5-Axis CNC Machined 7075 Aluminum Bicycle Crank Arms
These are lightweight bicycle crank arms and frame hardware, such as dropouts, seat clamps and derailleur hangers, machined on 5-axis CNC centers from 7075-T6 aluminum. Crank arms are hollowed or pocketed to save weight while keeping section strength. They are produced for bicycle brands and custom builders who want CNC-machined components rather than forged parts.
- Material
- Aluminum
- Tolerance
- to ±0.005 mm
- MOQ
- 1 piece
- Prototype lead time
- 3–7 days
- Two-setup 5-axis process with smooth tapered sections
- 7075-T6 crank arms, 6061-T6 sacrificial hangers
- Pedal and spindle interfaces gauge-checked
- Titanium Gr5 available for bolts and axles
Item ref. 1601683183889 ·
| Process | Simultaneous 5-axis CNC milling, CNC turning, threading |
|---|---|
| Materials | Aluminum 7075-T6, 6061-T6; titanium Gr5 |
| Tolerance | ±0.05 mm standard; down to ±0.005 mm on critical features |
| Surface Finish | Type II anodizing, Type III hard anodizing, laser engraving |
| Typical Parts | Crank arms, dropouts, hangers, seat clamps |
| MOQ | 1 piece; prototypes through mid-volume |
| Drawing Formats | STEP, IGES, X_T, STL, DWG, DXF, PDF |
| Lead Time | Prototypes typically 3–7 working days; production 10–20 |
| Inspection | First-article, in-process and CMM checks; reports on request |
Manufacturing
How we make this part
Process, material options and inspection for 5-axis cnc machined 7075 aluminum bicycle crank arms.
A 5-axis crank arm is cut from a solid 7075 plate in two main setups: one to profile the arm and machine the pedal and spindle interfaces, and one to finish the back side and any weight-saving pockets. Simultaneous 5-axis toolpaths produce smooth tapered transitions, which matter because sharp corners concentrate fatigue stress on a part that sees millions of load cycles.
7075-T6 is chosen over 6061-T6 for crank arms because its yield strength is far higher, allowing thinner sections. Its trade-off is lower corrosion resistance, so a sealed anodize layer is important. Dropouts and hangers may use 6061-T6, which bends before it breaks, protecting the frame in a crash. Titanium Gr5 is an option for premium bolts and axles.
Pedal thread (9/16" x 20 TPI) and spindle interfaces are verified with thread and plug gauges, and the first article is measured on a CMM. Every part is inspected for critical dimensions before packing, and cosmetic surfaces are checked after anodizing. Common uses include road, gravel and MTB crank arms, replaceable derailleur hangers, seat post clamps and thru-axle dropouts.
FAQ
Frequently asked questions
Is a CNC machined crank arm as strong as a forged one?
A forged crank has grain flow that follows its shape, which helps fatigue life. A well-designed CNC crank in 7075-T6 can still meet test standards, especially when edges and transitions are radiused. Many brands machine prototypes first and switch to forged blanks with CNC finishing for volume.
Why make derailleur hangers in 6061 instead of 7075?
A hanger is designed to bend or break before the frame does. 6061-T6 is more ductile than 7075-T6, so it can bend in a crash and often be straightened. That makes it the better sacrificial material, while 7075 is reserved for parts that must stay rigid.
How do I get a quote for 5-axis cnc machined 7075 aluminum bicycle crank arms?
Send a 3D model (STEP or IGES) and a 2D drawing with tolerances, material, finish and quantity through the quote form or by email. An engineer replies within 24 hours on business days with price, lead time and any DFM suggestions.
Request a quote
Quote this part
Attach drawings or send several parts at once from the full quote form.
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