Guides / Machining

How Shops Set Up Tooling and Cutting Data for PEEK

September 20, 2026

Sources: manufacturer datasheets and published standards. See editorial standards.

PEEK is not difficult to cut. It is difficult to cut badly without paying for it. The material cannot carry heat away, it holds internal stress and it yields under clamping load, so setup decides the part more than horsepower does.

This is what shops that run PEEK weekly do differently. If you are buying parts rather than cutting them, it is also a decent list of questions to ask a shop that is quoting you.

Tooling

Use tools kept for plastics. A carbide tool that has been in steel has a rounded edge and traces of workpiece material. In PEEK that means rubbing, and rubbing means a glazed surface and a part that grew while it was machined.

Geometry: positive rake, typically 5 to 15°, with a polished flute so chips release instead of sticking. Sharp edge preparation, minimal honing. Clearance angles on the generous side.

Material: uncoated fine grain carbide is the default. Polished carbide for finishing. Diamond coated or PCD tools pay for themselves in filled grades, where glass and carbon fibre destroy a plain carbide edge quickly.

Fewer flutes. Two or three flute cutters give the chip somewhere to go. A four flute cutter in a deep PEEK slot packs chips, melts them and welds them to the wall.

Starting cutting data

Treat these as a place to begin, then let the chip and the surface tell you what to change.

Operation	Starting point
Turning, unfilled	200 to 500 m/min, feed 0.05 to 0.25 mm/rev
Turning, filled	Lower end of that range, tool wear sets the limit
Milling, unfilled	200 to 400 m/min, 0.05 to 0.15 mm per tooth
Drilling	50 to 150 m/min, peck at 1 to 2 diameters
Finishing pass	Light depth, sharp tool, plenty of coolant

What the chip tells you: a clean continuous chip that comes off with colour unchanged is right. A chip that is brown, gummy or welded to the tool means heat, so raise the feed, drop the speed or improve the coolant. Dust and chipping rather than chips usually means a worn edge or a part that is unsupported.

Coolant

PEEK has thermal conductivity around 0.25 W/m·K, roughly 1/500 of aluminium. Every bit of heat you make stays in the cut zone.

• Air blast is enough for light cuts, shallow features and open profiles.
• Water soluble coolant is the norm for drilling, deep pockets and long finishing passes.
• Flood, not mist, when the cut is enclosed.
• Do not machine dry to protect a cosmetic surface. Dry cutting is what produces the glazed, stressed surface people are trying to avoid.

Drilling, threading and thin walls

Drilling. Slow helix or plastic specific drills, peck every one to two diameters, clear the chips properly. A drill that packs chips in a deep hole in PEEK will heat the wall and leave a bore that closes up after machining. For holes over about 20 mm deep, expect a roughing drill and a finishing bore.

Threading. Cut the thread, do not form it. A two flute tap with a polished flute and a slightly generous pitch diameter is normal practice. If the joint gets taken apart and reassembled, specify a metal insert. PEEK threads survive assembly, but not twenty assemblies.

Thin walls. Support them. Soft jaws, vacuum fixtures, sacrificial ribs machined away at the end, or a wax or low melt fixture for the finishing operation. Clamping pressure that would not mark aluminium will deform PEEK enough to matter at ±0.05 mm.

Stress, in the middle of the process

The single step that separates a shop that runs PEEK from one that does not: rough the part, send it to the oven, then finish it. Typical schedules from stock suppliers ramp slowly to about 200 °C, hold roughly two hours per 25 mm of thickness and cool at 20 to 25 °C per hour. Whatever movement the roughing released gets machined away in the finishing pass.

This is not optional on thin walls, deep pockets, long slender parts or tight bores. The full picture is in annealing PEEK parts.

The five mistakes that cost parts

1. A worn edge. In metal you get a poor finish. In PEEK you get heat, a glazed surface and a dimension that drifts.
2. Heavy clamping. Machining a part while it is squeezed out of shape.
3. Chips left in the cut. They melt, weld and ruin the wall.
4. No annealing step on a thin part. The part passes inspection and moves later.
5. Sharp internal corners. A stress concentration in service and a slow cutter path in the shop.

None of this is exotic, but all of it is specific. If a shop quoting your PEEK part talks only about cycle time and hourly rate, ask them which of these five they plan for. What else belongs on the drawing is in PEEK machining explained, and realistic tolerances are in PEEK machining tolerances.

Have a part and want it cut by someone who does this weekly? Send the drawing.

Frequently asked questions

Keep reading

• Which Thread Method Works for a PEEK Part: Tap, Mill or Insert
• Specifying Swiss-Type Turned PEEK Parts Without Burrs or Runout