PEEK & Ultem Feeds & Speeds Chart
Quick-look reference data for engineering-plastics milling and routing across PEEK, Ultem, Torlon, and Vespel. Use it as a chart-first start before you validate heat, cutter geometry, and setup limits in the plastics calculator.
Need Exact Engineering-Plastics Numbers?
Use this chart for a fast first pass. Then move to the plastics calculator when cutter diameter, finish strategy, or heat-risk tradeoffs need a setup-specific answer.
What This Chart Covers Best
First-pass milling and routing windows for high-temperature plastics where smearing, chip evacuation, and finish quality are the primary concerns.
Where It Needs Backup
Drilling needs feed-per-rev and breakthrough logic, while bar-stock turning needs lathe-specific finish and rigidity rules. Filled grades also need closer tool-wear validation.
Best Next Links
Branch to the plastics calculator, drilling calculator, or turning calculator when the setup gets specific.
PEEK (Polyether Ether Ketone)
The premium engineering plastic — continuous service temperature 250°C (482°F), FDA/USP Class VI compliant. Used for spinal fusion cages, semiconductor wafer handlers, and aerospace bushings. Glass transition at 143°C impacts surface finish above that temperature.
| Variant | Operation | SFM (Carbide) | Chip Load (1/2" EM) |
|---|---|---|---|
| Unfilled PEEK | Roughing | 400 - 800 | 0.004" - 0.008" |
| Unfilled PEEK | Finishing | 600 - 1000 | 0.002" - 0.004" |
| 30% Glass-Filled PEEK | Roughing | 300 - 600 | 0.003" - 0.006" |
| 30% Carbon-Filled PEEK | Roughing | 250 - 500 | 0.003" - 0.005" |
Use these rows as first-pass milling guidance. If the part becomes a drilling or bar-stock turning job, switch to the dedicated workflow before you release numbers.
Ultem (PEI — Polyetherimide)
Amber-colored high-temperature polymer used in aircraft interior components (FAR 25.853 flame-rated), medical sterilization trays, and electrical connectors. Continuous service temperature 170°C (338°F). More brittle than PEEK — prone to chipping.
| Grade | Operation | SFM (Carbide) | Chip Load (1/2" EM) |
|---|---|---|---|
| Ultem 1000 | Roughing | 500 - 900 | 0.004" - 0.007" |
| Ultem 1000 | Finishing | 700 - 1200 | 0.002" - 0.003" |
| Ultem 2300 (30% GF) | General | 350 - 700 | 0.003" - 0.005" |
Ultem chips cleanly but thin sections still need conservative handling. Holemaking and edge breakout should be validated separately in the drilling calculator.
Torlon (PAI) & Vespel (PI)
The highest-performance engineering plastics. Torlon (PAI) handles 260°C continuous. Vespel (polyimide) operates to 300°C+ and costs $2,000–$5,000/kg. Used in jet engine seals, semiconductor fixtures, and space applications.
| Material | Operation | SFM (Carbide) | Chip Load (1/2" EM) |
|---|---|---|---|
| Torlon 4203 | Roughing | 300 - 600 | 0.003" - 0.006" |
| Torlon 4203 | Finishing | 500 - 800 | 0.001" - 0.003" |
| Vespel SP-1 | General | 200 - 500 | 0.002" - 0.004" |
Torlon and Vespel often show up as turned or semi-finished stock. Treat this chart as milling reference only and move lathe work to the turning calculator.
Heat is the Enemy of Plastics
Unlike metals, engineering plastics soften and smear when overheated. The surface melts, re-solidifies, and creates a poor finish with embedded stress.
- Sharp tools only: Dull edges generate friction heat instead of cutting. Replace tools at the first sign of smearing.
- Compressed air cooling: Use directed air blast to keep the cutting zone below the glass transition temperature. Flood coolant works but contaminates medical/semiconductor parts.
- High feed, moderate speed: Move through the material quickly. Dwelling creates heat buildup. Faster feed = bigger chips = more heat removed in the chip.
- 2-flute tools: Maximize chip evacuation space. 4-flute tools pack chips and generate heat in plastics.
Frequently Asked Questions
What SFM should I use for PEEK?
Unfilled PEEK: 400–800 SFM roughing, 600–1000 SFM finishing. Glass-filled PEEK: 300–600 SFM (the glass fibers accelerate tool wear). Carbon-filled PEEK: 250–500 SFM. Use diamond-coated tools for filled variants.
What is the difference between PEEK and Ultem for machining?
PEEK is tougher and produces curled chips. Ultem (PEI) is more brittle and chips cleanly but is prone to micro-chipping at thin walls. PEEK handles higher temperatures (250°C vs 170°C) but costs 2-3x more per kg.
Should I use coolant when machining PEEK?
Compressed air is preferred for most applications — it cools without contaminating the surface. Flood coolant is acceptable for non-critical parts. Medical and semiconductor PEEK parts must be machined dry or with air only.
Why does my PEEK surface look melted?
The cutting temperature exceeded the glass transition point (143°C for unfilled PEEK). Solutions: increase feed rate, reduce RPM, use sharper tools, add air blast cooling, or switch to 2-flute geometry for better chip evacuation.