PL · engineering plastic
Polytetrafluoroethylene PTFE (unfilled and filled grades)
Soft and easy to cut, but it deforms under clamping pressure and creeps after machining, so holding a tolerance is harder than the cutting suggests.
Quoting this material
- Typical lead time
- 7–14 working days
- Condition
- Compression moulded or skived stock
- Achievable finish
- Ra 1.6 µm typical · Ra 0.8 µm best
Machined in-house to your drawing: see the precision CNC machining service and the machine and inspection capability it runs on.
Machinability
Our own 1–10 shop ranking, not a published index: 10 is free-cutting brass C360, 1 is Inconel 718. It ranks how a material behaves on the floor - cycle time, chip control and tool life together. Where a published index exists it is quoted in the note.
Soft and easy to cut, but it deforms under clamping pressure and creeps after machining, so holding a tolerance is harder than the cutting suggests.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Tensile strength | 23–30 | MPa |
| Modulus of elasticity | 0.5 | GPa |
| Hardness | 55 | Shore D |
| Continuous service temperature | 260 | °C |
| Thermal conductivity | 0.25 | W/m·K |
| Density | 2.16 | g/cm³ |
Hardness, tensile and thermal figures are typical published values for the condition stated. Actual mill certificates govern; send the specification with the drawing and we confirm against the certificate before the material is cut.
Condition
Compression moulded or skived stock
Heat treatment
No heat treatment. Filled grades (glass, carbon, bronze) exist precisely because unfilled PTFE is too soft and creeps too much for a bearing - with the glass and bronze fillers it becomes dimensionally usable, at the cost of tool wear.
Achievable surface finish
Ra 1.6 µm
Ra 0.8 µm
Takes a finish but the machined edge blurs rather than cutting cleanly; a sharp tool with a large rake angle does the best job.
Tooling and cutting parameters
Cutting speed
- 200–500 m/min (very sharp uncoated carbide)
Feed
- 0.10–0.30 mm/rev turning · 0.10–0.30 mm/tooth milling
Tooling
- Uncoated, polished, very sharp carbide; nothing dull will cut it cleanly
Coolant
- Air blast; flood is unnecessary
Starting points for carbide on a rigid setup, not a guarantee. The right numbers depend on the machine, the toolholder and the fixturing - ask and we will say what we would actually run.
Typical applications
- Seals, gaskets and lip seals
- Chemical handling components
- Electrical and RF insulation
- Low-friction wear strips
- Laboratory and food equipment
DFM notes for this grade
- Unfilled PTFE creeps under sustained load: a seal works because it is compressed, but a load-bearing part needs a filled grade or a different material
- Its friction coefficient is the lowest of any common plastic, so it is a bearing surface rather than a structural one
- Clamping deforms it immediately - machine it in soft jaws or on a vacuum plate, and never measure it while it is still clamped
Questions buyers ask
- Should I use a filled PTFE grade?
- Where the part carries load or wears. Glass-filled PTFE is more creep-resistant and harder; bronze-filled adds thermal conductivity and load capacity; carbon-filled adds strength and reduces deformation. Unfilled PTFE is for chemical resistance and low friction
- Can PTFE be machined to a tight tolerance?
- It can be cut to one, but it will not stay there. The material creeps and it changes dimension with temperature by roughly 10× the amount steel does, so a ±0.02 mm tolerance on a PTFE part is a statement about the measurement conditions more than the part.
Grades we would quote instead
PVDF
6/10Machines like a hard, slightly brittle plastic: clean chips, decent finish, and it holds a dimension far better than PTFE.
PEEK
5/10Machines cleanly for a plastic but it holds heat at the cut and the swarf will not break.
UHMW-PE
6/10Cuts easily but badly: it is soft, it moves under clamping and it produces a continuous string of swarf that has to be managed.