This guide explains how to design PTFE parts for CNC machining: why the material cuts cleanly, what to put on the drawing, and how thermal expansion moves a finished dimension between the shop and the operating temperature.
CNC machining suits complex PTFE shapes because it does not need mold tooling. For parts machined to your drawing, see custom CNC machined PTFE parts.
Why Machine PTFE?
PTFE is one of the most machinable of all engineering plastics. Key advantages:
- No special tooling required — standard HSS and carbide cutting tools work well
- No curing or cooling needed — PTFE machines dry, no coolant contamination issues
- Excellent chip formation — long, continuous chips that clear easily from the work area
- Very low cutting forces — thin-walled parts and complex profiles are achievable
- No fire hazard — unlike some plastics that melt and stick to tooling
What to Put on the Drawing
This section is a design checklist. Product details for parts made from a drawing are on custom CNC machined PTFE parts.
Tolerances
Per drawing (metric or inch drawings). Put the tolerance on each feature, and name the temperature at which it applies. Tolerances are confirmed against the drawing.
Materials
Name the grade: virgin PTFE, glass/carbon/graphite-filled PTFE, PEEK, UHMWPE, nylon, Delrin/POM, PCTFE, or PVDF. "PTFE" alone does not say which properties you need.
Geometry
CNC suits complex PTFE shapes because it does not need mold tooling. Dimension thin walls and undercuts; do not leave them as "typical".
Temperature note
PTFE expands much more than metal. State the temperature for critical tolerances, usually room temperature, so a shop measurement is not mixed with the service temperature.
File formats
PDF, DWG, DXF, STEP, STP, IGES, SLDPRT, and X_T are the usual files. A sketch can show the idea; the drawing still needs dimensions.
Inspection notes
Mark which features are functional. A sealing face needs a flatness note. A cosmetic edge usually does not.
PTFE Machining: Key Considerations
Tooling
PTFE machines with standard HSS tools for general work. For production runs and better surface finish, carbide tooling is preferred. Diamond-coated tools are used for very long production runs to minimize tool wear.
Key tool geometry for PTFE:
- Large rake angles (15-25°) — reduces cutting forces and improves chip flow
- Sharp cutting edge — PTFE dulls tools quickly; resharpen frequently
- Large chip gullets — accommodates PTFE's long, stringy chips
Cutting Speeds and Feeds
| Operation | Cutting Speed (m/min) | Feed Rate |
|---|---|---|
| Turning (rough) | 60-120 | 0.2-0.4 mm/rev |
| Turning (finish) | 150-200 | 0.05-0.15 mm/rev |
| Milling (rough) | 80-150 | 0.1-0.3 mm/tooth |
| Milling (finish) | 150-250 | 0.03-0.1 mm/tooth |
| Drilling | 40-80 | 0.1-0.3 mm/rev |
Cooling
PTFE machines well dry (no coolant) because it's self-lubricating and won't stick to the tool. However, for critical surface finish and tight tolerances, a light flood of water-soluble coolant helps control heat. Never use oil-based coolant — PTFE absorbs oil, degrading its properties.
Dimensional Stability
PTFE has a high coefficient of thermal expansion (120 x 10⁻⁶/°C) — approximately 10x that of steel. This means machined parts can change dimension significantly between the machine shop temperature and the operating environment. Key strategies:
- Machine critical dimensions last to minimize time between cutting and measurement
- Allow parts to equilibrate to room temperature before final measurement
- Account for thermal expansion in your design tolerance stack-up
Typical PTFE Machined Parts
Common applications for CNC machined PTFE parts:
- Pump components — impellers, bearings, shaft sleeves, piston rings, valve seats
- Sealing components — custom gaskets, V-rings, u-cups, flange seals, custom seal profiles
- Electrical insulators — standoff insulators, terminal blocks, high-frequency components
- Slide bearings — linear bearing rails, wear pads, guide bushings
- Process components — custom shapes for equipment builders
- Semiconductor handling — wafer carriers, process chamber components
- Chemical process parts — dip tubes, weir plates, spray nozzles, custom vessel internals
Filled PTFE Compounds
Virgin PTFE is very soft and wears quickly under abrasive conditions. For demanding applications, filled PTFE compounds offer improved mechanical properties:
| Fill Material | Property Improved | Application |
|---|---|---|
| Glass (15-25%) | Compressive strength, wear resistance | Static seals, pump parts |
| Carbon (25%) | Wear resistance, thermal conductivity | Dynamic seals, bearings |
| Graphite (15%) | Dry running, thermal conductivity | Dynamic seals, slide bearings |
| Carbon Fiber (25%) | High strength, dimensional stability | Structural parts, aerospace |
| Bronze (40-60%) | Wear resistance, thermal conductivity | Heavy-duty bearings |
What to Include on the Drawing
A drawing package for a machined PTFE part names three things already covered above:
- The drawing — PDF, CAD, or a sketch
- The material — virgin PTFE or a filled compound
- The quantity
Tolerances are confirmed against the drawing, whether it is metric or inch. For made-to-drawing parts, see custom CNC machined PTFE parts.
Parts Made to a Drawing
This page is a design guide. Product details are on the custom CNC machined PTFE parts page. Samples available.
Custom CNC machined PTFE parts