In industrial machines, spherical roller bearings is designed for handling large loads while accommodating slight misalignment of parts. Choosing the right size are as simple as seeing how each dimension in the chart relates to the expected load. If a gearbox has a shaft, it’s never exactly square with its housing, nor is it machined to optical specs. But despite these slight variances (and even the warming of the system), the bearing accommodate both the weight and small movement to keep machine running smoothly.
On this chart, we are looking at two sets of bearings running parallel: one with a normal width for its bore size and one that has a larger width to allow for use of the longer roller on the same shaft size. This wider size will be rated for a higher moving weight capacity (good if you have to endure a few shock loads or wish to stretch replacement times). It also shows the max. The angle the bearing can run at is generally one degree to about two and a half. That’s how much slope the housing or sag in the shaft can have without causing edge loading on the rollers.
How to Choose the Right Bearing Size
Typically, engineers starts with bore/shaft match, then outer diameter for fit to the housing. If these all work out, it’s time to talk about load. Dynamic capacity is given in chart above as kilonewtons, which means it’s necessary to convert this to estimated life at your operating speed(s) and force(s). The bearing might look oversize on paper, but it might be right because cost of downtime outweighs the price of a bigger unit.
To get the right bearing for the job, size isn’t everything; the mounting method matters too. Bearings can be hammered on. They can also has a tapered bore that slides onto an adapter sleeve. The width determines how much sleeve are needed to get the right fit. A bad mount will squeal in a few weeks.
Performance is temperature-sensitive, too. Standard chrome-steel bearings work well continuously up to 120 degrees Celsius. Hotter temperatures requires heat-stabilized versions and perhaps a wider internal clearance grouping to avoid preload when hot. Small choices in lubrication compound. Grease should of used sparingly to fill the housing a third to halfway; this will protect rollers without allowing them to churn or turn. If you have too much grease, it will cause friction-related overheating and if you don’t have enough grease there will be metal-on-metal contact until your next service stop.
How many ounces of grease? That’s what the chart doesn’t provide, though the size/shape of the rollers indicate interior volume allotted to the lube. A size number is not the answer, it’s only the beginning of the story. It tells you what it will hold and how much load the lab tested the bearings too handle. Then there’s reality like vibration, sometimes too much load, and settling under the tower and foundation. Because of this, bearing manufacturers publish their capacities with a safety factor that allows bearings to last well past their duty cycle in real world conditions. This keeps machine going shift after shift.
