Ball Bearing Part

Overview

A deep-groove ball bearing lets one part rotate against another with very little friction while carrying both radial and modest axial loads. It is one of the most reused components in this entire graph — it turns up inside motors, gearboxes, wheels, pumps, and spindles — which is why it is modelled as a single shared node.

Construction

The bearing has four parts: an inner ring (pressed onto the shaft), an outer ring (held in a housing), a set of hardened steel balls, and a cage that keeps the balls evenly spaced so they cannot rub against each other. Both rings have a precisely ground groove (the "race") whose curvature is slightly larger than the ball, so contact is nearly a point — that is what makes the friction so low.

Surfaces are made from through-hardened chrome steel (AISI 52100), ground and honed to micron tolerances, then matched into ABEC/ISO precision classes. Shields (ZZ) are non-contact metal washers that keep dirt out; seals (2RS) are rubber lips that also keep grease in, at the cost of a little more drag.

How it works and how it is rated

As the shaft turns, the balls roll between the races rather than sliding, so the coefficient of friction is tiny (~0.001–0.002). Bearings are rated by dynamic load capacity (C), which feeds the L10 life equation — the number of revolutions 90% of bearings survive at a given load. Life falls with the cube of load, so a bearing run at half its rated load lasts roughly eight times longer.

Lubrication, failure, and selection

Most are grease-packed for life; high-speed or high-temperature duty uses oil. The usual failure modes are fatigue spalling (flakes break off the race after millions of cycles), brinelling (dents from shock loads), contamination, and false brinelling from vibration while stationary. Selecting a bearing means matching bore to the shaft, checking the load and speed against the rating, and choosing the right seal for the environment — the trade-offs the surrounding assembly's designer makes every time this node appears in a BOM.