Material specification page for nu300 series cylindrical roller bearings in Pressed Steel Cage. Covers the grade designation (low-carbon sheet steel, two-piece riveted or ribbon type, rolling-element guided), what the material does inside the bearing, its temperature and environmental limits, the alternatives worth considering, and the sizes available to ISO 15 / DIN 5412-1 / GB/T 283.
Why Pressed Steel Cage for NU300 Series Cylindrical Roller Bearings
The standard cage of volume bearing production: light, cheap, tolerant of temperature and unaffected by the oils that age a polymer cage. In a nu300 series cylindrical roller bearings it is the cage, which spaces the rolling elements and keeps them from touching each other.
Pressed from sheet and guided by the rolling elements, it adds almost no mass and almost no cost, tolerates a wide temperature range, and is unaffected by lubricant chemistry. It is the default cage of the standard bearing ranges for good reasons.
Material Properties
| Grade designation | low-carbon sheet steel, two-piece riveted or ribbon type, rolling-element guided |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | Not the limiting element; the lubricant and the ring heat stabilization decide |
| Corrosion characteristic | As the rings — it relies on the lubricant and the seals |
Service Limits
It is a light-duty cage: it is guided by the rolling elements and it is not intended for heavy vibration, high acceleration or sustained very high speed, which is where the machined brass cage takes over. In a heavily shocked application, cage damage rather than raceway fatigue is what ends the bearing.
What the Material Changes About the Bearing
The cage carries no load, so it changes no rating. What it changes is the operating envelope: the maximum temperature, the maximum speed, the tolerance of shock and vibration, the noise, and the compatibility with the lubricant. A bearing is very often limited by its cage long before its rings are in any danger, which is why the cage suffix in a designation is not a detail.
Fitting a Steel Bearing in an Aluminum Housing
Aluminum has roughly twice the coefficient of thermal expansion of bearing steel, so a housing bore machined to a normal H7 fit at room temperature grows away from the outer ring as the machine reaches operating temperature. The outer ring then turns in its seat and wears the bore. Where the housing is aluminum and the temperature rise is more than about 30 degrees C, tighten the housing fit by one grade — J7 or K7 in place of H7 — or fit a steel sleeve into the aluminum. Check the resulting internal clearance: a tighter housing fit takes clearance out of the bearing, which is often why C3 is specified alongside it.
Sizes of NU300 Series Cylindrical Roller Bearings Available in Pressed Steel Cage
| Designation | Bore d (mm) | Outer diameter D (mm) | Width B (mm) | Chamfer r min (mm) | Rib arrangement |
|---|---|---|---|---|---|
| NU304 | 20 | 52 | 15 | 1.1 | No axial location, free at both ends |
| NU305 | 25 | 62 | 17 | 1.1 | No axial location, free at both ends |
| NU306 | 30 | 72 | 19 | 1.1 | No axial location, free at both ends |
| NU307 | 35 | 80 | 21 | 1.5 | No axial location, free at both ends |
| NU308 | 40 | 90 | 23 | 1.5 | No axial location, free at both ends |
| NU309 | 45 | 100 | 25 | 1.5 | No axial location, free at both ends |
| NU310 | 50 | 110 | 27 | 2 | No axial location, free at both ends |
| NU311 | 55 | 120 | 29 | 2 | No axial location, free at both ends |
| NU312 | 60 | 130 | 31 | 2.1 | No axial location, free at both ends |
| NU313 | 65 | 140 | 33 | 2.1 | No axial location, free at both ends |
| NU314 | 70 | 150 | 35 | 2.1 | No axial location, free at both ends |
| NU315 | 75 | 160 | 37 | 2.1 | No axial location, free at both ends |
| NU316 | 80 | 170 | 39 | 2.1 | No axial location, free at both ends |
| NU317 | 85 | 180 | 41 | 3 | No axial location, free at both ends |
| NU318 | 90 | 190 | 43 | 3 | No axial location, free at both ends |
| NU319 | 95 | 200 | 45 | 3 | No axial location, free at both ends |
| NU320 | 100 | 215 | 47 | 3 | No axial location, free at both ends |
| NU321 | 105 | 225 | 49 | 3 | No axial location, free at both ends |
| NU322 | 110 | 240 | 50 | 3 | No axial location, free at both ends |
