Guides / Grades
Which PEEK Grade Should Be on Your Drawing
September 20, 2026
Sources: manufacturer datasheets and published standards. See editorial standards.
Every one of these is sold as PEEK, and a drawing that just says PEEK leaves the most important decision to whoever cuts it. The differences show up in stiffness, in how the part moves with temperature, in wear and in price.
The short version
| Grade | Density (g/cm³) | Pick it for | Avoid it for |
|---|---|---|---|
| Unfilled | 1.30 to 1.32 | Steam, chemicals, toughness, impact | Loaded parts held hot for long periods |
| GF30 | 1.49 to 1.51 | Stiffness and creep resistance under load at temperature | Sliding surfaces, tight tolerance thin parts |
| CF30 | 1.40 to 1.44 | Dimensional stability, heat transfer, static dissipation | Parts that must be electrically insulating |
| Bearing grade | 1.44 to 1.46 | Dry running bushings, wear pads, seal parts | Structural parts carrying real load |
| Implant grade | 1.30 to 1.32 | Long term body contact with documentation | Anything where the paperwork is not needed |
Unfilled PEEK
Natural beige or black, no reinforcement, and the toughest member of the family. It takes impact, it survives hundreds of autoclave cycles and it is the default for fluid paths, fittings and instrument parts.
Its weaknesses are creep and movement. Held under load at 150 °C and above, unfilled PEEK slowly deforms. It also has the highest thermal expansion of the group, about 47 µm/m·K below the glass transition, so a fit that is correct cold can be wrong hot.
On the machine it is the easiest grade. It cuts cleanly with sharp tooling and it does not eat cutting edges.
PEEK GF30
Thirty percent short glass fibre raises stiffness and, more usefully, resists creep. A bracket or a bushing that has to hold a load while hot is the classic application.
The cost is toughness. Fibre reinforced PEEK is more brittle than unfilled, it is a poor sliding partner because the glass is abrasive to whatever it runs against, and it wears cutting tools quickly. Shops price in tool wear, and careful ones keep filled and unfilled tooling separate.
PEEK CF30
Thirty percent carbon fibre gives the highest stiffness of the common grades, roughly half the thermal expansion of unfilled PEEK and three to four times the thermal conductivity. Heat leaves the part instead of staying at the cutting edge, which is one reason CF30 often holds tighter tolerances than unfilled stock.
It is also conductive enough to bleed off static charge, which is why semiconductor and display handling parts are usually CF30. If your part needs to insulate electrically, that same property rules it out.
Carbon fibre is abrasive, and the dust is conductive. Shops that run it near electronics manage that.
Bearing grades
Bearing grade PEEK is a blend, typically carbon fibre with PTFE and graphite. It has the lowest friction and the best dry wear of the family, which makes it the choice for bushings, wear pads, seal elements and anything that slides without lubrication.
It is not a structural material. The additives that make it slide take away strength, so use it where a surface has to survive contact, not where the part carries the load.
Implant grade PEEK
Implant grade stock is supplied under a standard such as ASTM F2026 with lot traceability and documented biocompatibility testing. Mechanically it behaves like unfilled PEEK.
What you are really buying is a chain of documents and a shop that can keep it intact: controlled handling, clean tooling, documented cleaning and packaging. Ask for those before the first chip is cut, because reproducing the paperwork afterwards is not possible.
Temperature, and the number people miss
The glass transition of PEEK is 143 °C. Below it, expansion is around 47 µm/m·K for unfilled material. Above it, the material softens and expansion increases sharply. Continuous service temperature of about 250 °C is real, but strength and stiffness at 200 °C are not the values on the room temperature datasheet.
This matters for fits. If the part has to hold a tolerance hot, either a filled grade or a deliberately looser cold fit is the answer. Say on the drawing which temperature the tolerance applies at. Machining and inspection happen at 20 °C, and nobody can guess your service condition.
Choosing without overthinking it
- Steam, chemicals or impact: unfilled.
- Loaded and hot: GF30.
- Has to stay dimensionally still, or must dissipate static: CF30.
- Slides against something: bearing grade.
- Goes in a body long term: implant grade stock, plus the shop that can document it.
For the method that starts from the limit that governs the part and ends at the grade line of the RFQ, see our guide to PEEK grade selection.
Still unsure? Put the temperature, the load and the media on the RFQ and let the shops that quote suggest a grade. That is what the grade picker on our home page does in ten seconds, and what the shops confirm when you send the drawing.
For how these grades change price, see what machined PEEK parts cost. For what the implant grade paperwork actually documents, see implant grade PEEK compliance.
Frequently asked questions
What is the difference between PEEK GF30 and CF30?
GF30 is 30% glass fibre and adds stiffness and creep resistance at a lower material cost. CF30 is 30% carbon fibre and adds more stiffness, about half the thermal expansion and three to four times the thermal conductivity, plus enough conductivity to dissipate static.
Which PEEK grade is best for autoclave parts?
Unfilled PEEK. It is the toughest of the family and handles repeated steam cycles well. Filled grades are stiffer but more brittle, and the fibre ends at a machined surface give steam a path in.
Is implant grade PEEK a different material?
Mechanically it behaves like unfilled PEEK. What you pay for is documented biocompatibility testing, lot traceability and controlled handling under a standard such as ASTM F2026.
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