Material behaviour drives the tooling
Titanium, nickel alloys and hardened steels each fail tools differently, and the geometry and coating follow from the failure mode rather than from the material name.
| Material | Failure mode | Tooling response |
|---|---|---|
| Titanium alloys | Heat at the edge, spring-back, galling | High-helix variable-pitch end mills, sharp AlTiN edge, generous coolant |
| Nickel alloys (Inconel, Waspaloy) | Extreme heat, notch wear at depth of cut line | AlCrN coating, strong edge, through-coolant, conservative speed |
| Structural aluminium | Built-up edge, distortion on thin sections | Polished flutes, 2-3 flute, high helix, DLC or uncoated |
| Hardened steel | Abrasion, edge chipping | AlCrN or AlTiN hard milling geometry, negative rake, rigid holder |
Titanium: the heat problem
Titanium conducts heat poorly, so the heat generated by cutting stays in the tool rather than leaving with the chip. That limits cutting speed, and it makes coolant delivery and edge sharpness more important than coating hardness alone.
Titanium also springs away from the cutter and then relaxes, which produces chatter on thin sections and a taper on deep walls. Variable-pitch tooling and a rigid setup address the vibration; the spring-back is managed by leaving material and finishing in lighter passes.
Nickel alloys: notch wear and the depth-of-cut line
In nickel alloys the tool wears fastest at the boundary where it enters and leaves the cut, producing a notch that eventually propagates and breaks the edge. The countermeasures are a stronger edge preparation, a coating with high oxidation resistance such as AlCrN, and varying the depth of cut between passes so the notch does not form at the same place.
Through-coolant delivery matters more here than almost anywhere else, because it is the only way to get coolant to an edge that is buried in a deep pocket.
Thin sections and distortion
Aerospace parts are frequently thin-walled, which shifts the problem from the cutting edge to the setup. A wall that deflects under cutting force will not hold tolerance regardless of how good the tool is.
The practical answers are support during cutting, symmetric material removal so stress stays balanced, and lighter finishing passes after the part has been allowed to settle. Tooling that cuts freely with lower force, such as a high-helix geometry with a sharp edge, reduces the deflection rather than resisting it.
Documentation for aerospace supply chains
Aerospace buyers generally need traceability from the tool back to its carbide batch and coating run, and frequently a first article inspection report for a new geometry.
We supply material and coating batch certificates, dimensional inspection records against the agreed characteristics, and first article reports for new programmes. If your quality system requires records in a specific format or with your own characteristic numbering, tell us at drawing approval and the records are produced that way from the first batch.
Frequently asked questions
What coating is best for machining Inconel?
AlCrN, because it keeps its hardness and oxidation resistance at the temperatures nickel alloys generate. A strong edge preparation matters as much as the coating, since nickel alloys cause notch wear at the depth-of-cut line.
Why does titanium break tools so quickly?
Titanium conducts heat poorly, so cutting heat concentrates in the edge instead of leaving with the chip, and the edge softens and deforms. It also work-hardens and springs back, which produces chatter on thin sections. The response is lower cutting speed, generous coolant and a sharp edge.
How do I stop notch wear on the depth-of-cut line?
Vary the depth of cut between passes so the notch does not form at the same point on the edge, use a coating with high oxidation resistance, and keep the edge preparation strong enough to resist the load. Alternating axial depth is the most effective single measure.
Can you supply tooling with full traceability?
Yes. Carbide batch and coating run certificates are supplied, along with dimensional inspection records against the agreed characteristics. First article inspection reports are available for new geometries.
Do you make tooling for composite materials?
Yes, in geometries suited to abrasive, anisotropic materials: diamond-coated or PCD-tipped edges for carbon fibre, and sharp low-force geometries to reduce delamination at the exit face. Send the layup and the failure mode and we will propose a geometry.