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Hi..
There are several high speed spindles which work up to 24000 RPM.
On the other hand i have seen mills with max 2400 RPM, only a tenth of the speed.
But what would be a reasonable range, from low to high, of RPM for a hobbyist who wants to mill wood, plastic, aluminum, steel ?
Thanks..
I would say it depends on what kind of machine you have. Is it rigid enough and fast enough to match a 24000RPM spindle? If not, then all those RPMs will just go towards burning and breaking the tools.
Keep in mind that a high speed spindle will have a high minimum speed. Below that speed, it will either overheat, or not have any usable torque - or both. So, unfortunately, you cannot buy one spindle for drilling circuit boards at 24000RPM and for milling steel at 1200RPM.
Minimum speeds are mostly to do with cooling. I.e. Air cooled spindles that use a shaft fan cool well at high speed and less well as you reduce the speed.
Spindles cooled by water, electric fan or compressed air cool equally well at any speed so they can be used at a wider speed range. My electric fan spindle works from 1,000rpm to 24,000 rpm.
In general, the larger the tool, the slower the spindle speed. And, more torque is required for large tool / low rpm than small tool / high rpm.
Unless money is no object, you won't find a spindle that is good for steel as well as aluminum and wood.
A steel milling spindle ideally has high torque / low speed. This is usually achieved with gears on a belt drive spindle with a separate (and far larger) motor. I.e. One that hits 2hp at 1,800rpm instead of 18,000
You can cut aluminum, wood and plastic with any reasonably powerful 18,000 - 24,000rpm Chinese spindle with 6000-24000 range.
If you have the cash, this one is one of the most versatile hobby-level spindles I've seen:
https://www.damencnc.com/en/quicktoo...rpm/a3969?c=22
What makes it special is that it reaches 2.2kw at just 6000rpm while still have a top speed of 18,000. This gives it 4x the low speed torque of your typical cheap Chinese 2.2kw 24,000rpm spindle.
Plus, it's electric fan allows it to be used at lower rpm without overheating. It means you'd be able to use larger tools.
I'd suggest buying a seperate belt drive spindle if you want to mill steel or aluminum with large tools.