CNC Machined Bicycle Drivetrain Components

Precision-engineered chainrings, cassettes, crank arms, derailleur hangers, and pulley wheels that convert every pedal stroke into forward motion.

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±0.005
mm standard tolerance
±0.5°
tooth angular accuracy
300%
fatigue life improvement
5-7
day prototype turnaround

Why Precision Matters in Bicycle Drivetrains

According to our CNC machining knowledge base, sprockets are gears with teeth that engage with chains rather than another gear. They are primarily used in bicycles to transfer rotational motion. Sprockets are typically produced using methods like gear cutting, gear hobbing, and broaching. These machining processes ensure the accurate formation of teeth, which is essential for maintaining chain engagement and ensuring smooth motion.

CNC machines are often employed to achieve precision. At CNC Works AI, we machine chainrings, cassettes, and crank components with tooth profiles held to ±0.5° angular accuracy and bore concentricity to ±0.003mm. The result: faster shifting, longer chain life, and drivetrains that stay quiet under load.

Road & Gravel Mountain & Enduro BMX & Track E-Bike Torque Gear Hobbing 5-Axis Milling
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Drivetrain Components We Machine

Every tooth, bore, and interface engineered for efficient power transfer.

CNC machined bicycle chainring

Chainrings

Round, oval, and narrow-wide profiles in 1x and 2x configurations.

7075-T6Hard Anodize
CNC machined bicycle cassette

Cassettes

Steel or aluminum cogs with precise shift ramps and gates.

Steel / TiNitrided
CNC machined bicycle crank arm

Crank Arms

Hollow and forged-style crank arms with BB interface machining.

6061-T6±0.005mm
CNC machined derailleur hanger

Derailleur Hangers

Sacrificial hangers machined to exact frame dropout geometry.

7075-T6CMM Verified
CNC machined pulley wheel

Pulley Wheels

Sealed-bearing pulleys with low-friction tooth profiles.

Al / DelrinRa 0.4μm
CNC machined chainring spider adapter

Spider Adapters

Direct-mount and BCD adapters for crank-to-chainring fitment.

7075-T6Type III
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Component Engineering Deep-Dives

Detailed specifications for mission-critical drivetrain parts.

Bicycle chainring tooth profile CNC machined

Chainrings

According to our CNC machining knowledge base, gear hobbing is a specialty CNC machining process used to create gear teeth by progressively cutting them into a cylindrical piece of material using a cutting tool called a hob. For bicycle chainrings, hobbing is effective for achieving accurate tooth profiles.

  • Narrow-wide tooth profiles for chain retention
  • Oval (OCP) and round options available
  • BCD and direct-mount interfaces
  • Tooth angular accuracy ±0.5°
Quote Chainrings

Cassettes

Cassette cogs must balance wear resistance with weight. We machine steel cogs for durability and aluminum/titanium cogs for weight savings, with shift ramps and gates positioned to ±0.1mm for crisp, predictable gear changes under load.

  • Steel, aluminum, or titanium cogs
  • Shift ramps and gates to ±0.1mm
  • Compatible with 10/11/12-speed systems
  • Nitriding or hard anodizing available
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Bicycle cassette shift ramps CNC machined
Bicycle crank arm CNC machined

Crank Arms & Spiders

Crank arms transfer rider torque to the chainring. We machine forged blanks and billet crank arms with precise BB interfaces, pedal thread bores, and spider bolt circles. According to our CNC machining knowledge base, 6061 is easier and quicker to machine than 7075 due to lower hardness, while 7075 offers higher strength for high-load applications.

  • BB30, DUB, and 24mm interfaces
  • Pedal thread bores to Class 2B
  • 4-arm and 5-arm spider patterns
  • Fatigue-tested to ISO 4210
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Derailleur Hangers

Derailleur hangers are sacrificial components that protect the frame and derailleur in a crash. We machine them from 7075-T6 aluminum to exact frame-dropout geometry, ensuring precise derailleur alignment for crisp shifting.

  • Frame-specific geometry matching
  • 7075-T6 for strength-to-weight
  • M5 threads to Class 3B
  • Batch production for OEM spares
Quote Hangers
Bicycle derailleur hanger CNC machined
Bicycle derailleur pulley wheel CNC machined

Pulley Wheels & Cage Plates

Pulley wheels guide the chain through the derailleur cage. We machine aluminum and Delrin pulleys with sealed-bearing bores and low-friction tooth profiles, plus cage plates with precise pivot and mounting holes.

  • Sealed-bearing bore tolerances ±0.005mm
  • Aluminum or Delrin construction
  • Cage plates with hardened pivot bores
  • Ra 0.4μm running surfaces
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Materials Engineered for Drivetrain Loads

Every alloy balances wear resistance, weight, and machinability.

7075-T6 aluminum for chainrings

7075-T6 Aluminum

High strength comparable to many steels. Ideal for chainrings, hangers, and spider adapters.

6061-T6 aluminum for crank arms

6061-T6 Aluminum

Excellent machinability and weldability. Cost-effective choice for crank arms and cage plates.

Hardened steel for cassette cogs

Hardened Steel

Superior wear resistance for cassette cogs. Compatible with nitriding for extended life.

Titanium for lightweight cogs

Titanium

Lightweight and corrosion-resistant. Premium option for lightweight cassette cogs and hardware.

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Surface Finishes for Durability & Aesthetics

Finish
Specification
Application
Hard Anodizing (Type III)
MIL-A-8625, 25–100μm
Chainrings, hangers, abrasion resistance
Decorative Anodizing (Type II)
5–25μm, color options
Crank arms, cage plates, cosmetics
Nitriding
Gas or plasma, 60–70 HRC case
Steel cassette cogs, wear resistance
Powder Coating
UV-resistant, multiple colors
Crank arms, protective cosmetic layer
Passivation
Citric or nitric acid
Titanium and stainless components
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How We Machine a Bicycle Chainring

A process engineered specifically for chain engagement and shift performance.

📐
Tooth Profile Design

CAD model optimized for chain roller engagement and drop prevention.

🔧
Hob Selection

Custom or standard hob chosen based on tooth count and BCD.

💻
CAM Programming

Hobbing path for teeth + 5-axis toolpath for mounting features.

⚙️
CNC Machining

Teeth hobbed, bore reamed, and bolt circle drilled in controlled sequence.

📋
Gear Roll Test

Chain engagement verified under load on gear roll tester.

📦
Protective Pack

VCI packaging prevents corrosion before assembly.

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Drivetrain-Specific Quality Checks

Verifications that matter for chains, cogs, and cranks—not generic parts.

1

Tooth Profile

Gear roll tester checks chain engagement under simulated pedaling load.

2

BCD Runout

CMM verifies bolt-circle concentricity to prevent chainring wobble.

3

Shift Gates

Cassette shift ramps measured to ±0.05mm for crisp gear changes.

4

Wear Test

Sample cogs run through 5,000 km equivalent durability cycle.

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Need a Custom Drivetrain Component Not Listed Here?

We regularly machine chain guides, bash guards, chain stay protectors, and custom BCD adapters for boutique builders and OEMs. Send us your drawing—our engineers will respond within 4 hours.

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Frequently Asked Questions

We machine chainrings, cassettes, crank arms, spiders, derailleur hangers, pulley wheels, cage plates, and chainring spider adapters. We support road, gravel, mountain, BMX, track, and e-bike applications.

According to our CNC machining knowledge base, gear hobbing is a specialty CNC machining process used to create gear teeth by progressively cutting them into a cylindrical piece of material using a hob. We use hobbing and 5-axis profiling to maintain tooth angular accuracy to ±0.5°, with CMM verification on sample parts from every lot.

According to our CNC machining knowledge base, 6061 is typically easier and quicker to machine than 7075 due to lower hardness and tensile strength, making it cost-effective for crank arms and cage plates. However, 7075 offers higher strength and is preferred for chainrings, derailleur hangers, and spider adapters that see higher loads.

Yes. We machine narrow-wide chainrings for 1x road, gravel, and mountain bike setups. Tooth profiles are optimized for chain retention, and we offer direct-mount and BCD options for most major crank standards.

For steel cassette cogs, nitriding provides a hard, wear-resistant case of 60–70 HRC that significantly extends service life. For aluminum or titanium cogs, hard anodizing Type III offers good wear and corrosion resistance.

Our standard tolerance is ±0.005mm. For crank arms, we hold BB interface concentricity to ±0.003mm and pedal thread bores to Class 2B/3B. Every crank arm is inspected on CMM with full inspection reports.

Yes. We produce single-piece prototypes for custom builds and high-volume production runs for OEMs. Our quick-change tooling and automated pallet systems maintain efficiency at scale without sacrificing precision.

Standard prototypes ship in 5-7 business days. Rush service is available in 7–15 days. We maintain raw material stock for 6061-T6, 7075-T6, and common steels to reduce procurement delays.

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Power Transfer, Perfected

Every watt counts. Make sure your drivetrain components are machined to convert rider effort into speed with zero loss. Request your instant quote now.

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