Hi Azalin, my Skyfire SMV-0 mill has an ISO 20 taper.....when I ordered the mill from China I also ordered 10 tool holders with ER32 chucks mainly because there is nothing on EBAY to suit or cheap enough.....there are some ISO 20 tools with I think ER20 chucks but they're quite expensive.
The spindle is timing belt driven by a 1 HP BLDC motor....one pulley is fixed on the motor and two different sizes for the spindle to vary the torque and/or speed.....max speed is 7,000 rpm.
The power draw bar was electrically activated by a motorised thruster....worked very well while it was working..... but the motor failed and now for the time being I have a simple manual push down bolt on the top of the draw bar housing.
My own preference for a spindle I am building is a sealed double row angular contact bearing top and bottom with a spacer tube between the inner races and a nut on top of the pulley to apply preload etc.
The bottom bearing is fixed in the housing and the top bearing is allowed to float end wise in the top of the spindle body bore.
There is also a bearing retainer cap to hold the bottom bearing in the spindle bottom end.
Being sealed there is no need to have a seal at the bottom or top as the bearings are sealed for life.
On the subject of the ISO 20 taper I would have preffred to have an R8 taper....this is much more compact for height gain but I don't think it would lend itself to ATC. very easily...….the collets are quite long, but for manual tool changing it's a winner.
Ian.