How to Build a Simple Robotic Claw

Written by jordan gaither
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How to Build a Simple Robotic Claw
This giant crane-grabber is an example of an end effector designed for a specific purpose: hauling junk. (a crane grabber and a rusty metal heap image by Alexey Zarodov from

A robot is fine on its own, but if it's meant to interact with its world, it needs to have hands to do so. A robot's hands, or "end effectors," can come in a variety of shapes and functions depending on the robot's primary use. However, building a simple robotic claw, capable of the same actions as two pinching human fingers, is a relatively simple process.

Using some basic tools, materials and one popular gadget, you can build a simple robotic gripper in a well-spent afternoon.

Skill level:

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Things you need

  • "U" attachment and screws
  • 3 kilogram/sec DC motor
  • Plastic toy/prosthetic grabber
  • Screwdriver
  • Small hobby pulley wheel
  • Twine
  • Wire strippers
  • 9-volt battery

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  1. 1

    Fit the "U" attachment over the case of the motor, and screw it into place just below the handle of the grabber, parallel to the grabber's squeeze-handle.

    The motor's shaft should be positioned in line with the centre of the handle.

  2. 2

    Fit the pulley attachment to the end of the motor's shaft and tie one end of a 12-inch piece of twine to it.

  3. 3

    Loop the twine's other end up over the back end of the handle of the grabber, and then tie it around the squeeze-handle. Make sure the knot is secure.

  4. 4

    Strip a 1/2-inch of insulation from each of the motor's wires, and touch them to the terminals of the battery.

    When powered on, the motor will wind up the twine, pulling the handle back and closing the grabber. When unpowered, the motor will relax, the twine will unwind and the grabber will open.

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