In a 7200b series angular contact ball bearings, Machined Brass Cage is the cage, which spaces the rolling elements and keeps them from touching each other. The grade is machined cast or wrought brass, rolling-element or ring guided (suffix M, MA, MB or MP by maker); it is non-magnetic, and its usable service range is the cage itself is good well past the temperature at which the lubricant and the ring stabilization give out. This page covers what the material changes about the bearing, the limits it brings with it, and the sizes supplied.
Why Machined Brass Cage for 7200B Series Angular Contact Ball Bearings
Specified for large bearings, high speed, heavy shock and vibration, and wherever temperature or lubricant rules out polyamide. In a 7200b series angular contact ball bearings it is the cage, which spaces the rolling elements and keeps them from touching each other.
A machined brass cage is strong, stable at temperature, and unaffected by the oils and additives that age a polymer cage. It is what large bearings, high-speed bearings and heavily shocked bearings are supplied with.
Material Properties
| Grade designation | machined cast or wrought brass, rolling-element or ring guided (suffix M, MA, MB or MP by maker) |
|---|---|
| Magnetic response | Non-magnetic |
| Service temperature | The cage itself is good well past the temperature at which the lubricant and the ring stabilization give out |
| Corrosion characteristic | Good in most industrial environments; brass is attacked by ammonia, so it is not used in ammonia refrigeration plant |
Service Limits
Brass is attacked by ammonia, so a brass-caged bearing has no place in an ammonia refrigeration plant. The machined cage also weighs more than a pressed or moulded one, which matters for acceleration and for the cage forces at very high speed.
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 7200B Series Angular Contact Ball Bearings Available in Machined Brass Cage
| Designation | Bore d (mm) | Outer diameter D (mm) | Width B (mm) | Chamfer r min (mm) | Contact angle a (deg) |
|---|---|---|---|---|---|
| 7200B | 10 | 30 | 9 | 0.6 | 40 |
| 7201B | 12 | 32 | 10 | 0.6 | 40 |
| 7202B | 15 | 35 | 11 | 0.6 | 40 |
| 7203B | 17 | 40 | 12 | 0.6 | 40 |
| 7204B | 20 | 47 | 14 | 1 | 40 |
| 7205B | 25 | 52 | 15 | 1 | 40 |
| 7206B | 30 | 62 | 16 | 1 | 40 |
| 7207B | 35 | 72 | 17 | 1.1 | 40 |
| 7208B | 40 | 80 | 18 | 1.1 | 40 |
| 7209B | 45 | 85 | 19 | 1.1 | 40 |
| 7210B | 50 | 90 | 20 | 1.1 | 40 |
| 7211B | 55 | 100 | 21 | 1.5 | 40 |
| 7212B | 60 | 110 | 22 | 1.5 | 40 |
| 7213B | 65 | 120 | 23 | 1.5 | 40 |
| 7214B | 70 | 125 | 24 | 1.5 | 40 |
| 7215B | 75 | 130 | 25 | 1.5 | 40 |
| 7216B | 80 | 140 | 26 | 2 | 40 |
| 7217B | 85 | 150 | 28 | 2 | 40 |
| 7218B | 90 | 160 | 30 | 2 | 40 |
| 7219B | 95 | 170 | 32 | 2.1 | 40 |
| 7220B | 100 | 180 | 34 | 2.1 | 40 |
