Grades / Bearing grade PEEK
Bearing grade PEEK, for parts that slide dry
Bearing grade PEEK is a blend, typically carbon fibre with PTFE and graphite at roughly ten percent each. It exists because unfilled PEEK is not slippery and glass filled PEEK destroys whatever it touches. Use it where a surface has to survive contact, not where the part carries the load.
Bearing grade PEEK against the other grades
Typical published values. The full matrix, with what each row changes, is on the property data page.
| Property | Unit | Bearing grade PEEK | Unfilled | GF30 | CF30 | Bearing |
|---|---|---|---|---|---|---|
| Density | g/cm³ | 1.44 - 1.46 | 1.30 - 1.32 | 1.49 - 1.51 | 1.40 - 1.44 | 1.44 - 1.46 |
| Tensile strength | MPa | 90 - 110 | 90 - 100 | 150 - 170 | 130 - 140 | 90 - 110 |
| Tensile modulus | GPa | 7 - 9 | 3.5 - 4.0 | 9 - 11 | 12 - 14 | 7 - 9 |
| Coefficient of friction, dry against steel | µ | 0.10 - 0.20 | 0.30 - 0.40 | 0.35 - 0.45 | 0.20 - 0.30 | 0.10 - 0.20 |
| Thermal expansion, below Tg | µm/m·K | 18 - 24 | 45 - 50 | 20 - 24 | 14 - 18 | 18 - 24 |
| Thermal conductivity | W/m·K | 0.6 - 0.9 | 0.25 | 0.40 - 0.45 | 0.85 - 0.95 | 0.6 - 0.9 |
| Volume resistivity | Ω·cm | 10³ - 10⁶ | > 10¹⁵ | > 10¹⁵ | 10³ - 10⁶ | 10³ - 10⁶ |
| Tolerance a shop quotes | mm | ±0.05 | ±0.05 | ±0.05 | ±0.025 | ±0.05 |
Choose it when
- Dry runningFriction of 0.10 to 0.20 against steel, and far higher allowable PV than any other grade here.
- No lubricant allowedFood and pharma equipment, cleanroom mechanisms, vacuum systems where oil would outgas.
- Hot slidingIt keeps working where acetal and nylon have softened.
- Soft or delicate mating partsIt will not score a shaft the way hard bronze or glass filled plastic does.
Look elsewhere when
- Structural loadThe additives that make it slide take away strength. Do not use it for the bracket holding the bushing.
- Electrical insulationThe carbon fibre content means it does not insulate.
- High static load at room temperatureBronze or a metal backed bearing is still the better answer.
- ImpactThe most brittle of the four common grades.
What changes in the shop
What a shop prices differently for this grade, and what that means for your drawing.
Fit calculator and annealing calculator both use these numbers.
- Clearance at temperatureCalculate the fit hot, not at 20 °C. A press fit that is right cold can seize.
- Thin walls shed heatA thick bushing traps heat at the sliding surface, which raises wear.
- Bore after fittingA press fit compresses the bore, so machine it after fitting when the tolerance is tight.
- Counterface finishRa 0.2 to 0.4 µm on a hardened shaft. Too rough removes the transfer film, too polished stops it keying in.
Typical parts
Where this grade turns up in practice.
- Bushings and sleeve bearings
- Thrust washers
- Wear pads and strips
- Seal rings and backup rings
- Bearing cages
- Guide rollers and valve stem bushings
Questions about Bearing grade PEEK
More in the full question list.
What is bearing grade PEEK made of?
PEEK blended with carbon fibre, PTFE and graphite, commonly around ten percent each. Carbon carries load, PTFE lowers friction and graphite helps the transfer film form.
Can it run without any lubrication at all?
That is what it is designed for, within a PV limit that depends on temperature, speed and duty cycle. Ask the stock supplier for the PV chart at your conditions rather than a single number.
Is it better than bronze?
In hot, dry, corrosive or electrically sensitive service, usually. Under high static load at room temperature, usually not.