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Custom Eccentric Shaft Machining — Custom CNC Turning to 0.02 mm Concentricity

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Eccentric shaft machining case — alloy steel stepped shaft with offset journals, flange, and thread, concentricity within 0.02 mm

This stepped eccentric shaft is made of alloy steel. It has multiple bearing journals of different sizes, a middle flange with bolt holes, threaded sections and a groove for snap rings. Different shaft diameters are offset from the central axis, and this offset makes machining quite difficult.

We rough turned the blank first, then sent it for quenching and tempering to reach HRC 32 hardness, before carrying out finish turning. All journals that share the same axis have concentricity within 0.02 mm.

We checked the 0.02 mm concentricity of these journals in final inspection, together with the offset value, thread fit and groove position. For shafts like this, concentricity directly affects bearing operation. If the tolerance is off, bearings will run hot, and the eccentric movement won’t match the design.

Alloy steel works well for this part. It has good strength and fatigue resistance to handle repeated offset loads, and we don’t need extra thick sections as we would with mild steel. The finished parts met all drawing requirements and were delivered with no rework.

Need a Shaft Like This?

We machine custom eccentric shafts, stepped shafts and threaded spindles via CNC turning. We work with steel, stainless steel and aluminum. Our standard concentricity hits 0.02 mm, and we can hold even closer tolerances per drawing requirements.

Project Details

Part type: Custom Eccentric Shaft

Material: Alloy Steel 4140

Machining Process: CNC Turning

Surface Finish: As-Machined

Free Quote & Design Review

We provide custom CNC machining services for low-volume production and Rapid Prototyping for design verification.  Click Here to Upload Your CAD Files

Our Manufacturing Capabilities

5-axis CNC milling machine cutting an aluminum block during the manufacturing process.

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).

Factory Quality Assurance

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.

Order Fulfillment Process

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

From CAD to part.

Step 1: Upload & Quote

Upload your CAD files (.step) to our secure platform. Receive a detailed CNC quote and lead time estimate within 24 hours.

Step 2: Free DFM Review

Our engineers conduct a Design for Manufacturability (DFM) analysis to optimize your design for rapid machining and reduce costs.

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.

Step 5: Fast Delivery

We ship globally using major carriers (DHL, FedEx, UPS). Get your CNC prototypes delivered to your door in as little as 7 days.

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). If the part has threaded holes, tight tolerances, or specific surface finish requirements, a 2D PDF drawing must also be provided.

Not a problem at all. If you don’t have a 3D design, simply share your concept or requirements with us. We work with experienced partnered product designers who can help convert your ideas, hand-drawn sketches, or reference images into professional, manufacturing-ready 3D models.

Please note that 3D modeling services are subject to an additional design fee based on part complexity.

Absolutely. We offer full reverse engineering services for existing parts. Simply mail us your sample, and our engineering team will take care of the rest — from precise measurement and 3D modeling to final CNC production.

We take IP protection seriously. All files are stored securely, and we are willing to sign a Non-Disclosure Agreement (NDA) prior to receiving your data.

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

We ship globally using major carriers (DHL, FedEx, UPS).

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