Measuring time dilation of SR by a mechanical clock I think this is a very basic question, but relativity is always not intuitive to me.
When we say that time goes slow when moving (viewed by another inertial coordinate system), we just assume that there is a clock to measure time.
However, everyday clocks are mostly mechanical (like quartz clock). I know that quartz clock works using piezo-electric effect, so it's a  tuning fork that vibrates when you apply electricity. So it's a mechanical effect, and the accurately tuned frequency depends on many things, among them specifically length of the fork. (Tuning fork is a two cantilevers basically) 
So what seems confusing to me is that the length of the fork should be affected by relativity itself, (length contraction) and it would depend on the direction the clock moving. Is this effect real? If so, is it same as time dilation I've learned? But it seems to me that cannot be true, because time dilation is independent of moving direction but this seems not. I know that SR was tested many times, and I've not heard that they used special clocks (like atomic) in the experiments. 
 A: "… we say that time goes slow when moving (viewed by another inertial coordinate system)… " I don't say this, because I don't understand what it means. What I do say – having learnt from some excellent expositors – is this…
The time between two events, as measured in an inertial frame of reference in which the events occur in different places, using synchronised clocks at the locations of the events, is greater (by a factor of $\gamma$) than the time between the same events measured in the inertial frame in which the events occur in the same place (and therefore require a single stationary clock).
I know that this sounds complicated, but once you've grasped it, it's easy to apply and saves a lot of muddle. It brings out the key idea that time dilation is all about the inter-relatedness of time and space, and nothing to do with clock mechanisms being 'affected'. There's nothing to affect them: each clock is stationary in its own inertial frame and the laws of Physics are the same in all inertial frames.
It's true that clocks and the parts of which they are made are contracted in the direction of motion when correctly measured in a frame of reference in which they are moving, but this is quite irrelevant to the phenomenon of time dilation as defined in my second paragraph – even though length contraction, like time dilation, is a manifestation of the inter-relatedness of space and time!    
