.5 | 36 | 29 | — |
| 60/22 | 6.35 | 9 | 33 | 35.9 | 30.3 | — |
| 6706 | 1.588 | 25 | 33.5 | 34.1 | 32.7 | — |
| 6905 | 4.763 | 12 | 33.5 | 35.8 | 31.2 | 2 |
| 6204 | 7.938 | 8 | 34.5 | 38.3 | 30.7 | 6 |
| 6005 | 6.35 | 10 | 36 | 38.5 | 33.5 | 2 |
| 6304 | 9.525 | 7 | 36 | 40.7 | 31.9 | 2 |
| 6806 | 3.175 | 19 | 36 | 37.8 | 35.1 | 2 |
| 16005 | 5.556 | 12 | 37 | 39.6 | 34.4 | — |
| 6205 | 6.35 | 11 | 38.5 | 41.3 | 35.7 | 4 |
| 6906 | 4.763 | 14 | 38.5 | 40.8 | 36.2 | 1 |
| R16 | 7.938 | 9 | 38.5 | 42 | 35 | — |
| 60/28 | 7.144 | 10 | 40 | 43.6 | 36.6 | — |
| 63/22 | 10.319 | 7 | 40 | 44.5 | 35.5 | — |
| 6807 | 3.175 | 22 | 41 | 42.4 | 39.6 | — |
| 6006 | 7.144 | 11 | 43 | 46.3 | 39.8 | 3 |
| 62/28 | 9.525 | 8 | 43 | 47.2 | 39.2 | — |
| 6305 | 11.509 | 7 | 43.5 | 48.6 | 38.6 | 5 |
| 6907 | 5.953 | 13 | 45 | 48 | 42 | 1 |
| 6206 | 9.525 | 12 | 46 | 50.5 | 42.5 | 2 |
| 6808 | 3.175 | 25 | 46 | 47.7 | 44.6 | — |
| 63/28 | 12.7 | 7 | 48 | 53.8 | 43.4 | 2 |
| 6007 | 7.938 | 11 | 48.5 | 52.7 | 44.7 | 4 |
| 16007 | 6.35 | 14 | 49.5 | 52.3 | 46.7 | — |
| 6908 | 6.747 | 14 | 51 | 54.2 | 48.2 | 2 |
| 6809 | 3.175 | 28 | 51.5 | 53.2 | 50.1 | — |
| 6306 | 12 | 8 | 52 | 57 | 46.5 | 4 |
| 6207 | 10.716 | 9 | 53.5 | 59.4 | 49.7 | 2 |
| 16008 | 6.35 | 15 | 54 | 56.8 | 51.2 | — |
| 6008 | 7.938 | 18 | 54 | 57.55 | 51.15 | — |
| 6405 | 15.081 | 7 | 55 | 61.5 | 48.5 | — |
| 6710 | 3.175 | 27 | 57.15 | 58.6 | 55.7 | — |
| 6810 | 3.175 | 31 | 57.5 | 59.2 | 56.1 | 2 |
| 6909 | 6.747 | 15 | 57.5 | 61.5 | 53.8 | — |
| 6009 | 7.938 | 12 | 58.5 | 61.9 | 55.1 | 3 |
| 6307 | 13.494 | 8 | 58.5 | 65.6 | 51.6 | 1 |
| 6910 | 6.747 | 15 | 61 | 65.1 | 57.3 | 2 |
| 16009 | 7.144 | 15 | 62 | 65.5 | 58.5 | — |
| 6811 | 4.763 | 23 | 63.5 | 65.8 | 61.2 | 1 |
| 6010 | 9 | 13 | 65 | 69 | 61 | 1 |
| 6209 | 11.509 | 10 | 65 | 71.3 | 61 | 3 |
| 6308 | 15.081 | 8 | 65.5 | 73.5 | 58.4 | — |
| 16010 | 7.144 | 16 | 67 | 70.5 | 63.5 | — |
| 6911 | 6.747 | 17 | 67.5 | 70.5 | 64.5 | — |
| 6812 | 5.159 | 23 | 69 | 71.8 | 67.2 | 5 |
| 6713 | 3.175 | 33 | 69.85 | 71.5 | 68.1 | — |
| 6210 | 11.509 | 11 | 70.5 | 76.8 | 66.5 | — |
| 6309 | 16.669 | 8 | 72.5 | 81.7 | 66.7 | — |
| 6012 | 10.319 | 14 | 77.5 | 82 | 73 | 1 |
| 6211 | 14.288 | 10 | 79 | 85 | 73 | — |
| 6310 | 18.256 | 8 | 80 | 90 | 73.6 | 1 |
| 6814 | 5.556 | 26 | 80 | 82.5 | 77.5 | — |
| 6013 | 11.1 | 13 | 82.5 | 87.4 | 77.6 | 1 |
| 6715 | 3.175 | 39 | 82.5 | 84.1 | 80.9 | — |
| 6014 | 11.906 | 14 | 90 | 95.2 | 84.8 | 1 |
| 6816 | 4.763 | 32 | 90 | 92.3 | 87.7 | — |
| 6312 | 22.225 | 8 | 95 | 104.5 | 87 | — |
| 61820 | 7.144 | 25 | 112.2 | 115.5 | 108.9 | — |
| 61919 | 10.318 | 19 | 112.5 | 117.1 | 107.9 | — |
PA66-type cages are covered by the Chinese industry standard JB/T 7048 for engineering plastic cages of rolling bearings. Its 2002 edition specifies PA66 and PA66-GF15, GF25 and GF30, with other materials by agreement; PA66-GF25 has a service temperature range of −40 to 120 °C. PA46, PEEK and PAI cages are accepted to the drawing and agreed inspection items.
Typical inspection items: pocket dimensions, radial tensile strength, ball retention, free rotation, and appearance (short shots, flash, weld lines).
It depends on the material, lubricant and duration. PA66 cages have a lower long-term limit than PA46 or PEEK; confirm the actual limit for your design and lubricant, not from the resin melting point.
Each has its place. Polyamide cages are light, quiet and resist seizing; steel cages handle high temperatures and are inexpensive. For high temperature or heavy vibration, choose steel or brass.
Not on the material name alone. PEEK has low friction, but whether it can run with little or no lubricant depends on the compound, speed, load and heat dissipation, and must be proven by testing.
No. PAI is polyamide-imide and PI is polyimide; they are processed differently and perform differently, so the drawing must name the right one.
The bearing number is a starting point. We also need the ball count, ball diameter and pocket design, ideally from a sample or drawing.