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

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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

ISO 9001 quality system, 100% critical-dimension inspection

NDA on request; your drawings are never shared

Door-to-door shipping with export documents

Item ref. 1601683183889 ·

Specifications
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.