Frequently asked questions.
Frequently asked questions.
Get answers to your questions about self-lubricating bearings with our informative FAQs on this reliable bearing technology.
Can You Grease a Self-Lubricating Bushing?
Short answer: it depends on the lining. Adding lubricant helps one family, does nothing useful for one, and is actively harmful for one. The common one-line claim — “they run without oil” — is a design intent, not a maintenance instruction, and applied to the wrong type it can shorten service life. Below: the verdict by type, a diagnostic workflow, recovery steps if you already greased the wrong kind, and per-application guidance.
1. Why the common answer is incomplete
Many product pages state that self-lubricating bushings “run without oil.” That is true as a design intent, but it collapses three very different constructions into one claim. A bushing that carries its lubricant inside (graphite plugs, PTFE surface film, or impregnated oil) does not rely on a periodic grease gun — but the correct response to “can I add grease?” is not a universal yes or no. It is: which lining do you have?
2. Verdict by lining type
| Lining family | Grease / oil added? | What actually happens |
|---|---|---|
| Graphite-embedded bronze (solid-lubricant plugs in a copper alloy matrix; e.g. JDB-type) |
Keep dry | Designed for dry running. In dusty or gritty environments, added oil captures abrasive particles and forms a lapping slurry that accelerates three-body wear. Lubricant addition is counter-productive here. |
| PTFE / POM composite (steel backing + porous bronze + polymer surface layer) |
Do not grease | The polymer transfers a thin film onto the shaft during running. Packing grease onto the surface interferes with that transfer-film formation, raising friction rather than lowering it. External grease is not beneficial for this family. |
| Oil-impregnated sintered bronze (porous bronze saturated with lubricating oil) |
Occasionally, in small amount | The only family where added lubricant is generally compatible. When the impregnated reservoir is partly depleted by sustained high speed or heat, a small top-up of a compatible oil can extend service. This is the exception, not the rule. |
3. How to identify which type you have
- Graphite-embedded bronze: visible dark graphite plugs or grooves machined into the bore; metallic copper colour.
- PTFE / POM composite: thin matte polymer surface (often black or coloured) over a bronze/steel body; very low surface friction to the finger.
- Sintered bronze: matte, porous-looking bronze surface; may weep a slight oil film; not typically grooved with solid plugs.
If a material certificate or drawing is available, the lining specification removes guesswork. When in doubt, do not grease until the type is confirmed.
4. Diagnostic workflow — which rule applies
- Confirm the lining. Inspect for graphite plugs, a polymer surface film, or a porous bronze body. A material cert or drawing is decisive.
- Match to the rule:
- Graphite bronze → keep dry; in dust, seal or flush the environment — do not add oil.
- PTFE / POM composite → keep dry; external grease is not appropriate.
- Sintered bronze → a small compatible oil top-up is acceptable only if running hot or with a depleted reservoir.
- If you have already greased it, go to Section 5 for recovery steps.
- Still unsure? Send the lining photo + duty data (load, speed, temperature, environment) to the component supplier before any maintenance action — see the RFQ link at the end.
5. Already greased the wrong type? Recovery steps
| What was done | Recovery | Why |
|---|---|---|
| Grease packed on PTFE / POM composite | Remove excess; the transfer film re-forms during run-in at reduced load. Do not keep adding. | The polymer will re-coat the shaft once the surface is clean. |
| Oil added to graphite bronze in dust | Flush the bore with a compatible solvent, dry it, and move to a sealed or shielded arrangement. Do not re-oil. | The oil-plus-grit slurry is the source of wear; sealing stops re-contamination. |
| Sintered bronze over-greased | Wipe excess from the bore and outer surfaces so pores can breathe; resume normal running. | Clogged pores prevent the impregnated oil from returning. |
6. By application — quick reference
| Application | Typical lining | Grease guidance |
|---|---|---|
| General Engineering / Packaging | PTFE / POM or standard composite | Maintenance-free. Best used dry. If grease is applied, it may reduce the life of the self-lubricating layer unless specifically designed for it. |
| Dusty / mining / cement | Graphite-embedded bronze | Keep dry. Grease is harmful; use seals or a flush arrangement instead. |
| Electric motor / pump (light duty) | Oil-impregnated sintered bronze | Small compatible oil top-up acceptable when hot or depleted. |
7. Worked example — checking a dusty conveyor roller (illustrative)
The rule “keep graphite bronze dry in dust” is easier to apply with numbers. Consider a conveyor support roller in a cement environment:
- Radial load: 8 kN; shaft diameter: 40 mm; bushing length: 40 mm (L/d ≈ 1.0)
- Surface speed: 0.6 m/s (continuous rotation)
- Environment: high dust load
Step 1 — project pressure P. Contact area ≈ bore diameter × length = 40 mm × 40 mm = 1600 mm². P = 8000 N / 1600 mm² = 5.0 N/mm².
Step 2 — compute PV. PV = 5.0 N/mm² × 0.6 m/s = 3.0 N/mm²·m/s.
Step 3 — check against reference bands (from published lining data; treat as engineering boundaries, not guarantees):
| Lining | Reference PV upper limit | Verdict at PV = 3.0 |
|---|---|---|
| Oil-impregnated sintered bronze | ~1.0–1.8 | Exceeds — not suitable |
| Graphite-embedded bronze | ~1.65–3.25 | At/near the upper boundary — acceptable dry; keep dust out via seal |
| PTFE / POM composite | ~1.8–3.6 | Within range, but grease is still not appropriate |
The conclusion is not “graphite bronze is the top choice” — it is that at this duty sintered bronze is ruled out by PV, and graphite bronze is the dry-running candidate provided dust is excluded. That is precisely why greasing the graphite type here is counter-productive: it would bind the dust already present into a lapping slurry instead of keeping the bore clean. This is an illustrative calculation using reference PV bands; actual selection must use the specific material datasheet and measured duty.
8. Narrow cases where a trace of lubricant helps
For sintered bronze only: if the bushing runs hot or the oil reservoir is visibly depleted, a small amount of compatible oil can recover margin. For extreme PV duty or sustained temperature beyond the design envelope, a trace of a compatible lubricant may extend life — but the general guidance is to keep the bushing in its as-designed state; over-lubrication rarely improves and can worsen performance.
1. Identify the lining (plugs / polymer film / porous bronze).2. Graphite bronze → keep dry; in dust, seal or flush, do not grease.
3. PTFE / POM composite → keep dry; do not pack grease.
4. Sintered bronze → small compatible oil top-up only if running hot / depleted.
Frequently asked questions.
Frequently asked questions relating to bushings & bearings
Related Bushings & Bearings FAQs
A self-lubricating bearing is defined by where its lubricant resides — inside the structure, not supplied from outside. That one property is not a single material but three mechanisms, and it is why selection runs on the PV value and why "can I oil it?" has three different answers by lining.
August 27, 2026
