During the cutting out some parts with my homemade CNC mill I discovered that one of the spindle bearings has broken. The spindle was supported by two four bolt flange UCF204 housed bearings. It's far from perfect solution, as those bearings are not designed to bear axial load but having no lathe suitable to do proper spindle housing I was forced to use them. Those bearings were working fine for many hours, until it failed.


So the time has come to make a new one. After careful consideration of my budget I started  planning. The ER20 chuck have 20mm shaft so I decided to use two 32004 Single Row Taper Bearing, two 30x24x7 Shaft Bearings and to make the housing from 2 1/2"(63.5mm) dia Steel Rod +/-100mm long.

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Having done the drawing, I had nothing left but just go to the workshop and do the job. As an internal dia of the seal is bigger than shaft itself, I used 32mm steel dia bar to make an extra seal inserts. The top insert has two M5 Grub Screw which prevent chuck shaft from being displaced.


Two days, few hours spend in workshop in total, and the result is above. ER20 chuck with inserts, bearings and seals assembled plus spindle housing


My good old chuck with broken end mill. Damaged bearing caused quite violent vibrations.




Fully assembled spindle.