Ball joint armature intermediate version

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In the easy version, used the ball of the parts for radio control car. But originally you have to change the size of the ball used for the joint according to the size and design of the puppet. Also, if the material is not made to be “strength of the ball > strength of the plate sandwiching the ball”, the ball will be scratched and the move will be unstable. In Here I introduce the method how to use iron for the ball part. The iron ball can not be processed as it is. So once overheats it and cool it naturally, then the hardness is lowered. (it called “Annealing”)


Brass plate, brass square rod
Brass plates 2 mm thick and 6 mm wide.

ball (iron)
It will not scratch even if it is pinched with a brass plate.

In the example, I use a screw that can be turned with a hex wrench. Since the hexagonal wrench is thin, even after assembling the puppet, it can be inserted from the outside gap to adjust the hardness of the joint. In the example, I use M2 screws.


It is a ball joint for a small armature. The screw uses M2. Use balls with a diameter of 4 mm.
Heat the iron ball with a burner. The foundation is made of casting so as not to melt even at high temperature.

Heat until it glows orange as shown in the photo. Stop the burner just when a spark comes out.

Cool the iron ball slowly by heating with a low heat for 1 to 2 hours with a gas stove.

When cooling is completed, it changes like a photo. Then you can drill a hole.

Drill a hole with a diameter of 2 mm in the center of the ball with a drilling machine.

Insert a 2 mm diameter steel bar and solder it.

Make the plate sandwiching the ball just like the easy version.

It is an example of building a humanoid using joints made

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