Keyway Milling for Aerospace and Aircraft Landing Gear
Aircraft landing gear is among the most demanding applications in machining. Components like struts, axle shafts, torque links, and wheel assembly hubs must hold precise tolerances under extreme cyclic loads — and the keyways connecting those components to their mating parts are no exception.
When a landing gear print calls for an internal keyway in a blind bore, or specifies tight tolerances that standard broaching can’t reliably hold, or prohibits the addition of a relief hole that would compromise the part’s structural integrity — that’s the application NMT’s keyseat millers were built for.
We’ve supplied custom keyway tooling to aerospace manufacturers and their supply chain for over 100 years. The tool mills a full-depth internal keyway in a single pass, to your exact specifications, without modifying the part.
Keyway Applications in Aircraft Landing Gear
Internal keyways appear throughout landing gear assemblies wherever torque must be transmitted or rotational alignment must be held between mating components:
Strut assemblies — internal keyways in main strut cylinders and outer cylinders secure actuator components and alignment features during extension and retraction. These bores are often deep, close-tolerance, and cannot accept a relief hole without weakening the cylinder wall.
Axle shafts and axle beam bores — wheel hubs and brake assemblies mount to axle shafts via keyed connections that must maintain precise angular alignment under the shock loads of landing. Axle bore geometry often makes standard broaching difficult or impossible.
Torque links and trunnion bores — the scissor-link torque arm that prevents strut rotation requires precisely located keyways in its pivot bores to maintain alignment through the full range of strut travel.
Wheel assembly hubs — internal keyways in wheel hubs connect the wheel to the axle and must be accurate enough to avoid imbalance at landing and taxi speeds.
Actuator and lock mechanism housings — retraction actuators, downlock mechanisms, and uplock hooks all involve bored housings where internal keyways are required and part modification is typically not permitted.
Why Aerospace Landing Gear Keyways Are Difficult
Several characteristics of landing gear components make keyway machining harder than most industrial applications:
Print-prohibited part modification — aerospace parts are manufactured to engineering drawings that are controlled and revision-tracked. Adding a relief hole, undercut, or cross-hole to enable broaching often requires a drawing revision and DER approval. The part has to be machined as-designed.
Deep, close-tolerance blind bores — landing gear strut cylinders can have ID bores up to 70 inches long at tolerances that are difficult to hold even under ideal conditions. A keyway that’s off-center or out of tolerance means a rejected part — on a component that may have taken months and significant cost to reach that stage of production.
Hard and difficult-to-machine materials — landing gear components are commonly made from 300M ultra-high-strength steel, 4340 alloy steel, titanium alloys, and AerMet 100. These materials are tough on cutting tools and unforgiving of process variation.
No margin for rework — by the time a landing gear component reaches the keyway operation, it typically has significant value in machined material and labor. A failed keyway operation on a near-finished part is expensive.
NMT’s keyseat miller addresses all of these constraints directly. The tool requires no relief feature, mills to your exact print dimensions, and operates on the bore wall itself as a guide — so the keyway is consistently located and dimensioned without dependence on machine setup variables.
How the Keyseat Miller Works on Aerospace Components
The tool is custom-manufactured to your bore diameter and keyway dimensions. It mounts in a standard drill chuck, collet, or CNC tool holder and feeds axially into the bore. The bore wall acts as the guide for the cutter, which rotates and mills the keyway to full depth in a single pass.
Because the tool is guided by the bore rather than by a fixed stop or chip-clearance geometry, no relief hole at the end of the bore is required. The cutter completes the keyway exactly where the print says it should end, then retracts cleanly.
On CNC machining centers — horizontal or vertical — the tool loads from the carousel like any other tool and is called by the program at the keyway operation. No secondary setup, no part transfer, no separate machine.
Capabilities for Aerospace Applications
All tooling is custom-manufactured to print:
- Bore diameters: Under ½” to over 6″ — contact us for larger bore inquiries
- Keyslot widths: 1/16″ to 2½” (metric sizes available)
- Keyslot length: Up to 12″ in most materials
- Tolerances: Within ±0.0002″ on width
- Keyway types: Full depth, parallel/opposite, two-step, radius arc, straight splines
- Blind bores: Full-depth keyways with no relief hole required
- Materials: 300M, 4340, titanium alloys, AerMet 100, aluminum, stainless, and other aerospace alloys
- Machine compatibility: Manual equipment, horizontal CNC machining centers, vertical CNC machining centers
- Delivery: Custom tooling typically ships in 2–3 weeks
We begin with your print or application drawing. Our engineers design the tooling to your bore and keyway geometry and manufacture it for your specific machine setup.
Working With Aerospace Supply Chain
NMT works with both prime aerospace manufacturers and their Tier 1 and Tier 2 suppliers. We understand that aerospace machining environments have documentation requirements, traceability expectations, and quality standards that differ from general industrial work.
If your application has specific material certification, dimensional reporting, or first-article inspection requirements, discuss them when you request a quote. We’ve supplied aerospace keyway tooling long enough to know what those conversations look like.
Request a Quote for Your Aerospace Application
Have a landing gear or aerospace keyway application? Start with your print or a sketch of the bore and keyway geometry. We quote custom tooling from application drawings and typically respond within one business day.
Call us: 513-541-6682 Email: nationalmachinetoolco@gmail.com
National Machine Tool Co. — Cincinnati, OH — Over 100 years manufacturing precision keyseat millers.