It’s the method of making an armature made with parts of radio control car. Although there are drawbacks such as not being able to choose the size of the ball, But the basic structure does not change much from what the professional makes, I think that it is good to practice. There is practicality that you can use enough, if you are a small doll, so it might be nice to try making for a practice of animation.
Brass plate, Brass pipe, Brass square pipe
Brass plates are made of 2 mm thick and 6 mm wide.
It is a part for radio control car. There are some with diameters of 4 mm and 5 mm. You can save time and effort for creation, but as the size of the ball is limited.
Using the harder than brass, it is used for machining the installation part of the ball.
In the example below, I use 2mm screws.
It is a joint for a small armature. The screw uses M2. Use balls with a diameter of about 4 mm.
Cut two brass plates with a length of 15 mm.
Put the two pieces together and puncture them. drill a hole of 1.7 mm in diameter at two places of 2 mm and 5 mm from the end.
Expand the hole that holds the ball to 2 mm in diameter with a drill. and expand the hole on one side of the hole for the screw to 2 mm in diameter. Tap the hole for the screw on the other side and cut the screw hole for M2.
With a metal file, file down the edges of the side that sandwiches the ball.
Squeeze a metal ball with a diameter of 4 mm into the hole that holds the ball joint with vise. Dent the edge of the hole in the metal plate along the ball.
Cut off the part of the projection of the ball with filing.
Weld the ball to a 4 mm diameter brass pipe.
Cut a brass square pipe with a width of 3 mm to a length of 6 mm.
Sandwich the ball with brass square pipe and fix with M2 screw, solder square pipes.
It is completed by soldering a round pipe of 4 mm in diameter to a soldered square pipe. Adjust the hardness of the joint by the screw tightness.
It is a humanoid armature assembled using this joint.