Metal bearings that need constant oil are a liability where oil burns, contaminates product, or cannot reach the bearing at all. In furnaces, conveyors, pumps and hot process lines, graphite bearings run dry, handle high temperature and outlast lubricated metal — if they are specified correctly. This guide answers the five questions engineers ask most about graphite bearings before switching.

Dry-running bearings are matched by PV and temperature — Jiecheng Graphite (since 2003) sizes the grade to your shaft, housing and environment.

Fact 1 — yes, graphite bearings run dry

Graphite has an intrinsic layered crystal structure that makes it self-lubricating. Dry-running graphite bearings operate with little or no external lubrication in many applications, which removes oil handling, contamination and high-temperature oil breakdown.

Fact 2 — temperature is both a strength and a limit

Graphite bearings keep their load capacity at temperatures far beyond most polymers and greases, and are common in hot zones. But in air they oxidize as temperature rises, so confirm the grade’s oxidation limit and whether the application needs an inert or vacuum atmosphere or an oxidation-resistant treatment.

Fact 3 — load and speed determine the grade

The right bearing depends on the PV (pressure × velocity) value, the fit, and the running environment. Different grades — fine-grain, metal-impregnated or resin-bonded — are tuned for different load–speed–temperature windows. Ask the supplier to match the grade to your PV and environment rather than buying generic stock.

Fact 4 — fit and clearance matter

Graphite has a low but non-zero coefficient of thermal expansion, and thermal growth at operating temperature affects running clearance. Specify the fit for the operating temperature, not room temperature, so the bearing neither seizes when hot nor rattles when cold.

Fact 5 — they protect the shaft and the product

Graphite is softer than the shaft material and self-lubricating, so it wears preferentially instead of scoring the shaft. In food, glass and chemical processes it also avoids the contamination that oil introduces.

If a bearing seized or rattled before, Jiecheng Graphite confirms running clearance at operating temperature before machining.

Buying checklist

1. Define load, speed and PV value

2. State operating temperature and atmosphere

3. Choose the running clearance for operating temperature

4. Select grade — plain, impregnated or bonded

5. Confirm fit, tolerance and inspection report

FAQ

Do graphite bearings need lubrication?

Many run dry or with minimal lubrication; some applications use small amounts to reduce wear further. Confirm with the grade data.

How long do they last?

Life depends on PV, temperature and environment. Matched correctly, graphite bearings commonly outlast lubricated metal bearings in hot service.

Can you machine a bearing to my shaft size?

Yes — bearings are machined to shaft diameter, housing fit and clearance from your spec.

Bearing grades and where each fits

Plain graphite bearings serve general dry-running duty at moderate load and speed. Resin-bonded or metal-impregnated grades add strength and reduce wear for heavier loads and higher speeds, at some cost in temperature ceiling and lubricity. The grade you pick should be matched to the PV window — the product of surface pressure and sliding velocity — and to the atmosphere, because oxidation and moisture can change how a graphite bearing wears. State the load, speed and environment, and let the supplier match a grade rather than guessing.

Clearance, fit and thermal growth

Graphite bearings are usually fitted with clearance to running size rather than an interference press fit, because the material is more brittle than metal and does not yield. The running clearance must allow for the shaft, the housing and the bearing’s own thermal growth at operating temperature. Too little clearance and the bearing seizes when hot; too much and it rattles, wears unevenly and loses alignment. Specify the fit for the operating temperature and confirm it with the supplier before machining.

Verifying a graphite bearing

1. Confirm the grade matches the PV and temperature requirement

2. Measure bore and OD against the drawing

3. Check the running clearance at operating temperature

4. Verify surface finish on the bore

5. Keep the inspection report for traceability

Installation and running-in

Graphite bearings reward careful installation. Seat them cleanly with the correct clearance, avoid forcing them, and keep the shaft and housing free of grit that could embed and wear the bore. Many graphite bearings benefit from a short running-in period at reduced load and speed, letting the surfaces conform and polish before full service. Following the supplier’s fit and installation guidance measurably extends life.

Check the bearing’s running clearance at operating temperature, not just at assembly. Because thermal growth changes the fit, a bearing that feels right cold can seize hot, and one that rattles cold can fit correctly in service. Confirm the clearance with the supplier against your operating temperature and environment, and inspect the bearing at the same intervals you would inspect a lubricated metal bearing.

Jiecheng Graphite’s precision grinders and 100+ CNC machines produce bearings to shaft and housing fit, with inspection data.

Dongguan Jiecheng Graphite Products Co., Ltd. has machined graphite bearings and bushings since 2003. In its 3,000 m² Dalang, Dongguan plant, Jiecheng Graphite runs over 100 five-axis CNC machining centers and precision grinders, producing dry-running graphite bearings to customer shaft and housing fits and exporting worldwide with inspection data.