Quote Originally Posted by mactec54 View Post
When you get up to those speeds with any Spindle that uses Grease for lubrication, what Bearings are used is going to make the difference as to how well it will last it is right at the max for Bearings that are Grease Lubed, oil mist and you can go higher
How will I know if I'm getting beyond the limit of the spindle rpm? If I monitor temperature of the spindle and have the machine alarm out at a certain point, can I protect the spindle and keep it within it's limits? I'm not sure I feel safe just trusting that an aliexpress spindle can run at 14k rpm for hours and not eventually reach thermal runaway and blow up. I will be running long programs unattended. Am I safe if I use temp sensors with alarm? I'll be designing my own headstock so i can use a couple sensors and position them right at the bearings.

Also to add to that, can I increase the rpm limit of my spindle with active cooling in the headstock?