In my attempts to find the perfect spindle I have tried various combinations including one of those little model engines that rev to 30,000 RPM.
This is my latest but credit must go to the maker who sells these with a 110 volts sewing machine motor. All I did was source a 220 volt ac sewing machine motor for $16AUS and request a pulley bored to the correct shaft diameter for this motor.
Due to the change in voltage to 220 volt the spindle operates at far higher RPM and watts than the 110 version. Top speed of the spindle is 21,000RPM but I intend to run it at a more conservative speed. The setup is a lot quieter than a 3 phase spindle and VFD combination.
Here is a link to Paul's site and I found him easy to deal with and I can highly recommend his work.
The good news is you can put this together for under $200 AUS and it has many advantages over a Dremil type of spindle. For starters it has a ER11 collet chuck, with excellent run out tolerance and it is light and came with a machined mount. I was really lucky that the spindle tube was exactly the same diameter as the mount I had on the Chinese machine so it was slip in for me. The photos show it mounted on the Chinese mounting ready to be fitted to the machine. The motors are throw away and at $16 you can afford to have a spare waiting on the shelf. The dual belt drive is a safe guard so that if one belt brakes you continue cutting and put on a new belt when it is convenient. The three stage pulley has enough speed ratios to not bother with a electric speed control but the sewing machine motor did come with a foot speed control that could easily be utilised.
This setup isn't meant for a serious aluminum cutting CNC machine but it is very suitable for PCB work and light acrylic and timber work. In a week or so I should have the Chinese machine running with this setup.
I have a 60 VDC servo motor with a speed controller kindly made by our Bubinda mate so will trial that at some stage..
This post is something different to get your grey matter thinking outside the box.