Gap between stem and top of column
 

HI, im installing a new headset, but i know there have to be a gap between the steam and the column, but how big, right now there is a small gap mayve like 1/2 cm (half centimeter) is that enough or have to be more.
thanks

You need to go to the repair section at www,parktool.com and read up on threadless HS. The gap or clearance has to be between the steerer and topcap and about 3mm is usually enough. The idea is no interference between topcap and steerer.