Spherical plain bushings are sliding bearings — the inner ring slides directly against the outer ring through a thin film of grease. When that film breaks down, wear accelerates fast. Bearings that should last years can fail in weeks.
Step One: Know What Type You Have
PTFE-lined (maintenance-free) bushings should not be greased at the sliding surfaces. The PTFE layer is the lubricant — adding grease defeats the maintenance-free design. If you ordered from Ball Bushing Warehouse’s Maintenance Free line, these run dry for their service life.
Steel-on-steel bushings require regular relubrication. If your bearing has a grease fitting (Zerk), it needs regular attention. Everything below applies to that type.
Grease Selection
For steel-on-steel bushings, a lithium-complex NLGI Grade 2 grease with EP (extreme-pressure) additives is a solid default. These bearings carry heavy loads and move by slow oscillation, so the EP additives protect the sliding surfaces when the grease film thins. Expect a continuous range up to roughly 250–300°F (120–150°C) — confirm the exact rating on the data sheet.
Don’t assume moly is off-limits: many steel-on-steel bushings ship with a dry MoS₂ coating already on the sliding surface, and solid-lubricant additives can help under heavy, slow-oscillating loads. The rule is “follow the manufacturer’s recommendation,” not “avoid moly.” Just don’t put a moly grease into a PTFE-lined / maintenance-free bushing.
For wet or washdown environments, use a water-resistant calcium-sulfonate complex or lithium-complex NLGI 2 or 3. For sustained temperatures above ~300°F, switch to a polyurea or calcium-sulfonate complex grease.
Never mix greases with incompatible thickeners (e.g., lithium and polyurea). The oil can separate from the thickener, leaving the bearing with no effective lubricant even though grease appears present.
How Often to Regrease
There is no universal interval — it depends on load, oscillation frequency, temperature, and contamination. In demanding environments like construction or agricultural equipment, daily relubrication is not uncommon.
| Condition | Starting Interval |
|---|---|
| Light load, clean environment | Every 500–1,000 hours |
| Moderate load, typical factory | Every 200–500 hours |
| Heavy load or high contamination | Every 50–200 hours |
| Outdoor / heavy equipment | Follow equipment manufacturer’s schedule |
Pay attention to what purges when you regrease. Clean, pliable grease means the interval is about right. Dark, gritty, or hardened grease means shorten the interval or improve sealing.
How Much to Apply
Pump grease slowly until fresh grease just begins to emerge from the seal or relief, then stop. The goal is to push old grease out and replace it — not to pack the housing full. Excess pressure from overfilling can damage seals, which then allows contamination in.
Signs of Lubrication Failure
- Looseness or play at the joint — worn sliding surfaces
- Squeaking or grinding during oscillation — the bearing is running dry and needs grease immediately
- Heat at the pivot point — a well-lubricated bearing should not be notably hot after normal operation
- Rust around the bearing — moisture is getting in; check seals and shorten the relubrication interval
Questions about bushing type or maintenance schedules? Call Ball Bushing Warehouse at 860-693-1797 or visit ebushing.com.