I have several Kress 800-FME spindles, and have worn most of them out! They are excellent CNC engraving spindles!
Measuring the run out at the spindle's internal collet taper is more accurate than measuring the run out of a tool clamped in a low quality collet. There are several grades of collets available, and not all have the best TIR (Total Indicator Reading), while most are poorly made and have sloppy concentricity! You must read the fine print when buying spring collets!
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It's not what you take away, it's what you are left with that counts!