are you trying to say your hands dont move at the exact speed as the other in the exact movement of the other?, and therefore "one hand touches the other?" because the answer to that would be you are concentrated on it too much and you can only fix your eyes on one thing at a time, and when you look at one hand, you don't concentrate on the other, amd forget about it and it wobbles. You can practice this and practice it until you can do it with your eyes shut and you might attend perfection one day, but then again you say that they take turns touching each other, well, if something touches something else, both things are touching each other at the same time, even if one's velocity, alleleration or force is greater than the other, they are touching at the same time. and oh wow they took turns coming togheter, I think I know what you mean, Is this a science project or something? did any of that make any sense :D?

Rest a ruler on your two index fingers, and bring your fingers together. The ruler only moves against one finger at a time. This is explained by two aspects of friction: 1) the force of friction is roughly propotional to the weight and 2) the force of friction is greater when there is no relative motion. You'll have to try this to fully understand it: When you start the weight on your two fingers won't be exactly the same. As you start to bring your fingers together, the friction gives way on the less heavy side before the other, and once moving the friction forces immediately decrease, so there is no longer enough force to start the heavier side slipping. As the motion continues though, the ruler moves towards the slipping finger and the weight supported by that finger increases until the corresponding friction increases to the point where it equals the force necessary to get the other finger to slip, which has been decreasing as the weight supported by it decreases. The fricional force on the previously slipping finger has increased to the point where it can stop the ruler and cause it to slip on the other finger. This repeats over and over - and the difference in frictional forces between moving and stationary ensures that if keeping your fingers level, you can never bring them in smoothly.