I have been in contact with Chinese 2.2 kw, water cooled, 24k rpm spindle suppliers and a reseller here in the US. Notice I didn’t refer to them as manufacturers because I cannot figure out who makes what. Huanyang says they make their own but they also make spindles for others. Some of the others say they make their own. The reseller claims he sells his own OEM spindles which is clearly marked with a known Chinese brand’s logo!
I have also been in contact with a German manufacturer/supplier. Yes, they definitely make their own and they are very forthcoming with data, curves, and quickly answer your questions with no smoke screens.
From what I have been told it is best not to operate the Chinese spindles below 10k rpm. The German spindle will operate with constant torque down to 6k and can be run at 3k with no damage, albeit with much reduced torque but still usable.
So, does someone know what the physical difference in the Chinese spindles that causes them to have less turndown as compared to the German manufacturer? Is it that the German spindle uses higher quality VFDs with SVC (sensorless vector control)?
I want to occasionally machine some brass and turndown would be helpful.