Quote Originally Posted by Jonathan View Post
I thought you wanted higher speed than that?

To get '>6000rpm and 1000rpm should the need arise' is challenging. The vast majority of spindles use induction motors and to get the variable speed we use a VFD. The problem with this is you can only get full power down to about half the motor's rated rpm, then below that it drops linearly. So in short either you use a massively overrated motor, or have belts so you can change the drive ratio and keep the motor operating in the rated power region. On my micro lathe I went for the former, which would have been expensive except I had already got the motor.
Hi jonathan, the real requirement is the atc, and i had the idea that the chinese water cooled spindles could be converted but due to the questions that arose in the thread including tool balancing, questions about hollowing the shaft and physical workable material in the shaft i thought it may be better to opt for a tormach like solution with atc which is where the man i2i has come up with the goods, the speed was just a side effect of the spindle rather than a requirement for the project, sorry if i was not clear on that... but then i never was the sharpest pencil in the box ...