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  1. How to Connect Shafts

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     Shaft couplings play a key role in transferring power or torque for motors, pumps, compressors, conveyors, turbines, and other mechanical equipment. Rigid shaft couplings can achieve this goal and allow for different types of shaft connections. Stepped couplings can be used for connecting different size shafts.  Shaft adapters can solve compatibility issues, such as changes in shaft size or length. Inch-to-metric couplings can solve incompatibilities occurring when mating an English shaft to a metric one.  Custom shaft couplings and adapters can accommodate unusual variations or configurations not satisfied by standard products.

    Stafford Manufacturing produces shaft collars, rigid shaft couplings, and specialty mechanical products for motion control, power transmission, automation, and other MRO and OEM applications. Here we’ll discuss how to connect shafts, including those with different sizes, measurement systems, and other specifications.


    Two-Piece Split Clamp-Style Coupling

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    What If I Have Two Different Sized Shafts?

    Connecting shafts of different sizes is a common issue that can be solved with compatible rigid shaft couplings. Designed for perfectly aligned shafts, rigid shaft couplings mate shafts with identical or different diameters while maintaining high torque transfer and preventing backlash. Many configurations of our shaft couplings have stepped bores to connect shafts that differ in size. We offer standard and custom versions of these types of rigid shaft couplings:


    Two-Piece Split Precision Sleeve Coupling with Keyways

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     What If Need a Close Tolerance Fit?

    A close tolerance fit is a necessity whenever you are putting the coupling on a precision machined shaft. Precision sleeve couplings are uniquely suited for applications requiring extremely precise machined shaft alignment and a close tolerance shaft-to-coupling fit.


    Stafford’s exclusive Precision Sleeve Coupling features a solid center section that provides a close tolerance fit on ground shafting, includes a keyway, and the Accu-Clamp™ design which incorporates integral self-centering clamping collars at both ends. This product assures shaft alignment with zero backlash. To assure precise shaft alignment, it maintains <.001″ TIR concentricity while in use. It is precision machined, non-marring, easy to adjust, with high clamping power.

    Stafford offers the following types of Precision Sleeve Couplings:


    Inch-Metric Conversion Coupling

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    What If I’m Connecting an Inch Shaft to a Metric Shaft?

    Inch-metric conversion couplings have a bore on one side measured in inches and the other side in a metric size. Stafford Manufacturing carries a full range of common sizes in our selection of inch-metric conversion couplings. External dimensions and screws are in inches. These couplings can be further modified to include keyways if needed.

    Our inch-metric conversion couplings can mate inch and metric shafts with zero backlash and smooth bores, which protect the shafts from damage. They have superior torque capacity compared to set screw type couplings.

    Stafford offers the following types of inch-metric conversion couplings:


    Step-Up Shaft Adapter

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    What If I Need a Shaft Adapter?

    While shaft couplings can connect shafts of different diameters, shaft adapters enable connections when:

    • One or both shafts are not long enough to be effectively connected with a coupling
    • Shafts differ in diameter and a coupling does not accommodate the difference
    • Shaft damage would result in a poor transfer of power or motion
    • Shaft replacement is not recommended due to cost or other considerations

    Available in step-up or step-down configurations, shaft adapters act as both an extension to an existing shaft and as a way to increase or decrease shaft diameter using a straight-bore or standard stepped-bore coupling. Our rigid shaft adapters use a clamp-style attachment to avoid shaft damage and come in keyed and keyless styles. 


    Rigid Shaft Coupling Configurator

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    None of These Work for Me — What Do I Do?

    Uncommon sizes or combinations of shaft diameters, shapes, keyways, or other configurations can be solved with custom shaft couplings or adapters, avoiding the need for complete shaft replacement or system reconfiguration. Customers can custom-design couplings through our rigid shaft coupling configurator tool, which can provide product recommendations based on your specifications.

    Because manufacturing custom parts is our specialty, our expert team welcomes requests for customized rigid couplings to meet your precise requirements. Custom modifications we commonly make include:

    • Bores: adjustments for special diameters, keyways, and threadings
    • Outside Diameters: surface modifications (e.g. knurling, flats, pulley grooves, notches)
    • Holding Power: adjustments for extra heavy-duty operation
    • Circumferential Keyways: to control axial shift
    • Shaft Shapes: to connect different shaped shafts
    • Balancing: to minimize misalignment, vibration, and wear
    • Materials & Finishes: meeting customer material or surface finishing requirements
    • Shaft Extenders: to accommodate length, duty, configuration, or other needs

    Customers may also modify our fully machinable Shaft Adapter Max to meet their specific needs. It is available with keyways or without, offering multiple configurations to easily extend and adapt for hex, square, or threaded shafts.

    Custom Fabrication by Stafford Manufacturing

    At Stafford Manufacturing, we pride ourselves on our wide range of standard shaft couplings, collars, adapters, and related products. Our innovative designs, extensive catalog of stock components, and customization capabilities illustrate our commitment to industry-leading components and customer service. Contact us to learn more about our standard and custom components for power transmission, motion control, automation, and related applications, or request a quote for your next project.



    Stafford Manufacturing Corp.

    256 Andover St.

    Wilmington, MA 01887

    Phone: 978.657.8000