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CNC Machining of Single-Piece 4-Pinned Crank Hubs (15NiCr13)

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Top view of a custom CNC machined single-piece crank hub made from 15NiCr13 steel, displaying dual integral timing chain sprockets.

The component illustrated is a 4-Pinned Crank Hub, engineered as a high-performance replacement part for BMW S55 and N55 engine platforms. The OEM utilizes a three-piece friction-washer design, which is prone to rotational slippage under high torque loads.

To resolve this structural weakness, the upgraded hub body (including the dual timing sprockets) is produced via precision CNC milling as a single monolithic piece from a solid billet of 15NiCr13 steel. Four separately machined precision dowel pins are then securely fitted into tightly toleranced holes on the mating face. This custom crank hub machining process ensures strict accuracy, creating a positive mechanical interlock with the crankshaft to effectively eliminate hub spin.

Side profile of a 4-pinned crank hub upgrade with a nitrided surface finish, featuring four precision press-fit dowel pins.

4-Pin Locking Interface. Four independently machined dowel pins are press-fit into precision bored holes to provide a rigid mechanical interlock with the crankshaft. The dark grey surface indicates the nitriding treatment applied to maximize gear tooth wear resistance.

15NiCr13 (DIN 1.5752) is a high-grade, nickel-chromium case-hardening steel. It is characterized by its exceptionally high core toughness and impact resistance, primarily due to its ~3% nickel content. In high-torque automotive applications, 15NiCr13 is selected because it can absorb extreme shock loads and torsional shear forces without brittle fracture. When subjected to surface hardening treatments like nitriding, it provides a highly wear-resistant exterior for gear teeth while maintaining a ductile, shatter-proof core.

Project Details

Part type: Custom 4-Pinned Crank Hub

Material: 15NiCr13 Steel/EN36 Steel

Machining Process: CNC Turning, Gear Milling

Surface Finish: Nitriding (For wear resistance and core toughness)

Quantity: 30 pcs

Lead Time: 18 day

Custom CNC Automotive Part Machining

We provide custom CNC machining services for automotive parts across various vehicle models. Using 5-axis machining technology, we manufacture components strictly according to provided drawings. Our process addresses specific adaptation and precision requirements, supporting both vehicle restoration and performance modification projects.

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Capabilities include 3-Axis, 4-Axis, and 5-Axis CNC Milling, as well as CNC Turning operations. Standard materials processed include Aluminum alloys, Stainless Steel, Titanium, etc. and Engineering Plastics. Available secondary operations include Anodizing, Powder Coating, Bead Blasting, and Laser Engraving.

Capacity supports requirements ranging from single-unit Rapid Prototyping to Low-Volume Production runs (1-1,000+ units).

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A highly accurate ZEISS Coordinate Measuring Machine (CMM) inspecting the internal dimensions and tight tolerances of a custom CNC machined component.

A standardized Quality Management System (QMS) is applied to all manufacturing orders, regardless of part complexity or production volume. The following inspection stages are mandatory for every CNC machining project:

  • Material Verification: Raw material certification (chemical composition and mechanical properties) is verified upon receipt to ensure compliance with material specifications.

  • First Article Inspection (FAI): The first unit from any production run undergoes a full dimensional report to validate the machining setup and programming before volume processing begins.

  • In-Process Monitoring: Periodic checks are conducted during the machining cycle to monitor tool wear and ensure dimensional consistency is maintained throughout the batch.

  • Final Inspection: Completed components undergo a final dimensional and cosmetic verification using CMM (Coordinate Measuring Machine) and calibrated manual instruments prior to packaging.

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Finished CNC machined components securely packaged in custom foam inserts for global shipping.

From CAD to part.

Step 1: Upload & Quote

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Step 2: Free DFM Review

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Step 3: Precision Machining

We ensure your custom CNC parts meet strict tolerance requirements.

Step 4: Quality Control

Every part undergoes rigorous inspection before leaving our factory to ensure it matches your specifications perfectly.

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FAQs About CNC Machining Services

No. We support projects of all sizes, from a single prototype unit to low-volume production runs.

Standard lead times are typically 10–15 business days. Expedited services (Rapid Prototyping) can be completed in as little as 3–5 business days, depending on part complexity and material availability.

In most cases, we source materials from our approved suppliers to ensure quality control. However, we can machine customer-supplied materials for specialized alloys or specific requirements upon engineering review.

Unless otherwise specified, our general tolerance standard is ISO 2768-m (±0.125 mm) for metals and ±0.25 mm for plastics. Precision tolerances ±0.005 mm are achievable but must be explicitly stated in 2D technical drawings.

Our facility can accommodate parts up to 4000 x 1500 x 600 mm for milling and Ø200 mm x 500 mm for turning.

Yes. We can install inserts (e.g., Helicoils, PEM fasteners) and perform basic mechanical assembly of machined components prior to shipment.

To provide an accurate quote, we require a 3D CAD file (STEP, IGES, or X_T format). If the part has threaded holes, tight tolerances, or specific surface finish requirements, a 2D PDF drawing must also be provided.

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Yes. We can provide material certificates (COA) and dimensional inspection reports upon request. Please specify this requirement when placing your order.

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