Depending on what your system units are, 2 decimal places for precision might be too little (for example if your system units were set to meters, it would behave just as you describe).
Centimeters are for sure set as Display Units, that's visible in the screenshot, however System Units might be different. Just change the precision to four or more decimal places (restart might be needed, not sure about that), there's nothing it could make worse, quite the contrary.
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http://www.youtube.com/watch?v=MrAgsQ9PrfQ&feature=youtu.be
I want to weld a pot with a pottery but there's no way to weld only pot without the edge of the pottery.