Miyota 8215 is a very common movement and widely used. Due to its cheap price and good accuracy but I don't think is reliable. I have yet to damage a ETA or Ronda quartz yet. But Miyota quartz to me has a 40% failure rate after my handling.
I think many of you into watch making will have a headache trying to remove the stem of this movt from the main body. The usual advice is to 'Look for the stem release button and depressed it and you can remove the stem.'
Through my experience. There is no release button to work with for Miyota quartz. Chronograph, yes! But never the basic 8215/8205. I am so frustrated of trying to release the stem after searching high and low for stem release button that I finally give up. Disassemble the movt is the only way out. I always spit at any watch using the miyota quartz.
Recently, I finally devise a way to remove the miyota 8215/8205 stem without disassemble the movt body.
Look at the picture below
There are 2 things that hold the stem, one is the plastic board and another is the hacking metal plate. Use a sharp and flat pen knife and try to slot into it and lift it up abit. Just enough gap to release the stem will do. Once this 2 items are lifted up, pulling out the stem will be easy. Once you are done and try screwing back the stem to secure it. Use the penknife to press on the metal plate and plastic plate to is original position to secure the stem.
Be patient and careful. If you lift up too much of the plates. It will be disastrous because stem holder will not work and you will end up with a stem non secure. Hacking and time setting will be a problem. Then you will need to disassemble the quartz parts to get the stem in correct position before reassemble everything to make it work.
So far this method works flawlessly. I never need to disassemble the 8215 again. Hope it helps!!