The Claw.





Introduction: The Claw.

National Robotics Week Robot Contest

Second Prize in the
National Robotics Week Robot Contest

This is how to build... The Claw.

The Claw is my awesome 3 fingered robotic gripper. it is controlled with a servo, and can be attached to another servo which acts as a "wrist".

To see what it should look like, there is a video here

(for the NRW contest, I am 15)

Step 1: Laser Cut the Pieces

Below are the DXF designs to laser cut the pieces. It should be fairly self explanatory. If you don't have access to a laser cutter, then the designs are also below.

You will also need:
3 x 3mm bolt
3 x 3mm nylock
some multicore wire
some 3mm dowel
3 small pull springs
a drill
a servo
4 x 4mm bolt
4 x 4mm nut

Step 2: Assemble the Base

You should have 3 circular baseplates. one of them has two long rectangular slots in, put this to one side. Glue the other two plates together, making sure all the holes line up. I used bolts to make sure the holes were lined up. 

Step 3: Add the Jaw Mounts

Glue the 6 smallest pieces into the baseplate, ensuring they are perfectly upright.

Step 4: Mount the Servo Mounts

Bolt the servo into one of the two servo mounts using the 4mm bolts and nuts. Then, turn the baseplates over and glue the two mounts in.

Step 5: Add the Dowels

Cut 6 pieces of 3mm dowel to 50mm long. Insert them through the 6 outer holes on the two baseplates, so the ends are flush with the side opposite the servo. I found that scraping the ends with a pencil sharpener blade ensured a good fit. 

Step 6: Add the 3rd Baseplate

Hook the 3 springs over alternate dowels, making sure they are on the ones that sit between pairs of jaw mounts. Then, push the 3rd baseplate onto the dowels.

Step 7: Glue in the "wrist" Mounts

Glue the two "wrist" pieces into the 3rd baseplate.

(Sorry about the lack of picture, I appear to have forgotten to take one.)

Step 8: Add the Jaws

Drill a small hole horizontally into the hole nearest the centre. Also, file into each side of the other hole, so the spring will fit around. Then, feed the end of a piece of wire into the hole, and draw it out the side. Tie a knot in the end, and push it back into the hole. Then, bolt each jaw between the jaw mounts with a bolt and nylock.

Step 9: Finish Off

Bend the end of the spring enough to fit around the edge of the hole, before bending it back into place. Run the 3 jaw wires down the central hole, and tie them throught the holes in the servo head.

Step 10: Enjoy!

This can be mounted on another servo to form a wrist. The servo should pull the wires, which close the jaws. When the servo turns the other way, they should be pulled open by the springs.

Health and Safety:

Warning, claw may become sentient and eat your soul. Also, you may find small children or pets going missing.



    • Science of Cooking

      Science of Cooking
    • Trash to Treasure

      Trash to Treasure
    • Paper Contest 2018

      Paper Contest 2018

    We have a be nice policy.
    Please be positive and constructive.




    hey could i use a dremel

    so i can just use my dremel

    Don't let a completed Claw get hold of your Dremel! It will use it to build an army of Claws!

    (For the same reason, don't let your Claw into a hardware store!)

    I really like the design.

    I'll reproduce a tiny one but with a stepper motor and a screw instead of the cables.

    I made a claw using three one time but they were set with a two-one configuration, not circular like this. I used rubber bands instead of springs but have another thought. What about two wheels connected to the servo, feeding wire as in your plan, closing the claw, and the other feeding the opposite way to where the springs are attached? This would make the open and close completely dependent on the servo and no need for the springs.

    I thought about rubber bands, but decded springs were probably better. Also, I came up with your idea about wires pulling both ways myself, but it was simpler to build using springs. Thanks for the feedback though!!

    The springs are a much better idea. After about three days of playing with the design we had to replace the bands because the snapped. Let me tell you about the pain my hand went through while fine tuning everything...

    i saw your claws and arm with wrist on youtube and i just have to say they are great. im just wondering if you have this in a CAD file that i could use?? im trying to make the claw cuz it looks awesome.

    I can't release the files for the wrist and arm, because they are part of my IGCSE project, and the exam board might get funny. The file for the Claw above, though, is attached.