A manufacturer of gears sent us this Gleason GTR250 5 axis CNC Gear Chamfering spindle. Their complaint was the 40 taper was pitted and would not hold the tool accurately. Incoming inspection showed 35 microns of run out in the taper. The grease in the front bearing was washed out, and the rear bearings were contaminated. The shaft rear journal was under sized and the rear housing was over sized. The rear shaft journal and housing were ground, chrome plated and finish ground. The taper was finish ground and had 4 microns of run out. The spindle was then assembled using ABEC 7 precision bearings. Our assembly technician test ran the spindle for 6 hours; pre loaded the bearings and adjusted drawbar force. Quality control then inspected and gave the approval on the spindle.