Spider
Description
Forged Aluminum Bicycle Spider (Stepped): Five-Arm Chainring Carrier with Offset
The stepped forged aluminum bicycle spider is also a five-arm chainring carrier, but its hub is a deeper cup, the five arms step outward from the cup rim with a height change, and one arm carries an extra extended lug. The three-dimensional form creates an offset between the chainring mounting face and the hub to match the chainline of the crank and frame.
The deep cup and stepped arms make metal flow paths longer and more complex during forging. Al Forge Tech (AFT) plans billet and dies with QForm simulation and hot forges the cup and arms so grain flow turns from the cup wall into each arm. After heat treatment, the center bore, bolt holes and lug features are CNC-machined, and BCD, offset and flatness are verified on CMM.
Key Features
- Deep cup hub and stepped five arms forged in one piece
- 3D form provides chainring offset to match chainline
- Extended lug machinable as an extra mounting point
- BCD, offset and flatness measured on CMM
Forged Aluminum Bicycle Spider (Stepped) Specifications and Manufacturing Capability
| Item | Details |
|---|---|
| Product category | Aluminum Forging Bicycle Parts |
| Application | Chainring carriers for cranksets requiring a specific chainline offset |
| Primary process | Closed-die hot forging (hot forging presses 600T–8,000T) |
| Material | Selected to customer specification; 2xxx, 5xxx, 6xxx and 7xxx series aluminum alloys available (e.g. 2014, 6061, 6082, 7075) |
| Heat treatment | In-house T4 solution treatment (8 units) and T6 artificial aging (7 units), set by alloy and strength requirement |
| Secondary machining | CNC machining (52 machining centers, 30 lathes), deburring, vibratory finishing |
| Surface finish | Anodizing (including hard anodizing), shot blasting, e-coating or painting, as required |
| Inspection | Zeiss CMM (4 units), hardness testers, spectrometer, fluorescent penetrant inspection line |
| Dimensions and tolerances | Per customer 2D/3D drawings |
| Quality system | IATF 16949:2016, ISO 14001:2015 |
Forged Aluminum Bicycle Spider (Stepped) Manufacturing Process
- Drawing review and DFM: we confirm alloy, load direction and critical dimensions, then run QForm simulation to predict metal flow and defect risk.
- Die design and manufacturing: the number of die sets (for example, blocker and finisher dies) is planned around part complexity, and die contours are checked with a portable 3D scanner.
- Hot forging: closed-die forming on 600T–8,000T hot forging presses creates a continuous grain flow that follows the part contour.
- Heat treatment: T4 solution treatment and T6 artificial aging are performed in-house, with parameters set by alloy and strength requirement.
- CNC machining and finishing: holes, threads and mating surfaces are machined, followed by deburring, vibratory finishing, shot blasting or anodizing as required.
- Inspection and shipment: dimensions, hardness and chemical composition are verified with CMM, hardness testers and a spectrometer, with lot traceability kept under IATF 16949.
FAQ
What is spider offset, and what does it affect?
Offset is the axial distance between the chainring mounting face and the hub or crank mounting face. It sets the chainring’s lateral position on the bike, that is, the chainline. An incorrect chainline increases chain angle across the cassette, affecting shifting and wear. The stepped spider forges the required offset directly, reducing the need for spacers or extra machining.
What needs attention when forging a stepped spider?
The deep cup and stepped arms force material to travel a longer path, risking laps at cup-wall corners or underfill at the arm tips. AFT simulates metal flow with QForm first, adjusts billet, preform and die design based on the results, and confirms complete form through first-, middle- and last-piece checks.
Can you assess forging feasibility while the Forged Aluminum Bicycle Spider (Stepped) is still in design?
Yes. Al Forge Tech works mainly as an OEM supplier, and our engineers can give design-for-manufacturability (DFM) feedback at the concept or drawing stage, such as adjusting thin ribs, abrupt section changes or draft angles to avoid laps and underfill. QForm simulation predicts metal flow early, and the results are cross-checked against our die design experience.
Is heat treatment for the Forged Aluminum Bicycle Spider (Stepped) done in-house?
Yes. Al Forge Tech operates 8 T4 solution treatment units and 7 T6 artificial aging units on site, so the Forged Aluminum Bicycle Spider (Stepped) can be solution treated, quenched and aged in the same facility before machining and inspection. Keeping heat treatment in-house removes inter-plant transport, reduces lead-time risk and keeps lot traceability within one quality system. Parameters are set according to the alloy grade and your specification.
Can Al Forge Tech supply the Forged Aluminum Bicycle Spider (Stepped) from forging through machining?
Yes. Forging, heat treatment, CNC machining, surface finishing and inspection are integrated in one facility: 52 CNC machining centers (40 four-axis and 12 4.5-axis), 30 lathes (14 with robotic loading), plus broaching, burnishing and centerless grinding. The Forged Aluminum Bicycle Spider (Stepped) can be delivered as a forged blank, semi-finished or fully machined part.
Request a Quote for the Forged Aluminum Bicycle Spider (Stepped)
Developing a new Forged Aluminum Bicycle Spider (Stepped) or converting an existing part to aluminum forging? Send us your 3D/2D drawings, alloy and temper, annual volume and finishing requirements. Our engineering team will reply with a feasibility review, die plan and quotation.
- Online inquiry: Contact Us
- Email: [email protected]
To compare similar parts, browse Aluminum Forging Bicycle Parts and our automotive aluminum forging applications, or visit About Us for our equipment and certifications.
