This is my robotic arm made of 4mm hardboard with a 3-axis cnc, it is also printable. The servos are the most cheapest ones (TopLine standard servo RS 2 J/R and TopLine mini-servo ES-05 JR).
A little video:
More about the electronics and other info at:
About the mechanisms:
To meeting you take a lot of m3 nuts and bolts, for the gripper you need nylock nuts m3. To connect the horns of the servos to the parts you use small screws such as 2x10mm (or 1,5x10mm). The "bearings" are attached with double sided tape on the back of the servo. The "bearings" are made of plastic (PVC in my case) so it doesn't have a lot of friction.
The base is made of one servo with 12mm spacers with m3 screw tread in it and some washers. The bottom and top plate are attached with 45mm spacers and connected with m3 screws that are sunk in the wood. The servo horn is attached with some little screws like 2x10mm (or 1,5x10mm) to the servoplate.
The underarms are connected with 2x10mm (or 1,5x10mm) screws to the servohorns and the servo itself is connected with m3 nuts and bolts to the servomountplates. The servomountplates are stuck at the servoplate with a tiny press fit. Also u could use a paste for extra support.
The upper arms are attached on the servo with 15mm spacers with m3 twist tread in it, as you can see in the pictures.
The wrist is also attached by a press fit and some long m3x30 nuts and bolts to fasten the miniature servo.
For more support to lift something you can add a 45mm m3 spacer between the 2 servomountplates and a 15mm m3 spacer between the upperarm parts. Then you could attach a spring (or 2) between them.