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Question Keyway vs Keyless Gearbox Input for Rotary

Discussion in 'Motor actuators and drivers' started by RaaR, Jun 25, 2025 at 07:02.

  1. RaaR

    RaaR New Member

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    Im trying to buy some gearboxes and alot of what im seeing the input does not have a keyway. Does the input side not deliver enough torque to matter?

    Im looking at 80/90ST-M02430 servos the specs are a peak torque of 7.1 n-m. Looking to plug into a 50:1 reducer.

    Also if you know a good site to find steel couplers that would be fantastic
    RaaR, Jun 25, 2025 at 07:02
    #1
  2. Misanthrop

    Misanthrop Member

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    Keys are meant only for orientation, never for torque transmission
    Misanthrop, Jun 25, 2025 at 10:30
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  3. Joe Cortexian

    Joe Cortexian Active Member Gold Contributor

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    ChatGPT “Motor shaft keys (along with the matching keyways in the hub or gear) are *specifically designed to transmit torque* between the rotating shaft and the attached component, like a pulley, gear, or coupling. The key fits snugly into both the shaft and the mating part, so when the shaft turns, the key acts as the mechanical link that transfers rotational force to the load.”

    I had problems with the Amazon keys mostly that they were too small leading to slack. I was very satisfied with McMaster Carr. They have an oversized key which I need to hammer to get in. No slack. This is on the gear output side so we are talking 30nM of transmitted torque no slack, I bought a slide hammer to take them out.
    Joe Cortexian, Jun 25, 2025 at 11:55
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  4. Misanthrop

    Misanthrop Member

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    ChatGPT is always right, for sure....:rolleyes::popcorn

    So every engine manufacturer and industry designer should trust ChatGPT in the future, every knowledge from the past is obsolete.


    You have to use the right coupler for your use. Transmit high torque only with an key, will result in ware out of your shaft and coupler. A clutch that is clamped on the shaft can transmit much higher torques.
    Misanthrop, Jun 26, 2025 at 06:15
    #4