Hello everyone. I'm doing some research on spindles for a small mill.

Mostly for aluminium work, but has to be able to do steel as well.

So. Looking at aliexpress to see what is available there I've found two 18000rpm spindles with ER32.

One with square housing which the seller say is for woodworking and light metals, but not for steel.
The other is round and the seller says it is for metal.

As far as I can see there are little difference. The bearings ie. is the same in both. The metal spindle is heavier.


Wood:
https://www.aliexpress.com/item/3283...chweb201603_53
Metal:
https://www.aliexpress.com/item/1810...chweb201603_53


What do you think. Will either of these spindles survive light milling in steel (using smaller end mill is ok). Low speed power is not that good so it has be light either way.

I guess both is fine for aluminium and ligher metal work and the top speed is nice for high speed milling.