Major Update 2- techniques I have learned.

Creating the shoulder.
Because the shoulder has a curve  I design it in 2d with line.

Then in front view I move the two top vertexes, then with bezier corner I give them a curve.

I then go back to left view and extrude the 2d shape into 3d, Then i plase a box next to it and cut it with boolean. to get the desired shape. Then I add some more boxes and I substract them from the shoulder.


Pivot point
I also had a play around with pivot points. It seems when you group, attach or unite with boolean 2 shapes the pivot point goes somewhere between them. This is not always the desireble effect. In the image bellow I have grouped a cylinder (that rotates which raises or lowers the arm from the shoulder) with 3 cylinders which act as hydralics. I was not sure the angle I wanted the hydralics so I aligned the hydralics to the bottom of the rotatying cylinder. When I grouped and tried to rotate the hydralics did not spin around the cylinder.
So I went to the hierarchy and selected pivot only and then selected to aling to the cylinder, then unselect pivot only. Now the whole mechanism spins around the cylinder.

I do not know if it is needed but I also changed the pivot point for the claws setting it to the base of the claw, so now it i rotate the claw i gices the impresion of opening and closing.